[basic.exec] - C++20 → C++23

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@@ -9,10 +9,12 @@ the block and while the block is suspended (by a call of a function,
 suspension of a coroutine [[expr.await]], or receipt of a signal).
 A *constituent expression* is defined as follows:
 - The constituent expression of an expression is that expression.
 - The constituent expressions of a *braced-init-list* or of a (possibly
   parenthesized) *expression-list* are the constituent expressions of
   the elements of the respective list.
 - The constituent expressions of a *brace-or-equal-initializer* of the
   form `=` *initializer-clause* are the constituent expressions of the
@@ -50,13 +52,20 @@ or a subexpression of an immediate subexpression of E.
 [*Note 1*: Expressions appearing in the *compound-statement* of a
 *lambda-expression* are not subexpressions of the
 *lambda-expression*. — *end note*]
 A *full-expression* is
-- an unevaluated operand [[expr.prop]],
 - a *constant-expression* [[expr.const]],
 - an immediate invocation [[expr.const]],
 - an *init-declarator* [[dcl.decl]] or a *mem-initializer*
   [[class.base.init]], including the constituent expressions of the
   initializer,
@@ -140,20 +149,20 @@ overlap. — *end note*]
 Evaluations *A* and *B* are *indeterminately sequenced* when either *A*
 is sequenced before *B* or *B* is sequenced before *A*, but it is
 unspecified which.
 [*Note 4*: Indeterminately sequenced evaluations cannot overlap, but
-either could be executed first. — *end note*]
 An expression *X* is said to be sequenced before an expression *Y* if
 every value computation and every side effect associated with the
 expression *X* is sequenced before every value computation and every
 side effect associated with the expression *Y*.
 Every value computation and side effect associated with a
 full-expression is sequenced before every value computation and side
-effect associated with the next full-expression to be evaluated.[^26]
 Except where noted, evaluations of operands of individual operators and
 of subexpressions of individual expressions are unsequenced.
 [*Note 5*: In an expression that is evaluated more than once during the
@@ -184,22 +193,23 @@ void g(int i) {
 }
 ```
 — *end example*]
-When calling a function (whether or not the function is inline), every
-value computation and side effect associated with any argument
-expression, or with the postfix expression designating the called
-function, is sequenced before execution of every expression or statement
-in the body of the called function. For each function invocation *F*,
-for every evaluation *A* that occurs within *F* and every evaluation *B*
-that does not occur within *F* but is evaluated on the same thread and
-as part of the same signal handler (if any), either *A* is sequenced
-before *B* or *B* is sequenced before *A*.[^27]
-[*Note 7*: If *A* and *B* would not otherwise be sequenced then they
-are indeterminately sequenced. — *end note*]
 Several contexts in C++ cause evaluation of a function call, even though
 no corresponding function call syntax appears in the translation unit.
 [*Example 4*: Evaluation of a *new-expression* invokes one or more
@@ -208,37 +218,40 @@ example, invocation of a conversion function [[class.conv.fct]] can
 arise in contexts in which no function call syntax
 appears. — *end example*]
 The sequencing constraints on the execution of the called function (as
 described above) are features of the function calls as evaluated,
-whatever the syntax of the expression that calls the function might be.
 If a signal handler is executed as a result of a call to the
 `std::raise` function, then the execution of the handler is sequenced
 after the invocation of the `std::raise` function and before its return.
-[*Note 8*: When a signal is received for another reason, the execution
 of the signal handler is usually unsequenced with respect to the rest of
 the program. — *end note*]
 ### Multi-threaded executions and data races <a id="intro.multithread">[[intro.multithread]]</a>
 A *thread of execution* (also known as a *thread*) is a single flow of
 control within a program, including the initial invocation of a specific
 top-level function, and recursively including every function invocation
 subsequently executed by the thread.
 [*Note 1*: When one thread creates another, the initial call to the
 top-level function of the new thread is executed by the new thread, not
 by the creating thread. — *end note*]
 Every thread in a program can potentially access every object and
-function in a program.[^28] Under a hosted implementation, a C++ program
-can have more than one thread running concurrently. The execution of
-each thread proceeds as defined by the remainder of this document. The
-execution of the entire program consists of an execution of all of its
-threads.
 [*Note 2*: Usually the execution can be viewed as an interleaving of
 all its threads. However, some kinds of atomic operations, for example,
 allow executions inconsistent with a simple interleaving, as described
 below. — *end note*]
@@ -255,12 +268,12 @@ contains the signal handler invocation.
 The value of an object visible to a thread T at a particular point is
 the initial value of the object, a value assigned to the object by T, or
 a value assigned to the object by another thread, according to the rules
 below.
-[*Note 1*: In some cases, there may instead be undefined behavior. Much
-of this subclause is motivated by the desire to support atomic
 operations with explicit and detailed visibility constraints. However,
 it also implicitly supports a simpler view for more restricted
 programs. — *end note*]
 Two expression evaluations *conflict* if one of them modifies a memory
@@ -293,11 +306,11 @@ All modifications to a particular atomic object M occur in some
 particular total order, called the *modification order* of M.
 [*Note 3*: There is a separate order for each atomic object. There is
 no requirement that these can be combined into a single total order for
 all objects. In general this will be impossible since different threads
-may observe modifications to different objects in inconsistent
 orders. — *end note*]
 A *release sequence* headed by a release operation A on an atomic object
 M is a maximal contiguous sub-sequence of side effects in the
 modification order of M, where the first operation is A, and every
@@ -506,12 +519,12 @@ computation of an object being taken from the last side effect on that
 object in that interleaving. This is normally referred to as “sequential
 consistency”. However, this applies only to data-race-free programs, and
 data-race-free programs cannot observe most program transformations that
 do not change single-threaded program semantics. In fact, most
 single-threaded program transformations continue to be allowed, since
-any program that behaves differently as a result must perform an
-undefined operation. — *end note*]
 Two accesses to the same object of type `volatile std::sig_atomic_t` do
 not result in a data race if both occur in the same thread, even if one
 or more occurs in a signal handler. For each signal handler invocation,
 evaluations performed by the thread invoking a signal handler can be
@@ -527,17 +540,17 @@ potentially shared memory location that would not be modified by the
 abstract machine are generally precluded by this document, since such an
 assignment might overwrite another assignment by a different thread in
 cases in which an abstract machine execution would not have encountered
 a data race. This includes implementations of data member assignment
 that overwrite adjacent members in separate memory locations. Reordering
-of atomic loads in cases in which the atomics in question may alias is
-also generally precluded, since this may violate the coherence
 rules. — *end note*]
 [*Note 23*: Transformations that introduce a speculative read of a
-potentially shared memory location may not preserve the semantics of the
-C++ program as defined in this document, since they potentially
 introduce a data race. However, they are typically valid in the context
 of an optimizing compiler that targets a specific machine with
 well-defined semantics for data races. They would be invalid for a
 hypothetical machine that is not tolerant of races or provides hardware
 race detection. — *end note*]
@@ -560,25 +573,25 @@ Executions of atomic functions that are either defined to be lock-free
 [[atomics.flag]] or indicated as lock-free [[atomics.lockfree]] are
 *lock-free executions*.
 - If there is only one thread that is not blocked [[defns.block]] in a
   standard library function, a lock-free execution in that thread shall
-  complete. \[*Note 2*: Concurrently executing threads may prevent
   progress of a lock-free execution. For example, this situation can
   occur with load-locked store-conditional implementations. This
   property is sometimes termed obstruction-free. — *end note*]
 - When one or more lock-free executions run concurrently, at least one
   should complete. \[*Note 3*: It is difficult for some implementations
   to provide absolute guarantees to this effect, since repeated and
-  particularly inopportune interference from other threads may prevent
   forward progress, e.g., by repeatedly stealing a cache line for
   unrelated purposes between load-locked and store-conditional
-  instructions. Implementations should ensure that such effects cannot
- indefinitely delay progress under expected operating conditions, and
- that such anomalies can therefore safely be ignored by programmers.
-  Outside this document, this property is sometimes termed
-  lock-free. — *end note*]
 During the execution of a thread of execution, each of the following is
 termed an *execution step*:
 - termination of the thread of execution,
@@ -590,11 +603,11 @@ An invocation of a standard library function that blocks [[defns.block]]
 is considered to continuously execute execution steps while waiting for
 the condition that it blocks on to be satisfied.
 [*Example 1*: A library I/O function that blocks until the I/O
 operation is complete can be considered to continuously check whether
-the operation is complete. Each such check might consist of one or more
 execution steps, for example using observable behavior of the abstract
 machine. — *end example*]
 [*Note 4*: Because of this and the preceding requirement regarding what
 threads of execution have to perform eventually, it follows that no
@@ -609,30 +622,28 @@ concurrent threads that are not blocked in a standard library function
 For a thread of execution providing *concurrent forward progress
 guarantees*, the implementation ensures that the thread will eventually
 make progress for as long as it has not terminated.
 [*Note 5*: This is required regardless of whether or not other threads
-of executions (if any) have been or are making progress. To eventually
 fulfill this requirement means that this will happen in an unspecified
 but finite amount of time. — *end note*]
 It is *implementation-defined* whether the implementation-created thread
 of execution that executes `main` [[basic.start.main]] and the threads
 of execution created by `std::thread` [[thread.thread.class]] or
 `std::jthread` [[thread.jthread.class]] provide concurrent forward
-progress guarantees.
