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Arnd Bergmann authored
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: 420c4495 ("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> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com> Link: https://lore.kernel.org/linux-mtd/20230719190045.4007391-1-arnd@kernel.org
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