Messages in this thread | | | From | Miquel Raynal <> | Subject | Re: [PATCH] mtd: spi-nor: avoid holes in struct spi_mem_op | Date | Thu, 27 Jul 2023 17:17:38 +0200 |
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On Wed, 2023-07-19 at 19:00:25 UTC, Arnd Bergmann wrote: > From: Arnd Bergmann <arnd@arndb.de> > > gcc gets confused when -ftrivial-auto-var-init=pattern is used on sparse > bit fields such as 'struct spi_mem_op', which caused the previous false > positive warning about an uninitialized variable: > > drivers/mtd/spi-nor/spansion.c: error: 'op' is used uninitialized [-Werror=uninitialized] > > In fact, the variable is fully initialized and gcc does not see it being > used, so the warning is entirely bogus. The problem appears to be > a misoptimization in the initialization of single bit fields when the > rest of the bytes are not initialized. > > A previous workaround added another initialization, which ended up > shutting up the warning in spansion.c, though it apparently still happens > in other files as reported by Peter Foley in the gcc bugzilla. The > workaround of adding a fake initialization seems particularly bad > because it would set values that can never be correct but prevent the > compiler from warning about actually missing initializations. > > Revert the broken workaround and instead pad the structure to only > have bitfields that add up to full bytes, which should avoid this > behavior in all drivers. > > I also filed a new bug against gcc with what I found, so this can > hopefully be addressed in future gcc releases. At the moment, only > gcc-12 and gcc-13 are affected. > > Cc: Peter Foley <pefoley2@pefoley.com> > Cc: Pedro Falcato <pedro.falcato@gmail.com> > Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110743 > Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108402 > Link: https://godbolt.org/z/efMMsG1Kx > Fixes: 420c4495b5e56 ("mtd: spi-nor: spansion: make sure local struct does not contain garbage") > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > Acked-by: Mark Brown <broonie@kernel.org> > Acked-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Applied to https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git mtd/fixes, thanks.
Miquel
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