-[*Note 6*: General-purpose implementations should provide these
-guarantees. — *end note*]
 For a thread of execution providing *parallel forward progress
 guarantees*, the implementation is not required to ensure that the
 thread will eventually make progress if it has not yet executed any
 execution step; once this thread has executed a step, it provides
 concurrent forward progress guarantees.
-[*Note 7*: This does not specify a requirement for when to start this
 thread of execution, which will typically be specified by the entity
 that creates this thread of execution. For example, a thread of
 execution that provides concurrent forward progress guarantees and
 executes tasks from a set of tasks in an arbitrary order, one after the
 other, satisfies the requirements of parallel forward progress for these
@@ -640,57 +651,57 @@ tasks. — *end note*]
 For a thread of execution providing *weakly parallel forward progress
 guarantees*, the implementation does not ensure that the thread will
 eventually make progress.
-[*Note 8*: Threads of execution providing weakly parallel forward
 progress guarantees cannot be expected to make progress regardless of
 whether other threads make progress or not; however, blocking with
 forward progress guarantee delegation, as defined below, can be used to
 ensure that such threads of execution make progress
 eventually. — *end note*]
 Concurrent forward progress guarantees are stronger than parallel
 forward progress guarantees, which in turn are stronger than weakly
 parallel forward progress guarantees.
-[*Note 9*: For example, some kinds of synchronization between threads
-of execution may only make progress if the respective threads of
 execution provide parallel forward progress guarantees, but will fail to
 make progress under weakly parallel guarantees. — *end note*]
 When a thread of execution P is specified to *block with forward
 progress guarantee delegation* on the completion of a set S of threads
 of execution, then throughout the whole time of P being blocked on S,
 the implementation shall ensure that the forward progress guarantees
 provided by at least one thread of execution in S is at least as strong
 as P’s forward progress guarantees.
-[*Note 10*: It is unspecified which thread or threads of execution in S
 are chosen and for which number of execution steps. The strengthening is
 not permanent and not necessarily in place for the rest of the lifetime
 of the affected thread of execution. As long as P is blocked, the
 implementation has to eventually select and potentially strengthen a
 thread of execution in S. — *end note*]
 Once a thread of execution in S terminates, it is removed from S. Once S
 is empty, P is unblocked.
-[*Note 11*: A thread of execution B thus can temporarily provide an
 effectively stronger forward progress guarantee for a certain amount of
 time, due to a second thread of execution A being blocked on it with
 forward progress guarantee delegation. In turn, if B then blocks with
-forward progress guarantee delegation on C, this may also temporarily
 provide a stronger forward progress guarantee to C. — *end note*]
-[*Note 12*: If all threads of execution in S finish executing (e.g.,
 they terminate and do not use blocking synchronization incorrectly),
 then P’s execution of the operation that blocks with forward progress
 guarantee delegation will not result in P’s progress guarantee being
 effectively weakened. — *end note*]
-[*Note 13*: This does not remove any constraints regarding blocking
 synchronization for threads of execution providing parallel or weakly
 parallel forward progress guarantees because the implementation is not
 required to strengthen a particular thread of execution whose too-weak
 progress guarantee is preventing overall progress. — *end note*]
@@ -700,28 +711,26 @@ visible to all other threads in a finite period of time.
 ### Start and termination <a id="basic.start">[[basic.start]]</a>
 #### `main` function <a id="basic.start.main">[[basic.start.main]]</a>
-A program shall contain a global function called `main` attached to the
-global module. Executing a program starts a main thread of execution (
-[[intro.multithread]], [[thread.threads]]) in which the `main` function
-is invoked, and in which variables of static storage duration might be
-initialized [[basic.start.static]] and destroyed [[basic.start.term]].
-It is *implementation-defined* whether a program in a freestanding
-environment is required to define a `main` function.
 [*Note 1*: In a freestanding environment, startup and termination is
 *implementation-defined*; startup contains the execution of constructors
-for objects of namespace scope with static storage duration; termination
-contains the execution of destructors for objects with static storage
 duration. — *end note*]
-An implementation shall not predefine the `main` function. This function
-shall not be overloaded. Its type shall have C++ language linkage and it
-shall have a declared return type of type `int`, but otherwise its type
-is *implementation-defined*. An implementation shall allow both
 - a function of `()` returning `int` and
 - a function of `(int`, pointer to pointer to `char)` returning `int`
 as the type of `main` [[dcl.fct]]. In the latter form, for purposes of
@@ -734,33 +743,37 @@ characters of null-terminated multibyte strings (NTMBSs)
 [[multibyte.strings]] and `argv[0]` shall be the pointer to the initial
 character of a NTMBS that represents the name used to invoke the program
 or `""`. The value of `argc` shall be non-negative. The value of
 `argv[argc]` shall be 0.
-[*Note 2*: It is recommended that any further (optional) parameters be
-added after `argv`. — *end note*]
 The function `main` shall not be used within a program. The linkage
 [[basic.link]] of `main` is *implementation-defined*. A program that
 defines `main` as deleted or that declares `main` to be `inline`,
-`static`, or `constexpr` is ill-formed. The function `main` shall not be
-a coroutine [[dcl.fct.def.coroutine]]. The `main` function shall not be
-declared with a *linkage-specification* [[dcl.link]]. A program that
-declares a variable `main` at global scope, or that declares a function
-`main` at global scope attached to a named module, or that declares the
-name `main` with C language linkage (in any namespace) is ill-formed.
-The name `main` is not otherwise reserved.
 [*Example 1*: Member functions, classes, and enumerations can be called
 `main`, as can entities in other namespaces. — *end example*]
 Terminating the program without leaving the current block (e.g., by
 calling the function `std::exit(int)` [[support.start.term]]) does not
 destroy any objects with automatic storage duration [[class.dtor]]. If
-`std::exit` is called to end a program during the destruction of an
-object with static or thread storage duration, the program has undefined
-behavior.
 A `return` statement [[stmt.return]] in `main` has the effect of leaving
 the main function (destroying any objects with automatic storage
 duration) and calling `std::exit` with the return value as the argument.
 If control flows off the end of the *compound-statement* of `main`, the
@@ -778,16 +791,16 @@ phases of initiation, initialization occurs as follows.
 with static or thread storage duration is constant-initialized
 [[expr.const]]. If constant initialization is not performed, a variable
 with static storage duration [[basic.stc.static]] or thread storage
 duration [[basic.stc.thread]] is zero-initialized [[dcl.init]].
 Together, zero-initialization and constant initialization are called
-*static initialization*; all other initialization is *dynamic
-initialization*. All static initialization strongly happens before
-[[intro.races]] any dynamic initialization.
-[*Note 1*: The dynamic initialization of non-local variables is
-described in  [[basic.start.dynamic]]; that of local static variables is
 described in  [[stmt.dcl]]. — *end note*]
 An implementation is permitted to perform the initialization of a
 variable with static or thread storage duration as a static
 initialization even if such initialization is not required to be done
@@ -802,49 +815,48 @@ statically, provided that
   statically were initialized dynamically.
 [*Note 2*:
 As a consequence, if the initialization of an object `obj1` refers to an
-object `obj2` of namespace scope potentially requiring dynamic
-initialization and defined later in the same translation unit, it is
-unspecified whether the value of `obj2` used will be the value of the
-fully initialized `obj2` (because `obj2` was statically initialized) or
-will be the value of `obj2` merely zero-initialized. For example,
 ``` cpp
 inline double fd() { return 1.0; }
 extern double d1;
 double d2 = d1;     // unspecified:
-                    // may be statically initialized to 0.0 or
                     // dynamically initialized to 0.0 if d1 is
                     // dynamically initialized, or 1.0 otherwise
-double d1 = fd();   // may be initialized statically or dynamically to 1.0
 ```
 — *end note*]
-#### Dynamic initialization of non-local variables <a id="basic.start.dynamic">[[basic.start.dynamic]]</a>
-Dynamic initialization of a non-local variable with static storage
 duration is unordered if the variable is an implicitly or explicitly
 instantiated specialization, is partially-ordered if the variable is an
 inline variable that is not an implicitly or explicitly instantiated
 specialization, and otherwise is ordered.
-[*Note 1*: An explicitly specialized non-inline static data member or
-variable template specialization has ordered
-initialization. — *end note*]
 A declaration `D` is *appearance-ordered* before a declaration `E` if
 - `D` appears in the same translation unit as `E`, or
 - the translation unit containing `E` has an interface dependency on the
   translation unit containing `D`,
 in either case prior to `E`.
-Dynamic initialization of non-local variables `V` and `W` with static
 storage duration are ordered as follows:
 - If `V` and `W` have ordered initialization and the definition of `V`
   is appearance-ordered before the definition of `W`, or if `V` has
   partially-ordered initialization, `W` does not have unordered
@@ -866,25 +878,26 @@ storage duration are ordered as follows:
   sequenced.
 [*Note 2*: This definition permits initialization of a sequence of
 ordered variables concurrently with another sequence. — *end note*]
-A *non-initialization odr-use* is an odr-use [[basic.def.odr]] not
-caused directly or indirectly by the initialization of a non-local
-static or thread storage duration variable.
