tmp/tmpttzvz8e0/{from.md → to.md}
RENAMED
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@@ -29,12 +29,11 @@ to `const int`”.
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— *end example*]
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[*Note 1*: A reference can be thought of as a name of an
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object. — *end note*]
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ill-formed.
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A reference type that is declared using `&` is called an *lvalue
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reference*, and a reference type that is declared using `&&` is called
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an *rvalue reference*. Lvalue references and rvalue references are
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distinct types. Except where explicitly noted, they are semantically
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@@ -95,29 +94,57 @@ There shall be no references to references, no arrays of references, and
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no pointers to references. The declaration of a reference shall contain
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an *initializer* [[dcl.init.ref]] except when the declaration contains
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an explicit `extern` specifier [[dcl.stc]], is a class member
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[[class.mem]] declaration within a class definition, or is the
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declaration of a parameter or a return type [[dcl.fct]]; see
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[[basic.def]].
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[[
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If a *typedef-name* [[dcl.typedef]], [[temp.param]] or a
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*decltype-specifier* [[dcl.type.decltype]] denotes a type `TR` that is a
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reference to a type `T`, an attempt to create the type “lvalue reference
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to cv `TR`” creates the type “lvalue reference to `T`”, while an attempt
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to create the type “rvalue reference to cv `TR`” creates the type `TR`.
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[*Note 3*: This rule is known as reference collapsing. — *end note*]
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[*Example
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``` cpp
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int i;
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typedef int& LRI;
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typedef int&& RRI;
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— *end example*]
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[*Note 1*: A reference can be thought of as a name of an
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object. — *end note*]
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Forming the type “reference to cv `void`” is ill-formed.
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A reference type that is declared using `&` is called an *lvalue
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reference*, and a reference type that is declared using `&&` is called
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an *rvalue reference*. Lvalue references and rvalue references are
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distinct types. Except where explicitly noted, they are semantically
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no pointers to references. The declaration of a reference shall contain
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an *initializer* [[dcl.init.ref]] except when the declaration contains
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an explicit `extern` specifier [[dcl.stc]], is a class member
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[[class.mem]] declaration within a class definition, or is the
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declaration of a parameter or a return type [[dcl.fct]]; see
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[[basic.def]].
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Attempting to bind a reference to a function where the converted
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initializer is a glvalue whose type is not call-compatible [[expr.call]]
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with the type of the function’s definition results in undefined
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behavior. Attempting to bind a reference to an object where the
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converted initializer is a glvalue through which the object is not
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type-accessible [[basic.lval]] results in undefined behavior.
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[*Note 2*: The object designated by such a glvalue can be outside its
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lifetime [[basic.life]]. Because a null pointer value or a pointer past
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the end of an object does not point to an object, a reference in a
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well-defined program cannot refer to such things; see
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[[expr.unary.op]]. As described in [[class.bit]], a reference cannot be
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bound directly to a bit-field. — *end note*]
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The behavior of an evaluation of a reference
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[[expr.prim.id]], [[expr.ref]] that does not happen after
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[[intro.races]] the initialization of the reference is undefined.
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[*Example 3*:
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``` cpp
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int &f(int&);
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int &g();
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extern int &ir3;
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int *ip = 0;
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int &ir1 = *ip; // undefined behavior: null pointer
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int &ir2 = f(ir3); // undefined behavior: ir3 not yet initialized
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int &ir3 = g();
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int &ir4 = f(ir4); // undefined behavior: ir4 used in its own initializer
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char x alignas(int);
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int &ir5 = *reinterpret_cast<int *>(&x); // undefined behavior: initializer refers to char object
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```
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— *end example*]
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If a *typedef-name* [[dcl.typedef]], [[temp.param]] or a
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*decltype-specifier* [[dcl.type.decltype]] denotes a type `TR` that is a
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reference to a type `T`, an attempt to create the type “lvalue reference
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to cv `TR`” creates the type “lvalue reference to `T`”, while an attempt
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to create the type “rvalue reference to cv `TR`” creates the type `TR`.
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[*Note 3*: This rule is known as reference collapsing. — *end note*]
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[*Example 4*:
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``` cpp
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int i;
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typedef int& LRI;
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typedef int&& RRI;
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