void va_start( std::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 the parm_n is a pack expansion or an entity resulting from a lambda capture, the program is ill-formed, no diagnostic required.
(since C++11)If parm_n is of reference type, or of a type not compatible with the type that results from default argument promotions, the behavior is undefined.
[edit] Parameters ap - an object of the va_list type parm_n - the named parameter preceding the first variable parameter [edit] Expanded value(none)
[edit] Notesva_start is required to support parm_n with overloaded operator&.
#include <cstdarg>
#include <iostream>
int add_nums(int count...)
{
int result = 0;
std::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:
[edit] Defect reportsThe following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR Applied to Behavior as published Correct behavior CWG 273 C++98 it was unclear whetherva_start is required to
operator& required LWG 2099 C++98 the behavior was undefined if parm_n is
RetroSearch is an open source project built by @garambo | Open a GitHub Issue
Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo
HTML:
3.2
| Encoding:
UTF-8
| Version:
0.7.4