 It is *implementation-defined* whether the dynamic initialization of a
-non-local non-inline variable with static storage duration is sequenced
 before the first statement of `main` or is deferred. If it is deferred,
 it strongly happens before any non-initialization odr-use of any
 non-inline function or non-inline variable defined in the same
-translation unit as the variable to be initialized. [^29] It is
-*implementation-defined* in which threads and at which points in the
-program such deferred dynamic initialization occurs.
-[*Note 3*: Such points should be chosen in a way that allows the
-programmer to avoid deadlocks. — *end note*]
 [*Example 1*:
 ``` cpp
 // - File 1 -
@@ -921,27 +934,27 @@ point after the first statement of `main`, `b` will be initialized prior
 to its use in `A::A`.
 — *end example*]
 It is *implementation-defined* whether the dynamic initialization of a
-non-local inline variable with static storage duration is sequenced
 before the first statement of `main` or is deferred. If it is deferred,
 it strongly happens before any non-initialization odr-use of that
 variable. It is *implementation-defined* in which threads and at which
 points in the program such deferred dynamic initialization occurs.
 It is *implementation-defined* whether the dynamic initialization of a
-non-local non-inline variable with thread storage duration is sequenced
 before the first statement of the initial function of a thread or is
 deferred. If it is deferred, the initialization associated with the
 entity for thread *t* is sequenced before the first non-initialization
 odr-use by *t* of any non-inline variable with thread storage duration
 defined in the same translation unit as the variable to be initialized.
 It is *implementation-defined* in which threads and at which points in
 the program such deferred dynamic initialization occurs.
-If the initialization of a non-local variable with static or thread
 storage duration exits via an exception, the function `std::terminate`
 is called [[except.terminate]].
 #### Termination <a id="basic.start.term">[[basic.start.term]]</a>
@@ -968,23 +981,25 @@ of the constructor or dynamic initialization of an object with thread
 storage duration is sequenced before that of another, the completion of
 the destructor of the second is sequenced before the initiation of the
 destructor of the first. If an object is initialized statically, the
 object is destroyed in the same order as if the object was dynamically
 initialized. For an object of array or class type, all subobjects of
-that object are destroyed before any block-scope object with static
-storage duration initialized during the construction of the subobjects
-is destroyed. If the destruction of an object with static or thread
-storage duration exits via an exception, the function `std::terminate`
-is called [[except.terminate]].
-If a function contains a block-scope object of static or thread storage
 duration that has been destroyed and the function is called during the
 destruction of an object with static or thread storage duration, the
 program has undefined behavior if the flow of control passes through the
-definition of the previously destroyed block-scope object. Likewise, the
-behavior is undefined if the block-scope object is used indirectly
-(i.e., through a pointer) after its destruction.
 If the completion of the initialization of an object with static storage
 duration strongly happens before a call to `std::atexit` (see
 `<cstdlib>`, [[support.start.term]]), the call to the function passed to
 `std::atexit` is sequenced before the call to the destructor for the
@@ -1001,11 +1016,11 @@ If there is a use of a standard library object or function not permitted
 within signal handlers [[support.runtime]] that does not happen before
 [[intro.multithread]] completion of destruction of objects with static
 storage duration and execution of `std::atexit` registered functions
 [[support.start.term]], the program has undefined behavior.
-[*Note 2*: If there is a use of an object with static storage duration
 that does not happen before the object’s destruction, the program has
 undefined behavior. Terminating every thread before a call to
 `std::exit` or the exit from `main` is sufficient, but not necessary, to
 satisfy these requirements. These requirements permit thread managers as
 static-storage-duration objects. — *end note*]
@@ -1013,49 +1028,50 @@ static-storage-duration objects. — *end note*]
 Calling the function `std::abort()` declared in `<cstdlib>` terminates
 the program without executing any destructors and without calling the
 functions passed to `std::atexit()` or `std::at_quick_exit()`.
 <!-- Link reference definitions -->
-[allocator.members]: utilities.md#allocator.members
-[allocator.traits.members]: utilities.md#allocator.traits.members
-[atomics]: atomics.md#atomics
-[atomics.flag]: atomics.md#atomics.flag
-[atomics.lockfree]: atomics.md#atomics.lockfree
-[atomics.order]: atomics.md#atomics.order
 [bad.alloc]: support.md#bad.alloc
 [basic]: #basic
 [basic.align]: #basic.align
 [basic.compound]: #basic.compound
 [basic.def]: #basic.def
 [basic.def.odr]: #basic.def.odr
 [basic.exec]: #basic.exec
 [basic.fundamental]: #basic.fundamental
 [basic.fundamental.width]: #basic.fundamental.width
-[basic.funscope]: #basic.funscope
 [basic.indet]: #basic.indet
 [basic.life]: #basic.life
 [basic.link]: #basic.link
 [basic.lookup]: #basic.lookup
 [basic.lookup.argdep]: #basic.lookup.argdep
-[basic.lookup.classref]: #basic.lookup.classref
 [basic.lookup.elab]: #basic.lookup.elab
 [basic.lookup.qual]: #basic.lookup.qual
 [basic.lookup.udir]: #basic.lookup.udir
 [basic.lookup.unqual]: #basic.lookup.unqual
 [basic.lval]: expr.md#basic.lval
 [basic.memobj]: #basic.memobj
 [basic.namespace]: dcl.md#basic.namespace
 [basic.pre]: #basic.pre
 [basic.scope]: #basic.scope
 [basic.scope.block]: #basic.scope.block
 [basic.scope.class]: #basic.scope.class
-[basic.scope.declarative]: #basic.scope.declarative
 [basic.scope.enum]: #basic.scope.enum
-[basic.scope.hiding]: #basic.scope.hiding
 [basic.scope.namespace]: #basic.scope.namespace
 [basic.scope.param]: #basic.scope.param
 [basic.scope.pdecl]: #basic.scope.pdecl
 [basic.scope.temp]: #basic.scope.temp
 [basic.start]: #basic.start
 [basic.start.dynamic]: #basic.start.dynamic
 [basic.start.main]: #basic.start.main
 [basic.start.static]: #basic.start.static
@@ -1063,22 +1079,25 @@ functions passed to `std::atexit()` or `std::at_quick_exit()`.
 [basic.stc]: #basic.stc
 [basic.stc.auto]: #basic.stc.auto
 [basic.stc.dynamic]: #basic.stc.dynamic
 [basic.stc.dynamic.allocation]: #basic.stc.dynamic.allocation
 [basic.stc.dynamic.deallocation]: #basic.stc.dynamic.deallocation
-[basic.stc.dynamic.safety]: #basic.stc.dynamic.safety
 [basic.stc.inherit]: #basic.stc.inherit
 [basic.stc.static]: #basic.stc.static
 [basic.stc.thread]: #basic.stc.thread
 [basic.type.qualifier]: #basic.type.qualifier
 [basic.type.qualifier.rel]: #basic.type.qualifier.rel
 [basic.types]: #basic.types
-[bit.cast]: numerics.md#bit.cast
-[c.malloc]: utilities.md#c.malloc
 [class]: class.md#class
 [class.abstract]: class.md#class.abstract
 [class.access]: class.md#class.access
 [class.base.init]: class.md#class.base.init
 [class.bit]: class.md#class.bit
 [class.cdtor]: class.md#class.cdtor
 [class.conv.fct]: class.md#class.conv.fct
 [class.copy.assign]: class.md#class.copy.assign
@@ -1087,26 +1106,24 @@ functions passed to `std::atexit()` or `std::at_quick_exit()`.
 [class.default.ctor]: class.md#class.default.ctor
 [class.derived]: class.md#class.derived
 [class.dtor]: class.md#class.dtor
 [class.free]: class.md#class.free
 [class.friend]: class.md#class.friend
-[class.local]: class.md#class.local
 [class.mem]: class.md#class.mem
-[class.member.lookup]: class.md#class.member.lookup
 [class.mfct]: class.md#class.mfct
-[class.mfct.non-static]: class.md#class.mfct.non-static
 [class.name]: class.md#class.name
-[class.nest]: class.md#class.nest
 [class.pre]: class.md#class.pre
 [class.prop]: class.md#class.prop
 [class.qual]: #class.qual
 [class.spaceship]: class.md#class.spaceship
 [class.static]: class.md#class.static
 [class.static.data]: class.md#class.static.data
 [class.temporary]: #class.temporary
-[class.this]: class.md#class.this
 [class.union]: class.md#class.union
 [class.virtual]: class.md#class.virtual
 [conv]: expr.md#conv
 [conv.array]: expr.md#conv.array
 [conv.func]: expr.md#conv.func
 [conv.integral]: expr.md#conv.integral
@@ -1134,11 +1151,10 @@ functions passed to `std::atexit()` or `std::at_quick_exit()`.
 [dcl.fct.default]: dcl.md#dcl.fct.default
 [dcl.init]: dcl.md#dcl.init
 [dcl.init.aggr]: dcl.md#dcl.init.aggr
 [dcl.init.list]: dcl.md#dcl.init.list
 [dcl.init.ref]: dcl.md#dcl.init.ref
-[dcl.inline]: dcl.md#dcl.inline
 [dcl.link]: dcl.md#dcl.link
 [dcl.meaning]: dcl.md#dcl.meaning
 [dcl.mptr]: dcl.md#dcl.mptr
 [dcl.name]: dcl.md#dcl.name
 [dcl.pre]: dcl.md#dcl.pre
@@ -1146,34 +1162,31 @@ functions passed to `std::atexit()` or `std::at_quick_exit()`.
