[library] - C++14 → C++17

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@@ -28,11 +28,11 @@ framework for reporting errors in a C++program, including predefined
 exception classes.
 The general utilities library (Clause  [[utilities]]) includes
 components used by other library elements, such as a predefined storage
 allocator for dynamic storage management ([[basic.stc.dynamic]]), and
-components used as infrastructure in C++programs, such as a tuples,
 function wrappers, and time facilities.
 The strings library (Clause  [[strings]]) provides support for
 manipulating text represented as sequences of type `char`, sequences of
 type `char16_t`, sequences of type `char32_t`, sequences of type
@@ -73,194 +73,150 @@ communication.
 The C++standard library also makes available the facilities of the C
 standard library, suitably adjusted to ensure static type safety.
 The descriptions of many library functions rely on the C standard
-library for the signatures and semantics of those functions. In all such
-cases, any use of the `restrict` qualifier shall be omitted.
 ## Definitions <a id="definitions">[[definitions]]</a>
-#### 1 arbitrary-positional stream <a id="defns.arbitrary.stream">[[defns.arbitrary.stream]]</a>
 a stream (described in Clause  [[input.output]]) that can seek to any
 integral position within the length of the stream
-Every arbitrary-positional stream is also a repositional stream.
-#### 2 block <a id="defns.block">[[defns.block]]</a>
-place a thread in the blocked state
-#### 3 blocked thread <a id="defns.blocked">[[defns.blocked]]</a>
-a thread that is waiting for some condition (other than the availability
-of a processor) to be satisfied before it can continue execution[^1]
-#### 4 character <a id="defns.character">[[defns.character]]</a>
-\<Clauses  [[strings]], [[localization]], [[input.output]], and
-[[re]]\> any object which, when treated sequentially, can represent
-text
-The term does not mean only `char`, `char16_t`, `char32_t`, and
-`wchar_t` objects, but any value that can be represented by a type that
-provides the definitions specified in these Clauses.
-#### 5 character container type <a id="defns.character.container">[[defns.character.container]]</a>
 a class or a type used to represent a *character*
-It is used for one of the template parameters of the string, iostream,
-and regular expression class templates. A character container type is a
-POD ([[basic.types]]) type.
-#### 6 comparison function <a id="defns.comparison">[[defns.comparison]]</a>
 an operator function ([[over.oper]]) for any of the equality (
 [[expr.eq]]) or relational ([[expr.rel]]) operators
-#### 7 component <a id="defns.component">[[defns.component]]</a>
 a group of library entities directly related as members, parameters, or
 return types
-For example, the class template `basic_string` and the non-member
-function templates that operate on strings are referred to as the
-*string component*.
-#### 8 deadlock <a id="defns.deadlock">[[defns.deadlock]]</a>
 one or more threads are unable to continue execution because each is
 blocked waiting for one or more of the others to satisfy some condition
-#### 9 default behavior <a id="defns.default.behavior.impl">[[defns.default.behavior.impl]]</a>
-\<implementation\> any specific behavior provided by the implementation,
-within the scope of the *required behavior*
-#### 10 default behavior <a id="defns.default.behavior.func">[[defns.default.behavior.func]]</a>
-\<specification\> a description of *replacement function* and *handler
-function* semantics
-#### 11 handler function <a id="defns.handler">[[defns.handler]]</a>
 a *non-reserved function* whose definition may be provided by a
 C++program
-A C++program may designate a handler function at various points in its
-execution by supplying a pointer to the function when calling any of the
-library functions that install handler functions (Clause
-[[language.support]]).
-#### 12 iostream class templates <a id="defns.iostream.templates">[[defns.iostream.templates]]</a>
 templates, defined in Clause  [[input.output]], that take two template
 arguments
-The arguments are named `charT` and `traits`. The argument `charT` is a
-character container class, and the argument `traits` is a class which
-defines additional characteristics and functions of the character type
-represented by `charT` necessary to implement the iostream class
-templates.
-#### 13 modifier function <a id="defns.modifier">[[defns.modifier]]</a>
 a class member function ([[class.mfct]]) other than a constructor,
 assignment operator, or destructor that alters the state of an object of
 the class
-#### 14 move construction <a id="defns.move.constr">[[defns.move.constr]]</a>
-direct-initialization of an object of some type with an rvalue of the
-same type
-#### 15 move assignment <a id="defns.move.assign">[[defns.move.assign]]</a>
 assignment of an rvalue of some object type to a modifiable lvalue of
 the same type
-#### 16 object state <a id="defns.obj.state">[[defns.obj.state]]</a>
-the current value of all non-static class members of an object (
-[[class.mem]])
-The state of an object can be obtained by using one or more *observer
-functions*.
-#### 17 NTCTS <a id="defns.ntcts">[[defns.ntcts]]</a>
 a sequence of values that have *character type* that precede the
 terminating null character type value `charT()`
-#### 18 observer function <a id="defns.observer">[[defns.observer]]</a>
 a class member function ([[class.mfct]]) that accesses the state of an
 object of the class but does not alter that state
-Observer functions are specified as `const` member functions (
-[[class.this]]).
-#### 19 referenceable type <a id="defns.referenceable">[[defns.referenceable]]</a>
-An object type, a function type that does not have cv-qualifiers or a
-*ref-qualifier*, or a reference type. The term describes a type to which
-a reference can be created, including reference types.
-#### 20 replacement function <a id="defns.replacement">[[defns.replacement]]</a>
 a *non-reserved function* whose definition is provided by a C++program
-Only one definition for such a function is in effect for the duration of
-the program’s execution, as the result of creating the program (
-[[lex.phases]]) and resolving the definitions of all translation units (
-[[basic.link]]).
-#### 21 repositional stream <a id="defns.repositional.stream">[[defns.repositional.stream]]</a>
 a stream (described in Clause  [[input.output]]) that can seek to a
 position that was previously encountered
-#### 22 required behavior <a id="defns.required.behavior">[[defns.required.behavior]]</a>
 a description of *replacement function* and *handler function* semantics
 applicable to both the behavior provided by the implementation and the
 behavior of any such function definition in the program
-If such a function defined in a C++program fails to meet the required
-behavior when it executes, the behavior is undefined.
-#### 23 reserved function <a id="defns.reserved.function">[[defns.reserved.function]]</a>
 a function, specified as part of the C++standard library, that must be
 defined by the implementation
-If a C++program provides a definition for any reserved function, the
-results are undefined.
-#### 24 stable algorithm <a id="defns.stable">[[defns.stable]]</a>
 an algorithm that preserves, as appropriate to the particular algorithm,
 the order of elements
-Requirements for stable algorithms are given in  [[algorithm.stable]].
-#### 25 traits class <a id="defns.traits">[[defns.traits]]</a>
 a class that encapsulates a set of types and functions necessary for
 class templates and function templates to manipulate objects of types
 for which they are instantiated
-Traits classes defined in Clauses  [[strings]], [[localization]] and
-[[input.output]] are *character traits*, which provide the character
-handling support needed by the string and iostream classes.
-#### 26 unblock <a id="defns.unblock">[[defns.unblock]]</a>
-place a thread in the unblocked state
-#### 27 valid but unspecified state <a id="defns.valid">[[defns.valid]]</a>
-an object state that is not specified except that the object’s
 invariants are met and operations on the object behave as specified for
 its type
-If an object `x` of type `std::vector<int>` is in a valid but
-unspecified state, `x.empty()` can be called unconditionally, and
-`x.front()` can be called only if `x.empty()` returns `false`.
-## Additional definitions <a id="defns.additional">[[defns.additional]]</a>
-[[intro.defs]] defines additional terms used elsewhere in this
-International Standard.
 ## Method of description (Informative) <a id="description">[[description]]</a>
 This subclause describes the conventions used to specify the C++standard
 library. [[structure]] describes the structure of the normative Clauses
@@ -269,16 +225,16 @@ library. [[structure]] describes the structure of the normative Clauses
 ### Structure of each clause <a id="structure">[[structure]]</a>
 #### Elements <a id="structure.elements">[[structure.elements]]</a>
-Each library clause contains the following elements, as applicable:[^2]
 - Summary
 - Requirements
 - Detailed specifications
-- References to the Standard C library
 #### Summary <a id="structure.summary">[[structure.summary]]</a>
 The Summary provides a synopsis of the category, and introduces the
 first-level subclauses. Each subclause also provides a summary, listing
@@ -312,12 +268,12 @@ The string and iostream components use an explicit representation of
 operations required of template arguments. They use a class template
 `char_traits` to define these constraints.
 Interface convention requirements are stated as generally as possible.
 Instead of stating “class X has to define a member function
-`operator++()`,” the interface requires “for any object `x` of class
-`X`, `++x` is defined.” That is, whether the operator is a member is
 unspecified.
 Requirements are stated in terms of well-defined expressions that define
 valid terms of the types that satisfy the requirements. For every set of
 well-defined expression requirements there is a table that specifies an
@@ -330,34 +286,34 @@ Template argument requirements are sometimes referenced by name. See
 [[type.descriptions]].
 In some cases the semantic requirements are presented as C++code. Such
 code is intended as a specification of equivalence of a construct to
 another construct, not necessarily as the way the construct must be
-implemented.[^3]
 #### Detailed specifications <a id="structure.specifications">[[structure.specifications]]</a>
 The detailed specifications each contain the following elements:
 - name and brief description
-- synopsis (class definition or function prototype, as appropriate)
 - restrictions on template arguments, if any
 - description of class invariants
 - description of function semantics
 Descriptions of class member functions follow the order (as
-appropriate):[^4]
 - constructor(s) and destructor
 - copying, moving & assignment functions
 - comparison functions
 - modifier functions
 - observer functions
 - operators and other non-member functions
 Descriptions of function semantics contain the following elements (as
-appropriate):[^5]
 - *Requires:* the preconditions for calling the function
 - *Effects:* the actions performed by the function
 - *Synchronization:* the synchronization operations (
   [[intro.multithread]]) applicable to the function
@@ -366,24 +322,23 @@ appropriate):[^5]
 - *Throws:* any exceptions thrown by the function, and the conditions
   that would cause the exception
 - *Complexity:* the time and/or space complexity of the function
 - *Remarks:* additional semantic constraints on the function
 - *Error conditions:* the error conditions for error codes reported by
-  the function.
-- *Notes:* non-normative comments about the function
 Whenever the *Effects:* element specifies that the semantics of some
 function `F` are *Equivalent to* some code sequence, then the various
 elements are interpreted as follows. If `F`’s semantics specifies a
 *Requires:* element, then that requirement is logically imposed prior to
 the *equivalent-to* semantics. Next, the semantics of the code sequence
-are determined by the *Requires:* , *Effects:* , *Postconditions:* ,
-*Returns:* , *Throws:* , *Complexity:* , *Remarks:* , *Error
-conditions:* , and *Notes:* specified for the function invocations
 contained in the code sequence. The value returned from `F` is specified
 by `F`’s *Returns:* element, or if `F` has no *Returns:* element, a
-non-`void` return from `F` is specified by the *Returns:* elements in
 the code sequence. If `F`’s semantics contains a *Throws:* ,
 *Postconditions:* , or *Complexity:* element, then that supersedes any
 occurrences of that element in the code sequence.
 For non-reserved replacement and handler functions, Clause
@@ -394,11 +349,11 @@ describes a function definition provided by the implementation. The
 provided by either the implementation or a C++program. Where no
 distinction is explicitly made in the description, the behavior
 described is the required behavior.
 If the formulation of a complexity requirement calls for a negative
-number of operations, the actual requirement is zero operations.[^6]
 Complexity requirements specified in the library clauses are upper
 bounds, and implementations that provide better complexity guarantees
 satisfy the requirements.
@@ -407,12 +362,11 @@ conditions are listed, together with a suitable explanation, as the
 `enum class errc` constants ([[syserr]]).
 #### C library <a id="structure.see.also">[[structure.see.also]]</a>
 Paragraphs labeled “” contain cross-references to the relevant portions
-of this International Standard and the ISO C standard, which is
-incorporated into this International Standard by reference.
 ### Other conventions <a id="conventions">[[conventions]]</a>
 This subclause describes several editorial conventions used to describe
 the contents of the C++standard library. These conventions are for
@@ -422,37 +376,58 @@ member functions ([[functions.within.classes]]).
 #### Type descriptions <a id="type.descriptions">[[type.descriptions]]</a>
 ##### General <a id="type.descriptions.general">[[type.descriptions.general]]</a>
 The Requirements subclauses may describe names that are used to specify
-constraints on template arguments.[^7] These names are used in library
 Clauses to describe the types that may be supplied as arguments by a
 C++program when instantiating template components from the library.
 Certain types defined in Clause  [[input.output]] are used to describe
 implementation-defined types. They are based on other types, but with
 added constraints.
 ##### Enumerated types <a id="enumerated.types">[[enumerated.types]]</a>
 Several types defined in Clause  [[input.output]] are *enumerated
 types*. Each enumerated type may be implemented as an enumeration or as
-a synonym for an enumeration.[^8]
-The enumerated type *enumerated* can be written:
 ``` cpp
-enum enumerated { V0, V1, V2, V3, ..... };
-static const enumerated C0 (V0);
-static const enumerated C1 (V1);
-static const enumerated C2 (V2);
-static const enumerated C3 (V3);
   .....
 ```
-Here, the names *C0*, *C1*, etc. represent *enumerated elements* for
 this particular enumerated type. All such elements have distinct values.
 ##### Bitmask types <a id="bitmask.types">[[bitmask.types]]</a>
 Several types defined in Clauses  [[language.support]] through
@@ -462,20 +437,19 @@ operators, as an integer type, or as a `bitset` ([[template.bitset]]).
 The bitmask type *bitmask* can be written:
 ``` cpp
 // For exposition only.
-// int_type is an integral type capable of
-// representing all values of the bitmask type.
 enum bitmask : int_type {
- V0 = 1 << 0, V1 = 1 << 1, V2 = 1 << 2, V3 = 1 << 3, .....
 };
-constexpr bitmask C0(V0{});
-constexpr bitmask C1(V1{});
-constexpr bitmask C2(V2{});
-constexpr bitmask C3(V3{});
   .....
 constexpr bitmask{} operator&(bitmask{} X, bitmask{} Y) {
   return static_cast<bitmask{}>(
     static_cast<int_type>(X) & static_cast<int_type>(Y));
@@ -500,14 +474,14 @@ bitmask{}& operator|=(bitmask{}& X, bitmask{} Y) {
 bitmask{}& operator^=(bitmask{}& X, bitmask{} Y) {
   X = X ^ Y; return X;
 }
 ```
-Here, the names *C0*, *C1*, etc. represent *bitmask elements* for this
 particular bitmask type. All such elements have distinct, nonzero values
-such that, for any pair *Ci* and *Cj* where *i* != *j*, *Ci* & *Ci* is
-nonzero and *Ci* & *Cj* is zero. Additionally, the value 0 is used to
 represent an *empty bitmask*, in which no bitmask elements are set.
 The following terms apply to objects and values of bitmask types:
 - To *set* a value *Y* in an object *X* is to evaluate the expression
@@ -521,87 +495,91 @@ The following terms apply to objects and values of bitmask types:
 The C standard library makes widespread use of characters and character
 sequences that follow a few uniform conventions:
 - A *letter* is any of the 26 lowercase or 26 uppercase letters in the
-  basic execution character set.[^9]
 - The *decimal-point character* is the (single-byte) character used by
   functions that convert between a (single-byte) character sequence and
   a value of one of the floating-point types. It is used in the
   character sequence to denote the beginning of a fractional part. It is
   represented in Clauses  [[language.support]] through  [[thread]] and
   Annex  [[depr]] by a period, `'.'`, which is also its value in the
   `"C"` locale, but may change during program execution by a call to
-  `setlocale(int, const char*)`,[^10] or by a change to a `locale`
   object, as described in Clauses  [[locales]] and  [[input.output]].
-- A *character sequence* is an array object ([[dcl.array]]) *A* that
-  can be declared as `T A[N]`, where *T* is any of the types `char`,
   `unsigned char`, or `signed char` ([[basic.fundamental]]), optionally
   qualified by any combination of `const` or `volatile`. The initial
   elements of the array have defined contents up to and including an
   element determined by some predicate. A character sequence can be
-  designated by a pointer value *S* that points to its first element.
 ###### Byte strings <a id="byte.strings">[[byte.strings]]</a>
 A *null-terminated byte string*, or NTBS, is a character sequence whose
 highest-addressed element with defined content has the value zero (the
 *terminating null* character); no other element in the sequence has the
-value zero. [^11]
 The *length* of an NTBS is the number of elements that precede the
 terminating null character. An *empty* NTBS has a length of zero.
 The *value* of an NTBS is the sequence of values of the elements up to
 and including the terminating null character.
-A *static* NTBS is an NTBSwith static storage duration.[^12]
 ###### Multibyte strings <a id="multibyte.strings">[[multibyte.strings]]</a>
-A *null-terminated multibyte string,* or NTMBS, is an NTBSthat
 constitutes a sequence of valid multibyte characters, beginning and
-ending in the initial shift state.[^13]
 A *static* NTMBS is an NTMBSwith static storage duration.
