Selectiv on/off-turning of warnings

[Joern Rennecke]

> I think there would be a long debate whether it is reasonable. For one
> thing, some people claim that #pragma is not reasonable. Since the
> standard says a compiler can do anything it wants when it sees a
> #pragma, I believe some version of gcc used to invoke Emacs when it
> saw a #pragma :-)

The code is still in cccp.c, although it is #ifdefed out these days:

#if 0
/* This was a fun hack, but #pragma seems to start to be useful.
   By failing to recognize it, we pass it through unchanged to cc1.  */

/* The behavior of the #pragma directive is implementation defined.
   this implementation defines it as follows.  */

static int
do_pragma ()
{
  close (0);
  if (open ("/dev/tty", O_RDONLY, 0666) != 0)
    goto nope;
  close (1);
  if (open ("/dev/tty", O_WRONLY, 0666) != 1)
    goto nope;
  execl ("/usr/games/hack", "#pragma", 0);
  execl ("/usr/games/rogue", "#pragma", 0);
  execl ("/usr/new/emacs", "-f", "hanoi", "9", "-kill", 0);
  execl ("/usr/local/emacs", "-f", "hanoi", "9", "-kill", 0);
nope:
  fatal ("You are in a maze of twisty compiler features, all different");
}
#endif