https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65901
Bug ID: 65901
Summary: no warning or error for va_arg (ap, void)
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: minor
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: vries at gcc dot gnu.org
Target Milestone: ---
We have va_arg (ap, void) somewhere in the testsuite
(gcc.c-torture/compile/pr48767.c).
AFAIU, using void in va_arg is undefined behaviour in c.
Currently, we just compile it without warning or error:
...
$ cat ~/va-arg-void.c
#include <stdarg.h>
int
f (int d, ...)
{
int res;
va_list ap;
va_start (ap, d);
va_arg (ap, void);
res = va_arg (ap, int);
va_end (ap);
return res;
}
int
main (void)
{
return f (1, 2, 3);
}
$ gcc -O2 ~/va-arg-void.c
$ ./a.out ; echo $?
3
...
Btw, note that va_arg (ap, void) has an effect on ap.
