6.5.2.2 Function calls
Constraints
1
The expression that denotes the called function77) shall have type pointer to function
returning void or returning an object type other than an array type.
2
If the expression that denotes the called function has a type that includes a prototype, the
number of arguments shall agree with the number of parameters. Each argument shall
have a type such that its value may be assigned to an object with the unqualified version
of the type of its corresponding parameter.
Semantics
3
A postfix expression followed by parentheses () containing a possibly empty, comma-
separated list of expressions is a function call. The postfix expression denotes the called
function. The list of expressions specifies the arguments to the function.
4
An argument may be an expression of any object type. In preparing for the call to a
function, the arguments are evaluated, and each parameter is assigned the value of the
corresponding argument.78)
5
If the expression that denotes the called function has type pointer to function returning an
object type, the function call expression has the same type as that object type, and has the
value determined as specified in 6.8.6.4. Otherwise, the function call has type void. If
an attempt is made to modify the result of a function call or to access it after the next
sequence point, the behavior is undefined.
6
If the expression that denotes the called function has a type that does not include a
prototype:
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the integer promotions are performed on each argument, and arguments that
have type float are promoted to double. These are called the default argument
promotions. If the number of arguments does not equal the number of parameters, the
behavior is undefined. If the function is defined with a type that includes a prototype, and
either the prototype ends with an ellipsis (, ...) or the types of the arguments after
promotion are not compatible with the types of the parameters, the behavior is undefined.
If the function is defined with a type that does not include a prototype, and the types of
the arguments after promotion are not compatible with those of the parameters after
promotion, the behavior is undefined, except for the following cases:
- one promoted type is a signed integer type, the other promoted type is the
corresponding unsigned integer type, and the value is representable in both types;
- both types are pointers to qualified or unqualified versions of a character type or
void.
7
If the expression that denotes the called function has a type that does include a prototype:
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the arguments are implicitly converted, as if by assignment, to the types of the
corresponding parameters, taking the type of each parameter to be the unqualified version
of its declared type. The ellipsis notation in a function prototype declarator causes
argument type conversion to stop after the last declared parameter. The default argument
promotions are performed on trailing arguments.
8
No other conversions are performed implicitly; in particular, the number and types of
arguments are not compared with those of the parameters in a function definition that
does not include a function prototype declarator.
9
If the function is defined with a type that is not compatible with the type (of the
expression) pointed to by the expression that denotes the called function, the behavior is
undefined.
10
The order of evaluation of the function designator, the actual arguments, and
subexpressions within the actual arguments is unspecified, but there is a sequence point
before the actual call.
11
Recursive function calls shall be permitted, both directly and indirectly through any chain
of other functions.
va_arg():
If there is no actual next argument, or if
type is not compatible with the type of the actual next argument (as promoted according
to the default argument promotions), the behavior is undefined, except for the following
cases:
- one type is a signed integer type, the other type is the corresponding unsigned integer
type, and the value is representable in both types;
- one type is pointer to void and the other is a pointer to a character type. |
