Function definitions have the form
function-definition: attribute-specifier-seqopt decl-specifier-seqopt declarator virt-specifier-seqopt function-body
function-body: ctor-initializeropt 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.
[ 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 ]
[ 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.103 [ Example:
struct S { S() : s(__func__) { } // OK const char* s; }; void f(const char* s = __func__); // error: __func__ is undeclared
— end example ]
Implementations are permitted to provide additional predefined variables with names that are reserved to the implementation. If a predefined variable is not odr-used, its string value need not be present in the program image.