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 .

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

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

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

— end note

]

[ Note

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.93

[ Example

struct S {
  S() : s(__func__) { }             // OK
  const char* s;
};
void f(const char* s = __func__);   // error: __func__ is undeclared

— end example

]

93)

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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