 [dcl.ref]: dcl.md#dcl.ref
 [dcl.spec]: dcl.md#dcl.spec
 [dcl.spec.auto]: dcl.md#dcl.spec.auto
 [dcl.stc]: dcl.md#dcl.stc
 [dcl.struct.bind]: dcl.md#dcl.struct.bind
 [dcl.type.elab]: dcl.md#dcl.type.elab
 [dcl.typedef]: dcl.md#dcl.typedef
 [defns.block]: intro.md#defns.block
-[defns.signature]: intro.md#defns.signature
-[defns.signature.templ]: intro.md#defns.signature.templ
 [depr.local]: future.md#depr.local
 [depr.static.constexpr]: future.md#depr.static.constexpr
 [diff.cpp11.basic]: compatibility.md#diff.cpp11.basic
 [enum.udecl]: dcl.md#enum.udecl
 [except.handle]: except.md#except.handle
 [except.pre]: except.md#except.pre
 [except.spec]: except.md#except.spec
 [except.terminate]: except.md#except.terminate
 [except.throw]: except.md#except.throw
-[expr]: expr.md#expr
 [expr.add]: expr.md#expr.add
 [expr.alignof]: expr.md#expr.alignof
 [expr.arith.conv]: expr.md#expr.arith.conv
 [expr.ass]: expr.md#expr.ass
 [expr.await]: expr.md#expr.await
 [expr.call]: expr.md#expr.call
 [expr.cast]: expr.md#expr.cast
 [expr.comma]: expr.md#expr.comma
-[expr.compound]: expr.md#expr.compound
 [expr.cond]: expr.md#expr.cond
 [expr.const]: expr.md#expr.const
 [expr.const.cast]: expr.md#expr.const.cast
 [expr.context]: expr.md#expr.context
 [expr.delete]: expr.md#expr.delete
@@ -1183,12 +1196,12 @@ functions passed to `std::atexit()` or `std::at_quick_exit()`.
 [expr.log.or]: expr.md#expr.log.or
 [expr.mptr.oper]: expr.md#expr.mptr.oper
 [expr.new]: expr.md#expr.new
 [expr.pre]: expr.md#expr.pre
 [expr.prim.id]: expr.md#expr.prim.id
-[expr.prim.id.dtor]: expr.md#expr.prim.id.dtor
 [expr.prim.id.qual]: expr.md#expr.prim.id.qual
 [expr.prim.lambda]: expr.md#expr.prim.lambda
 [expr.prim.lambda.capture]: expr.md#expr.prim.lambda.capture
 [expr.prim.lambda.closure]: expr.md#expr.prim.lambda.closure
 [expr.prim.this]: expr.md#expr.prim.this
 [expr.prop]: expr.md#expr.prop
@@ -1204,184 +1217,175 @@ functions passed to `std::atexit()` or `std::at_quick_exit()`.
 [get.new.handler]: support.md#get.new.handler
 [headers]: library.md#headers
 [intro.execution]: #intro.execution
 [intro.memory]: #intro.memory
 [intro.multithread]: #intro.multithread
 [intro.object]: #intro.object
 [intro.progress]: #intro.progress
 [intro.races]: #intro.races
 [lex.charset]: lex.md#lex.charset
 [lex.name]: lex.md#lex.name
 [lex.separate]: lex.md#lex.separate
-[locale]: localization.md#locale
-[meta.trans.other]: utilities.md#meta.trans.other
 [module.context]: module.md#module.context
 [module.global.frag]: module.md#module.global.frag
-[module.import]: module.md#module.import
 [module.interface]: module.md#module.interface
 [module.reach]: module.md#module.reach
 [module.unit]: module.md#module.unit
 [multibyte.strings]: library.md#multibyte.strings
 [namespace.def]: dcl.md#namespace.def
-[namespace.memdef]: dcl.md#namespace.memdef
 [namespace.qual]: #namespace.qual
 [namespace.udecl]: dcl.md#namespace.udecl
 [namespace.udir]: dcl.md#namespace.udir
 [new.delete]: support.md#new.delete
 [new.delete.array]: support.md#new.delete.array
 [new.delete.placement]: support.md#new.delete.placement
 [new.delete.single]: support.md#new.delete.single
 [new.handler]: support.md#new.handler
 [over]: over.md#over
 [over.literal]: over.md#over.literal
 [over.match]: over.md#over.match
 [over.oper]: over.md#over.oper
 [over.over]: over.md#over.over
-[ptr.align]: utilities.md#ptr.align
 [ptr.launder]: support.md#ptr.launder
 [replacement.functions]: library.md#replacement.functions
 [special]: class.md#special
 [stmt.block]: stmt.md#stmt.block
 [stmt.dcl]: stmt.md#stmt.dcl
 [stmt.expr]: stmt.md#stmt.expr
-[stmt.goto]: stmt.md#stmt.goto
 [stmt.if]: stmt.md#stmt.if
-[stmt.label]: stmt.md#stmt.label
 [stmt.ranged]: stmt.md#stmt.ranged
 [stmt.return]: stmt.md#stmt.return
 [support.dynamic]: support.md#support.dynamic
-[support.limits]: support.md#support.limits
 [support.runtime]: support.md#support.runtime
 [support.start.term]: support.md#support.start.term
 [support.types]: support.md#support.types
 [temp.deduct.guide]: temp.md#temp.deduct.guide
 [temp.dep]: temp.md#temp.dep
 [temp.dep.candidate]: temp.md#temp.dep.candidate
 [temp.expl.spec]: temp.md#temp.expl.spec
 [temp.explicit]: temp.md#temp.explicit
 [temp.local]: temp.md#temp.local
 [temp.names]: temp.md#temp.names
-[temp.nondep]: temp.md#temp.nondep
 [temp.over]: temp.md#temp.over
 [temp.param]: temp.md#temp.param
 [temp.point]: temp.md#temp.point
 [temp.pre]: temp.md#temp.pre
 [temp.res]: temp.md#temp.res
 [temp.spec]: temp.md#temp.spec
 [temp.type]: temp.md#temp.type
 [thread]: thread.md#thread
 [thread.jthread.class]: thread.md#thread.jthread.class
 [thread.thread.class]: thread.md#thread.thread.class
 [thread.threads]: thread.md#thread.threads
-[util.dynamic.safety]: utilities.md#util.dynamic.safety
 [^1]: Appearing inside the brace-enclosed *declaration-seq* in a
     *linkage-specification* does not affect whether a declaration is a
     definition.
 [^2]: An implementation is not required to call allocation and
     deallocation functions from constructors or destructors; however,
     this is a permissible implementation technique.
-[^3]: This refers to unqualified names that occur, for instance, in a
- type or default argument in the *parameter-declaration-clause* or
-    used in the function body.
-[^4]: This refers to unqualified names following the class name; such a
-    name may be used in a *base-specifier* or in the
-    *member-specification* of the class definition.
-[^5]: This lookup applies whether the definition of `X` is nested within
-    `Y`’s definition or whether `X`’s definition appears in a namespace
-    scope enclosing `Y`’s definition [[class.nest]].
-[^6]: That is, an unqualified name that occurs, for instance, in a type
-    in the *parameter-declaration-clause* or in the
-    *noexcept-specifier*.
-[^7]: This lookup applies whether the member function is defined within
-    the definition of class `X` or whether the member function is
-    defined in a namespace scope enclosing `X`’s definition.
-[^8]: Lookups in which function names are ignored include names
     appearing in a *nested-name-specifier*, an
     *elaborated-type-specifier*, or a *base-specifier*.
-[^9]: The number of bits in a byte is reported by the macro `CHAR_BIT`
     in the header `<climits>`.
-[^10]: Under the “as-if” rule an implementation is allowed to store two
     objects at the same machine address or not store an object at all if
     the program cannot observe the difference [[intro.execution]].
-[^11]: For example, before the construction of a global object that is
- initialized via a user-provided constructor [[class.cdtor]].
-[^12]: That is, an object for which a destructor will be called
     implicitly—upon exit from the block for an object with automatic
     storage duration, upon exit from the thread for an object with
     thread storage duration, or upon exit from the program for an object
     with static storage duration.
-[^13]: Some implementations might define that copying an invalid pointer
     value causes a system-generated runtime fault.
-[^14]: The intent is to have `operator new()` implementable by calling
     `std::malloc()` or `std::calloc()`, so the rules are substantially
     the same. C++ differs from C in requiring a zero request to return a
     non-null pointer.
-[^15]: The global `operator delete(void*, std::size_t)` precludes use of
     an allocation function `void operator new(std::size_t, std::size_t)`
-    as a placement allocation function ([[diff.cpp11.basic]]).
-[^16]: This subclause does not impose restrictions on indirection
-    through pointers to memory not allocated by `::operator new`. This
-    maintains the ability of many C++ implementations to use binary
-    libraries and components written in other languages. In particular,
-    this applies to C binaries, because indirection through pointers to
-    memory allocated by `std::malloc` is not restricted.
-[^17]: The same rules apply to initialization of an `initializer_list`
     object [[dcl.init.list]] with its underlying temporary array.
-[^18]: By using, for example, the library functions [[headers]]
     `std::memcpy` or `std::memmove`.
