https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110866
Bug ID: 110866
Summary: No UDC lookup with va_arg
Product: gcc
Version: 13.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: jengelh at inai dot de
Target Milestone: ---
Bugtype: enhancement
Version: 13.1.1 20230720 [revision 9aac37ab8a7b919a89c6d64bc7107a8436996e93]
(SUSE Linux)
Input
=====
#include <cstdarg>
struct va_wrap {
~va_wrap() { if (engaged) va_end(vl); }
va_list vl;
operator va_list &() { return vl; }
bool engaged = false;
};
void f(const char *fmt, ...)
{
va_wrap va;
va_start(va, fmt); va.engaged = 1;
va_arg(va, int);
if (0)
va_copy(va, va);
if (0)
va_end(va);
}
int main()
{
f("", 42);
}
Observed output
===============
$ g++ -c x.cpp
x.cpp:12:20: error: first argument to ‘va_arg’ not of type ‘va_list’
Expected output
===============
Succeed.
If va_start and va_end can take a va_wrap and have the user-defined conversion
operator invoked, surely va_arg could do so too.
