GNU bug report logs - #9262
test.c runs afoul of GCC 4.6.1 bug if --enable-gcc-warnings

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: bug-coreutils <at> gnu.org
Subject: test.c runs afoul of GCC 4.6.1 bug if --enable-gcc-warnings
Date: Mon, 08 Aug 2011 11:55:04 -0700

I'm running into a problem with GCC 4.6.1 x86-64 when
compiling coreutils (latest git version), configured
with --enable-gcc-warnings.  A bogus warning is generated,
causing "make" to fail.  The warning is "function might be
candidate for attribute 'pure' if it is known to return
normally [-Wsuggest-attribute=pure]", and it points to the
"advance" function in test.c.  The warning is also generated
for lbracket.c, which includes test.c.

This is due to a GCC bug that has just been confirmed; see
<http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50021>.

For now I'm leaving this alone, but I thought I'd give
others a heads-up.  The coreutils code is pretty
crufty but on the other hand I dislike modifying code just
to work around bugs in static checkers.

Message #8 received at 9262 <at> debbugs.gnu.org (full text, mbox):

From: Jim Meyering <jim <at> meyering.net>
To: Paul Eggert <eggert <at> cs.ucla.edu>
Cc: 9262 <at> debbugs.gnu.org
Subject: Re: bug#9262: test.c runs afoul of GCC 4.6.1 bug if
	--enable-gcc-warnings
Date: Mon, 08 Aug 2011 23:10:47 +0200

Paul Eggert wrote:
> I'm running into a problem with GCC 4.6.1 x86-64 when
> compiling coreutils (latest git version), configured
> with --enable-gcc-warnings.  A bogus warning is generated,
> causing "make" to fail.  The warning is "function might be
> candidate for attribute 'pure' if it is known to return
> normally [-Wsuggest-attribute=pure]", and it points to the
> "advance" function in test.c.  The warning is also generated
> for lbracket.c, which includes test.c.
>
> This is due to a GCC bug that has just been confirmed; see
> <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50021>.
>
> For now I'm leaving this alone, but I thought I'd give
> others a heads-up.  The coreutils code is pretty
> crufty but on the other hand I dislike modifying code just
> to work around bugs in static checkers.

Thanks for the heads up.
This came up in July:

    http://thread.gmane.org/gmane.comp.gnu.coreutils.general/1399

This is why I now build with gcc-4.7.x.
With it, I no longer get that invalid warning.

Ideally, configure would check for the buggy compiler
and disable the offending option when found.

If you're not going to work on that, what do you
think about sending a message to control <at> debbugs.gnu.org
with this in the body?

tags 9262 + notabug
close 9262

Since this isn't a bug in coreutils, and I'm trying to close
issues we're not likely to work on.

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