-[^19]: By using, for example, the library functions [[headers]]
     `std::memcpy` or `std::memmove`.
-[^20]: The intent is that the memory model of C++ is compatible with
     that of ISO/IEC 9899 Programming Language C.
-[^21]: The size and layout of an instance of an incompletely-defined
     object type is unknown.
-[^22]: This is also known as two’s complement representation.
-[^23]: Static class members are objects or functions, and pointers to
     them are ordinary pointers to objects or functions.
-[^24]: For an object that is not within its lifetime, this is the first
     byte in memory that it will occupy or used to occupy.
-[^25]: The same representation and alignment requirements are meant to
     imply interchangeability as arguments to functions, return values
     from functions, and non-static data members of unions.
-[^26]: As specified in  [[class.temporary]], after a full-expression is
     evaluated, a sequence of zero or more invocations of destructor
     functions for temporary objects takes place, usually in reverse
     order of the construction of each temporary object.
-[^27]: In other words, function executions do not interleave with each
     other.
-[^28]: An object with automatic or thread storage duration [[basic.stc]]
     is associated with one specific thread, and can be accessed by a
     different thread only indirectly through a pointer or reference
     [[basic.compound]].
-[^29]: A non-local variable with static storage duration having
     initialization with side effects is initialized in this case, even
-    if it is not itself odr-used ([[basic.def.odr]],
-    [[basic.stc.static]]).

 suspension of a coroutine [[expr.await]], or receipt of a signal).
 A *constituent expression* is defined as follows:
 - The constituent expression of an expression is that expression.
+- The constituent expression of a conversion is the corresponding
+  implicit function call, if any, or the converted expression otherwise.
 - The constituent expressions of a *braced-init-list* or of a (possibly
   parenthesized) *expression-list* are the constituent expressions of
   the elements of the respective list.
 - The constituent expressions of a *brace-or-equal-initializer* of the
   form `=` *initializer-clause* are the constituent expressions of the
 [*Note 1*: Expressions appearing in the *compound-statement* of a
 *lambda-expression* are not subexpressions of the
 *lambda-expression*. — *end note*]
+The *potentially-evaluated subexpressions* of an expression, conversion,
+or *initializer* E are
+- the constituent expressions of E and
+- the subexpressions thereof that are not subexpressions of a nested
+  unevaluated operand [[term.unevaluated.operand]].
 A *full-expression* is
+- an unevaluated operand [[expr.context]],
 - a *constant-expression* [[expr.const]],
 - an immediate invocation [[expr.const]],
 - an *init-declarator* [[dcl.decl]] or a *mem-initializer*
   [[class.base.init]], including the constituent expressions of the
   initializer,
 Evaluations *A* and *B* are *indeterminately sequenced* when either *A*
 is sequenced before *B* or *B* is sequenced before *A*, but it is
 unspecified which.
 [*Note 4*: Indeterminately sequenced evaluations cannot overlap, but
+either can be executed first. — *end note*]
 An expression *X* is said to be sequenced before an expression *Y* if
 every value computation and every side effect associated with the
 expression *X* is sequenced before every value computation and every
 side effect associated with the expression *Y*.
 Every value computation and side effect associated with a
 full-expression is sequenced before every value computation and side
+effect associated with the next full-expression to be evaluated.[^22]
 Except where noted, evaluations of operands of individual operators and
 of subexpressions of individual expressions are unsequenced.
 [*Note 5*: In an expression that is evaluated more than once during the
 }
 ```
 — *end example*]
+When invoking a function (whether or not the function is inline), every
+argument expression and the postfix expression designating the called
+function are sequenced before every expression or statement in the body
+of the called function. For each function invocation or evaluation of an
+*await-expression* *F*, each evaluation that does not occur within *F*
+but is evaluated on the same thread and as part of the same signal
+handler (if any) is either sequenced before all evaluations that occur
+within *F* or sequenced after all evaluations that occur within
+*F*;[^23]
+if *F* invokes or resumes a coroutine [[expr.await]], only evaluations
+subsequent to the previous suspension (if any) and prior to the next
+suspension (if any) are considered to occur within *F*.
 Several contexts in C++ cause evaluation of a function call, even though
 no corresponding function call syntax appears in the translation unit.
 [*Example 4*: Evaluation of a *new-expression* invokes one or more
 arise in contexts in which no function call syntax
 appears. — *end example*]
 The sequencing constraints on the execution of the called function (as
 described above) are features of the function calls as evaluated,
+regardless of the syntax of the expression that calls the function.
 If a signal handler is executed as a result of a call to the
 `std::raise` function, then the execution of the handler is sequenced
 after the invocation of the `std::raise` function and before its return.
+[*Note 7*: When a signal is received for another reason, the execution
 of the signal handler is usually unsequenced with respect to the rest of
 the program. — *end note*]
 ### Multi-threaded executions and data races <a id="intro.multithread">[[intro.multithread]]</a>
+#### General <a id="intro.multithread.general">[[intro.multithread.general]]</a>
 A *thread of execution* (also known as a *thread*) is a single flow of
 control within a program, including the initial invocation of a specific
 top-level function, and recursively including every function invocation
 subsequently executed by the thread.
 [*Note 1*: When one thread creates another, the initial call to the
 top-level function of the new thread is executed by the new thread, not
 by the creating thread. — *end note*]
 Every thread in a program can potentially access every object and
+function in a program.[^24]
+Under a hosted implementation, a C++ program can have more than one
+thread running concurrently. The execution of each thread proceeds as
+defined by the remainder of this document. The execution of the entire
+program consists of an execution of all of its threads.
 [*Note 2*: Usually the execution can be viewed as an interleaving of
 all its threads. However, some kinds of atomic operations, for example,
 allow executions inconsistent with a simple interleaving, as described
 below. — *end note*]
 The value of an object visible to a thread T at a particular point is
 the initial value of the object, a value assigned to the object by T, or
 a value assigned to the object by another thread, according to the rules
 below.
+[*Note 1*: In some cases, there might instead be undefined behavior.
+Much of this subclause is motivated by the desire to support atomic
 operations with explicit and detailed visibility constraints. However,
 it also implicitly supports a simpler view for more restricted
 programs. — *end note*]
 Two expression evaluations *conflict* if one of them modifies a memory
 particular total order, called the *modification order* of M.
 [*Note 3*: There is a separate order for each atomic object. There is
 no requirement that these can be combined into a single total order for
 all objects. In general this will be impossible since different threads
+can observe modifications to different objects in inconsistent
 orders. — *end note*]
 A *release sequence* headed by a release operation A on an atomic object
 M is a maximal contiguous sub-sequence of side effects in the
 modification order of M, where the first operation is A, and every
 object in that interleaving. This is normally referred to as “sequential
 consistency”. However, this applies only to data-race-free programs, and
 data-race-free programs cannot observe most program transformations that
 do not change single-threaded program semantics. In fact, most
 single-threaded program transformations continue to be allowed, since
+any program that behaves differently as a result has undefined
+behavior. — *end note*]
 Two accesses to the same object of type `volatile std::sig_atomic_t` do
 not result in a data race if both occur in the same thread, even if one
 or more occurs in a signal handler. For each signal handler invocation,
 evaluations performed by the thread invoking a signal handler can be
 abstract machine are generally precluded by this document, since such an
 assignment might overwrite another assignment by a different thread in
 cases in which an abstract machine execution would not have encountered
 a data race. This includes implementations of data member assignment
 that overwrite adjacent members in separate memory locations. Reordering
+of atomic loads in cases in which the atomics in question might alias is
+also generally precluded, since this could violate the coherence
 rules. — *end note*]
 [*Note 23*: Transformations that introduce a speculative read of a
+potentially shared memory location might not preserve the semantics of
+the C++ program as defined in this document, since they potentially
 introduce a data race. However, they are typically valid in the context
 of an optimizing compiler that targets a specific machine with
 well-defined semantics for data races. They would be invalid for a
 hypothetical machine that is not tolerant of races or provides hardware
 race detection. — *end note*]
 [[atomics.flag]] or indicated as lock-free [[atomics.lockfree]] are
 *lock-free executions*.
 - If there is only one thread that is not blocked [[defns.block]] in a
   standard library function, a lock-free execution in that thread shall
+  complete. \[*Note 2*: Concurrently executing threads might prevent
   progress of a lock-free execution. For example, this situation can
   occur with load-locked store-conditional implementations. This
   property is sometimes termed obstruction-free. — *end note*]
 - When one or more lock-free executions run concurrently, at least one
   should complete. \[*Note 3*: It is difficult for some implementations
   to provide absolute guarantees to this effect, since repeated and
+  particularly inopportune interference from other threads could prevent
   forward progress, e.g., by repeatedly stealing a cache line for
   unrelated purposes between load-locked and store-conditional
+  instructions. For implementations that follow this recommendation and
+ ensure that such effects cannot indefinitely delay progress under
+ expected operating conditions, such anomalies can therefore safely be
+ ignored by programmers. Outside this document, this property is
+ sometimes termed lock-free. — *end note*]
 During the execution of a thread of execution, each of the following is
 termed an *execution step*:
 - termination of the thread of execution,
 is considered to continuously execute execution steps while waiting for
 the condition that it blocks on to be satisfied.
