This flag turns off several other warnings that would
be useful. Most notably -warn_unused_result is disabled.
All of the following warnings are currently disabled:
UnusedValue
|-UnusedComparison
|-warn_unused_comparison
|-UnusedResult
|-warn_unused_result
|-UnevaluatedExpression
|-PotentiallyEvaluatedExpression
|-warn_side_effects_typeid
|-warn_side_effects_unevaluated_context
|-warn_unused_expr
|-warn_unused_voidptr
|-warn_unused_container_subscript_expr
|-warn_unused_call
With this flag removed there are ~10 warnings.
Patches have been submitted for each of these warnings.
Reported-by: Nick Desaulniers <ndesaulniers@google.com>
Cc: clang-built-linux@googlegroups.com
Link: https://github.com/ClangBuiltLinux/linux/issues/520
Signed-off-by: Nathan Huckleberry <nhuck@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
This helps fine very dodgy behavior through both -Wuninitialized
(warning that a variable is always uninitialized) and
-Wsometimes-uninitialized (warning that a variable is sometimes
uninitialized, like GCC's -Wmaybe-uninitialized). These warnings
catch things that GCC doesn't such as:
https://lore.kernel.org/lkml/86649ee4-9794-77a3-502c-f4cd10019c36@lca.pw/
We very much want to catch these so turn this warning on so that CI is
aware of it.
Link: https://github.com/ClangBuiltLinux/linux/issues/381
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
It makes little sense to pass -Waggregate-return these days since large
part of the linux kernel rely on returning struct(s). For instance:
../include/linux/timekeeping.h: In function 'show_uptime':
../include/linux/ktime.h:91:34: error: function call has aggregate value [-Werror=aggregate-return]
#define ktime_to_timespec64(kt) ns_to_timespec64((kt))
^~~~~~~~~~~~~~~~~~~~~~
../include/linux/timekeeping.h:166:8: note: in expansion of macro 'ktime_to_timespec64'
*ts = ktime_to_timespec64(ktime_get_coarse_boottime());
Remove this warning from W=2 completely.
Signed-off-by: Mathieu Malaterre <malat@debian.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
We do not support old Clang versions. Upgrade your clang version
if any of these flags is unsupported.
Let's add all flags inside ifdef CONFIG_CC_IS_CLANG unconditionally.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Sedat Dilek <sedat.dilek@gmail.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
These flags are documented in the GCC 4.6 manual, and recognized by
Clang as well. Let's rip off the cc-option / cc-disable-warning switches.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Evaluating cc-name invokes the compiler every time even when you are
not compiling anything, like 'make help'. This is not efficient.
The compiler type has been already detected in the Kconfig stage.
Use CONFIG_CC_IS_CLANG, instead.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Acked-by: Paul Burton <paul.burton@mips.com> (MIPS)
Acked-by: Joel Stanley <joel@jms.id.au>
This is an effort to disentangle the include/linux/compiler*.h headers
and bring them up to date.
The main idea behind the series is to use feature checking macros
(i.e. __has_attribute) instead of compiler version checks (e.g. GCC_VERSION),
which are compiler-agnostic (so they can be shared, reducing the size
of compiler-specific headers) and version-agnostic.
Other related improvements have been performed in the headers as well,
which on top of the use of __has_attribute it has amounted to a significant
simplification of these headers (e.g. GCC_VERSION is now only guarding
a few non-attribute macros).
This series should also help the efforts to support compiling the kernel
with clang and icc. A fair amount of documentation and comments have also
been added, clarified or removed; and the headers are now more readable,
which should help kernel developers in general.
The series was triggered due to the move to gcc >= 4.6. In turn, this series
has also triggered Sparse to gain the ability to recognize __has_attribute
on its own.
Finally, the __nonstring variable attribute series has been also applied
on top; plus two related patches from Nick Desaulniers for unreachable()
that came a bit afterwards.
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Merge tag 'compiler-attributes-for-linus-4.20-rc1' of https://github.com/ojeda/linux
Pull compiler attribute updates from Miguel Ojeda:
"This is an effort to disentangle the include/linux/compiler*.h headers
and bring them up to date.
The main idea behind the series is to use feature checking macros
(i.e. __has_attribute) instead of compiler version checks (e.g.
GCC_VERSION), which are compiler-agnostic (so they can be shared,
reducing the size of compiler-specific headers) and version-agnostic.
Other related improvements have been performed in the headers as well,
which on top of the use of __has_attribute it has amounted to a
significant simplification of these headers (e.g. GCC_VERSION is now
only guarding a few non-attribute macros).
This series should also help the efforts to support compiling the
kernel with clang and icc. A fair amount of documentation and comments
have also been added, clarified or removed; and the headers are now
more readable, which should help kernel developers in general.
