gcc/testsuite/c-c++-common/Wvarargs-2.c

/*
   { dg-options "-Wno-varargs" }
   { dg-do compile }
 */

#include <stdarg.h>

void
err (int a)
{
  va_list vp;
  va_start (vp, a); // { dg-error "used in function with fixed arguments" }
}

void
foo0 (int a, int b, ...)
{
    va_list vp;
    /* 'a' is not the last argument of the enclosing function, but
       don't warn because we are ignoring -Wvarargs.  */
    va_start (vp, a);
    va_end (vp);
}

void
foo1 (int a, register int b, ...)	// { dg-warning "ISO C\\+\\+17 does not allow 'register' storage class specifier" "" { target c++17 } }
{
    va_list vp;
    /* 'b' is declared with register storage, but don't warn
       because we are ignoring -Wvarargs.  */
    va_start (vp, b);
    va_end (vp);
}