 [*Example 1*: A library I/O function that blocks until the I/O
 operation is complete can be considered to continuously check whether
+the operation is complete. Each such check consists of one or more
 execution steps, for example using observable behavior of the abstract
 machine. — *end example*]
 [*Note 4*: Because of this and the preceding requirement regarding what
 threads of execution have to perform eventually, it follows that no
 For a thread of execution providing *concurrent forward progress
 guarantees*, the implementation ensures that the thread will eventually
 make progress for as long as it has not terminated.
 [*Note 5*: This is required regardless of whether or not other threads
+of execution (if any) have been or are making progress. To eventually
 fulfill this requirement means that this will happen in an unspecified
 but finite amount of time. — *end note*]
 It is *implementation-defined* whether the implementation-created thread
 of execution that executes `main` [[basic.start.main]] and the threads
 of execution created by `std::thread` [[thread.thread.class]] or
 `std::jthread` [[thread.jthread.class]] provide concurrent forward
+progress guarantees. General-purpose implementations should provide
+these guarantees.
 For a thread of execution providing *parallel forward progress
 guarantees*, the implementation is not required to ensure that the
 thread will eventually make progress if it has not yet executed any
 execution step; once this thread has executed a step, it provides
 concurrent forward progress guarantees.
+[*Note 6*: This does not specify a requirement for when to start this
 thread of execution, which will typically be specified by the entity
 that creates this thread of execution. For example, a thread of
 execution that provides concurrent forward progress guarantees and
 executes tasks from a set of tasks in an arbitrary order, one after the
 other, satisfies the requirements of parallel forward progress for these
 For a thread of execution providing *weakly parallel forward progress
 guarantees*, the implementation does not ensure that the thread will
 eventually make progress.
+[*Note 7*: Threads of execution providing weakly parallel forward
 progress guarantees cannot be expected to make progress regardless of
 whether other threads make progress or not; however, blocking with
 forward progress guarantee delegation, as defined below, can be used to
 ensure that such threads of execution make progress
 eventually. — *end note*]
 Concurrent forward progress guarantees are stronger than parallel
 forward progress guarantees, which in turn are stronger than weakly
 parallel forward progress guarantees.
+[*Note 8*: For example, some kinds of synchronization between threads
+of execution might only make progress if the respective threads of
 execution provide parallel forward progress guarantees, but will fail to
 make progress under weakly parallel guarantees. — *end note*]
 When a thread of execution P is specified to *block with forward
 progress guarantee delegation* on the completion of a set S of threads
 of execution, then throughout the whole time of P being blocked on S,
 the implementation shall ensure that the forward progress guarantees
 provided by at least one thread of execution in S is at least as strong
 as P’s forward progress guarantees.
+[*Note 9*: It is unspecified which thread or threads of execution in S
 are chosen and for which number of execution steps. The strengthening is
 not permanent and not necessarily in place for the rest of the lifetime
 of the affected thread of execution. As long as P is blocked, the
 implementation has to eventually select and potentially strengthen a
 thread of execution in S. — *end note*]
 Once a thread of execution in S terminates, it is removed from S. Once S
 is empty, P is unblocked.
+[*Note 10*: A thread of execution B thus can temporarily provide an
 effectively stronger forward progress guarantee for a certain amount of
 time, due to a second thread of execution A being blocked on it with
 forward progress guarantee delegation. In turn, if B then blocks with
+forward progress guarantee delegation on C, this can also temporarily
 provide a stronger forward progress guarantee to C. — *end note*]
+[*Note 11*: If all threads of execution in S finish executing (e.g.,
 they terminate and do not use blocking synchronization incorrectly),
 then P’s execution of the operation that blocks with forward progress
 guarantee delegation will not result in P’s progress guarantee being
 effectively weakened. — *end note*]
+[*Note 12*: This does not remove any constraints regarding blocking
 synchronization for threads of execution providing parallel or weakly
 parallel forward progress guarantees because the implementation is not
 required to strengthen a particular thread of execution whose too-weak
 progress guarantee is preventing overall progress. — *end note*]
 ### Start and termination <a id="basic.start">[[basic.start]]</a>
 #### `main` function <a id="basic.start.main">[[basic.start.main]]</a>
+A program shall contain exactly one function called `main` that belongs
+to the global scope. Executing a program starts a main thread of
+execution [[intro.multithread]], [[thread.threads]] in which the `main`
+function is invoked. It is *implementation-defined* whether a program in
+a freestanding environment is required to define a `main` function.
 [*Note 1*: In a freestanding environment, startup and termination is
 *implementation-defined*; startup contains the execution of constructors
+for non-local objects with static storage duration; termination contains
+the execution of destructors for objects with static storage
 duration. — *end note*]
+An implementation shall not predefine the `main` function. Its type
+shall have C++ language linkage and it shall have a declared return type
+of type `int`, but otherwise its type is *implementation-defined*. An
+implementation shall allow both
 - a function of `()` returning `int` and
 - a function of `(int`, pointer to pointer to `char)` returning `int`
 as the type of `main` [[dcl.fct]]. In the latter form, for purposes of
 [[multibyte.strings]] and `argv[0]` shall be the pointer to the initial
 character of a NTMBS that represents the name used to invoke the program
 or `""`. The value of `argc` shall be non-negative. The value of
 `argv[argc]` shall be 0.
+*Recommended practice:* Any further (optional) parameters should be
+added after `argv`.
 The function `main` shall not be used within a program. The linkage
 [[basic.link]] of `main` is *implementation-defined*. A program that
 defines `main` as deleted or that declares `main` to be `inline`,
+`static`, `constexpr`, or `consteval` is ill-formed. The function `main`
+shall not be a coroutine [[dcl.fct.def.coroutine]]. The `main` function
+shall not be declared with a *linkage-specification* [[dcl.link]]. A
+program that declares
+- a variable `main` that belongs to the global scope, or
+- a function `main` that belongs to the global scope and is attached to
+  a named module, or
+- a function template `main` that belongs to the global scope, or
+- an entity named `main` with C language linkage (in any namespace)
+is ill-formed. The name `main` is not otherwise reserved.
 [*Example 1*: Member functions, classes, and enumerations can be called
 `main`, as can entities in other namespaces. — *end example*]
 Terminating the program without leaving the current block (e.g., by
 calling the function `std::exit(int)` [[support.start.term]]) does not
 destroy any objects with automatic storage duration [[class.dtor]]. If
+`std::exit` is invoked during the destruction of an object with static
+or thread storage duration, the program has undefined behavior.
 A `return` statement [[stmt.return]] in `main` has the effect of leaving
 the main function (destroying any objects with automatic storage
 duration) and calling `std::exit` with the return value as the argument.
 If control flows off the end of the *compound-statement* of `main`, the
 with static or thread storage duration is constant-initialized
 [[expr.const]]. If constant initialization is not performed, a variable
 with static storage duration [[basic.stc.static]] or thread storage
 duration [[basic.stc.thread]] is zero-initialized [[dcl.init]].
 Together, zero-initialization and constant initialization are called
+*static initialization*; all other initialization is
+*dynamic initialization*. All static initialization strongly happens
+before [[intro.races]] any dynamic initialization.
+[*Note 1*: The dynamic initialization of non-block variables is
+described in  [[basic.start.dynamic]]; that of static block variables is
 described in  [[stmt.dcl]]. — *end note*]
 An implementation is permitted to perform the initialization of a
 variable with static or thread storage duration as a static
 initialization even if such initialization is not required to be done
   statically were initialized dynamically.
 [*Note 2*:
 As a consequence, if the initialization of an object `obj1` refers to an
+object `obj2` potentially requiring dynamic initialization and defined
+later in the same translation unit, it is unspecified whether the value
+of `obj2` used will be the value of the fully initialized `obj2`
+(because `obj2` was statically initialized) or will be the value of
+`obj2` merely zero-initialized. For example,
 ``` cpp
 inline double fd() { return 1.0; }
 extern double d1;
 double d2 = d1;     // unspecified:
+                    // either statically initialized to 0.0 or
                     // dynamically initialized to 0.0 if d1 is
                     // dynamically initialized, or 1.0 otherwise
+double d1 = fd();   // either initialized statically or dynamically to 1.0
 ```
 — *end note*]
+#### Dynamic initialization of non-block variables <a id="basic.start.dynamic">[[basic.start.dynamic]]</a>
+Dynamic initialization of a non-block variable with static storage
 duration is unordered if the variable is an implicitly or explicitly
 instantiated specialization, is partially-ordered if the variable is an
 inline variable that is not an implicitly or explicitly instantiated
 specialization, and otherwise is ordered.
+[*Note 1*: A non-inline explicit specialization of a templated variable
+has ordered initialization. — *end note*]
 A declaration `D` is *appearance-ordered* before a declaration `E` if
 - `D` appears in the same translation unit as `E`, or
 - the translation unit containing `E` has an interface dependency on the
   translation unit containing `D`,
 in either case prior to `E`.
+Dynamic initialization of non-block variables `V` and `W` with static
 storage duration are ordered as follows:
 - If `V` and `W` have ordered initialization and the definition of `V`
   is appearance-ordered before the definition of `W`, or if `V` has
   partially-ordered initialization, `W` does not have unordered
   sequenced.
 [*Note 2*: This definition permits initialization of a sequence of
 ordered variables concurrently with another sequence. — *end note*]
+A *non-initialization odr-use* is an odr-use [[term.odr.use]] not caused
+directly or indirectly by the initialization of a non-block static or
+thread storage duration variable.