 #### Functions within classes <a id="functions.within.classes">[[functions.within.classes]]</a>
 For the sake of exposition, Clauses  [[language.support]] through
 [[thread]] and Annex  [[depr]] do not describe copy/move constructors,
 assignment operators, or (non-virtual) destructors with the same
 apparent semantics as those that can be generated by default (
-[[class.ctor]], [[class.dtor]], [[class.copy]]).
-It is unspecified whether the implementation provides explicit
-definitions for such member function signatures, or for virtual
-destructors that can be generated by default.
 #### Private members <a id="objects.within.classes">[[objects.within.classes]]</a>
 Clauses  [[language.support]] through  [[thread]] and Annex  [[depr]] do
 not specify the representation of classes, and intentionally omit
 specification of class members ([[class.mem]]). An implementation may
 define static or non-static class members, or both, as needed to
 implement the semantics of the member functions specified in Clauses
 [[language.support]] through  [[thread]] and Annex  [[depr]].
-Objects of certain classes are sometimes required by the external
-specifications of their classes to store data, apparently in member
-objects. For the sake of exposition, some subclauses provide
-representative declarations, and semantic requirements, for private
-member objects of classes that meet the external specifications of the
-classes. The declarations for such member objects and the definitions of
-related member types are followed by a comment that ends with
-*exposition only*, as in:
 ``` cpp
 streambuf* sb;  // exposition only
 ```
 An implementation may use any technique that provides equivalent
-external behavior.
 ## Library-wide requirements <a id="requirements">[[requirements]]</a>
 This subclause specifies requirements that apply to the entire
 C++standard library. Clauses  [[language.support]] through  [[thread]]
@@ -618,59 +596,65 @@ constraints on types and functions used with the C++standard library,
 [[constraints]] describes constraints on well-formed C++programs, and
 [[conforming]] describes constraints on conforming implementations.
 ### Library contents and organization <a id="organization">[[organization]]</a>
-[[contents]] describes the entities defined in the C++standard library.
-[[headers]] lists the standard library headers and some constraints on
-those headers. [[compliance]] lists requirements for a freestanding
-implementation of the C++ standard library.
 #### Library contents <a id="contents">[[contents]]</a>
-The C++standard library provides definitions for the following types of
-entities: macros, values, types, templates, classes, functions, objects.
-All library entities except macros, `operator new` and `operator delete`
-are defined within the namespace `std` or namespaces nested within
-namespace `std`.[^14] It is unspecified whether names declared in a
-specific namespace are declared directly in that namespace or in an
-inline namespace inside that namespace.[^15]
 Whenever a name `x` defined in the standard library is mentioned, the
 name `x` is assumed to be fully qualified as `::std::x`, unless
-explicitly described otherwise. For example, if the Effects section for
-library function `F` is described as calling library function `G`, the
-function `::std::G` is meant.
 #### Headers <a id="headers">[[headers]]</a>
 Each element of the C++standard library is declared or defined (as
-appropriate) in a *header*.[^16]
-The C++standard library provides 53 *C++library headers*, as shown in
 Table  [[tab:cpp.library.headers]].
 **Table: C++library headers** <a id="tab:cpp.library.headers">[tab:cpp.library.headers]</a>
-|                        |                      |             |                      |                   |
-| ---------------------- | -------------------- | ----------- | -------------------- | ----------------- |
-| `<algorithm>`          | `<fstream>` | `<list>` | `<regex>` | `<tuple>`         |
-| `<array>` | `<functional>`       | `<locale>`  | `<scoped_allocator>` | `<type_traits>` |
-| `<atomic>` | `<future>` | `<map>` | `<set>` | `<typeindex>`     |
-| `<bitset>`             | `<initializer_list>` | `<memory>` | `<sstream>` | `<typeinfo>`      |
-| `<chrono>`             | `<iomanip>` | `<mutex>` | `<stack>` | `<unordered_map>` |
-| `<codecvt>` | `<ios>` | `<new>` | `<stdexcept>` | `<unordered_set>` |
-| `<complex>`            | `<iosfwd>` | `<numeric>` | `<streambuf>` | `<utility>`       |
-| `<condition_variable>` | `<iostream>`         | `<ostream>` | `<string>`           | `<valarray>`      |
-| `<deque>`              | `<istream>`          | `<queue>` | `<strstream>` | `<vector>` |
-| `<exception>` | `<iterator>` | `<random>` | `<system_error>` |                   |
-| `<forward_list>` | `<limits>`           | `<ratio>` | `<thread>` |                   |
-The facilities of the C standard Library are provided in 26 additional
-headers, as shown in Table  [[tab:cpp.c.headers]].
 **Table: C++headers for C library facilities** <a id="tab:cpp.c.headers">[tab:cpp.c.headers]</a>
 |              |               |               |             |             |
 | ------------ | ------------- | ------------- | ----------- | ----------- |
@@ -680,34 +664,77 @@ headers, as shown in Table  [[tab:cpp.c.headers]].
 | `<cerrno>`   | `<clocale>`   | `<cstdbool>`  | `<ctgmath>` |             |
 | `<cfenv>`    | `<cmath>`     | `<cstddef>`   | `<ctime>`   |             |
 | `<cfloat>`   | `<csetjmp>`   | `<cstdint>`   | `<cuchar>`  |             |
-Except as noted in Clauses  [[language.support]] through  [[thread]] and
-Annex  [[depr]], the contents of each header `cname` shall be the same
-as that of the corresponding header `name.h`, as specified in the C
-standard library ([[intro.refs]]) or the C Unicode TR, as appropriate,
-as if by inclusion. In the C++standard library, however, the
 declarations (except for names which are defined as macros in C) are
 within namespace scope ([[basic.scope.namespace]]) of the namespace
-`std.` It is unspecified whether these names are first declared within
-the global namespace scope and are then injected into namespace `std` by
-explicit *using-declaration*s ([[namespace.udecl]]).
 Names which are defined as macros in C shall be defined as macros in the
 C++ standard library, even if C grants license for implementation as
-functions. The names defined as macros in C include the following:
-`assert`, `offsetof`, `setjmp`, `va_arg`, `va_end`, and `va_start`.
 Names that are defined as functions in C shall be defined as functions
-in the C++standard library.[^17]
 Identifiers that are keywords or operators in C++shall not be defined as
-macros in C++standard library headers.[^18]
 [[depr.c.headers]], C standard library headers, describes the effects of
-using the `name.h` (C header) form in a C++program.[^19]
 #### Freestanding implementations <a id="compliance">[[compliance]]</a>
 Two kinds of implementations are defined: *hosted* and *freestanding* (
 [[intro.compliance]]). For a hosted implementation, this International
@@ -718,23 +745,24 @@ headers. This set shall include at least the headers shown in Table
 [[tab:cpp.headers.freestanding]].
 **Table: C++headers for freestanding implementations** <a id="tab:cpp.headers.freestanding">[tab:cpp.headers.freestanding]</a>
 | Subclause                                     |                           | Header                            |
-| ---------------------- | ------------------------- | -------------------------------------- |
 |                                               |                           | `<ciso646>`                       |
 | [[support.types]]                             | Types                     | `<cstddef>`                       |
 | [[support.limits]]                            | Implementation properties | `<cfloat>` `<limits>` `<climits>` |
 | [[cstdint]]                                   | Integer types             | `<cstdint>`                       |
 | [[support.start.term]]                        | Start and termination     | `<cstdlib>`                       |
 | [[support.dynamic]]                           | Dynamic memory management | `<new>`                           |
 | [[support.rtti]]                              | Type identification       | `<typeinfo>`                      |
 | [[support.exception]]                         | Exception handling        | `<exception>`                     |
 | [[support.initlist]]                          | Initializer lists         | `<initializer_list>`              |
-| [[support.runtime]] | Other runtime support     | `<cstdalign>` `<cstdarg>` `<cstdbool>` |
 | [[meta]]                                      | Type traits               | `<type_traits>`                   |
 | [[atomics]]                                   | Atomics                   | `<atomic>`                        |
 The supplied version of the header `<cstdlib>` shall declare at least
 the functions `abort`, `atexit`, `at_quick_exit`, `exit`, and
 `quick_exit` ([[support.start.term]]). The other headers listed in this
@@ -757,13 +785,13 @@ appropriate `#include` preprocessing directive ([[cpp.include]]).
 A translation unit may include library headers in any order (Clause
 [[lex]]). Each may be included more than once, with no effect different
 from being included exactly once, except that the effect of including
 either `<cassert>` or `<assert.h>` depends each time on the lexically
-current definition of `NDEBUG`.[^20]
-A translation unit shall include a header only outside of any external
 declaration or definition, and shall include the header lexically before
 the first reference in that translation unit to any of the entities
 declared in that header. No diagnostic is required.
 #### Linkage <a id="using.linkage">[[using.linkage]]</a>
@@ -773,17 +801,17 @@ Entities in the C++standard library have external linkage (
 the default `extern "C++"` linkage ([[dcl.link]]).
 Whether a name from the C standard library declared with external
 linkage has `extern "C"` or `extern "C++"` linkage is
 *implementation-defined*. It is recommended that an implementation use
-`extern "C++"` linkage for this purpose.[^21]
 Objects and functions defined in the library and required by a
 C++program are included in the program prior to program startup.
-replacement functions ([[replacement.functions]]), run-time changes (
-[[handler.functions]]).
 ### Requirements on types and expressions <a id="utility.requirements">[[utility.requirements]]</a>
 [[utility.arg.requirements]] describes requirements on types and
 expressions used to instantiate templates defined in the C++standard
@@ -796,77 +824,71 @@ describes the requirements on hash function objects.
 allocators.
 #### Template argument requirements <a id="utility.arg.requirements">[[utility.arg.requirements]]</a>
 The template definitions in the C++standard library refer to various
-named requirements whose details are set out in tables
-[[equalitycomparable]]– [[destructible]]. In these tables, `T` is an
-object or reference type to be supplied by a C++program instantiating a
-template; `a`, `b`, and `c` are values of type (possibly `const`) `T`;
-`s` and `t` are modifiable lvalues of type `T`; `u` denotes an
-identifier; `rv` is an rvalue of type `T`; and `v` is an lvalue of type
-(possibly `const`) `T` or an rvalue of type `const T`.
 In general, a default constructor is not required. Certain container
 class member function signatures specify `T()` as a default argument.
 `T()` shall be a well-defined expression ([[dcl.init]]) if one of those
 signatures is called using the default argument ([[dcl.fct.default]]).
 **Table: `EqualityComparable` requirements** <a id="equalitycomparable">[equalitycomparable]</a>
-| | |                                                                                                                                                                          |
-| -------- | --------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
 | `a == b`   | convertible to `bool` | `==` is an equivalence relation, that is, it has the following properties: For all `a`, `a == a`.; If `a == b`, then `b == a`.; If `a == b` and `b == c`, then `a == c`. |
 **Table: `LessThanComparable` requirements** <a id="lessthancomparable">[lessthancomparable]</a>
-| | | |
-| ------- | --------------------- | --------------------------------------------------------- |
 | `a < b`    | convertible to `bool` | `<` is a strict weak ordering relation~([[alg.sorting]]) |
 **Table: `DefaultConstructible` requirements** <a id="defaultconstructible">[defaultconstructible]</a>
-| | |
-| -------- | --------------------------------------------------- |
 | `T t;`         | object `t` is default-initialized                                   |
-| `T u{};` | object `u` is value-initialized |
-| `T()` | a temporary object of type `T` is value-initialized |
-| `T{}`    |                                                     |
-**Table: `MoveConstructible` requirements** <a id="moveconstructible">[moveconstructible]</a>
-|             |                                                                    |
-| ----------- | ------------------------------------------------------------------ |
-| `T u = rv;` | `u` is equivalent to the value of `rv` before the construction     |
-| `T(rv)`     | `T(rv)` is equivalent to the value of `rv` before the construction |
-| *[spans 2 columns]*  `rv`'s state is unspecified \enternote `rv` must still meet the requirements of the library component that is using it. The operations listed in those requirements must work as specified whether `rv` has been moved from or not. \exitnote |
 **Table: `CopyConstructible` requirements (in addition to `MoveConstructible`)** <a id="copyconstructible">[copyconstructible]</a>
-| | |
 | ---------- | --------------------------------------------------------- |
 | `T u = v;` | the value of `v` is unchanged and is equivalent to ` u`   |
 | `T(v)`     | the value of `v` is unchanged and is equivalent to `T(v)` |
-**Table: `MoveAssignable` requirements** <a id="moveassignable">[moveassignable]</a>
-|          |      |     |                                                              |
-| -------- | ---- | --- | ------------------------------------------------------------ |
-| `t = rv` | `T&` | `t` | `t` is equivalent to the value of `rv` before the assignment |
-| *[spans 4 columns]*  `rv`'s state is unspecified. \enternote\ `rv` must still meet the requirements of the library component that is using it. The operations listed in those requirements must work as specified whether `rv` has been moved from or not. \exitnote |
 **Table: `CopyAssignable` requirements (in addition to `MoveAssignable`)** <a id="copyassignable">[copyassignable]</a>
-| | | | |
-| ------- | ---- | --- | ------------------------------------------------------- |
 | `t = v`    | `T&`        | `t`          | `t` is equivalent to `v`, the value of `v` is unchanged |
 **Table: `Destructible` requirements** <a id="destructible">[destructible]</a>
-| | |
-| -------- | --------------------------------------------------------------------- |
 | `u.~T()`   | All resources owned by `u` are reclaimed, no exception is propagated. |
 #### `Swappable` requirements <a id="swappable.requirements">[[swappable.requirements]]</a>
@@ -890,28 +912,30 @@ overload resolution ([[over.match]]) on a candidate set that includes:
 - the two `swap` function templates defined in `<utility>` (
   [[utility]]) and
 - the lookup set produced by argument-dependent lookup (
   [[basic.lookup.argdep]]).
-If `T` and `U` are both fundamental types or arrays of fundamental types
-and the declarations from the header `<utility>` are in scope, the
-overall lookup set described above is equivalent to that of the
-qualified name lookup applied to the expression `std::swap(t, u)` or
-`std::swap(u, t)` as appropriate.
-It is unspecified whether a library component that has a swappable
-requirement includes the header `<utility>` to ensure an appropriate
-evaluation context.
 An rvalue or lvalue `t` is *swappable* if and only if `t` is swappable
 with any rvalue or lvalue, respectively, of type `T`.
 A type `X` satisfying any of the iterator requirements (
 [[iterator.requirements]]) satisfies the requirements of
 `ValueSwappable` if, for any dereferenceable object `x` of type `X`,
 `*x` is swappable.
 User code can ensure that the evaluation of `swap` calls is performed in
 an appropriate context under the various conditions as follows:
 ``` cpp
 #include <utility>
@@ -924,11 +948,11 @@ void value_swap(T&& t, U&& u) {
                                                 // for rvalues and lvalues
 }
 // Requires: lvalues of T shall be swappable.
 template <class T>
-void lv_swap(T& t1 T& t2) {
   using std::swap;
   swap(t1, t2);                                 // OK: uses swappable conditions for
 }                                               // lvalues of type T
 namespace N {
@@ -952,48 +976,52 @@ int main() {
   value_swap(a1, proxy(a2));
   assert(a1.m == -5 && a2.m == 5);
 }
 ```
 #### `NullablePointer` requirements <a id="nullablepointer.requirements">[[nullablepointer.requirements]]</a>
 A `NullablePointer` type is a pointer-like type that supports null
 values. A type `P` meets the requirements of `NullablePointer` if:
 - `P` satisfies the requirements of `EqualityComparable`,
   `DefaultConstructible`, `CopyConstructible`, `CopyAssignable`, and
   `Destructible`,
 - lvalues of type `P` are swappable ([[swappable.requirements]]),
-- the expressions shown in Table  [[nullablepointer]] are valid and have
-  the indicated semantics, and
 - `P` satisfies all the other requirements of this subclause.
 A value-initialized object of type `P` produces the null value of the
 type. The null value shall be equivalent only to itself. A
 default-initialized object of type `P` may have an indeterminate value.
-Operations involving indeterminate values may cause undefined behavior.
 An object `p` of type `P` can be contextually converted to `bool`
 (Clause  [[conv]]). The effect shall be as if `p != nullptr` had been
 evaluated in place of `p`.
 No operation which is part of the `NullablePointer` requirements shall
 exit via an exception.
-In Table  [[nullablepointer]], `u` denotes an identifier, `t` denotes a
-non-`const` lvalue of type `P`, `a` and `b` denote values of type
-(possibly `const`) `P`, and `np` denotes a value of type (possibly
 `const`) `std::nullptr_t`.
 **Table: `NullablePointer` requirements** <a id="nullablepointer">[nullablepointer]</a>
 |                |                                    |                                    |
-| -------------- | ---------------------------------- | ------------------------ |
-| `P u(np);`<br> |                                    | post: `u == nullptr`     |
 | `P u = np;`    |                                    |                                    |
-| `P(np)`        |                                    | post: `P(np) == nullptr` |
-| `t = np`       | `P&`                               | post: `t == nullptr`     |
 | `a != b`       | contextually convertible to `bool` | `!(a == b)`                        |
 | `a == np`      | contextually convertible to `bool` | `a == P()`                         |
 | `np == a`      |                                    |                                    |
 | `a != np`      | contextually convertible to `bool` | `!(a == np)`                       |
 | `np != a`      |                                    |                                    |
@@ -1004,25 +1032,21 @@ non-`const` lvalue of type `P`, `a` and `b` denote values of type
 A type `H` meets the `Hash` requirements if:
 - it is a function object type ([[function.objects]]),
 - it satisfies the requirements of `CopyConstructible` and
   `Destructible` ([[utility.arg.requirements]]), and
-- the expressions shown in Table  [[hash]] are valid and have the
   indicated semantics.
