[Bug c/84229] A valid code rejected with -flto

[hubicka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84229

--- Comment #4 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
For reference, this is open implementation from Jessie version of glibc that
trigeers the issue
__fortify_function int                                                          
open (const char *__path, int __oflag, ...)                                     
{                                                                               
  if (__va_arg_pack_len () > 1)                                                 
    __open_too_many_args ();                                                    

  if (__builtin_constant_p (__oflag))                                           
    {                                                                           
      if (__OPEN_NEEDS_MODE (__oflag) && __va_arg_pack_len () < 1)              
        {                                                                       
          __open_missing_mode ();                                               
          return __open_2 (__path, __oflag);                                    
        }                                                                       
      return __open_alias (__path, __oflag, __va_arg_pack ());                  
    }                                                                           

  if (__va_arg_pack_len () < 1)                                                 
    return __open_2 (__path, __oflag);                                          

  return __open_alias (__path, __oflag, __va_arg_pack ());                      
}                                                                               

I am testing patch to prevent signature changes here. I suppose that those
functions are meant to be inlined and thus function signature changes are not
that important.

Still it would be nice to error on use in nonvariadic functions.