Re: coreutils and GCC -fanalyzer

[Pádraig Brady]

On 21/05/2020 01:49, Paul Eggert wrote:
> The coreutils patch installed on May 10 to pacify GCC 10 -fanalyzer
> caused problems when I built coreutils with GCC 10.1.0. Some of the
> newly-introduced pragmas generated diagnostics, and the pragmas didn't
> seem to be needed in GCC 10.1.0 anyway. As 10.1.0 is the first public
> release of GCC 10 I doubt whether we need to support GCC internal
> versions (before GCC 10.1.0) that had problems with -fanalyze.
>
> Also, the patch seems to have introduced a bug in tsort.c due to a typo.
> Less importantly, it introduced some new overhead in dd.c's non-lint
> code (to save some pointers in global variables) that isn't needed and
> might cause problems with other static checkers.
>
> To try to fix all this I installed the attached patches.
>
> At some point I hope this GCC 10 stuff settles down, as GCC 10.1.0 still
> has bugs in the -fanalyzer area (e.g., see GCC bugs 93644, 95044, 95072)
> and we don't want these bugs to adversely affect coreutils etc.

Previously I was testing with the first Fedora 32 (public) GCC:
  gcc (GCC) 10.0.1 20200328 (Red Hat 10.0.1-0.11)

After just upgrading:
  sudo dnf upgrade --advisory=FEDORA-2020-2c6c85202d
  gcc (GCC) 10.1.1 20200507 (Red Hat 10.1.1-1)

I can confirm that the comm.c pragma causes issues for gcc 10.1
  src/comm.c:21:33: error: unknown option after '#pragma GCC diagnostic' kind 
[-Werror=pragmas]
   21 | # pragma GCC diagnostic ignored "-Wanalyzer-use-of-uninitialized-value"

The good news is that this is no longer needed to suppress
-fanalyzer warnings, so we can just remove it.

The other pragmas are still needed though to suppress -fanalyzer warnings.

Also the dd change has minimal overhead and makes valgrind output cleaner.

Good spot on the misplaced #endif in tsort.

I would have went for the smaller attached change,
to avoid the -fanalyzer failures?

thanks for the fixes,
Pádraig

coreutils-gcc-fanalyze-fix.patch
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