 Given `Key` is an argument type for function objects of type `H`, in
-Table  [[hash]] `h` is a value of type (possibly `const`) `H`, `u` is an
-lvalue of type `Key`, and `k` is a value of a type convertible to
 (possibly `const`) `Key`.
-**Table: `Hash` requirements** <a id="hash">[hash]</a>
-|        |          |                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
-| ------ | -------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
-| `h(k)` | `size_t` | The value returned shall depend only on the argument `k` for the duration of the program. \enternote Thus all evaluations of the expression `h(k)` with the same value for `k` yield the same result for a given execution of the program. \exitnote \enternote For two different values `t1` and `t2`, the probability that `h(t1)` and `h(t2)` compare equal should be very small, approaching `1.0 / numeric_limits<size_t>::max()`. \exitnote |
-| `h(u)` | `size_t` | Shall not modify `u`.                                                                                                                                                                                                                                                                                                                                                                                                                             |
 #### Allocator requirements <a id="allocator.requirements">[[allocator.requirements]]</a>
 The library describes a standard set of requirements for *allocators*,
 which are class-type objects that encapsulate the information about an
@@ -1032,12 +1056,12 @@ this allocation model, as well as the memory allocation and deallocation
 primitives for it. All of the string types (Clause  [[strings]]),
 containers (Clause  [[containers]]) (except array), string buffers and
 string streams (Clause  [[input.output]]), and `match_results` (Clause
 [[re]]) are parameterized in terms of allocators.
-The template struct `allocator_traits` ([[allocator.traits]]) supplies
-a uniform interface to all allocator types. Table  [[tab:desc.var.def]]
 describes the types manipulated through allocators. Table
 [[tab:utilities.allocator.requirements]] describes the requirements on
 allocator types and thus on types used to instantiate
 `allocator_traits`. A requirement is optional if the last column of
 Table  [[tab:utilities.allocator.requirements]] specifies a default for
@@ -1048,31 +1072,47 @@ of `allocator_traits` may provide different defaults and may provide
 defaults for different requirements than the primary template. Within
 Tables  [[tab:desc.var.def]] and
 [[tab:utilities.allocator.requirements]], the use of `move` and
 `forward` always refers to `std::move` and `std::forward`, respectively.
 Note A: The member class template `rebind` in the table above is
-effectively a typedef template. In general, if the name `Allocator` is
-bound to `SomeAllocator<T>`, then `Allocator::rebind<U>::other` is the
-same type as `SomeAllocator<U>`, where `SomeAllocator<T>::value_type` is
-`T` and `SomeAllocator<U>::{}value_type` is `U`. If `Allocator` is a
-class template instantiation of the form `SomeAllocator<T, Args>`, where
-`Args` is zero or more type arguments, and `Allocator` does not supply a
-`rebind` member template, the standard `allocator_traits` template uses
-`SomeAllocator<U, Args>` in place of `Allocator::{}rebind<U>::other` by
-default. For allocator types that are not template instantiations of the
-above form, no default is provided.
 An allocator type `X` shall satisfy the requirements of
 `CopyConstructible` ([[utility.arg.requirements]]). The `X::pointer`,
 `X::const_pointer`, `X::void_pointer`, and `X::const_void_pointer` types
 shall satisfy the requirements of `NullablePointer` (
-[[nullablepointer.requirements]]). No constructor, comparison operator,
-copy operation, move operation, or swap operation on these types shall
-exit via an exception. `X::pointer` and `X::const_pointer` shall also
-satisfy the requirements for a random access iterator (
-[[iterator.requirements]]).
 Let `x1` and `x2` denote objects of (possibly different) types
 `X::void_pointer`, `X::const_void_pointer`, `X::pointer`, or
 `X::const_pointer`. Then, `x1` and `x2` are *equivalently-valued*
 pointer values, if and only if both `x1` and `x2` can be explicitly
@@ -1106,15 +1146,18 @@ p1 - p2
 either or both objects may be replaced by an equivalently-valued object
 of type `X::const_pointer` with no change in semantics.
 An allocator may constrain the types on which it can be instantiated and
-the arguments for which its `construct` member may be called. If a type
-cannot be used with a particular allocator, the allocator class or the
-call to `construct` may fail to instantiate.
-the following is an allocator class template supporting the minimal
 interface that satisfies the requirements of Table
 [[tab:utilities.allocator.requirements]]:
 ``` cpp
 template <class Tp>
@@ -1132,15 +1175,29 @@ template <class T, class U>
 bool operator==(const SimpleAllocator<T>&, const SimpleAllocator<U>&);
 template <class T, class U>
 bool operator!=(const SimpleAllocator<T>&, const SimpleAllocator<U>&);
 ```
 If the alignment associated with a specific over-aligned type is not
 supported by an allocator, instantiation of the allocator for that type
 may fail. The allocator also may silently ignore the requested
-alignment. Additionally, the member function `allocate` for that type
-may fail by throwing an object of type `std::bad_alloc`.
 ### Constraints on programs <a id="constraints">[[constraints]]</a>
 #### Overview <a id="constraints.overview">[[constraints.overview]]</a>
@@ -1161,20 +1218,21 @@ The behavior of a C++program is undefined if it adds declarations or
 definitions to namespace `std` or to a namespace within namespace `std`
 unless otherwise specified. A program may add a template specialization
 for any standard library template to namespace `std` only if the
 declaration depends on a user-defined type and the specialization meets
 the standard library requirements for the original template and is not
-explicitly prohibited.[^22]
 The behavior of a C++program is undefined if it declares
 - an explicit specialization of any member function of a standard
   library class template, or
 - an explicit specialization of any member function template of a
   standard library class or class template, or
 - an explicit or partial specialization of any member class template of
-  a standard library class or class template.
 A program may explicitly instantiate a template defined in the standard
 library only if the declaration depends on the name of a user-defined
 type and the instantiation meets the standard library requirements for
 the original template.
@@ -1187,10 +1245,20 @@ namespace ([[namespace.def]]).
 The behavior of a C++program is undefined if it adds declarations or
 definitions to namespace `posix` or to a namespace within namespace
 `posix` unless otherwise specified. The namespace `posix` is reserved
 for use by ISO/IEC 9945 and other POSIX standards.
 #### Reserved names <a id="reserved.names">[[reserved.names]]</a>
 The C++standard library reserves the following kinds of names:
 - macros
@@ -1199,61 +1267,81 @@ The C++standard library reserves the following kinds of names:
 If a program declares or defines a name in a context where it is
 reserved, other than as explicitly allowed by this Clause, its behavior
 is undefined.
 ##### Macro names <a id="macro.names">[[macro.names]]</a>
 A translation unit that includes a standard library header shall not
 `#define` or `#undef` names declared in any standard library header.
 A translation unit shall not `#define` or `#undef` names lexically
 identical to keywords, to the identifiers listed in Table
 [[tab:identifiers.special]], or to the *attribute-token*s described in
 [[dcl.attr]].
-##### Global names <a id="global.names">[[global.names]]</a>
-Certain sets of names and function signatures are always reserved to the
-implementation:
-- Each name that contains a double underscore `__` or begins with an
-  underscore followed by an uppercase letter ([[lex.key]]) is reserved
-  to the implementation for any use.
-- Each name that begins with an underscore is reserved to the
-  implementation for use as a name in the global namespace.
 ##### External linkage <a id="extern.names">[[extern.names]]</a>
 Each name declared as an object with external linkage in a header is
 reserved to the implementation to designate that library object with
-external linkage, [^23] both in namespace `std` and in the global
 namespace.
 Each global function signature declared with external linkage in a
 header is reserved to the implementation to designate that function
-signature with external linkage. [^24]
-Each name from the Standard C library declared with external linkage is
 reserved to the implementation for use as a name with `extern "C"`
-linkage, both in namespace std and in the global namespace.
-Each function signature from the Standard C library declared with
 external linkage is reserved to the implementation for use as a function
-signature with both `extern "C"` and `extern "C++"` linkage, [^25] or as
 a name of namespace scope in the global namespace.
 ##### Types <a id="extern.types">[[extern.types]]</a>
-For each type T from the Standard C library,[^26] the types `::T` and
 `std::T` are reserved to the implementation and, when defined, `::T`
 shall be identical to `std::T`.
 ##### User-defined literal suffixes <a id="usrlit.suffix">[[usrlit.suffix]]</a>
-Literal suffix identifiers that do not start with an underscore are
-reserved for future standardization.
 #### Headers <a id="alt.headers">[[alt.headers]]</a>
 If a file with a name equivalent to the derived file name for one of the
 C++standard library headers is not provided as part of the
@@ -1273,55 +1361,73 @@ Clauses  [[language.support]] through  [[thread]] and Annex  [[depr]]
 describe the behavior of numerous functions defined by the C++standard
 library. Under some circumstances, however, certain of these function
 descriptions also apply to replacement functions defined in the
 program ([[definitions]]).
-A C++program may provide the definition for any of twelve dynamic memory
-allocation function signatures declared in header `<new>` (
 [[basic.stc.dynamic]], [[support.dynamic]]):
-- `operator new(std::size_t)`
-- `operator new(std::size_t, const std::nothrow_t&)`
-- `operator new[](std::size_t)`
-- `operator new[](std::size_t, const std::nothrow_t&)`
-- `operator delete(void*)`
-- `operator delete(void*, const std::nothrow_t&)`
-- `operator delete[](void*)`
-- `operator delete[](void*, const std::nothrow_t&)`
-- `operator delete(void*, std::size_t)`
-- `operator delete(void*, std::size_t, const std::nothrow_t&)`
-- `operator delete[](void*, std::size_t)`
-- `operator delete[](void*, std::size_t, const std::nothrow_t&)`
 The program’s definitions are used instead of the default versions
 supplied by the implementation ([[support.dynamic]]). Such replacement
 occurs prior to program startup ([[basic.def.odr]], [[basic.start]]).
-The program’s definitions shall not be specified as `inline`. No
 diagnostic is required.
 #### Handler functions <a id="handler.functions">[[handler.functions]]</a>
-The C++standard library provides default versions of the following
-handler functions (Clause  [[language.support]]):
-- `unexpected_handler`
 - `terminate_handler`
 A C++program may install different handler functions during execution,
 by supplying a pointer to a function defined in the program or the
 library as an argument to (respectively):
 - `set_new_handler`
-- `set_unexpected`
-- `set_terminate` subclauses  [[alloc.errors]], Storage allocation
-  errors, and  [[support.exception]], Exception handling.
 A C++program can get a pointer to the current handler function by
 calling the following functions:
 - `get_new_handler`
-- `get_unexpected`
 - `get_terminate`
 Calling the `set_*` and `get_*` functions shall not incur a data race. A
 call to any of the `set_*` functions shall synchronize with subsequent
 calls to the same `set_*` function and to the corresponding `get_*`
@@ -1330,26 +1436,26 @@ function.
 #### Other functions <a id="res.on.functions">[[res.on.functions]]</a>
 In certain cases (replacement functions, handler functions, operations
 on types used to instantiate standard library template components), the
 C++standard library depends on components supplied by a C++program. If
-these components do not meet their requirements, the Standard places no
-requirements on the implementation.
 In particular, the effects are undefined in the following cases:
 - for replacement functions ([[new.delete]]), if the installed
   replacement function does not implement the semantics of the
   applicable *Required behavior:* paragraph.
-- for handler functions ([[new.handler]], [[terminate.handler]],
- [[unexpected.handler]]), if the installed handler function does not
- implement the semantics of the applicable *Required behavior:*
-  paragraph
 - for types used as template arguments when instantiating a template
   component, if the operations on the type do not implement the
-  semantics of the applicable subclause ([[allocator.requirements]],
-  [[container.requirements]], [[iterator.requirements]],
   [[numeric.requirements]]). Operations on such types can report a
   failure by throwing an exception unless otherwise specified.
 - if any replacement function or handler function or destructor
   operation exits via an exception, unless specifically allowed in the
   applicable *Required behavior:* paragraph.
@@ -1370,37 +1476,40 @@ the C++standard library, unless explicitly stated otherwise.
   address computations and accesses to objects (that would be valid if
   the pointer did point to the first element of such an array) are in
   fact valid.
 - If a function argument binds to an rvalue reference parameter, the
   implementation may assume that this parameter is a unique reference to
-  this argument. If the parameter is a generic parameter of the form
-  `T&&` and an lvalue of type `A` is bound, the argument binds to an
-  lvalue reference ([[temp.deduct.call]]) and thus is not covered by
-  the previous sentence. If a program casts an lvalue to an xvalue while
- passing that lvalue to a library function (e.g. by calling the
-  function with the argument `move(x)`), the program is effectively
- asking that function to treat that lvalue as a temporary. The
- implementation is free to optimize away aliasing checks which might be
-  needed if the argument was an lvalue.
-#### Shared objects and the library <a id="res.on.objects">[[res.on.objects]]</a>
 The behavior of a program is undefined if calls to standard library
 functions from different threads may introduce a data race. The
 conditions under which this may occur are specified in
-[[res.on.data.races]]. Modifying an object of a standard library type
-that is shared between threads risks undefined behavior unless objects
-of that type are explicitly specified as being sharable without data
-races or the user supplies a locking mechanism.
-In particular, the program is required to ensure that completion of the
-constructor of any object of a class type defined in the standard
-library happens before any other member function invocation on that
-object and, unless otherwise specified, to ensure that completion of any
-member function invocation other than destruction on such an object
-happens before destruction of that object. This applies even to objects
-such as mutexes intended for thread synchronization.
 #### Requires paragraph <a id="res.on.required">[[res.on.required]]</a>
 Violation of the preconditions specified in a function’s *Requires:*
 paragraph results in undefined behavior unless the function’s *Throws:*
@@ -1413,13 +1522,13 @@ violated.
 This section describes the constraints upon, and latitude of,
 implementations of the C++standard library.
 An implementation’s use of headers is discussed in  [[res.on.headers]],
-its use of macros in  [[res.on.macro.definitions]], global functions in
-[[global.functions]], member functions in  [[member.functions]], data
-race avoidance in  [[res.on.data.races]], access specifiers in
 [[protection.within.classes]], class derivation in  [[derivation]], and
 exceptions in  [[res.on.exception.handling]].
 #### Headers <a id="res.on.headers">[[res.on.headers]]</a>
@@ -1432,12 +1541,13 @@ headers.
 Certain types and macros are defined in more than one header. Every such
 entity shall be defined such that any header that defines it may be
 included after any other header that also defines it (
 [[basic.def.odr]]).
-The C standard headers ([[depr.c.headers]]) shall include only their
-corresponding C++standard header, as described in  [[headers]].
 #### Restrictions on macro definitions <a id="res.on.macro.definitions">[[res.on.macro.definitions]]</a>
 The names and global function signatures described in  [[contents]] are
 reserved to the implementation.
@@ -1445,66 +1555,71 @@ reserved to the implementation.
 All object-like macros defined by the C standard library and described
 in this Clause as expanding to integral constant expressions are also
 suitable for use in `#if` preprocessing directives, unless explicitly
 stated otherwise.
-#### Global and non-member functions <a id="global.functions">[[global.functions]]</a>
-It is unspecified whether any global or non-member functions in the
-C++standard library are defined as `inline` ([[dcl.fct.spec]]).
-A call to a global or non-member function signature described in
-Clauses  [[language.support]] through  [[thread]] and Annex  [[depr]]
-shall behave as if the implementation declared no additional global or
-non-member function signatures.[^27]
-An implementation shall not declare a global or non-member function
-signature with additional default arguments.
-Unless otherwise specified, global and non-member functions in the
-standard library shall not use functions from another namespace which
-are found through *argument-dependent name lookup* (
-[[basic.lookup.argdep]]). The phrase “unless otherwise specified” is
-intended to allow argument-dependent lookup in cases like that of
-`ostream_iterator::operator=` ([[ostream.iterator.ops]]):
 *Effects:*
 ``` cpp
 *out_stream << value;
 if (delim != 0)
   *out_stream << delim;
 return *this;
 ```
 #### Member functions <a id="member.functions">[[member.functions]]</a>
 It is unspecified whether any member functions in the C++standard
-library are defined as `inline` ([[dcl.fct.spec]]).
-An implementation may declare additional non-virtual member function
-signatures within a class:
-- by adding arguments with default values to a member function
-  signature; [^28] An implementation may not add arguments with default
-  values to virtual, global, or non-member functions.
-- by replacing a member function signature with default values by two or
-  more member function signatures with equivalent behavior; and
-- by adding a member function signature for a member function name.
-A call to a member function signature described in the C++standard
-library behaves as if the implementation declares no additional member
-function signatures.[^29]
-#### `constexpr` functions and constructors <a id="constexpr.functions">[[constexpr.functions]]</a>
-This standard explicitly requires that certain standard library
-functions are `constexpr` ([[dcl.constexpr]]). An implementation shall
-not declare any standard library function signature as `constexpr`
-except for those where it is explicitly required. Within any header that
-provides any non-defining declarations of `constexpr` functions or
-constructors an implementation shall provide corresponding definitions.
