9 Declarations [dcl.dcl]

9.5 Function definitions [dcl.fct.def]

9.5.1 In general [dcl.fct.def.general]

Function definitions have the form

function-definition:
attribute-specifier-seq

_{o p t}

decl-specifier-seq

_{o p t}

declarator virt-specifier-seq

_{o p t}

function-body
attribute-specifier-seq

_{o p t}

decl-specifier-seq

_{o p t}

declarator requires-clause function-body

function-body:
ctor-initializer

_{o p t}

compound-statement
function-try-block
= default ;
= delete ;

Any informal reference to the body of a function should be interpreted as a reference to the non-terminal function-body.

The optional attribute-specifier-seq in a function-definition appertains to the function.

A virt-specifier-seq can be part of a function-definition only if it is a member-declaration ([class.mem]).

In a function-definition, either void declarator ; or declarator ; shall be a well-formed function declaration as described in [dcl.fct].

A function shall be defined only in namespace or class scope.

The type of a parameter or the return type for a function definition shall not be a (possibly cv-qualified) class type that is incomplete or abstract within the function body unless the function is deleted ([dcl.fct.def.delete]).

[Example 1:

A simple example of a complete function definition is int max(int a, int b, int c) { int m = (a > b) ? a : b; return (m > c) ? m : c; }

Here int is the decl-specifier-seq; max(int a, int b, int c) is the declarator; { /* ... */ } is the function-body.

— end example]

A ctor-initializer is used only in a constructor; see [class.ctor] and [class.init].

[Note 1:

A cv-qualifier-seq affects the type of this in the body of a member function; see [expr.prim.this].

— end note]

[Note 2:

Unused parameters need not be named.

For example,

void print(int a, int) { std::printf("a = %d\n",a); } — end note]

In the function-body, a function-local predefined variable denotes a block-scope object of static storage duration that is implicitly defined (see [basic.scope.block]).

The function-local predefined variable __func__ is defined as if a definition of the form static const char __func__[] = "function-name"; had been provided, where function-name is an implementation-defined string.

It is unspecified whether such a variable has an address distinct from that of any other object in the program.97

[Example 2: struct S { S() : s(__func__) { } // OK const char* s; }; void f(const char* s = __func__); // error: __func__ is undeclared — end example]

97)

Implementations are permitted to provide additional predefined variables with names that are reserved to the implementation ([lex.name]).

If a predefined variable is not odr-used ([basic.def.odr]), its string value need not be present in the program image.

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