[Bug testsuite/108675] FAIL: gcc.c-torture/execute/builtins/*printf.c when stdio.h includes definitions

["zack+srcbugz at owlfolio dot org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108675

--- Comment #6 from Zack Weinberg <zack+srcbugz at owlfolio dot org> ---
Note that what you (mingw) have in this header is a pretty serious
anti-optimization.  Functions that call __builtin_va_start cannot be inlined
under any circumstances whatsoever (try tagging it
__attribute__((always_inline)) and see what happens) so you're emitting a
redundant copy of this function in every translation unit that calls fprintf,
and you're not getting any actual codegen improvement in exchange.

You _could_ do like glibc bits/stdio2.h

__mingw_ovr
__attribute__((__format__ (gnu_printf, 1, 2))) __MINGW_ATTRIB_NONNULL(1)
int printf (const char *__format, ...)
{
  return __mingw_fprintf(stdout, __format, __builtin_va_arg_pack());
}

but this doesn't let you synthesize a direct call to __mingw_vfprintf.

I'd recommend scrapping the entire mess, abandoning the idea of getting direct
calls to v*printf/v*scanf, and using asm() symbol renaming to add the __mingw_
prefix.  That should also avoid stepping on the GCC testcases' toes.