 #### Requirements for stable algorithms <a id="algorithm.stable">[[algorithm.stable]]</a>
 When the requirements for an algorithm state that it is “stable” without
 further elaboration, it means:
@@ -1518,12 +1633,12 @@ further elaboration, it means:
   original order) precede the elements from the second range (preserving
   their original order).
 #### Reentrancy <a id="reentrancy">[[reentrancy]]</a>
-Except where explicitly specified in this standard, it is
-*implementation-defined* which functions in the Standard C++ library may
 be recursively reentered.
 #### Data race avoidance <a id="res.on.data.races">[[res.on.data.races]]</a>
 This section specifies requirements that implementations shall meet to
@@ -1540,36 +1655,38 @@ via the function’s arguments, including `this`.
 A C++standard library function shall not directly or indirectly modify
 objects ([[intro.multithread]]) accessible by threads other than the
 current thread unless the objects are accessed directly or indirectly
 via the function’s non-const arguments, including `this`.
-This means, for example, that implementations can’t use a static object
-for internal purposes without synchronization because it could cause a
-data race even in programs that do not explicitly share objects between
-threads.
 A C++standard library function shall not access objects indirectly
 accessible via its arguments or via elements of its container arguments
 except by invoking functions required by its specification on those
 container elements.
 Operations on iterators obtained by calling a standard library container
 or string member function may access the underlying container, but shall
-not modify it. In particular, container operations that invalidate
 iterators conflict with operations on iterators associated with that
-container.
 Implementations may share their own internal objects between threads if
 the objects are not visible to users and are protected against data
 races.
 Unless otherwise specified, C++standard library functions shall perform
 all operations solely within the current thread if those operations have
 effects that are visible ([[intro.multithread]]) to users.
-This allows implementations to parallelize operations if there are no
-visible side effects.
 #### Protection within classes <a id="protection.within.classes">[[protection.within.classes]]</a>
 It is unspecified whether any function signature or class described in
 Clauses  [[language.support]] through  [[thread]] and Annex  [[depr]] is
@@ -1587,64 +1704,74 @@ through a hierarchy of base classes with names reserved to the
 implementation.
 In any case:
 - Every base class described as `virtual` shall be virtual;
-- Every base class described as non-`virtual` shall not be virtual;
 - Unless explicitly stated otherwise, types with distinct names shall be
-  distinct types.[^30]
 #### Restrictions on exception handling <a id="res.on.exception.handling">[[res.on.exception.handling]]</a>
 Any of the functions defined in the C++standard library can report a
-failure by throwing an exception of a type described in its paragraph.
-An implementation may strengthen the *exception-specification* for a
-non-virtual function by adding a non-throwing *noexcept-specification*.
-A function may throw an object of a type not listed in its clause if its
-type is derived from a type named in the clause and would be caught by
-an exception handler for the base type.
-Functions from the C standard library shall not throw exceptions [^31]
 except when such a function calls a program-supplied function that
-throws an exception.[^32]
 Destructor operations defined in the C++standard library shall not throw
 exceptions. Every destructor in the C++standard library shall behave as
-if it had a non-throwing exception specification. Any other functions
-defined in the C++standard library that do not have an
-*exception-specification* may throw *implementation-defined* exceptions
-unless otherwise specified.[^33] An implementation may strengthen this
-implicit *exception-specification* by adding an explicit one.[^34]
 #### Restrictions on storage of pointers <a id="res.on.pointer.storage">[[res.on.pointer.storage]]</a>
 Objects constructed by the standard library that may hold a
 user-supplied pointer value or an integer of type `std::intptr_t` shall
 store such values in a traceable pointer location (
-[[basic.stc.dynamic.safety]]). Other libraries are strongly encouraged
-to do the same, since not doing so may result in accidental use of
-pointers that are not safely derived. Libraries that store pointers
-outside the user’s address space should make it appear that they are
-stored and retrieved from a traceable pointer location.
 #### Value of error codes <a id="value.error.codes">[[value.error.codes]]</a>
 Certain functions in the C++standard library report errors via a
 `std::error_code` ([[syserr.errcode.overview]]) object. That object’s
 `category()` member shall return `std::system_category()` for errors
 originating from the operating system, or a reference to an
 *implementation-defined* `error_category` object for errors originating
 elsewhere. The implementation shall define the possible values of
-`value()` for each of these error categories. For operating systems that
-are based on POSIX, implementations are encouraged to define the
-`std::system_category()` values as identical to the POSIX `errno`
-values, with additional values as defined by the operating system’s
-documentation. Implementations for operating systems that are not based
-on POSIX are encouraged to define values identical to the operating
-system’s values. For errors that do not originate from the operating
-system, the implementation may provide enums for the associated values.
 #### Moved-from state of library types <a id="lib.types.movedfrom">[[lib.types.movedfrom]]</a>
 Objects of types defined in the C++standard library may be moved from (
 [[class.copy]]). Move operations may be explicitly specified or
@@ -1654,18 +1781,21 @@ objects shall be placed in a valid but unspecified state.
 <!-- Link reference definitions -->
 [alg.c.library]: algorithms.md#alg.c.library
 [alg.sorting]: algorithms.md#alg.sorting
 [algorithm.stable]: #algorithm.stable
 [algorithms]: algorithms.md#algorithms
 [alloc.errors]: language.md#alloc.errors
 [allocator.requirements]: #allocator.requirements
 [allocator.traits]: utilities.md#allocator.traits
 [alt.headers]: #alt.headers
 [atomics]: atomics.md#atomics
 [bad.alloc]: language.md#bad.alloc
 [basic.def.odr]: basic.md#basic.def.odr
 [basic.fundamental]: basic.md#basic.fundamental
 [basic.link]: basic.md#basic.link
 [basic.lookup.argdep]: basic.md#basic.lookup.argdep
 [basic.scope.namespace]: basic.md#basic.scope.namespace
 [basic.start]: basic.md#basic.start
 [basic.stc.dynamic]: basic.md#basic.stc.dynamic
@@ -1674,10 +1804,11 @@ objects shall be placed in a valid but unspecified state.
 [bitmask.types]: #bitmask.types
 [byte.strings]: #byte.strings
 [c.locales]: localization.md#c.locales
 [c.strings]: strings.md#c.strings
 [character.seq]: #character.seq
 [class.copy]: special.md#class.copy
 [class.ctor]: special.md#class.ctor
 [class.dtor]: special.md#class.dtor
 [class.mem]: class.md#class.mem
 [class.mfct]: class.md#class.mfct
@@ -1698,49 +1829,50 @@ objects shall be placed in a valid but unspecified state.
 [cstdint]: language.md#cstdint
 [dcl.array]: dcl.md#dcl.array
 [dcl.attr]: dcl.md#dcl.attr
 [dcl.constexpr]: dcl.md#dcl.constexpr
 [dcl.fct.default]: dcl.md#dcl.fct.default
-[dcl.fct.spec]: dcl.md#dcl.fct.spec
 [dcl.init]: dcl.md#dcl.init
 [dcl.link]: dcl.md#dcl.link
 [definitions]: #definitions
-[defns.additional]: #defns.additional
 [depr]: future.md#depr
 [depr.c.headers]: future.md#depr.c.headers
 [derivation]: #derivation
 [derived.classes]: #derived.classes
 [description]: #description
-[destructible]: #destructible
 [diagnostics]: diagnostics.md#diagnostics
 [enumerated.types]: #enumerated.types
-[equalitycomparable]: #equalitycomparable
 [except]: except.md#except
 [expr.delete]: expr.md#expr.delete
 [expr.eq]: expr.md#expr.eq
 [expr.new]: expr.md#expr.new
 [expr.rel]: expr.md#expr.rel
 [extern.names]: #extern.names
 [extern.types]: #extern.types
 [function.objects]: utilities.md#function.objects
 [functions.within.classes]: #functions.within.classes
 [global.functions]: #global.functions
-[global.names]: #global.names
 [handler.functions]: #handler.functions
-[hash]: #hash
 [hash.requirements]: #hash.requirements
 [headers]: #headers
 [input.output]: input.md#input.output
 [intro.compliance]: intro.md#intro.compliance
 [intro.defs]: intro.md#intro.defs
 [intro.multithread]: intro.md#intro.multithread
 [intro.refs]: intro.md#intro.refs
 [iterator.requirements]: iterators.md#iterator.requirements
 [iterators]: iterators.md#iterators
 [language.support]: language.md#language.support
 [lex]: lex.md#lex
-[lex.key]: lex.md#lex.key
 [lex.phases]: lex.md#lex.phases
 [lib.types.movedfrom]: #lib.types.movedfrom
 [library]: #library
 [library.c]: #library.c
 [library.general]: #library.general
@@ -1750,25 +1882,27 @@ objects shall be placed in a valid but unspecified state.
 [member.functions]: #member.functions
 [meta]: utilities.md#meta
 [multibyte.strings]: #multibyte.strings
 [namespace.constraints]: #namespace.constraints
 [namespace.def]: dcl.md#namespace.def
 [namespace.posix]: #namespace.posix
 [namespace.std]: #namespace.std
 [namespace.udecl]: dcl.md#namespace.udecl
 [new.delete]: language.md#new.delete
 [new.handler]: language.md#new.handler
-[nullablepointer]: #nullablepointer
 [nullablepointer.requirements]: #nullablepointer.requirements
 [numeric.requirements]: numerics.md#numeric.requirements
 [numerics]: numerics.md#numerics
 [objects.within.classes]: #objects.within.classes
 [organization]: #organization
 [ostream.iterator.ops]: iterators.md#ostream.iterator.ops
 [over.match]: over.md#over.match
 [over.oper]: over.md#over.oper
 [protection.within.classes]: #protection.within.classes
 [re]: re.md#re
 [reentrancy]: #reentrancy
 [replacement.functions]: #replacement.functions
 [requirements]: #requirements
 [res.on.arguments]: #res.on.arguments
@@ -1799,164 +1933,151 @@ objects shall be placed in a valid but unspecified state.
 [support.start.term]: language.md#support.start.term
 [support.types]: language.md#support.types
 [swappable.requirements]: #swappable.requirements
 [syserr]: diagnostics.md#syserr
 [syserr.errcode.overview]: diagnostics.md#syserr.errcode.overview
 [tab:cpp.c.headers]: #tab:cpp.c.headers
 [tab:cpp.headers.freestanding]: #tab:cpp.headers.freestanding
 [tab:cpp.library.headers]: #tab:cpp.library.headers
 [tab:desc.var.def]: #tab:desc.var.def
 [tab:identifiers.special]: lex.md#tab:identifiers.special
 [tab:library.categories]: #tab:library.categories
 [tab:utilities.allocator.requirements]: #tab:utilities.allocator.requirements
 [temp.deduct.call]: temp.md#temp.deduct.call
 [template.bitset]: utilities.md#template.bitset
 [terminate.handler]: language.md#terminate.handler
 [thread]: thread.md#thread
 [type.descriptions]: #type.descriptions
 [type.descriptions.general]: #type.descriptions.general
-[unexpected.handler]: future.md#unexpected.handler
 [using]: #using
 [using.headers]: #using.headers
 [using.linkage]: #using.linkage
 [using.overview]: #using.overview
 [usrlit.suffix]: #usrlit.suffix
 [utilities]: utilities.md#utilities
 [utility]: utilities.md#utility
 [utility.arg.requirements]: #utility.arg.requirements
 [utility.requirements]: #utility.requirements
 [value.error.codes]: #value.error.codes
-[^1]: This definition is taken from POSIX.
-[^2]: To save space, items that do not apply to a Clause are omitted.
     For example, if a Clause does not specify any requirements, there
     will be no “Requirements” subclause.
-[^3]: Although in some cases the code given is unambiguously the optimum
     implementation.
-[^4]: To save space, items that do not apply to a class are omitted. For
     example, if a class does not specify any comparison functions, there
     will be no “Comparison functions” subclause.
-[^5]: To save space, items that do not apply to a function are omitted.
     For example, if a function does not specify any further
-    preconditions, there will be no “Requires” paragraph.
-[^6]: This simplifies the presentation of complexity requirements in
     some cases.
-[^7]: Examples from  [[utility.requirements]] include:
     `EqualityComparable`, `LessThanComparable`, `CopyConstructible`.
     Examples from  [[iterator.requirements]] include: `InputIterator`,
-    `ForwardIterator`, `Function`, `Predicate`.
-[^8]: Such as an integer type, with constant integer values (
     [[basic.fundamental]]).
-[^9]: Note that this definition differs from the definition in ISO C
-    7.1.1.
-[^10]: declared in `<clocale>` ([[c.locales]]).
-[^11]: Many of the objects manipulated by function signatures declared
-    in `<cstring>` ([[c.strings]]) are character sequences or NTBSs.
-    The size of some of these character sequences is limited by a length
     value, maintained separately from the character sequence.
-[^12]: A string literal, such as `"abc"`, is a static NTBS.
-[^13]: An NTBSthat contains characters only from the basic execution
     character set is also an NTMBS. Each multibyte character then
     consists of a single byte.
-[^14]: The C standard library headers (Annex  [[depr.c.headers]]) also
     define names within the global namespace, while the C++headers for C
     library facilities ([[headers]]) may also define names within the
     global namespace.
-[^15]: This gives implementers freedom to use inline namespaces to
     support multiple configurations of the library.
-[^16]: A header is not necessarily a source file, nor are the sequences
     delimited by `<` and `>` in header names necessarily valid source
     file names ([[cpp.include]]).
-[^17]: This disallows the practice, allowed in C, of providing a masking
     macro in addition to the function prototype. The only way to achieve
     equivalent inline behavior in C++is to provide a definition as an
     extern inline function.
-[^18]: In particular, including the standard header `<iso646.h>` or
     `<ciso646>` has no effect.
-[^19]: The `".h"` headers dump all their names into the global
     namespace, whereas the newer forms keep their names in namespace
     `std`. Therefore, the newer forms are the preferred forms for all
     uses except for C++programs which are intended to be strictly
     compatible with C.
-[^20]: This is the same as the Standard C library.
-[^21]: The only reliable way to declare an object or function signature
-    from the Standard C library is by including the header that declares
     it, notwithstanding the latitude granted in 7.1.4 of the C Standard.
-[^22]: Any library code that instantiates other library templates must
     be prepared to work adequately with any user-supplied specialization
-    that meets the minimum requirements of the Standard.
-[^23]: The list of such reserved names includes `errno`, declared or
     defined in `<cerrno>`.
-[^24]: The list of such reserved function signatures with external
     linkage includes `setjmp(jmp_buf)`, declared or defined in
     `<csetjmp>`, and `va_end(va_list)`, declared or defined in
     `<cstdarg>`.
-[^25]: The function signatures declared in `<cuchar>`, `<cwchar>`, and
     `<cwctype>` are always reserved, notwithstanding the restrictions
     imposed in subclause 4.5.1 of Amendment 1 to the C Standard for
     these headers.
-[^26]: These types are `clock_t`, `div_t`, `FILE`, `fpos_t`, `lconv`,
     `ldiv_t`, `mbstate_t`, `ptrdiff_t`, `sig_atomic_t`, `size_t`,
     `time_t`, `tm`, `va_list`, `wctrans_t`, `wctype_t`, and `wint_t`.
-[^27]: A valid C++program always calls the expected library global or
- non-member function. An implementation may also define additional
- global or non-member functions that would otherwise not be called by
-    a valid C++program.
-[^28]: Hence, the address of a member function of a class in the
-    C++standard library has an unspecified type.
-[^29]: A valid C++program always calls the expected library member
-    function, or one with equivalent behavior. An implementation may
-    also define additional member functions that would otherwise not be
-    called by a valid C++program.
-[^30]: There is an implicit exception to this rule for types that are
     described as synonyms for basic integral types, such as `size_t` (
     [[support.types]]) and `streamoff` ([[stream.types]]).
-[^31]: That is, the C library functions can all be treated as if they
     are marked `noexcept`. This allows implementations to make
     performance optimizations based on the absence of exceptions at
     runtime.
-[^32]: The functions `qsort()` and `bsearch()` ([[alg.c.library]]) meet
     this condition.
-[^33]: In particular, they can report a failure to allocate storage by
     throwing an exception of type `bad_alloc`, or a class derived from
-    `bad_alloc` ([[bad.alloc]]). Library implementations should report
-    errors by throwing exceptions of or derived from the standard
-    exception classes ([[bad.alloc]], [[support.exception]],
-    [[std.exceptions]]).
-[^34]: That is, an implementation may provide an explicit
-    *exception-specification* that defines the subset of “any”
-    exceptions thrown by that function. This implies that the
-    implementation may list implementation-defined types in such an
-    *exception-specification*.

 exception classes.
 The general utilities library (Clause  [[utilities]]) includes
 components used by other library elements, such as a predefined storage
 allocator for dynamic storage management ([[basic.stc.dynamic]]), and
+components used as infrastructure in C++programs, such as tuples,
 function wrappers, and time facilities.
 The strings library (Clause  [[strings]]) provides support for
 manipulating text represented as sequences of type `char`, sequences of
 type `char16_t`, sequences of type `char32_t`, sequences of type
 The C++standard library also makes available the facilities of the C
 standard library, suitably adjusted to ensure static type safety.
