Re: optimization/4130: gcc 3.0 -O2 and printf optimization

[Richard Henderson <rth@redhat.com>]

The following reply was made to PR optimization/4130; it has been noted by GNATS.

From: Richard Henderson <rth@redhat.com>
To: Richard Kettlewell <rjk@greenend.org.uk>
Cc: gcc-bugs@gcc.gnu.org, gcc-gnats@gcc.gnu.org
Subject: Re: optimization/4130: gcc 3.0 -O2 and printf optimization
Date: Wed, 3 Apr 2002 10:23:13 -0800

 ----- Forwarded message from "Kaveh R. Ghazi" <ghazi@caip.rutgers.edu> -----
 
 In addition, the builtin printf optimization (really all stdio
 builtins) are not performed if the return value is examined.  This is
 specifically to address the particular problem of how these functions
 all differently handle return values and errno.  So if you're actually
 going to examine errno, you should do it as I've done below.  (Code
 rewritten from the example provided in the PR):
 
  > #include <stdio.h>
  > #include <errno.h>
  > int main(void)
  > {
  >   if (printf ("foo\xC0\n") < 0)
  >     perror("printf");
  >   return 0;
  > }
 
 or something similar.  In this case, the optimization to `puts' is not
 done.