| Message ID | 20200326194155.29107-1-natechancellor@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] kbuild: Enable -Wtautological-compare | expand |
On Fri, Mar 27, 2020 at 4:42 AM Nathan Chancellor <natechancellor@gmail.com> wrote: > > 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@gmail.com> > --- > > v1 -> v2: https://lore.kernel.org/lkml/20200219045423.54190-7-natechancellor@gmail.com/ > > * 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@gmail.com/ > * https://lore.kernel.org/lkml/20200220051011.26113-1-natechancellor@gmail.com/ OK, I will queue this up and send it to Linus in the second week of MW. I hope all warnings will be fixed by that time.
On Sun, Mar 29, 2020 at 08:31:26PM +0900, Masahiro Yamada wrote: > On Fri, Mar 27, 2020 at 4:42 AM Nathan Chancellor > <natechancellor@gmail.com> wrote: > > > > 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@gmail.com> > > --- > > > > v1 -> v2: https://lore.kernel.org/lkml/20200219045423.54190-7-natechancellor@gmail.com/ > > > > * 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@gmail.com/ > > * https://lore.kernel.org/lkml/20200220051011.26113-1-natechancellor@gmail.com/ > > > OK, I will queue this up and send it to Linus > in the second week of MW. > > I hope all warnings will be fixed by that time. Just a follow up, those two patches have been picked up and should be in this coming release: https://git.kernel.org/balbi/usb/c/58582220d2d34228e5a1e1585e41b735713988bb https://git.kernel.org/rostedt/linux-trace/c/bf2cbe044da275021b2de5917240411a19e5c50d As of next-20200331, with the former applied (because it is not there yet) along with this patch, I see no warnings on arm, arm64, x86_64 all{mod,yes}config. Cheers, Nathan
On Tue, Mar 31, 2020 at 3:11 AM Nathan Chancellor <natechancellor@gmail.com> wrote: > Just a follow up, those two patches have been picked up and should be in > this coming release: > > https://git.kernel.org/balbi/usb/c/58582220d2d34228e5a1e1585e41b735713988bb > https://git.kernel.org/rostedt/linux-trace/c/bf2cbe044da275021b2de5917240411a19e5c50d > > As of next-20200331, with the former applied (because it is not there > yet) along with this patch, I see no warnings on arm, arm64, x86_64 > all{mod,yes}config. kbuild test robot is testing more arch's than that with Clang so it may report if it finds more instances of that warning in those.
On Tue, Mar 31, 2020 at 09:02:19AM -0700, 'Nick Desaulniers' via Clang Built Linux wrote: > On Tue, Mar 31, 2020 at 3:11 AM Nathan Chancellor > <natechancellor@gmail.com> wrote: > > Just a follow up, those two patches have been picked up and should be in > > this coming release: > > > > https://git.kernel.org/balbi/usb/c/58582220d2d34228e5a1e1585e41b735713988bb > > https://git.kernel.org/rostedt/linux-trace/c/bf2cbe044da275021b2de5917240411a19e5c50d > > > > As of next-20200331, with the former applied (because it is not there > > yet) along with this patch, I see no warnings on arm, arm64, x86_64 > > all{mod,yes}config. > > kbuild test robot is testing more arch's than that with Clang so it > may report if it finds more instances of that warning in those. > > -- > Thanks, > ~Nick Desaulniers > I'll keep an eye out. Hopefully not too many more are lurking but we have definitely caught some bad behavior with this warning already so getting it turned on so that all CI systems can benefit from it is important. Cheers, Nathan
On Wed, Apr 1, 2020 at 4:26 AM Nathan Chancellor <natechancellor@gmail.com> wrote: > > On Tue, Mar 31, 2020 at 09:02:19AM -0700, 'Nick Desaulniers' via Clang Built Linux wrote: > > On Tue, Mar 31, 2020 at 3:11 AM Nathan Chancellor > > <natechancellor@gmail.com> wrote: > > > Just a follow up, those two patches have been picked up and should be in > > > this coming release: > > > > > > https://git.kernel.org/balbi/usb/c/58582220d2d34228e5a1e1585e41b735713988bb > > > https://git.kernel.org/rostedt/linux-trace/c/bf2cbe044da275021b2de5917240411a19e5c50d > > > > > > As of next-20200331, with the former applied (because it is not there > > > yet) along with this patch, I see no warnings on arm, arm64, x86_64 > > > all{mod,yes}config. > > > > kbuild test robot is testing more arch's than that with Clang so it > > may report if it finds more instances of that warning in those. > > > > -- > > Thanks, > > ~Nick Desaulniers > > > > I'll keep an eye out. Hopefully not too many more are lurking but we > have definitely caught some bad behavior with this warning already so > getting it turned on so that all CI systems can benefit from it is > important. > > Cheers, > Nathan Applied to linux-kbuild. I will rebase my branch during this MW, so the commit ID will be unstable. Please do not record it until it lands in Linus' tree.
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
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@gmail.com> --- v1 -> v2: https://lore.kernel.org/lkml/20200219045423.54190-7-natechancellor@gmail.com/ * 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@gmail.com/ * https://lore.kernel.org/lkml/20200220051011.26113-1-natechancellor@gmail.com/ Makefile | 2 -- scripts/Makefile.extrawarn | 1 + 2 files changed, 1 insertion(+), 2 deletions(-)