On Wed, 25 Nov 2020, Nick Desaulniers wrote:
On Wed, Nov 25, 2020 at 1:33 PM Finn Thain firstname.lastname@example.org wrote:
Or do you think that a codebase can somehow satisfy multiple checkers and their divergent interpretations of the language spec?
Have we found any cases yet that are divergent? I don't think so.
You mean, aside from -Wimplicit-fallthrough? I'm glad you asked. How about -Wincompatible-pointer-types and -Wframe-larger-than?
All of the following files have been affected by divergent diagnostics produced by clang and gcc.
arch/arm64/include/asm/neon-intrinsics.h arch/powerpc/xmon/Makefile drivers/gpu/drm/i915/Makefile drivers/gpu/drm/i915/i915_utils.h drivers/staging/media/atomisp/pci/atomisp_subdev.c fs/ext4/super.c include/trace/events/qla.h net/mac80211/rate.c tools/lib/string.c tools/perf/util/setup.py tools/scripts/Makefile.include
And if I searched for 'smatch' or 'coverity' instead of 'clang' I'd probably find more divergence.
Here are some of the relevant commits.
0738c8b5915c7eaf1e6007b441008e8f3b460443 9c87156cce5a63735d1218f0096a65c50a7a32aa babaab2f473817f173a2d08e410c25abf5ed0f6b 065e5e559555e2f100bc95792a8ef1b609bbe130 93f56de259376d7e4fff2b2d104082e1fa66e237 6c4798d3f08b81c2c52936b10e0fa872590c96ae b7a313d84e853049062011d78cb04b6decd12f5c 093b75ef5995ea35d7f6bdb6c7b32a42a1999813
And before you object, "but -Wconstant-logical-operand is a clang-only warning! it can't be divergent with gcc!", consider that the special cases added to deal with clang-only warnings have to be removed when gcc catches up, which is more churn. Now multiply that by the number of checkers you care about.