 The descriptions of many library functions rely on the C standard
+library for the semantics of those functions. In some cases, the
+signatures specified in this International Standard may be different
+from the signatures in the C standard library, and additional overloads
+may be declared in this International Standard, but the behavior and the
+preconditions (including any preconditions implied by the use of an ISO
+C `restrict` qualifier) are the same unless otherwise stated.
 ## Definitions <a id="definitions">[[definitions]]</a>
+[*Note 1*: Clause [[intro.defs]] defines additional terms used
+elsewhere in this International Standard. — *end note*]
 a stream (described in Clause  [[input.output]]) that can seek to any
 integral position within the length of the stream
+[*Note 2*: Every arbitrary-positional stream is also a repositional
+stream. — *end note*]
+\defncontext{Clauses~ [[strings]], [[localization]], [[input.output]], and~ [[re]]}
+any object which, when treated sequentially, can represent text
+[*Note 3*: The term does not mean only `char`, `char16_t`, `char32_t`,
+and `wchar_t` objects, but any value that can be represented by a type
+that provides the definitions specified in these Clauses. — *end note*]
 a class or a type used to represent a *character*
+[*Note 4*: It is used for one of the template parameters of the string,
+iostream, and regular expression class templates. A character container
+type is a POD ([[basic.types]]) type. — *end note*]
 an operator function ([[over.oper]]) for any of the equality (
 [[expr.eq]]) or relational ([[expr.rel]]) operators
 a group of library entities directly related as members, parameters, or
 return types
+[*Note 5*: For example, the class template `basic_string` and the
+non-member function templates that operate on strings are referred to as
+the *string component*. — *end note*]
+an expression whose evaluation as subexpression of a
+*conditional-expression* `CE` ([[expr.cond]]) would not prevent `CE`
+from being a core constant expression ([[expr.const]])
 one or more threads are unable to continue execution because each is
 blocked waiting for one or more of the others to satisfy some condition
+any specific behavior provided by the implementation, within the scope
+of the *required behavior*
+a description of *replacement function* and *handler function* semantics
+a direct-initialization ([[dcl.init]]) that is not
+list-initialization ([[dcl.init.list]])
 a *non-reserved function* whose definition may be provided by a
 C++program
+[*Note 6*: A C++program may designate a handler function at various
+points in its execution by supplying a pointer to the function when
+calling any of the library functions that install handler functions
+(Clause  [[language.support]]). — *end note*]
 templates, defined in Clause  [[input.output]], that take two template
 arguments
+[*Note 7*: The arguments are named `charT` and `traits`. The argument
+`charT` is a character container class, and the argument `traits` is a
+class which defines additional characteristics and functions of the
+character type represented by `charT` necessary to implement the
+iostream class templates. — *end note*]
 a class member function ([[class.mfct]]) other than a constructor,
 assignment operator, or destructor that alters the state of an object of
 the class
 assignment of an rvalue of some object type to a modifiable lvalue of
 the same type
+direct-initialization of an object of some type with an rvalue of the
+same type
 a sequence of values that have *character type* that precede the
 terminating null character type value `charT()`
 a class member function ([[class.mfct]]) that accesses the state of an
 object of the class but does not alter that state
+[*Note 8*: Observer functions are specified as `const` member
+functions ([[class.this]]). — *end note*]
+an object type, a function type that does not have cv-qualifiers or a
+*ref-qualifier*, or a reference type
+[*Note 9*: The term describes a type to which a reference can be
+created, including reference types. — *end note*]
 a *non-reserved function* whose definition is provided by a C++program
+[*Note 10*: Only one definition for such a function is in effect for
+the duration of the program’s execution, as the result of creating the
+program ([[lex.phases]]) and resolving the definitions of all
+translation units ([[basic.link]]). — *end note*]
 a stream (described in Clause  [[input.output]]) that can seek to a
 position that was previously encountered
 a description of *replacement function* and *handler function* semantics
 applicable to both the behavior provided by the implementation and the
 behavior of any such function definition in the program
+[*Note 11*: If such a function defined in a C++program fails to meet
+the required behavior when it executes, the behavior is undefined.
+ — *end note*]
 a function, specified as part of the C++standard library, that must be
 defined by the implementation
+[*Note 12*: If a C++program provides a definition for any reserved
+function, the results are undefined.  — *end note*]
 an algorithm that preserves, as appropriate to the particular algorithm,
 the order of elements
+[*Note 13*: Requirements for stable algorithms are given in
+[[algorithm.stable]]. — *end note*]
 a class that encapsulates a set of types and functions necessary for
 class templates and function templates to manipulate objects of types
 for which they are instantiated
+a value of an object that is not specified except that the object’s
 invariants are met and operations on the object behave as specified for
 its type
+[*Example 1*: If an object `x` of type `std::vector<int>` is in a valid
+but unspecified state, `x.empty()` can be called unconditionally, and
+`x.front()` can be called only if `x.empty()` returns
+`false`. — *end example*]
 ## Method of description (Informative) <a id="description">[[description]]</a>
 This subclause describes the conventions used to specify the C++standard
 library. [[structure]] describes the structure of the normative Clauses
 ### Structure of each clause <a id="structure">[[structure]]</a>
 #### Elements <a id="structure.elements">[[structure.elements]]</a>
+Each library clause contains the following elements, as applicable:[^1]
 - Summary
 - Requirements
 - Detailed specifications
+- References to the C standard library
 #### Summary <a id="structure.summary">[[structure.summary]]</a>
 The Summary provides a synopsis of the category, and introduces the
 first-level subclauses. Each subclause also provides a summary, listing
 operations required of template arguments. They use a class template
 `char_traits` to define these constraints.
 Interface convention requirements are stated as generally as possible.
 Instead of stating “class X has to define a member function
+`operator++()`”, the interface requires “for any object `x` of class
+`X`, `++x` is defined”. That is, whether the operator is a member is
 unspecified.
 Requirements are stated in terms of well-defined expressions that define
 valid terms of the types that satisfy the requirements. For every set of
 well-defined expression requirements there is a table that specifies an
 [[type.descriptions]].
 In some cases the semantic requirements are presented as C++code. Such
 code is intended as a specification of equivalence of a construct to
 another construct, not necessarily as the way the construct must be
+implemented.[^2]
 #### Detailed specifications <a id="structure.specifications">[[structure.specifications]]</a>
 The detailed specifications each contain the following elements:
 - name and brief description
+- synopsis (class definition or function declaration, as appropriate)
 - restrictions on template arguments, if any
 - description of class invariants
 - description of function semantics
 Descriptions of class member functions follow the order (as
+appropriate):[^3]
 - constructor(s) and destructor
 - copying, moving & assignment functions
 - comparison functions
 - modifier functions
 - observer functions
 - operators and other non-member functions
 Descriptions of function semantics contain the following elements (as
+appropriate):[^4]
 - *Requires:* the preconditions for calling the function
 - *Effects:* the actions performed by the function
 - *Synchronization:* the synchronization operations (
   [[intro.multithread]]) applicable to the function
 - *Throws:* any exceptions thrown by the function, and the conditions
   that would cause the exception
 - *Complexity:* the time and/or space complexity of the function
 - *Remarks:* additional semantic constraints on the function
 - *Error conditions:* the error conditions for error codes reported by
+  the function
 Whenever the *Effects:* element specifies that the semantics of some
 function `F` are *Equivalent to* some code sequence, then the various
 elements are interpreted as follows. If `F`’s semantics specifies a
 *Requires:* element, then that requirement is logically imposed prior to
 the *equivalent-to* semantics. Next, the semantics of the code sequence
+are determined by the *Requires:* , *Effects:* , *Synchronization:* ,
+*Postconditions:* , *Returns:* , *Throws:* , *Complexity:* , *Remarks:*
+, and *Error conditions:* specified for the function invocations
 contained in the code sequence. The value returned from `F` is specified
 by `F`’s *Returns:* element, or if `F` has no *Returns:* element, a
+non-`void` return from `F` is specified by the `return` statements in
 the code sequence. If `F`’s semantics contains a *Throws:* ,
 *Postconditions:* , or *Complexity:* element, then that supersedes any
 occurrences of that element in the code sequence.
 For non-reserved replacement and handler functions, Clause
 provided by either the implementation or a C++program. Where no
 distinction is explicitly made in the description, the behavior
 described is the required behavior.
 If the formulation of a complexity requirement calls for a negative
+number of operations, the actual requirement is zero operations.[^5]
 Complexity requirements specified in the library clauses are upper
 bounds, and implementations that provide better complexity guarantees
 satisfy the requirements.
 `enum class errc` constants ([[syserr]]).
 #### C library <a id="structure.see.also">[[structure.see.also]]</a>
 Paragraphs labeled “” contain cross-references to the relevant portions
+of this International Standard and the ISO C standard.
 ### Other conventions <a id="conventions">[[conventions]]</a>
 This subclause describes several editorial conventions used to describe
 the contents of the C++standard library. These conventions are for
 #### Type descriptions <a id="type.descriptions">[[type.descriptions]]</a>
 ##### General <a id="type.descriptions.general">[[type.descriptions.general]]</a>
 The Requirements subclauses may describe names that are used to specify
+constraints on template arguments.[^6] These names are used in library
 Clauses to describe the types that may be supplied as arguments by a
 C++program when instantiating template components from the library.
 Certain types defined in Clause  [[input.output]] are used to describe
 implementation-defined types. They are based on other types, but with
 added constraints.
+##### Exposition-only types <a id="expos.only.types">[[expos.only.types]]</a>
+Several types defined in Clauses  [[language.support]] through
+[[thread]] and Annex  [[depr]] that are used as function parameter or
+return types are defined for the purpose of exposition only in order to
+capture their language linkage. The declarations of such types are
+followed by a comment ending in *exposition only*.
+[*Example 1*:
+``` cpp
+namespace std {
+  extern "C" using some-handler = int(int, void*, double);  // exposition only
+}
+```
+The type placeholder `some-handler` can now be used to specify a
+function that takes a callback parameter with C language linkage.
+— *end example*]
 ##### Enumerated types <a id="enumerated.types">[[enumerated.types]]</a>
 Several types defined in Clause  [[input.output]] are *enumerated
 types*. Each enumerated type may be implemented as an enumeration or as
+a synonym for an enumeration.[^7]
+The enumerated type `enumerated` can be written:
 ``` cpp
+enum enumerated { V₀, V₁, V₂, V₃, ..... };
+inline const enumerated C₀(V₀);
+inline const enumerated C₁(V₁);
+inline const enumerated C₂(V₂);
+inline const enumerated C₃(V₃);
   .....
 ```
+Here, the names `C₀`, `C₁`, etc. represent *enumerated elements* for
 this particular enumerated type. All such elements have distinct values.
 ##### Bitmask types <a id="bitmask.types">[[bitmask.types]]</a>
 Several types defined in Clauses  [[language.support]] through
 The bitmask type *bitmask* can be written:
 ``` cpp
 // For exposition only.
+// int_type is an integral type capable of representing all values of the bitmask type.
 enum bitmask : int_type {
+ V₀ = 1 << 0, V₁ = 1 << 1, V₂ = 1 << 2, V₃ = 1 << 3, .....
 };
+inline constexpr bitmask C₀(V₀{});
+inline constexpr bitmask C₁(V₁{});
+inline constexpr bitmask C₂(V₂{});
+inline constexpr bitmask C₃(V₃{});
   .....
 constexpr bitmask{} operator&(bitmask{} X, bitmask{} Y) {
   return static_cast<bitmask{}>(
     static_cast<int_type>(X) & static_cast<int_type>(Y));
 bitmask{}& operator^=(bitmask{}& X, bitmask{} Y) {
   X = X ^ Y; return X;
 }
 ```
+Here, the names `C₀`, `C₁`, etc. represent *bitmask elements* for this
 particular bitmask type. All such elements have distinct, nonzero values
+such that, for any pair `Cᵢ` and `Cⱼ` where i ≠ j, `C_i & C_i` is
+nonzero and `C_i & C_j` is zero. Additionally, the value `0` is used to
 represent an *empty bitmask*, in which no bitmask elements are set.
 The following terms apply to objects and values of bitmask types:
 - To *set* a value *Y* in an object *X* is to evaluate the expression
 The C standard library makes widespread use of characters and character
 sequences that follow a few uniform conventions:
 - A *letter* is any of the 26 lowercase or 26 uppercase letters in the
+  basic execution character set.
 - The *decimal-point character* is the (single-byte) character used by
   functions that convert between a (single-byte) character sequence and
   a value of one of the floating-point types. It is used in the
   character sequence to denote the beginning of a fractional part. It is
   represented in Clauses  [[language.support]] through  [[thread]] and
   Annex  [[depr]] by a period, `'.'`, which is also its value in the
   `"C"` locale, but may change during program execution by a call to
+  `setlocale(int, const char*)`,[^8] or by a change to a `locale`
   object, as described in Clauses  [[locales]] and  [[input.output]].
+- A *character sequence* is an array object ([[dcl.array]]) `A` that
+  can be declared as `T A[N]`, where `T` is any of the types `char`,
   `unsigned char`, or `signed char` ([[basic.fundamental]]), optionally
   qualified by any combination of `const` or `volatile`. The initial
   elements of the array have defined contents up to and including an
   element determined by some predicate. A character sequence can be
+  designated by a pointer value `S` that points to its first element.
 ###### Byte strings <a id="byte.strings">[[byte.strings]]</a>
 A *null-terminated byte string*, or NTBS, is a character sequence whose
 highest-addressed element with defined content has the value zero (the
 *terminating null* character); no other element in the sequence has the
+value zero. [^9]
 The *length* of an NTBS is the number of elements that precede the
 terminating null character. An *empty* NTBS has a length of zero.
 The *value* of an NTBS is the sequence of values of the elements up to
 and including the terminating null character.
+A *static* NTBS is an NTBSwith static storage duration.[^10]
 ###### Multibyte strings <a id="multibyte.strings">[[multibyte.strings]]</a>
+A *null-terminated multibyte string*, or NTMBS, is an NTBSthat
 constitutes a sequence of valid multibyte characters, beginning and
+ending in the initial shift state.[^11]
 A *static* NTMBS is an NTMBSwith static storage duration.
 #### Functions within classes <a id="functions.within.classes">[[functions.within.classes]]</a>
 For the sake of exposition, Clauses  [[language.support]] through
 [[thread]] and Annex  [[depr]] do not describe copy/move constructors,
 assignment operators, or (non-virtual) destructors with the same
 apparent semantics as those that can be generated by default (
+[[class.ctor]], [[class.dtor]], [[class.copy]]). It is unspecified
+whether the implementation provides explicit definitions for such member
+function signatures, or for virtual destructors that can be generated by
+default.
+For the sake of exposition, the library clauses sometimes annotate
+constructors with \EXPLICIT. Such a constructor is conditionally
+declared as either explicit or non-explicit ([[class.conv.ctor]]).
+[*Note 1*: This is typically implemented by declaring two such
+constructors, of which at most one participates in overload
+resolution. — *end note*]
 #### Private members <a id="objects.within.classes">[[objects.within.classes]]</a>
 Clauses  [[language.support]] through  [[thread]] and Annex  [[depr]] do
 not specify the representation of classes, and intentionally omit
 specification of class members ([[class.mem]]). An implementation may
 define static or non-static class members, or both, as needed to
 implement the semantics of the member functions specified in Clauses
 [[language.support]] through  [[thread]] and Annex  [[depr]].
+For the sake of exposition, some subclauses provide representative
+declarations, and semantic requirements, for private members of classes
+that meet the external specifications of the classes. The declarations
+for such members are followed by a comment that ends with *exposition
+only*, as in:
 ``` cpp
 streambuf* sb;  // exposition only
 ```
 An implementation may use any technique that provides equivalent
+observable behavior.
 ## Library-wide requirements <a id="requirements">[[requirements]]</a>
 This subclause specifies requirements that apply to the entire
 C++standard library. Clauses  [[language.support]] through  [[thread]]
 [[constraints]] describes constraints on well-formed C++programs, and
 [[conforming]] describes constraints on conforming implementations.
 ### Library contents and organization <a id="organization">[[organization]]</a>
+[[contents]] describes the entities and macros defined in the
+C++standard library. [[headers]] lists the standard library headers and
+some constraints on those headers. [[compliance]] lists requirements for
+a freestanding implementation of the C++ standard library.
 #### Library contents <a id="contents">[[contents]]</a>
+The C++standard library provides definitions for the entities and macros
+described in the synopses of the C++standard library headers (
+[[headers]]).
+All library entities except `operator new` and `operator delete` are
+defined within the namespace `std` or namespaces nested within namespace
+`std`.[^12] It is unspecified whether names declared in a specific
+namespace are declared directly in that namespace or in an inline
+namespace inside that namespace.[^13]
 Whenever a name `x` defined in the standard library is mentioned, the
 name `x` is assumed to be fully qualified as `::std::x`, unless
+explicitly described otherwise. For example, if the *Effects:* section
+for library function `F` is described as calling library function `G`,
+the function `::std::G` is meant.
 #### Headers <a id="headers">[[headers]]</a>
 Each element of the C++standard library is declared or defined (as
+appropriate) in a *header*.[^14]
+The C++standard library provides the *C++library headers*, shown in
 Table  [[tab:cpp.library.headers]].
