9 Declarations [dcl]

9.3 Declarators [dcl.decl]

9.3.4 Meaning of declarators [dcl.meaning]

9.3.4.6 Functions [dcl.fct]

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In a declaration T D where T may be empty and D has the form
D1 ( parameter-declaration-clause ) cv-qualifier-seq
   ref-qualifier noexcept-specifier attribute-specifier-seq trailing-return-type
a derived-declarator-type-list is determined as follows:
The declared return type U of the function type is determined as follows:
The type of the declarator-id in D is “derived-declarator-type-list noexcept function of parameter-type-list cv-qualifier-seq ref-qualifier returning U”, where
Such a type is a function type.69
The optional attribute-specifier-seq appertains to the function type.
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The optional attribute-specifier-seq in a parameter-declaration appertains to the parameter.
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The parameter-declaration-clause determines the arguments that can be specified, and their processing, when the function is called.
[Note 1: 
The parameter-declaration-clause is used to convert the arguments specified on the function call; see [expr.call].
— end note]
If the parameter-declaration-clause is empty, the function takes no arguments.
A parameter list consisting of a single unnamed non-object parameter of non-dependent type void is equivalent to an empty parameter list.
Except for this special case, a parameter shall not have type cv void.
A parameter with volatile-qualified type is deprecated; see [depr.volatile.type].
If the parameter-declaration-clause terminates with an ellipsis or a function parameter pack ([temp.variadic]), the number of arguments shall be equal to or greater than the number of parameters that do not have a default argument and are not function parameter packs.
Where syntactically correct and where “...” is not part of an abstract-declarator, “...” is synonymous with “, ...”.
[Example 1: 
The declaration int printf(const char*, ...); declares a function that can be called with varying numbers and types of arguments.
printf("hello world"); printf("a=%d b=%d", a, b);
However, the first argument must be of a type that can be converted to a const char*.
— end example]
[Note 2: 
The standard header <cstdarg> contains a mechanism for accessing arguments passed using the ellipsis (see [expr.call] and [support.runtime]).
— end note]
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The type of a function is determined using the following rules.
The type of each parameter (including function parameter packs) is determined from its own parameter-declaration ([dcl.decl]).
After determining the type of each parameter, any parameter of type “array of T” or of function type T is adjusted to be “pointer to T”.
After producing the list of parameter types, any top-level cv-qualifiers modifying a parameter type are deleted when forming the function type.
The resulting list of transformed parameter types and the presence or absence of the ellipsis or a function parameter pack is the function's parameter-type-list.
[Note 3: 
This transformation does not affect the types of the parameters.
For example, int(*)(const int p, decltype(p)*) and int(*)(int, const int*) are identical types.
— end note]
[Example 2: void f(char*); // #1 void f(char[]) {} // defines #1 void f(const char*) {} // OK, another overload void f(char *const) {} // error: redefines #1 void g(char(*)[2]); // #2 void g(char[3][2]) {} // defines #2 void g(char[3][3]) {} // OK, another overload void h(int x(const int)); // #3 void h(int (*)(int)) {} // defines #3 — end example]
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A function with a parameter-type-list that has an ellipsis is termed a vararg function.
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An explicit-object-parameter-declaration shall appear only as the first parameter-declaration of a parameter-declaration-list of one of:
A member-declarator with an explicit-object-parameter-declaration shall not include a ref-qualifier or a cv-qualifier-seq and shall not be declared static or virtual.
[Example 3: struct C { void f(this C& self); template <typename Self> void g(this Self&& self, int); void h(this C) const; // error: const not allowed here }; void test(C c) { c.f(); // OK, calls C​::​f c.g(42); // OK, calls C​::​g<C&> std::move(c).g(42); // OK, calls C​::​g<C> } — end example]
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A function parameter declared with an explicit-object-parameter-declaration is an explicit object parameter.
An explicit object parameter shall not be a function parameter pack ([temp.variadic]).
An explicit object member function is a non-static member function with an explicit object parameter.
An implicit object member function is a non-static member function without an explicit object parameter.
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The object parameter of a non-static member function is either the explicit object parameter or the implicit object parameter ([over.match.funcs]).
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