The series was triggered due to the move to gcc >= 4.6. In turn, this
series has also triggered Sparse to gain the ability to recognize
__has_attribute on its own.
Finally, the __nonstring variable attribute series has been also
applied on top; plus two related patches from Nick Desaulniers for
unreachable() that came a bit afterwards"
* tag 'compiler-attributes-for-linus-4.20-rc1' of https://github.com/ojeda/linux:
compiler-gcc: remove comment about gcc 4.5 from unreachable()
compiler.h: update definition of unreachable()
Compiler Attributes: ext4: remove local __nonstring definition
Compiler Attributes: auxdisplay: panel: use __nonstring
Compiler Attributes: enable -Wstringop-truncation on W=1 (gcc >= 8)
Compiler Attributes: add support for __nonstring (gcc >= 8)
Compiler Attributes: add MAINTAINERS entry
Compiler Attributes: add Doc/process/programming-language.rst
Compiler Attributes: remove uses of __attribute__ from compiler.h
Compiler Attributes: KENTRY used twice the "used" attribute
Compiler Attributes: use feature checks instead of version checks
Compiler Attributes: add missing SPDX ID in compiler_types.h
Compiler Attributes: remove unneeded sparse (__CHECKER__) tests
Compiler Attributes: homogenize __must_be_array
Compiler Attributes: remove unneeded tests
Compiler Attributes: always use the extra-underscores syntax
Compiler Attributes: remove unused attributes
Commit 217c3e0196 ("disable stringop truncation warnings for now")
disabled -Wstringop-truncation since it was too noisy.
Having __nonstring available allows us to let GCC know that a string
is not meant to be NUL-terminated, which helps suppressing some
-Wstringop-truncation warnings.
Note that using __nonstring actually triggers other warnings
(-Wstringop-overflow, which is on by default) which may be real
problems. Therefore, cleaning up -Wstringop-truncation warnings
also buys us the ability to uncover further potential problems.
To encourage the use of __nonstring, we put the warning back at W=1.
In the future, if we end up with a fairly warning-free tree,
we might want to enable it by default.
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # on top of v4.19-rc5, clang 7
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
gcc-8 reports many -Wpacked-not-aligned warnings. The below are some
examples.
./include/linux/ceph/msgr.h:67:1: warning: alignment 1 of 'struct
ceph_entity_addr' is less than 8 [-Wpacked-not-aligned]
} __attribute__ ((packed));
./include/linux/ceph/msgr.h:67:1: warning: alignment 1 of 'struct
ceph_entity_addr' is less than 8 [-Wpacked-not-aligned]
} __attribute__ ((packed));
./include/linux/ceph/msgr.h:67:1: warning: alignment 1 of 'struct
ceph_entity_addr' is less than 8 [-Wpacked-not-aligned]
} __attribute__ ((packed));
This patch suppresses this kind of warnings for default setting.
Signed-off-by: Xiongfeng Wang <xiongfeng.wang@linaro.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.
By default all files without license information are under the default
license of the kernel, which is GPL version 2.
Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.
This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.
How this work was done:
Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,
Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.
The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.
The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.
Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).
All documentation files were explicitly excluded.
The following heuristics were used to determine which SPDX license
identifiers to apply.
- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.
For non */uapi/* files that summary was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139
and resulted in the first patch in this series.
If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930
and resulted in the second patch in this series.
- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:
SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1
and that resulted in the third patch in this series.
- when the two scanners agreed on the detected license(s), that became
the concluded license(s).
- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.
- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).
- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.
- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.
In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.
Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.
Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.
In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.
Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct
This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.
These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
We have lots of dead defines and macros in drivers, lets offer users a way
to detect and eventually remove them.
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Since commit c3f0d0bc5b ("kbuild, LLVMLinux: Add -Werror to
cc-option to support clang"), cc-option and friends work nicely
for clang.
However, -Wno-unknown-warning-option makes clang happy with any
unknown warning options even if -Werror is specified.
Once -Wno-unknown-warning-option is added, any succeeding call of
cc-disable-warning is evaluated positive, then unknown warning
options are accepted. This should be dropped.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Previously the warnings were added back at the W=1 level and above, this
now turns them on again by default, assuming that we have addressed all
warnings and again have a clean build for v4.10.
I found a number of new warnings in linux-next already and submitted
bugfixes for those. Hopefully they are caught by the 0day builder in
the future as soon as this patch is merged.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Traditionally, we have always had warnings about uninitialized variables
enabled, as this is part of -Wall, and generally a good idea [1], but it
also always produced false positives, mainly because this is a variation
of the halting problem and provably impossible to get right in all cases
[2].
Various people have identified cases that are particularly bad for false
positives, and in commit e74fc973b6 ("Turn off -Wmaybe-uninitialized
when building with -Os"), I turned off the warning for any build that
was done with CC_OPTIMIZE_FOR_SIZE. This drastically reduced the number
of false positive warnings in the default build but unfortunately had
the side effect of turning the warning off completely in 'allmodconfig'
builds, which in turn led to a lot of warnings (both actual bugs, and
remaining false positives) to go in unnoticed.