 **Table: C++library headers** <a id="tab:cpp.library.headers">[tab:cpp.library.headers]</a>
+|                        |                      |                      |                   |
+| ---------------------- | -------------------- | -------------------- | ----------------- |
+| `<algorithm>`          | `<future>` | `<numeric>` | `<strstream>` |
+| `<any>` | `<initializer_list>` | `<optional>` | `<system_error>` |
+| `<array>` | `<iomanip>` | `<ostream>` | `<thread>` |
+| `<atomic>`             | `<ios>` | `<queue>` | `<tuple>` |
+| `<bitset>`             | `<iosfwd>` | `<random>` | `<type_traits>` |
+| `<chrono>` | `<iostream>` | `<ratio>` | `<typeindex>` |
+| `<codecvt>`            | `<istream>` | `<regex>` | `<typeinfo>` |
+| `<complex>` | `<iterator>`         | `<scoped_allocator>` | `<unordered_map>` |
+| `<condition_variable>` | `<limits>` | `<set>` | `<unordered_set>` |
+| `<deque>` | `<list>` | `<shared_mutex>` | `<utility>` |
+| `<exception>` | `<locale>`           | `<sstream>` | `<valarray>` |
+| `<execution>`          | `<map>`              | `<stack>`            | `<variant>`       |
+| `<filesystem>`         | `<memory>`           | `<stdexcept>`        | `<vector>`        |
+| `<forward_list>`       | `<memory_resource>`  | `<streambuf>`        |                   |
+| `<fstream>`            | `<mutex>`            | `<string>`           |                   |
+| `<functional>`         | `<new>`              | `<string_view>`      |                   |
+The facilities of the C standard library are provided in the additional
+headers shown in Table  [[tab:cpp.c.headers]]. [^15]
 **Table: C++headers for C library facilities** <a id="tab:cpp.c.headers">[tab:cpp.c.headers]</a>
 |              |               |               |             |             |
 | ------------ | ------------- | ------------- | ----------- | ----------- |
 | `<cerrno>`   | `<clocale>`   | `<cstdbool>`  | `<ctgmath>` |             |
 | `<cfenv>`    | `<cmath>`     | `<cstddef>`   | `<ctime>`   |             |
 | `<cfloat>`   | `<csetjmp>`   | `<cstdint>`   | `<cuchar>`  |             |
+Except as noted in Clauses  [[library]] through  [[thread]] and Annex
+[[depr]], the contents of each header `cname` is the same as that of the
+corresponding header `name.h` as specified in the C standard library
+(Clause  [[intro.refs]]). In the C++standard library, however, the
 declarations (except for names which are defined as macros in C) are
 within namespace scope ([[basic.scope.namespace]]) of the namespace
+`std`. It is unspecified whether these names (including any overloads
+added in Clauses  [[language.support]] through  [[thread]] and Annex
+[[depr]]) are first declared within the global namespace scope and are
+then injected into namespace `std` by explicit *using-declaration*s (
+[[namespace.udecl]]).
 Names which are defined as macros in C shall be defined as macros in the
 C++ standard library, even if C grants license for implementation as
+functions.
+[*Note 1*: The names defined as macros in C include the following:
+`assert`, `offsetof`, `setjmp`, `va_arg`, `va_end`, and
+`va_start`. — *end note*]
 Names that are defined as functions in C shall be defined as functions
+in the C++standard library.[^16]
 Identifiers that are keywords or operators in C++shall not be defined as
+macros in C++standard library headers.[^17]
 [[depr.c.headers]], C standard library headers, describes the effects of
+using the `name.h` (C header) form in a C++program.[^18]
+Annex K of the C standard describes a large number of functions, with
+associated types and macros, which “promote safer, more secure
+programming” than many of the traditional C library functions. The names
+of the functions have a suffix of `_s`; most of them provide the same
+service as the C library function with the unsuffixed name, but
+generally take an additional argument whose value is the size of the
+result array. If any C++header is included, it is
+*implementation-defined* whether any of these names is declared in the
+global namespace. (None of them is declared in namespace `std`.)
+Table  [[tab:c.annex.k.names]] lists the Annex K names that may be
+declared in some header. These names are also subject to the
+restrictions of  [[macro.names]].
+**Table: C standard Annex K names** <a id="tab:c.annex.k.names">[tab:c.annex.k.names]</a>
+|                        |                            |                |               |
+| ---------------------- | -------------------------- | -------------- | ------------- |
+| `abort_handler_s`      | `mbstowcs_s`               | `strncat_s`    | `vswscanf_s`  |
+| `asctime_s`            | `memcpy_s`                 | `strncpy_s`    | `vwprintf_s`  |
+| `bsearch_s`            | `memmove_s`                | `strtok_s`     | `vwscanf_s`   |
+| `constraint_handler_t` | `memset_s`                 | `swprintf_s`   | `wcrtomb_s`   |
+| `ctime_s`              | `printf_s`                 | `swscanf_s`    | `wcscat_s`    |
+| `errno_t`              | `qsort_s`                  | `tmpfile_s`    | `wcscpy_s`    |
+| `fopen_s`              | `RSIZE_MAX`                | `TMP_MAX_S`    | `wcsncat_s`   |
+| `fprintf_s`            | `rsize_t`                  | `tmpnam_s`     | `wcsncpy_s`   |
+| `freopen_s`            | `scanf_s`                  | `vfprintf_s`   | `wcsnlen_s`   |
+| `fscanf_s`             | `set_constraint_handler_s` | `vfscanf_s`    | `wcsrtombs_s` |
+| `fwprintf_s`           | `snprintf_s`               | `vfwprintf_s`  | `wcstok_s`    |
+| `fwscanf_s`            | `snwprintf_s`              | `vfwscanf_s`   | `wcstombs_s`  |
+| `getenv_s`             | `sprintf_s`                | `vprintf_s`    | `wctomb_s`    |
+| `gets_s`               | `sscanf_s`                 | `vscanf_s`     | `wmemcpy_s`   |
+| `gmtime_s`             | `strcat_s`                 | `vsnprintf_s`  | `wmemmove_s`  |
+| `ignore_handler_s`     | `strcpy_s`                 | `vsnwprintf_s` | `wprintf_s`   |
+| `L_tmpnam_s`           | `strerror_s`               | `vsprintf_s`   | `wscanf_s`    |
+| `localtime_s`          | `strerrorlen_s`            | `vsscanf_s`    |               |
+| `mbsrtowcs_s`          | `strlen_s`                 | `vswprintf_s`  |               |
 #### Freestanding implementations <a id="compliance">[[compliance]]</a>
 Two kinds of implementations are defined: *hosted* and *freestanding* (
 [[intro.compliance]]). For a hosted implementation, this International
 [[tab:cpp.headers.freestanding]].
 **Table: C++headers for freestanding implementations** <a id="tab:cpp.headers.freestanding">[tab:cpp.headers.freestanding]</a>
 | Subclause                                     |                           | Header                            |
+| --------------------------------------------- | ------------------------- | --------------------------------- |
 |                                               |                           | `<ciso646>`                       |
 | [[support.types]]                             | Types                     | `<cstddef>`                       |
 | [[support.limits]]                            | Implementation properties | `<cfloat>` `<limits>` `<climits>` |
 | [[cstdint]]                                   | Integer types             | `<cstdint>`                       |
 | [[support.start.term]]                        | Start and termination     | `<cstdlib>`                       |
 | [[support.dynamic]]                           | Dynamic memory management | `<new>`                           |
 | [[support.rtti]]                              | Type identification       | `<typeinfo>`                      |
 | [[support.exception]]                         | Exception handling        | `<exception>`                     |
 | [[support.initlist]]                          | Initializer lists         | `<initializer_list>`              |
+| [[support.runtime]] | Other runtime support     | `<cstdarg>` |
 | [[meta]]                                      | Type traits               | `<type_traits>`                   |
 | [[atomics]]                                   | Atomics                   | `<atomic>`                        |
+| [[depr.cstdalign.syn]], [[depr.cstdbool.syn]] | Deprecated headers        | `<cstdalign>` `<cstdbool>`        |
 The supplied version of the header `<cstdlib>` shall declare at least
 the functions `abort`, `atexit`, `at_quick_exit`, `exit`, and
 `quick_exit` ([[support.start.term]]). The other headers listed in this
 A translation unit may include library headers in any order (Clause
 [[lex]]). Each may be included more than once, with no effect different
 from being included exactly once, except that the effect of including
 either `<cassert>` or `<assert.h>` depends each time on the lexically
+current definition of `NDEBUG`.[^19]
+A translation unit shall include a header only outside of any
 declaration or definition, and shall include the header lexically before
 the first reference in that translation unit to any of the entities
 declared in that header. No diagnostic is required.
 #### Linkage <a id="using.linkage">[[using.linkage]]</a>
 the default `extern "C++"` linkage ([[dcl.link]]).
 Whether a name from the C standard library declared with external
 linkage has `extern "C"` or `extern "C++"` linkage is
 *implementation-defined*. It is recommended that an implementation use
+`extern "C++"` linkage for this purpose.[^20]
 Objects and functions defined in the library and required by a
 C++program are included in the program prior to program startup.
+See also replacement functions ([[replacement.functions]]), runtime
+changes ([[handler.functions]]).
 ### Requirements on types and expressions <a id="utility.requirements">[[utility.requirements]]</a>
 [[utility.arg.requirements]] describes requirements on types and
 expressions used to instantiate templates defined in the C++standard
 allocators.
 #### Template argument requirements <a id="utility.arg.requirements">[[utility.arg.requirements]]</a>
 The template definitions in the C++standard library refer to various
+named requirements whose details are set out in Tables
+[[tab:equalitycomparable]]– [[tab:destructible]]. In these tables, `T`
+is an object or reference type to be supplied by a C++program
+instantiating a template; `a`, `b`, and `c` are values of type (possibly
+`const`) `T`; `s` and `t` are modifiable lvalues of type `T`; `u`
+denotes an identifier; `rv` is an rvalue of type `T`; and `v` is an
+lvalue of type (possibly `const`) `T` or an rvalue of type `const T`.
 In general, a default constructor is not required. Certain container
 class member function signatures specify `T()` as a default argument.
 `T()` shall be a well-defined expression ([[dcl.init]]) if one of those
 signatures is called using the default argument ([[dcl.fct.default]]).
 **Table: `EqualityComparable` requirements** <a id="equalitycomparable">[equalitycomparable]</a>
+| Expression | Return type |
+| ---------- | ----------- |
 | `a == b`   | convertible to `bool` | `==` is an equivalence relation, that is, it has the following properties: For all `a`, `a == a`.; If `a == b`, then `b == a`.; If `a == b` and `b == c`, then `a == c`. |
 **Table: `LessThanComparable` requirements** <a id="lessthancomparable">[lessthancomparable]</a>
+| Expression | Return type           | Requirement                                               |
+| ---------- | --------------------- | --------------------------------------------------------- |
 | `a < b`    | convertible to `bool` | `<` is a strict weak ordering relation~([[alg.sorting]]) |
 **Table: `DefaultConstructible` requirements** <a id="defaultconstructible">[defaultconstructible]</a>
+| Expression     | Post-condition                                                      |
+| -------------- | ------------------------------------------------------------------- |
 | `T t;`         | object `t` is default-initialized                                   |
+| `T u{};` | object `u` is value-initialized or aggregate-initialized            |
+| `T()`<br>`T{}` | an object of type `T` is value-initialized or aggregate-initialized |
+[*Note 1*: `rv` must still meet the requirements of the library
+component that is using it. The operations listed in those requirements
+must work as specified whether `rv` has been moved from or
+not. — *end note*]
 **Table: `CopyConstructible` requirements (in addition to `MoveConstructible`)** <a id="copyconstructible">[copyconstructible]</a>
+| Expression | Post-condition                                            |
 | ---------- | --------------------------------------------------------- |
 | `T u = v;` | the value of `v` is unchanged and is equivalent to ` u`   |
 | `T(v)`     | the value of `v` is unchanged and is equivalent to `T(v)` |
+[*Note 2*:  `rv` must still meet the requirements of the library
+component that is using it, whether or not `t` and `rv` refer to the
+same object. The operations listed in those requirements must work as
+specified whether `rv` has been moved from or not. — *end note*]
 **Table: `CopyAssignable` requirements (in addition to `MoveAssignable`)** <a id="copyassignable">[copyassignable]</a>
+| Expression | Return type | Return value | Post-condition                                          |
+| ---------- | ----------- | ------------ | ------------------------------------------------------- |
 | `t = v`    | `T&`        | `t`          | `t` is equivalent to `v`, the value of `v` is unchanged |
 **Table: `Destructible` requirements** <a id="destructible">[destructible]</a>
+| Expression | Post-condition                                                        |
+| ---------- | --------------------------------------------------------------------- |
 | `u.~T()`   | All resources owned by `u` are reclaimed, no exception is propagated. |
 #### `Swappable` requirements <a id="swappable.requirements">[[swappable.requirements]]</a>
 - the two `swap` function templates defined in `<utility>` (
   [[utility]]) and
 - the lookup set produced by argument-dependent lookup (
   [[basic.lookup.argdep]]).
+[*Note 1*: If `T` and `U` are both fundamental types or arrays of
+fundamental types and the declarations from the header `<utility>` are
+in scope, the overall lookup set described above is equivalent to that
+of the qualified name lookup applied to the expression `std::swap(t, u)`
+or `std::swap(u, t)` as appropriate. — *end note*]
+[*Note 2*: It is unspecified whether a library component that has a
+swappable requirement includes the header `<utility>` to ensure an
+appropriate evaluation context. — *end note*]
 An rvalue or lvalue `t` is *swappable* if and only if `t` is swappable
 with any rvalue or lvalue, respectively, of type `T`.
 A type `X` satisfying any of the iterator requirements (
 [[iterator.requirements]]) satisfies the requirements of
 `ValueSwappable` if, for any dereferenceable object `x` of type `X`,
 `*x` is swappable.
+[*Example 1*:
 User code can ensure that the evaluation of `swap` calls is performed in
 an appropriate context under the various conditions as follows:
 ``` cpp
 #include <utility>
                                                 // for rvalues and lvalues
 }
 // Requires: lvalues of T shall be swappable.
 template <class T>
+void lv_swap(T& t1, T& t2) {
   using std::swap;
   swap(t1, t2);                                 // OK: uses swappable conditions for
 }                                               // lvalues of type T
 namespace N {
   value_swap(a1, proxy(a2));
   assert(a1.m == -5 && a2.m == 5);
 }
 ```
+— *end example*]
 #### `NullablePointer` requirements <a id="nullablepointer.requirements">[[nullablepointer.requirements]]</a>
 A `NullablePointer` type is a pointer-like type that supports null
 values. A type `P` meets the requirements of `NullablePointer` if:
 - `P` satisfies the requirements of `EqualityComparable`,
   `DefaultConstructible`, `CopyConstructible`, `CopyAssignable`, and
   `Destructible`,
 - lvalues of type `P` are swappable ([[swappable.requirements]]),
+- the expressions shown in Table  [[tab:nullablepointer]] are valid and
+ have the indicated semantics, and
 - `P` satisfies all the other requirements of this subclause.
 A value-initialized object of type `P` produces the null value of the
 type. The null value shall be equivalent only to itself. A
 default-initialized object of type `P` may have an indeterminate value.
+[*Note 1*: Operations involving indeterminate values may cause
+undefined behavior. — *end note*]
 An object `p` of type `P` can be contextually converted to `bool`
 (Clause  [[conv]]). The effect shall be as if `p != nullptr` had been
 evaluated in place of `p`.
 No operation which is part of the `NullablePointer` requirements shall
 exit via an exception.
+In Table  [[tab:nullablepointer]], `u` denotes an identifier, `t`
+denotes a non-`const` lvalue of type `P`, `a` and `b` denote values of
+type (possibly `const`) `P`, and `np` denotes a value of type (possibly
 `const`) `std::nullptr_t`.
 **Table: `NullablePointer` requirements** <a id="nullablepointer">[nullablepointer]</a>
 |                |                                    |                                    |
+| -------------- | ---------------------------------- | ---------------------------------- |
+| `P u(np);`<br> |                                    | Postconditions: `u == nullptr`     |
 | `P u = np;`    |                                    |                                    |
+| `P(np)`        |                                    | Postconditions: `P(np) == nullptr` |
+| `t = np`       | `P&`                               | Postconditions: `t == nullptr`     |
 | `a != b`       | contextually convertible to `bool` | `!(a == b)`                        |
 | `a == np`      | contextually convertible to `bool` | `a == P()`                         |
 | `np == a`      |                                    |                                    |
 | `a != np`      | contextually convertible to `bool` | `!(a == np)`                       |
 | `np != a`      |                                    |                                    |
 A type `H` meets the `Hash` requirements if:
 - it is a function object type ([[function.objects]]),
 - it satisfies the requirements of `CopyConstructible` and
   `Destructible` ([[utility.arg.requirements]]), and
+- the expressions shown in Table  [[tab:hash]] are valid and have the
   indicated semantics.
 Given `Key` is an argument type for function objects of type `H`, in
+Table  [[tab:hash]] `h` is a value of type (possibly `const`) `H`, `u`
+is an lvalue of type `Key`, and `k` is a value of a type convertible to
 (possibly `const`) `Key`.