 It is *implementation-defined* whether the dynamic initialization of a
+non-block non-inline variable with static storage duration is sequenced
 before the first statement of `main` or is deferred. If it is deferred,
 it strongly happens before any non-initialization odr-use of any
 non-inline function or non-inline variable defined in the same
+translation unit as the variable to be initialized.[^25]
+It is *implementation-defined* in which threads and at which points in
+the program such deferred dynamic initialization occurs.
+*Recommended practice:* An implementation should choose such points in a
+way that allows the programmer to avoid deadlocks.
 [*Example 1*:
 ``` cpp
 // - File 1 -
 to its use in `A::A`.
 — *end example*]
 It is *implementation-defined* whether the dynamic initialization of a
+non-block inline variable with static storage duration is sequenced
 before the first statement of `main` or is deferred. If it is deferred,
 it strongly happens before any non-initialization odr-use of that
 variable. It is *implementation-defined* in which threads and at which
 points in the program such deferred dynamic initialization occurs.
 It is *implementation-defined* whether the dynamic initialization of a
+non-block non-inline variable with thread storage duration is sequenced
 before the first statement of the initial function of a thread or is
 deferred. If it is deferred, the initialization associated with the
 entity for thread *t* is sequenced before the first non-initialization
 odr-use by *t* of any non-inline variable with thread storage duration
 defined in the same translation unit as the variable to be initialized.
 It is *implementation-defined* in which threads and at which points in
 the program such deferred dynamic initialization occurs.
+If the initialization of a non-block variable with static or thread
 storage duration exits via an exception, the function `std::terminate`
 is called [[except.terminate]].
 #### Termination <a id="basic.start.term">[[basic.start.term]]</a>
 storage duration is sequenced before that of another, the completion of
 the destructor of the second is sequenced before the initiation of the
 destructor of the first. If an object is initialized statically, the
 object is destroyed in the same order as if the object was dynamically
 initialized. For an object of array or class type, all subobjects of
+that object are destroyed before any block variable with static storage
+duration initialized during the construction of the subobjects is
+destroyed. If the destruction of an object with static or thread storage
+duration exits via an exception, the function `std::terminate` is called
+[[except.terminate]].
+If a function contains a block variable of static or thread storage
 duration that has been destroyed and the function is called during the
 destruction of an object with static or thread storage duration, the
 program has undefined behavior if the flow of control passes through the
+definition of the previously destroyed block variable.
+[*Note 2*: Likewise, the behavior is undefined if the block variable is
+used indirectly (e.g., through a pointer) after its
+destruction. — *end note*]
 If the completion of the initialization of an object with static storage
 duration strongly happens before a call to `std::atexit` (see
 `<cstdlib>`, [[support.start.term]]), the call to the function passed to
 `std::atexit` is sequenced before the call to the destructor for the
 within signal handlers [[support.runtime]] that does not happen before
 [[intro.multithread]] completion of destruction of objects with static
 storage duration and execution of `std::atexit` registered functions
 [[support.start.term]], the program has undefined behavior.
+[*Note 3*: If there is a use of an object with static storage duration
 that does not happen before the object’s destruction, the program has
 undefined behavior. Terminating every thread before a call to
 `std::exit` or the exit from `main` is sufficient, but not necessary, to
 satisfy these requirements. These requirements permit thread managers as
 static-storage-duration objects. — *end note*]
 Calling the function `std::abort()` declared in `<cstdlib>` terminates
 the program without executing any destructors and without calling the
 functions passed to `std::atexit()` or `std::at_quick_exit()`.
 <!-- Link reference definitions -->
+[allocator.members]: mem.md#allocator.members
+[allocator.traits.members]: mem.md#allocator.traits.members
+[atomics]: thread.md#atomics
+[atomics.flag]: thread.md#atomics.flag
+[atomics.lockfree]: thread.md#atomics.lockfree
+[atomics.order]: thread.md#atomics.order
 [bad.alloc]: support.md#bad.alloc
 [basic]: #basic
 [basic.align]: #basic.align
 [basic.compound]: #basic.compound
 [basic.def]: #basic.def
 [basic.def.odr]: #basic.def.odr
 [basic.exec]: #basic.exec
+[basic.extended.fp]: #basic.extended.fp
 [basic.fundamental]: #basic.fundamental
 [basic.fundamental.width]: #basic.fundamental.width
 [basic.indet]: #basic.indet
 [basic.life]: #basic.life
 [basic.link]: #basic.link
 [basic.lookup]: #basic.lookup
 [basic.lookup.argdep]: #basic.lookup.argdep
 [basic.lookup.elab]: #basic.lookup.elab
+[basic.lookup.general]: #basic.lookup.general
 [basic.lookup.qual]: #basic.lookup.qual
+[basic.lookup.qual.general]: #basic.lookup.qual.general
 [basic.lookup.udir]: #basic.lookup.udir
 [basic.lookup.unqual]: #basic.lookup.unqual
 [basic.lval]: expr.md#basic.lval
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 [basic.pre]: #basic.pre
 [basic.scope]: #basic.scope
 [basic.scope.block]: #basic.scope.block
 [basic.scope.class]: #basic.scope.class
 [basic.scope.enum]: #basic.scope.enum
+[basic.scope.lambda]: #basic.scope.lambda
 [basic.scope.namespace]: #basic.scope.namespace
 [basic.scope.param]: #basic.scope.param
 [basic.scope.pdecl]: #basic.scope.pdecl
+[basic.scope.scope]: #basic.scope.scope
 [basic.scope.temp]: #basic.scope.temp
 [basic.start]: #basic.start
 [basic.start.dynamic]: #basic.start.dynamic
 [basic.start.main]: #basic.start.main
 [basic.start.static]: #basic.start.static
 [basic.stc]: #basic.stc
 [basic.stc.auto]: #basic.stc.auto
 [basic.stc.dynamic]: #basic.stc.dynamic
 [basic.stc.dynamic.allocation]: #basic.stc.dynamic.allocation
 [basic.stc.dynamic.deallocation]: #basic.stc.dynamic.deallocation
+[basic.stc.dynamic.general]: #basic.stc.dynamic.general
+[basic.stc.general]: #basic.stc.general
 [basic.stc.inherit]: #basic.stc.inherit
 [basic.stc.static]: #basic.stc.static
 [basic.stc.thread]: #basic.stc.thread
 [basic.type.qualifier]: #basic.type.qualifier
 [basic.type.qualifier.rel]: #basic.type.qualifier.rel
 [basic.types]: #basic.types
+[basic.types.general]: #basic.types.general
+[bit.cast]: utilities.md#bit.cast
+[c.malloc]: mem.md#c.malloc
 [class]: class.md#class
 [class.abstract]: class.md#class.abstract
 [class.access]: class.md#class.access
+[class.access.base]: class.md#class.access.base
 [class.base.init]: class.md#class.base.init
 [class.bit]: class.md#class.bit
 [class.cdtor]: class.md#class.cdtor
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 [class.dtor]: class.md#class.dtor
 [class.free]: class.md#class.free
 [class.friend]: class.md#class.friend
 [class.mem]: class.md#class.mem
+[class.member.lookup]: #class.member.lookup
 [class.mfct]: class.md#class.mfct
+[class.mfct.non.static]: class.md#class.mfct.non.static
 [class.name]: class.md#class.name
 [class.pre]: class.md#class.pre
 [class.prop]: class.md#class.prop
 [class.qual]: #class.qual
 [class.spaceship]: class.md#class.spaceship
 [class.static]: class.md#class.static
 [class.static.data]: class.md#class.static.data
 [class.temporary]: #class.temporary
 [class.union]: class.md#class.union
+[class.union.anon]: class.md#class.union.anon
 [class.virtual]: class.md#class.virtual
 [conv]: expr.md#conv
 [conv.array]: expr.md#conv.array
 [conv.func]: expr.md#conv.func
 [conv.integral]: expr.md#conv.integral
 [dcl.fct.default]: dcl.md#dcl.fct.default
 [dcl.init]: dcl.md#dcl.init
 [dcl.init.aggr]: dcl.md#dcl.init.aggr
 [dcl.init.list]: dcl.md#dcl.init.list
 [dcl.init.ref]: dcl.md#dcl.init.ref
 [dcl.link]: dcl.md#dcl.link
 [dcl.meaning]: dcl.md#dcl.meaning
 [dcl.mptr]: dcl.md#dcl.mptr
 [dcl.name]: dcl.md#dcl.name
 [dcl.pre]: dcl.md#dcl.pre
 [dcl.ref]: dcl.md#dcl.ref
 [dcl.spec]: dcl.md#dcl.spec
 [dcl.spec.auto]: dcl.md#dcl.spec.auto
 [dcl.stc]: dcl.md#dcl.stc
 [dcl.struct.bind]: dcl.md#dcl.struct.bind
+[dcl.type.decltype]: dcl.md#dcl.type.decltype
 [dcl.type.elab]: dcl.md#dcl.type.elab
 [dcl.typedef]: dcl.md#dcl.typedef
 [defns.block]: intro.md#defns.block
 [depr.local]: future.md#depr.local
