Currently, we disable -Wtautological-compare, which in turn disables a bunch of more specific tautological comparison warnings that are useful for the kernel such as -Wtautological-bitwise-compare. See clang's documentation below for the other warnings that are suppressed by -Wtautological-compare. Now that all of the major/noisy warnings have been fixed, enable -Wtautological-compare so that more issues can be caught at build time by various continuous integration setups. -Wtautological-constant-out-of-range-compare is kept disabled under a normal build but visible at W=1 because there are places in the kernel where a constant or variable size can change based on the kernel configuration. These are not fixed in a clean/concise way and the ones I have audited so far appear to be harmless. It is not a subgroup but rather just one warning so we do not lose out on much coverage by default. Link: https://github.com/ClangBuiltLinux/linux/issues/488 Link: http://releases.llvm.org/10.0.0/tools/clang/docs/DiagnosticsReference.html#wtautological-compare Link: https://bugs.llvm.org/show_bug.cgi?id=42666 Signed-off-by: Nathan Chancellor <natechancellor@xxxxxxxxx> --- v1 -> v2: https://lore.kernel.org/lkml/20200219045423.54190-7-natechancellor@xxxxxxxxx/ * Expand commit message a bit by adding more reasoning behind change. * Disable -Wtautological-constant-out-of-range-compare under a normal build but allow it to show up at W=1 for easy auditing. I hope this can be accepted for 5.7. There are two warnings that I see still across a bunch of allyesconfig/allmodconfig builds that have patches sent but not accepted. I will ping them today. * https://lore.kernel.org/lkml/20191023002014.22571-1-natechancellor@xxxxxxxxx/ * https://lore.kernel.org/lkml/20200220051011.26113-1-natechancellor@xxxxxxxxx/ Makefile | 2 -- scripts/Makefile.extrawarn | 1 + 2 files changed, 1 insertion(+), 2 deletions(-) diff --git a/Makefile b/Makefile index db442a9ee6b2..05f9f50dda3e 100644 --- a/Makefile +++ b/Makefile @@ -746,8 +746,6 @@ ifdef CONFIG_CC_IS_CLANG KBUILD_CPPFLAGS += -Qunused-arguments KBUILD_CFLAGS += -Wno-format-invalid-specifier KBUILD_CFLAGS += -Wno-gnu -# Quiet clang warning: comparison of unsigned expression < 0 is always false -KBUILD_CFLAGS += -Wno-tautological-compare # CLANG uses a _MergedGlobals as optimization, but this breaks modpost, as the # source of a reference will be _MergedGlobals and not on of the whitelisted names. # See modpost pattern 2 diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn index ca08f2fe7c34..4aea7cf71d11 100644 --- a/scripts/Makefile.extrawarn +++ b/scripts/Makefile.extrawarn @@ -49,6 +49,7 @@ KBUILD_CFLAGS += -Wno-format KBUILD_CFLAGS += -Wno-sign-compare KBUILD_CFLAGS += -Wno-format-zero-length KBUILD_CFLAGS += $(call cc-disable-warning, pointer-to-enum-cast) +KBUILD_CFLAGS += -Wno-tautological-constant-out-of-range-compare endif endif -- 2.26.0