+[*Note 1*: Thus all evaluations of the expression `h(k)` with the same
+value for `k` yield the same result for a given execution of the
+program. — *end note*]
 #### Allocator requirements <a id="allocator.requirements">[[allocator.requirements]]</a>
 The library describes a standard set of requirements for *allocators*,
 which are class-type objects that encapsulate the information about an
 primitives for it. All of the string types (Clause  [[strings]]),
 containers (Clause  [[containers]]) (except array), string buffers and
 string streams (Clause  [[input.output]]), and `match_results` (Clause
 [[re]]) are parameterized in terms of allocators.
+The class template `allocator_traits` ([[allocator.traits]]) supplies a
+uniform interface to all allocator types. Table  [[tab:desc.var.def]]
 describes the types manipulated through allocators. Table
 [[tab:utilities.allocator.requirements]] describes the requirements on
 allocator types and thus on types used to instantiate
 `allocator_traits`. A requirement is optional if the last column of
 Table  [[tab:utilities.allocator.requirements]] specifies a default for
 defaults for different requirements than the primary template. Within
 Tables  [[tab:desc.var.def]] and
 [[tab:utilities.allocator.requirements]], the use of `move` and
 `forward` always refers to `std::move` and `std::forward`, respectively.
+[*Note 1*: If `n == 0`, the return value is unspecified. — *end note*]
 Note A: The member class template `rebind` in the table above is
+effectively a typedef template.
+[*Note 2*: In general, if the name `Allocator` is bound to
+`SomeAllocator<T>`, then `Allocator::rebind<U>::other` is the same type
+as `SomeAllocator<U>`, where `SomeAllocator<T>::value_type` is `T` and
+`SomeAllocator<U>::{}value_type` is `U`. — *end note*]
+If `Allocator` is a class template instantiation of the form
+`SomeAllocator<T, Args>`, where `Args` is zero or more type arguments,
+and `Allocator` does not supply a `rebind` member template, the standard
+`allocator_traits` template uses `SomeAllocator<U, Args>` in place of
+`Allocator::{}rebind<U>::other` by default. For allocator types that are
+not template instantiations of the above form, no default is provided.
+Note B: If `X::propagate_on_container_copy_assignment::value` is `true`,
+`X` shall satisfy the `CopyAssignable` requirements (Table
+[[tab:copyassignable]]) and the copy operation shall not throw
+exceptions. If `X::propagate_on_container_move_assignment::value` is
+`true`, `X` shall satisfy the `MoveAssignable` requirements (Table
+[[tab:moveassignable]]) and the move operation shall not throw
+exceptions. If `X::propagate_on_container_swap::value` is `true`,
+lvalues of type `X` shall be swappable ([[swappable.requirements]]) and
+the `swap` operation shall not throw exceptions.
 An allocator type `X` shall satisfy the requirements of
 `CopyConstructible` ([[utility.arg.requirements]]). The `X::pointer`,
 `X::const_pointer`, `X::void_pointer`, and `X::const_void_pointer` types
 shall satisfy the requirements of `NullablePointer` (
+[[nullablepointer.requirements]]). No constructor, comparison function,
+copy operation, move operation, or swap operation on these pointer types
+shall exit via an exception. `X::pointer` and `X::const_pointer` shall
+also satisfy the requirements for a random access iterator (
+[[random.access.iterators]]) and of a contiguous iterator (
+[[iterator.requirements.general]]).
 Let `x1` and `x2` denote objects of (possibly different) types
 `X::void_pointer`, `X::const_void_pointer`, `X::pointer`, or
 `X::const_pointer`. Then, `x1` and `x2` are *equivalently-valued*
 pointer values, if and only if both `x1` and `x2` can be explicitly
 either or both objects may be replaced by an equivalently-valued object
 of type `X::const_pointer` with no change in semantics.
 An allocator may constrain the types on which it can be instantiated and
+the arguments for which its `construct` or `destroy` members may be
+called. If a type cannot be used with a particular allocator, the
+allocator class or the call to `construct` or `destroy` may fail to
+instantiate.
+[*Example 1*:
+The following is an allocator class template supporting the minimal
 interface that satisfies the requirements of Table
 [[tab:utilities.allocator.requirements]]:
 ``` cpp
 template <class Tp>
 bool operator==(const SimpleAllocator<T>&, const SimpleAllocator<U>&);
 template <class T, class U>
 bool operator!=(const SimpleAllocator<T>&, const SimpleAllocator<U>&);
 ```
+— *end example*]
 If the alignment associated with a specific over-aligned type is not
 supported by an allocator, instantiation of the allocator for that type
 may fail. The allocator also may silently ignore the requested
+alignment.
+[*Note 3*: Additionally, the member function `allocate` for that type
+may fail by throwing an object of type `bad_alloc`. — *end note*]
+##### Allocator completeness requirements <a id="allocator.requirements.completeness">[[allocator.requirements.completeness]]</a>
+If `X` is an allocator class for type `T`, `X` additionally satisfies
+the allocator completeness requirements if, whether or not `T` is a
+complete type:
+- `X` is a complete type, and
+- all the member types of `allocator_traits<X>` ([[allocator.traits]])
+  other than `value_type` are complete types.
 ### Constraints on programs <a id="constraints">[[constraints]]</a>
 #### Overview <a id="constraints.overview">[[constraints.overview]]</a>
 definitions to namespace `std` or to a namespace within namespace `std`
 unless otherwise specified. A program may add a template specialization
 for any standard library template to namespace `std` only if the
 declaration depends on a user-defined type and the specialization meets
 the standard library requirements for the original template and is not
+explicitly prohibited.[^21]
 The behavior of a C++program is undefined if it declares
 - an explicit specialization of any member function of a standard
   library class template, or
 - an explicit specialization of any member function template of a
   standard library class or class template, or
 - an explicit or partial specialization of any member class template of
+  a standard library class or class template, or
+- a deduction guide for any standard library class template.
 A program may explicitly instantiate a template defined in the standard
 library only if the declaration depends on the name of a user-defined
 type and the instantiation meets the standard library requirements for
 the original template.
 The behavior of a C++program is undefined if it adds declarations or
 definitions to namespace `posix` or to a namespace within namespace
 `posix` unless otherwise specified. The namespace `posix` is reserved
 for use by ISO/IEC 9945 and other POSIX standards.
+##### Namespaces for future standardization <a id="namespace.future">[[namespace.future]]</a>
+Top level namespaces with a name starting with `std` and followed by a
+non-empty sequence of digits are reserved for future standardization.
+The behavior of a C++program is undefined if it adds declarations or
+definitions to such a namespace.
+[*Example 1*: The top level namespace `std2` is reserved for use by
+future revisions of this International Standard. — *end example*]
 #### Reserved names <a id="reserved.names">[[reserved.names]]</a>
 The C++standard library reserves the following kinds of names:
 - macros
 If a program declares or defines a name in a context where it is
 reserved, other than as explicitly allowed by this Clause, its behavior
 is undefined.
+##### Zombie names <a id="zombie.names">[[zombie.names]]</a>
+In namespace `std`, the following names are reserved for previous
+standardization:
+- `auto_ptr`,
+- `binary_function`,
+- `bind1st`,
+- `bind2nd`,
+- `binder1st`,
+- `binder2nd`,
+- `const_mem_fun1_ref_t`,
+- `const_mem_fun1_t`,
+- `const_mem_fun_ref_t`,
+- `const_mem_fun_t`,
+- `get_unexpected`,
+- `mem_fun1_ref_t`,
+- `mem_fun1_t`,
+- `mem_fun_ref_t`,
+- `mem_fun_ref`,
+- `mem_fun_t`,
+- `mem_fun`,
+- `pointer_to_binary_function`,
+- `pointer_to_unary_function`,
+- `ptr_fun`,
+- `random_shuffle`,
+- `set_unexpected`,
+- `unary_function`,
+- `unexpected`, and
+- `unexpected_handler`.
 ##### Macro names <a id="macro.names">[[macro.names]]</a>
 A translation unit that includes a standard library header shall not
 `#define` or `#undef` names declared in any standard library header.
 A translation unit shall not `#define` or `#undef` names lexically
 identical to keywords, to the identifiers listed in Table
 [[tab:identifiers.special]], or to the *attribute-token*s described in
 [[dcl.attr]].
 ##### External linkage <a id="extern.names">[[extern.names]]</a>
 Each name declared as an object with external linkage in a header is
 reserved to the implementation to designate that library object with
+external linkage, [^22] both in namespace `std` and in the global
 namespace.
 Each global function signature declared with external linkage in a
 header is reserved to the implementation to designate that function
+signature with external linkage.[^23]
+Each name from the C standard library declared with external linkage is
 reserved to the implementation for use as a name with `extern "C"`
+linkage, both in namespace `std` and in the global namespace.
+Each function signature from the C standard library declared with
 external linkage is reserved to the implementation for use as a function
+signature with both `extern "C"` and `extern "C++"` linkage,[^24] or as
 a name of namespace scope in the global namespace.
 ##### Types <a id="extern.types">[[extern.types]]</a>
+For each type T from the C standard library,[^25] the types `::T` and
 `std::T` are reserved to the implementation and, when defined, `::T`
 shall be identical to `std::T`.
 ##### User-defined literal suffixes <a id="usrlit.suffix">[[usrlit.suffix]]</a>
+Literal suffix identifiers ([[over.literal]]) that do not start with an
+underscore are reserved for future standardization.
 #### Headers <a id="alt.headers">[[alt.headers]]</a>
 If a file with a name equivalent to the derived file name for one of the
 C++standard library headers is not provided as part of the
 describe the behavior of numerous functions defined by the C++standard
 library. Under some circumstances, however, certain of these function
 descriptions also apply to replacement functions defined in the
 program ([[definitions]]).
+A C++program may provide the definition for any of the following dynamic
+memory allocation function signatures declared in header `<new>` (
 [[basic.stc.dynamic]], [[support.dynamic]]):
+``` cpp
+operator new(std::size_t)
+operator new(std::size_t, std::align_val_t)
+operator new(std::size_t, const std::nothrow_t&)
+operator new(std::size_t, std::align_val_t, const std::nothrow_t&)
+```
+``` cpp
+operator delete(void*)
+operator delete(void*, std::size_t)
+operator delete(void*, std::align_val_t)
+operator delete(void*, std::size_t, std::align_val_t)
+operator delete(void*, const std::nothrow_t&)
+operator delete(void*, std::align_val_t, const std::nothrow_t&)
+```
+``` cpp
+operator new[](std::size_t)
+operator new[](std::size_t, std::align_val_t)
+operator new[](std::size_t, const std::nothrow_t&)
+operator new[](std::size_t, std::align_val_t, const std::nothrow_t&)
+```
+``` cpp
+operator delete[](void*)
+operator delete[](void*, std::size_t)
+operator delete[](void*, std::align_val_t)
+operator delete[](void*, std::size_t, std::align_val_t)
+operator delete[](void*, const std::nothrow_t&)
+operator delete[](void*, std::align_val_t, const std::nothrow_t&)
+```
 The program’s definitions are used instead of the default versions
 supplied by the implementation ([[support.dynamic]]). Such replacement
 occurs prior to program startup ([[basic.def.odr]], [[basic.start]]).
+The program’s declarations shall not be specified as `inline`. No
 diagnostic is required.
 #### Handler functions <a id="handler.functions">[[handler.functions]]</a>
+The C++standard library provides a default version of the following
+handler function (Clause  [[language.support]]):
 - `terminate_handler`
 A C++program may install different handler functions during execution,
 by supplying a pointer to a function defined in the program or the
 library as an argument to (respectively):
 - `set_new_handler`
+- `set_terminate`
+See also subclauses  [[alloc.errors]], Storage allocation errors, and
+[[support.exception]], Exception handling.
 A C++program can get a pointer to the current handler function by
 calling the following functions:
 - `get_new_handler`
 - `get_terminate`
 Calling the `set_*` and `get_*` functions shall not incur a data race. A
 call to any of the `set_*` functions shall synchronize with subsequent
 calls to the same `set_*` function and to the corresponding `get_*`
 #### Other functions <a id="res.on.functions">[[res.on.functions]]</a>
 In certain cases (replacement functions, handler functions, operations
 on types used to instantiate standard library template components), the
 C++standard library depends on components supplied by a C++program. If
+these components do not meet their requirements, this International
+Standard places no requirements on the implementation.
 In particular, the effects are undefined in the following cases:
 - for replacement functions ([[new.delete]]), if the installed
   replacement function does not implement the semantics of the
   applicable *Required behavior:* paragraph.
+- for handler functions ([[new.handler]], [[terminate.handler]]), if
+  the installed handler function does not implement the semantics of the
+  applicable *Required behavior:* paragraph
 - for types used as template arguments when instantiating a template
   component, if the operations on the type do not implement the
+  semantics of the applicable *Requirements* subclause (
+  [[allocator.requirements]], [[container.requirements]],
+  [[iterator.requirements]], [[algorithms.requirements]],
   [[numeric.requirements]]). Operations on such types can report a
   failure by throwing an exception unless otherwise specified.
 - if any replacement function or handler function or destructor
   operation exits via an exception, unless specifically allowed in the
   applicable *Required behavior:* paragraph.
   address computations and accesses to objects (that would be valid if
   the pointer did point to the first element of such an array) are in
   fact valid.
 - If a function argument binds to an rvalue reference parameter, the
   implementation may assume that this parameter is a unique reference to
+  this argument. \[*Note 1*: If the parameter is a generic parameter of
+ the form `T&&` and an lvalue of type `A` is bound, the argument binds
+ to an lvalue reference ([[temp.deduct.call]]) and thus is not covered
+ by the previous sentence. — *end note*] \[*Note 2*: If a program
+ casts an lvalue to an xvalue while passing that lvalue to a library
+  function (e.g. by calling the function with the argument
+ `std::move(x)`), the program is effectively asking that function to
+ treat that lvalue as a temporary. The implementation is free to
+ optimize away aliasing checks which might be needed if the argument
+  was an lvalue. — *end note*]
+#### Library object access <a id="res.on.objects">[[res.on.objects]]</a>
 The behavior of a program is undefined if calls to standard library
 functions from different threads may introduce a data race. The
 conditions under which this may occur are specified in
+[[res.on.data.races]].
+[*Note 1*: Modifying an object of a standard library type that is
+shared between threads risks undefined behavior unless objects of that
+type are explicitly specified as being sharable without data races or
+the user supplies a locking mechanism. — *end note*]
+If an object of a standard library type is accessed, and the beginning
+of the object’s lifetime ([[basic.life]]) does not happen before the
+access, or the access does not happen before the end of the object’s
+lifetime, the behavior is undefined unless otherwise specified.
+[*Note 2*: This applies even to objects such as mutexes intended for
+thread synchronization. — *end note*]
 #### Requires paragraph <a id="res.on.required">[[res.on.required]]</a>
 Violation of the preconditions specified in a function’s *Requires:*
 paragraph results in undefined behavior unless the function’s *Throws:*
 This section describes the constraints upon, and latitude of,
 implementations of the C++standard library.
 An implementation’s use of headers is discussed in  [[res.on.headers]],
+its use of macros in  [[res.on.macro.definitions]], non-member functions
+in  [[global.functions]], member functions in  [[member.functions]],
+data race avoidance in  [[res.on.data.races]], access specifiers in
 [[protection.within.classes]], class derivation in  [[derivation]], and
 exceptions in  [[res.on.exception.handling]].
 #### Headers <a id="res.on.headers">[[res.on.headers]]</a>
 Certain types and macros are defined in more than one header. Every such
 entity shall be defined such that any header that defines it may be
 included after any other header that also defines it (
 [[basic.def.odr]]).
+The C standard library headers ([[depr.c.headers]]) shall include only
+their corresponding C++standard library header, as described in
+[[headers]].
 #### Restrictions on macro definitions <a id="res.on.macro.definitions">[[res.on.macro.definitions]]</a>
 The names and global function signatures described in  [[contents]] are
 reserved to the implementation.
 All object-like macros defined by the C standard library and described
 in this Clause as expanding to integral constant expressions are also
 suitable for use in `#if` preprocessing directives, unless explicitly
 stated otherwise.
+#### Non-member functions <a id="global.functions">[[global.functions]]</a>
+It is unspecified whether any non-member functions in the C++standard
+library are defined as `inline` ([[dcl.inline]]).
+A call to a non-member function signature described in Clauses
+[[language.support]] through  [[thread]] and Annex  [[depr]] shall
+behave as if the implementation declared no additional non-member
+function signatures.[^26]
+An implementation shall not declare a non-member function signature with
+additional default arguments.
+Unless otherwise specified, calls made by functions in the standard
+library to non-operator, non-member functions do not use functions from
+another namespace which are found through *argument-dependent name
+lookup* ([[basic.lookup.argdep]]).
+[*Note 1*:
+The phrase “unless otherwise specified” applies to cases such as the
+swappable with requirements ([[swappable.requirements]]). The exception
+for overloaded operators allows argument-dependent lookup in cases like
+that of `ostream_iterator::operator=` ([[ostream.iterator.ops]]):
 *Effects:*
 ``` cpp
 *out_stream << value;
 if (delim != 0)
   *out_stream << delim;
 return *this;
 ```
+— *end note*]
 #### Member functions <a id="member.functions">[[member.functions]]</a>
 It is unspecified whether any member functions in the C++standard
+library are defined as `inline` ([[dcl.inline]]).
