9 Declarations [dcl.dcl]

9.5 Function definitions [dcl.fct.def]

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

1
#
function-body:
ctor-initializer 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.
2
#
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]).
3
#
[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
]
4
#
A ctor-initializer is used only in a constructor; see [class.ctor] and [class.init].
5
#
[Note
:
A cv-qualifier-seq affects the type of this in the body of a member function; see [expr.prim.this].
— end note
]
6
#
[Note
:
Unused parameters need not be named.
For example,
void print(int a, int) {
  std::printf("a = %d\n",a);
}
— end note
]
7
#
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]).
8
#
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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