Defined in header <cstdarg> | ||
---|---|---|
void va_start( va_list ap, parm_n ); |
The va_start
macro enables access to the variable arguments following the named argument parm_n
.
va_start
should be invoked with an instance to a valid va_list
object ap
before any calls to va_arg
.
If parm_n
is declared with reference type or with a type not compatible with the type that results from default argument promotions, the behavior is undefined.
ap | - | an instance of the va_list type |
parm_n | - | the named parameter preceding the first variable parameter |
(none).
va_start
is required to support parm_n
with overloaded operator&
.
#include <iostream> #include <cstdarg> int add_nums(int count, ...) { int result = 0; va_list args; va_start(args, count); for (int i = 0; i < count; ++i) { result += va_arg(args, int); } va_end(args); return result; } int main() { std::cout << add_nums(4, 25, 25, 50, 50) << '\n'; }
Output:
150
accesses the next variadic function argument (function macro) |
|
ends traversal of the variadic function arguments (function macro) |
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