 [depr.static.constexpr]: future.md#depr.static.constexpr
 [diff.cpp11.basic]: compatibility.md#diff.cpp11.basic
 [enum.udecl]: dcl.md#enum.udecl
 [except.handle]: except.md#except.handle
 [except.pre]: except.md#except.pre
 [except.spec]: except.md#except.spec
 [except.terminate]: except.md#except.terminate
 [except.throw]: except.md#except.throw
 [expr.add]: expr.md#expr.add
 [expr.alignof]: expr.md#expr.alignof
 [expr.arith.conv]: expr.md#expr.arith.conv
 [expr.ass]: expr.md#expr.ass
 [expr.await]: expr.md#expr.await
 [expr.call]: expr.md#expr.call
 [expr.cast]: expr.md#expr.cast
 [expr.comma]: expr.md#expr.comma
 [expr.cond]: expr.md#expr.cond
 [expr.const]: expr.md#expr.const
 [expr.const.cast]: expr.md#expr.const.cast
 [expr.context]: expr.md#expr.context
 [expr.delete]: expr.md#expr.delete
 [expr.log.or]: expr.md#expr.log.or
 [expr.mptr.oper]: expr.md#expr.mptr.oper
 [expr.new]: expr.md#expr.new
 [expr.pre]: expr.md#expr.pre
 [expr.prim.id]: expr.md#expr.prim.id
 [expr.prim.id.qual]: expr.md#expr.prim.id.qual
+[expr.prim.id.unqual]: expr.md#expr.prim.id.unqual
 [expr.prim.lambda]: expr.md#expr.prim.lambda
 [expr.prim.lambda.capture]: expr.md#expr.prim.lambda.capture
 [expr.prim.lambda.closure]: expr.md#expr.prim.lambda.closure
 [expr.prim.this]: expr.md#expr.prim.this
 [expr.prop]: expr.md#expr.prop
 [get.new.handler]: support.md#get.new.handler
 [headers]: library.md#headers
 [intro.execution]: #intro.execution
 [intro.memory]: #intro.memory
 [intro.multithread]: #intro.multithread
+[intro.multithread.general]: #intro.multithread.general
 [intro.object]: #intro.object
 [intro.progress]: #intro.progress
 [intro.races]: #intro.races
 [lex.charset]: lex.md#lex.charset
+[lex.fcon]: lex.md#lex.fcon
 [lex.name]: lex.md#lex.name
 [lex.separate]: lex.md#lex.separate
 [module.context]: module.md#module.context
 [module.global.frag]: module.md#module.global.frag
 [module.interface]: module.md#module.interface
 [module.reach]: module.md#module.reach
 [module.unit]: module.md#module.unit
 [multibyte.strings]: library.md#multibyte.strings
 [namespace.def]: dcl.md#namespace.def
 [namespace.qual]: #namespace.qual
 [namespace.udecl]: dcl.md#namespace.udecl
 [namespace.udir]: dcl.md#namespace.udir
+[namespace.unnamed]: dcl.md#namespace.unnamed
 [new.delete]: support.md#new.delete
 [new.delete.array]: support.md#new.delete.array
 [new.delete.placement]: support.md#new.delete.placement
 [new.delete.single]: support.md#new.delete.single
 [new.handler]: support.md#new.handler
+[new.syn]: support.md#new.syn
+[obj.lifetime]: mem.md#obj.lifetime
 [over]: over.md#over
 [over.literal]: over.md#over.literal
 [over.match]: over.md#over.match
+[over.match.funcs]: over.md#over.match.funcs
 [over.oper]: over.md#over.oper
 [over.over]: over.md#over.over
+[ptr.align]: mem.md#ptr.align
 [ptr.launder]: support.md#ptr.launder
 [replacement.functions]: library.md#replacement.functions
 [special]: class.md#special
+[std.modules]: library.md#std.modules
+[stdfloat.syn]: support.md#stdfloat.syn
 [stmt.block]: stmt.md#stmt.block
 [stmt.dcl]: stmt.md#stmt.dcl
 [stmt.expr]: stmt.md#stmt.expr
 [stmt.if]: stmt.md#stmt.if
+[stmt.iter]: stmt.md#stmt.iter
+[stmt.pre]: stmt.md#stmt.pre
 [stmt.ranged]: stmt.md#stmt.ranged
 [stmt.return]: stmt.md#stmt.return
+[stmt.select]: stmt.md#stmt.select
 [support.dynamic]: support.md#support.dynamic
 [support.runtime]: support.md#support.runtime
 [support.start.term]: support.md#support.start.term
 [support.types]: support.md#support.types
+[temp.concept]: temp.md#temp.concept
 [temp.deduct.guide]: temp.md#temp.deduct.guide
 [temp.dep]: temp.md#temp.dep
 [temp.dep.candidate]: temp.md#temp.dep.candidate
+[temp.dep.constexpr]: temp.md#temp.dep.constexpr
+[temp.dep.type]: temp.md#temp.dep.type
 [temp.expl.spec]: temp.md#temp.expl.spec
 [temp.explicit]: temp.md#temp.explicit
+[temp.friend]: temp.md#temp.friend
 [temp.local]: temp.md#temp.local
 [temp.names]: temp.md#temp.names
 [temp.over]: temp.md#temp.over
+[temp.over.link]: temp.md#temp.over.link
 [temp.param]: temp.md#temp.param
 [temp.point]: temp.md#temp.point
 [temp.pre]: temp.md#temp.pre
 [temp.res]: temp.md#temp.res
 [temp.spec]: temp.md#temp.spec
+[temp.spec.partial]: temp.md#temp.spec.partial
 [temp.type]: temp.md#temp.type
+[term.incomplete.type]: #term.incomplete.type
+[term.odr.use]: #term.odr.use
+[term.unevaluated.operand]: expr.md#term.unevaluated.operand
 [thread]: thread.md#thread
 [thread.jthread.class]: thread.md#thread.jthread.class
 [thread.thread.class]: thread.md#thread.thread.class
 [thread.threads]: thread.md#thread.threads
 [^1]: Appearing inside the brace-enclosed *declaration-seq* in a
     *linkage-specification* does not affect whether a declaration is a
     definition.
 [^2]: An implementation is not required to call allocation and
     deallocation functions from constructors or destructors; however,
     this is a permissible implementation technique.
+[^3]: An implicit object parameter [[over.match.funcs]] is not part of
+    the parameter-type-list.
+[^4]: Lookups in which function names are ignored include names
     appearing in a *nested-name-specifier*, an
     *elaborated-type-specifier*, or a *base-specifier*.
+[^5]: Unicode® is a registered trademark of Unicode, Inc. This
+    information is given for the convenience of users of this document
+    and does not constitute an endorsement by ISO or IEC of this
+    product.
+[^6]: The number of bits in a byte is reported by the macro `CHAR_BIT`
     in the header `<climits>`.
+[^7]: Under the “as-if” rule an implementation is allowed to store two
     objects at the same machine address or not store an object at all if
     the program cannot observe the difference [[intro.execution]].
+[^8]: For example, before the dynamic initialization of an object with
+ static storage duration [[basic.start.dynamic]].
+[^9]: That is, an object for which a destructor will be called
     implicitly—upon exit from the block for an object with automatic
     storage duration, upon exit from the thread for an object with
     thread storage duration, or upon exit from the program for an object
     with static storage duration.
+[^10]: Some implementations might define that copying an invalid pointer
     value causes a system-generated runtime fault.
+[^11]: The intent is to have `operator new()` implementable by calling
     `std::malloc()` or `std::calloc()`, so the rules are substantially
     the same. C++ differs from C in requiring a zero request to return a
     non-null pointer.
+[^12]: The global `operator delete(void*, std::size_t)` precludes use of
     an allocation function `void operator new(std::size_t, std::size_t)`
+    as a placement allocation function [[diff.cpp11.basic]].
+[^13]: The same rules apply to initialization of an `initializer_list`
     object [[dcl.init.list]] with its underlying temporary array.
+[^14]: By using, for example, the library functions [[headers]]
     `std::memcpy` or `std::memmove`.
+[^15]: By using, for example, the library functions [[headers]]
     `std::memcpy` or `std::memmove`.
+[^16]: The intent is that the memory model of C++ is compatible with
     that of ISO/IEC 9899 Programming Language C.
+[^17]: The size and layout of an instance of an incompletely-defined
     object type is unknown.
+[^18]: This is also known as two’s complement representation.
+[^19]: Static class members are objects or functions, and pointers to
     them are ordinary pointers to objects or functions.
+[^20]: For an object that is not within its lifetime, this is the first
     byte in memory that it will occupy or used to occupy.
+[^21]: The same representation and alignment requirements are meant to
     imply interchangeability as arguments to functions, return values
     from functions, and non-static data members of unions.
+[^22]: As specified in  [[class.temporary]], after a full-expression is
     evaluated, a sequence of zero or more invocations of destructor
     functions for temporary objects takes place, usually in reverse
     order of the construction of each temporary object.
+[^23]: In other words, function executions do not interleave with each
     other.
+[^24]: An object with automatic or thread storage duration [[basic.stc]]
     is associated with one specific thread, and can be accessed by a
     different thread only indirectly through a pointer or reference
     [[basic.compound]].
+[^25]: A non-block variable with static storage duration having
     initialization with side effects is initialized in this case, even
+    if it is not itself odr-used [[term.odr.use]], [[basic.stc.static]].

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