GCC Bugzilla Bug 36513

Compiling the following code with gcc-4.3 -Wlogical-op -O1

int main ()
{
  char *s, t;
  strchr (s, t);
}

leads to this warning:
test2.c: In function ‘main’:
test2.c:7: warning: logical ‘&&’ with non-zero constant will always evaluate as
true

This is because libc defines strchr to a macro in bits/string.h. It looks to me
like gcc should not warn about optimizations like __builtin_constant_p
optimizations as those are diectly targeted at being optimized out.

Well also I think glibc should not need to optimise strchr really and let the
compiler do it.

We need a reproducible preprocessed testcase. 
See http://gcc.gnu.org/bugs.html#detailed

Benjamin, note that -Wlogical-op will be enabled by -Wextra in GCC 4.5. 

I am willing to give it a try to fix this before 4.5 is released. However, I
cannot reproduce this problem, so please, provide a preprocessed testcase.

I cannot reproduce this anymore with gcc 4.3.3 from Ubuntu 9.04, so I consider
this fixed.

FIXED per previous comment.

I get this error when building swfdec with gcc 4.4.2 on Fedora 12.

Also tried the simple test case described in the bug description, although it
needs to add #include <string.h> at the top.

The warning is still there.

Created an attachment (id=19148) [edit]
Preprocessed source file

Created a preprocessed source file producing the warning.

(In reply to comment #6)
> I get this error when building swfdec with gcc 4.4.2 on Fedora 12.

It is a warning that you need to enable with -Wlogical-op explicitly.

I cannot reproduce the preprocessed testcase with GCC 4.5 rev 150311. If you
can reproduce it with a more recent revision, please let us know. Since this is
not a regression (it was a new warning in GCC 4.3), I don't think anyone will
try to fix it in GCC 4.3.x or GCC 4.4.x.

Now that we have a preprocessed testcase, I will try to reduce it and add it to
the testsuite to avoid regressing here.

Now that we have a preprocessed testcase, I will try to reduce it and add it to
the testsuite to avoid regressing here.