+For a non-virtual member function described in the C++standard library,
+an implementation may declare a different set of member function
+signatures, provided that any call to the member function that would
+select an overload from the set of declarations described in this
+International Standard behaves as if that overload were selected.
+[*Note 1*: For instance, an implementation may add parameters with
+default values, or replace a member function with default arguments with
+two or more member functions with equivalent behavior, or add additional
+signatures for a member function name. — *end note*]
+#### Constexpr functions and constructors <a id="constexpr.functions">[[constexpr.functions]]</a>
+This International Standard explicitly requires that certain standard
+library functions are `constexpr` ([[dcl.constexpr]]). An
+implementation shall not declare any standard library function signature
+as `constexpr` except for those where it is explicitly required. Within
+any header that provides any non-defining declarations of constexpr
+functions or constructors an implementation shall provide corresponding
+definitions.
 #### Requirements for stable algorithms <a id="algorithm.stable">[[algorithm.stable]]</a>
 When the requirements for an algorithm state that it is “stable” without
 further elaboration, it means:
   original order) precede the elements from the second range (preserving
   their original order).
 #### Reentrancy <a id="reentrancy">[[reentrancy]]</a>
+Except where explicitly specified in this International Standard, it is
+*implementation-defined* which functions in the C++standard library may
 be recursively reentered.
 #### Data race avoidance <a id="res.on.data.races">[[res.on.data.races]]</a>
 This section specifies requirements that implementations shall meet to
 A C++standard library function shall not directly or indirectly modify
 objects ([[intro.multithread]]) accessible by threads other than the
 current thread unless the objects are accessed directly or indirectly
 via the function’s non-const arguments, including `this`.
+[*Note 1*: This means, for example, that implementations can’t use a
+static object for internal purposes without synchronization because it
+could cause a data race even in programs that do not explicitly share
+objects between threads. — *end note*]
 A C++standard library function shall not access objects indirectly
 accessible via its arguments or via elements of its container arguments
 except by invoking functions required by its specification on those
 container elements.
 Operations on iterators obtained by calling a standard library container
 or string member function may access the underlying container, but shall
+not modify it.
+[*Note 2*: In particular, container operations that invalidate
 iterators conflict with operations on iterators associated with that
+container. — *end note*]
 Implementations may share their own internal objects between threads if
 the objects are not visible to users and are protected against data
 races.
 Unless otherwise specified, C++standard library functions shall perform
 all operations solely within the current thread if those operations have
 effects that are visible ([[intro.multithread]]) to users.
+[*Note 3*: This allows implementations to parallelize operations if
+there are no visible side effects. — *end note*]
 #### Protection within classes <a id="protection.within.classes">[[protection.within.classes]]</a>
 It is unspecified whether any function signature or class described in
 Clauses  [[language.support]] through  [[thread]] and Annex  [[depr]] is
 implementation.
 In any case:
 - Every base class described as `virtual` shall be virtual;
+- Every base class not specified as `virtual` shall not be virtual;
 - Unless explicitly stated otherwise, types with distinct names shall be
+  distinct types.[^27]
+All types specified in the C++standard library shall be non-`final`
+types unless otherwise specified.
 #### Restrictions on exception handling <a id="res.on.exception.handling">[[res.on.exception.handling]]</a>
 Any of the functions defined in the C++standard library can report a
+failure by throwing an exception of a type described in its *Throws:*
+paragraph, or of a type derived from a type named in the *Throws:*
+paragraph that would be caught by an exception handler for the base
+type.
+Functions from the C standard library shall not throw exceptions [^28]
 except when such a function calls a program-supplied function that
+throws an exception.[^29]
 Destructor operations defined in the C++standard library shall not throw
 exceptions. Every destructor in the C++standard library shall behave as
+if it had a non-throwing exception specification.
+Functions defined in the C++standard library that do not have a
+*Throws:* paragraph but do have a potentially-throwing exception
+specification may throw *implementation-defined* exceptions. [^30]
+Implementations should report errors by throwing exceptions of or
+derived from the standard exception classes ([[bad.alloc]],
+[[support.exception]], [[std.exceptions]]).
+An implementation may strengthen the exception specification for a
+non-virtual function by adding a non-throwing exception specification.
 #### Restrictions on storage of pointers <a id="res.on.pointer.storage">[[res.on.pointer.storage]]</a>
 Objects constructed by the standard library that may hold a
 user-supplied pointer value or an integer of type `std::intptr_t` shall
 store such values in a traceable pointer location (
+[[basic.stc.dynamic.safety]]).
+[*Note 1*: Other libraries are strongly encouraged to do the same,
+since not doing so may result in accidental use of pointers that are not
+safely derived. Libraries that store pointers outside the user’s address
+space should make it appear that they are stored and retrieved from a
+traceable pointer location. — *end note*]
 #### Value of error codes <a id="value.error.codes">[[value.error.codes]]</a>
 Certain functions in the C++standard library report errors via a
 `std::error_code` ([[syserr.errcode.overview]]) object. That object’s
 `category()` member shall return `std::system_category()` for errors
 originating from the operating system, or a reference to an
 *implementation-defined* `error_category` object for errors originating
 elsewhere. The implementation shall define the possible values of
+`value()` for each of these error categories.
+[*Example 1*: For operating systems that are based on POSIX,
+implementations are encouraged to define the `std::system_category()`
+values as identical to the POSIX `errno` values, with additional values
+as defined by the operating system’s documentation. Implementations for
+operating systems that are not based on POSIX are encouraged to define
+values identical to the operating system’s values. For errors that do
+not originate from the operating system, the implementation may provide
+enums for the associated values. — *end example*]
 #### Moved-from state of library types <a id="lib.types.movedfrom">[[lib.types.movedfrom]]</a>
 Objects of types defined in the C++standard library may be moved from (
 [[class.copy]]). Move operations may be explicitly specified or
 <!-- Link reference definitions -->
 [alg.c.library]: algorithms.md#alg.c.library
 [alg.sorting]: algorithms.md#alg.sorting
 [algorithm.stable]: #algorithm.stable
 [algorithms]: algorithms.md#algorithms
+[algorithms.requirements]: algorithms.md#algorithms.requirements
 [alloc.errors]: language.md#alloc.errors
 [allocator.requirements]: #allocator.requirements
+[allocator.requirements.completeness]: #allocator.requirements.completeness
 [allocator.traits]: utilities.md#allocator.traits
 [alt.headers]: #alt.headers
 [atomics]: atomics.md#atomics
 [bad.alloc]: language.md#bad.alloc
 [basic.def.odr]: basic.md#basic.def.odr
 [basic.fundamental]: basic.md#basic.fundamental
+[basic.life]: basic.md#basic.life
 [basic.link]: basic.md#basic.link
 [basic.lookup.argdep]: basic.md#basic.lookup.argdep
 [basic.scope.namespace]: basic.md#basic.scope.namespace
 [basic.start]: basic.md#basic.start
 [basic.stc.dynamic]: basic.md#basic.stc.dynamic
 [bitmask.types]: #bitmask.types
 [byte.strings]: #byte.strings
 [c.locales]: localization.md#c.locales
 [c.strings]: strings.md#c.strings
 [character.seq]: #character.seq
+[class.conv.ctor]: special.md#class.conv.ctor
 [class.copy]: special.md#class.copy
 [class.ctor]: special.md#class.ctor
 [class.dtor]: special.md#class.dtor
 [class.mem]: class.md#class.mem
 [class.mfct]: class.md#class.mfct
 [cstdint]: language.md#cstdint
 [dcl.array]: dcl.md#dcl.array
 [dcl.attr]: dcl.md#dcl.attr
 [dcl.constexpr]: dcl.md#dcl.constexpr
 [dcl.fct.default]: dcl.md#dcl.fct.default
 [dcl.init]: dcl.md#dcl.init
+[dcl.init.list]: dcl.md#dcl.init.list
+[dcl.inline]: dcl.md#dcl.inline
 [dcl.link]: dcl.md#dcl.link
 [definitions]: #definitions
 [depr]: future.md#depr
 [depr.c.headers]: future.md#depr.c.headers
+[depr.cstdalign.syn]: future.md#depr.cstdalign.syn
+[depr.cstdbool.syn]: future.md#depr.cstdbool.syn
 [derivation]: #derivation
 [derived.classes]: #derived.classes
 [description]: #description
 [diagnostics]: diagnostics.md#diagnostics
 [enumerated.types]: #enumerated.types
 [except]: except.md#except
+[expos.only.types]: #expos.only.types
+[expr.cond]: expr.md#expr.cond
+[expr.const]: expr.md#expr.const
 [expr.delete]: expr.md#expr.delete
 [expr.eq]: expr.md#expr.eq
 [expr.new]: expr.md#expr.new
 [expr.rel]: expr.md#expr.rel
 [extern.names]: #extern.names
 [extern.types]: #extern.types
 [function.objects]: utilities.md#function.objects
 [functions.within.classes]: #functions.within.classes
 [global.functions]: #global.functions
 [handler.functions]: #handler.functions
 [hash.requirements]: #hash.requirements
 [headers]: #headers
 [input.output]: input.md#input.output
 [intro.compliance]: intro.md#intro.compliance
 [intro.defs]: intro.md#intro.defs
 [intro.multithread]: intro.md#intro.multithread
 [intro.refs]: intro.md#intro.refs
 [iterator.requirements]: iterators.md#iterator.requirements
+[iterator.requirements.general]: iterators.md#iterator.requirements.general
 [iterators]: iterators.md#iterators
 [language.support]: language.md#language.support
 [lex]: lex.md#lex
 [lex.phases]: lex.md#lex.phases
 [lib.types.movedfrom]: #lib.types.movedfrom
 [library]: #library
 [library.c]: #library.c
 [library.general]: #library.general
 [member.functions]: #member.functions
 [meta]: utilities.md#meta
 [multibyte.strings]: #multibyte.strings
 [namespace.constraints]: #namespace.constraints
 [namespace.def]: dcl.md#namespace.def
+[namespace.future]: #namespace.future
 [namespace.posix]: #namespace.posix
 [namespace.std]: #namespace.std
 [namespace.udecl]: dcl.md#namespace.udecl
 [new.delete]: language.md#new.delete
 [new.handler]: language.md#new.handler
 [nullablepointer.requirements]: #nullablepointer.requirements
 [numeric.requirements]: numerics.md#numeric.requirements
 [numerics]: numerics.md#numerics
 [objects.within.classes]: #objects.within.classes
 [organization]: #organization
 [ostream.iterator.ops]: iterators.md#ostream.iterator.ops
+[over.literal]: over.md#over.literal
 [over.match]: over.md#over.match
 [over.oper]: over.md#over.oper
 [protection.within.classes]: #protection.within.classes
+[random.access.iterators]: iterators.md#random.access.iterators
 [re]: re.md#re
 [reentrancy]: #reentrancy
 [replacement.functions]: #replacement.functions
 [requirements]: #requirements
 [res.on.arguments]: #res.on.arguments
 [support.start.term]: language.md#support.start.term
 [support.types]: language.md#support.types
 [swappable.requirements]: #swappable.requirements
 [syserr]: diagnostics.md#syserr
 [syserr.errcode.overview]: diagnostics.md#syserr.errcode.overview
+[tab:c.annex.k.names]: #tab:c.annex.k.names
+[tab:copyassignable]: #tab:copyassignable
 [tab:cpp.c.headers]: #tab:cpp.c.headers
 [tab:cpp.headers.freestanding]: #tab:cpp.headers.freestanding
 [tab:cpp.library.headers]: #tab:cpp.library.headers
 [tab:desc.var.def]: #tab:desc.var.def
+[tab:destructible]: #tab:destructible
+[tab:equalitycomparable]: #tab:equalitycomparable
+[tab:hash]: #tab:hash
 [tab:identifiers.special]: lex.md#tab:identifiers.special
 [tab:library.categories]: #tab:library.categories
+[tab:moveassignable]: #tab:moveassignable
+[tab:nullablepointer]: #tab:nullablepointer
 [tab:utilities.allocator.requirements]: #tab:utilities.allocator.requirements
 [temp.deduct.call]: temp.md#temp.deduct.call
 [template.bitset]: utilities.md#template.bitset
 [terminate.handler]: language.md#terminate.handler
 [thread]: thread.md#thread
 [type.descriptions]: #type.descriptions
 [type.descriptions.general]: #type.descriptions.general
 [using]: #using
 [using.headers]: #using.headers
 [using.linkage]: #using.linkage
 [using.overview]: #using.overview
 [usrlit.suffix]: #usrlit.suffix
 [utilities]: utilities.md#utilities
 [utility]: utilities.md#utility
 [utility.arg.requirements]: #utility.arg.requirements
 [utility.requirements]: #utility.requirements
 [value.error.codes]: #value.error.codes
+[zombie.names]: #zombie.names
+[^1]: To save space, items that do not apply to a Clause are omitted.
     For example, if a Clause does not specify any requirements, there
     will be no “Requirements” subclause.
+[^2]: Although in some cases the code given is unambiguously the optimum
     implementation.
+[^3]: To save space, items that do not apply to a class are omitted. For
     example, if a class does not specify any comparison functions, there
     will be no “Comparison functions” subclause.
+[^4]: To save space, items that do not apply to a function are omitted.
     For example, if a function does not specify any further
+    preconditions, there will be no *Requires:* paragraph.
+[^5]: This simplifies the presentation of complexity requirements in
     some cases.
+[^6]: Examples from  [[utility.requirements]] include:
     `EqualityComparable`, `LessThanComparable`, `CopyConstructible`.
     Examples from  [[iterator.requirements]] include: `InputIterator`,
+    `ForwardIterator`.
+[^7]: Such as an integer type, with constant integer values (
     [[basic.fundamental]]).
+[^8]: declared in `<clocale>` ([[c.locales]]).
+[^9]: Many of the objects manipulated by function signatures declared in
+    `<cstring>` ([[c.strings]]) are character sequences or NTBSs. The
+    size of some of these character sequences is limited by a length
     value, maintained separately from the character sequence.
+[^10]: A string literal, such as `"abc"`, is a static NTBS.
+[^11]: An NTBSthat contains characters only from the basic execution
     character set is also an NTMBS. Each multibyte character then
     consists of a single byte.
+[^12]: The C standard library headers (Annex  [[depr.c.headers]]) also
     define names within the global namespace, while the C++headers for C
     library facilities ([[headers]]) may also define names within the
     global namespace.
+[^13]: This gives implementers freedom to use inline namespaces to
     support multiple configurations of the library.
+[^14]: A header is not necessarily a source file, nor are the sequences
     delimited by `<` and `>` in header names necessarily valid source
     file names ([[cpp.include]]).
+[^15]: It is intentional that there is no C++header for any of these C
+    headers: `<stdatomic.h>`, `<stdnoreturn.h>`, `<threads.h>`.
+[^16]: This disallows the practice, allowed in C, of providing a masking
     macro in addition to the function prototype. The only way to achieve
     equivalent inline behavior in C++is to provide a definition as an
     extern inline function.
+[^17]: In particular, including the standard header `<iso646.h>` or
     `<ciso646>` has no effect.
+[^18]: The `".h"` headers dump all their names into the global
     namespace, whereas the newer forms keep their names in namespace
     `std`. Therefore, the newer forms are the preferred forms for all
     uses except for C++programs which are intended to be strictly
     compatible with C.
+[^19]: This is the same as the C standard library.
+[^20]: The only reliable way to declare an object or function signature
+    from the C standard library is by including the header that declares
     it, notwithstanding the latitude granted in 7.1.4 of the C Standard.
+[^21]: Any library code that instantiates other library templates must
     be prepared to work adequately with any user-supplied specialization
+    that meets the minimum requirements of this International Standard.
+[^22]: The list of such reserved names includes `errno`, declared or
     defined in `<cerrno>`.
+[^23]: The list of such reserved function signatures with external
     linkage includes `setjmp(jmp_buf)`, declared or defined in
     `<csetjmp>`, and `va_end(va_list)`, declared or defined in
     `<cstdarg>`.
+[^24]: The function signatures declared in `<cuchar>`, `<cwchar>`, and
     `<cwctype>` are always reserved, notwithstanding the restrictions
     imposed in subclause 4.5.1 of Amendment 1 to the C Standard for
     these headers.
+[^25]: These types are `clock_t`, `div_t`, `FILE`, `fpos_t`, `lconv`,
     `ldiv_t`, `mbstate_t`, `ptrdiff_t`, `sig_atomic_t`, `size_t`,
     `time_t`, `tm`, `va_list`, `wctrans_t`, `wctype_t`, and `wint_t`.
+[^26]: A valid C++program always calls the expected library non-member
+    function. An implementation may also define additional non-member
+    functions that would otherwise not be called by a valid C++program.
+[^27]: There is an implicit exception to this rule for types that are
     described as synonyms for basic integral types, such as `size_t` (
     [[support.types]]) and `streamoff` ([[stream.types]]).
+[^28]: That is, the C library functions can all be treated as if they
     are marked `noexcept`. This allows implementations to make
     performance optimizations based on the absence of exceptions at
     runtime.
+[^29]: The functions `qsort()` and `bsearch()` ([[alg.c.library]]) meet
     this condition.
+[^30]: In particular, they can report a failure to allocate storage by
     throwing an exception of type `bad_alloc`, or a class derived from
+    `bad_alloc` ([[bad.alloc]]).

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