With commit 877417e6ff ("Kbuild: change CC_OPTIMIZE_FOR_SIZE
definition") enabled the warning again for allmodconfig builds in v4.7
and in v4.8-rc1, I had finally managed to address all warnings I get in
an ARM allmodconfig build and most other maybe-uninitialized warnings
for ARM randconfig builds.
However, commit 6e8d666e92 ("Disable "maybe-uninitialized" warning
globally") was merged at the same time and disabled it completely for
all configurations, because of false-positive warnings on x86 that I had
not addressed until then. This caused a lot of actual bugs to get
merged into mainline, and I sent several dozen patches for these during
the v4.9 development cycle. Most of these are actual bugs, some are for
correct code that is safe because it is only called under external
constraints that make it impossible to run into the case that gcc sees,
and in a few cases gcc is just stupid and finds something that can
obviously never happen.
I have now done a few thousand randconfig builds on x86 and collected
all patches that I needed to address every single warning I got (I can
provide the combined patch for the other warnings if anyone is
interested), so I hope we can get the warning back and let people catch
the actual bugs earlier.
This reverts the change to disable the warning completely and for now
brings it back at the "make W=1" level, so we can get it merged into
mainline without introducing false positives. A follow-up patch enables
it on all levels unless some configuration option turns it off because
of false-positives.
Link: https://rusty.ozlabs.org/?p=232 [1]
Link: https://gcc.gnu.org/wiki/Better_Uninitialized_Warnings [2]
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
gcc-6 started warning by default about variables that are not
used anywhere and that are marked 'const', generating many
false positives in an allmodconfig build, e.g.:
arch/arm/mach-davinci/board-da830-evm.c:282:20: warning: 'da830_evm_emif25_pins' defined but not used [-Wunused-const-variable=]
arch/arm/plat-omap/dmtimer.c:958:34: warning: 'omap_timer_match' defined but not used [-Wunused-const-variable=]
drivers/bluetooth/hci_bcm.c:625:39: warning: 'acpi_bcm_default_gpios' defined but not used [-Wunused-const-variable=]
drivers/char/hw_random/omap-rng.c:92:18: warning: 'reg_map_omap4' defined but not used [-Wunused-const-variable=]
drivers/devfreq/exynos/exynos5_bus.c:381:32: warning: 'exynos5_busfreq_int_pm' defined but not used [-Wunused-const-variable=]
drivers/dma/mv_xor.c:1139:34: warning: 'mv_xor_dt_ids' defined but not used [-Wunused-const-variable=]
This is similar to the existing -Wunused-but-set-variable warning
that was added in an earlier release and that we disable by default
now and only enable when W=1 is set, so it makes sense to do
the same here. Once we have eliminated the majority of the
warnings for both, we can put them back into the default list.
We probably want this in backport kernels as well, to allow building
them with gcc-6 without introducing extra warnings.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Lee Jones <lee.jones@linaro.org>
Cc: stable@vger.kernel.org
Signed-off-by: Michal Marek <mmarek@suse.com>
Ideally, a kernel compile with W=1 enabled should complete cleanly;
however, when we run one currently we are presented with ~25k warnings.
'sign-compare' accounts for ~22k of those ~25k.
In this patch we're demoting 'sign-compare' warnings to W=2, with a view
to fixing the remaining 3k W=1 warnings required for a clean build.
Arnd adds:
"As per our discussion, I'd add that this was inadvertedly introduced
by Behan when he moved the clang specific warnings into an ifdef block
and did not notice that -Wsign-compare was interpreted by both gcc
and clang.
Earlier, it was introduced in just the same way by Jan-Simon as part
of 3d3d6b8474 ("kbuild: LLVMLinux: Adapt warnings for compilation
with clang")."
Acked-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 26ea6bb1fe ("kbuild, LLVMLinux: Supress warnings unless W=1-3")
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Michal Marek <mmarek@suse.com>
We cannot detect clang before including the arch Makefile, because that
can set the default cross compiler. We also cannot detect clang after
including the arch Makefile, because powerpc wants to know about clang.
Solve this by using an deferred variable. This costs us a few shell
invocations, but this is only a constant number.
Reported-by: Behan Webster <behanw@converseincode.com>
Reported-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michal Marek <mmarek@suse.com>
clang has more warnings enabled by default. Turn them off unless W is
set. This patch fixes a logic bug where warnings in clang were disabled
when W was set.
Signed-off-by: Behan Webster <behanw@converseincode.com>
Signed-off-by: Jan-Simon Möller <dl9pf@gmx.de>
Signed-off-by: Mark Charlebois <charlebm@gmail.com>
Cc: bp@alien8.de
Signed-off-by: Michal Marek <mmarek@suse.cz>
W=... provides extra gcc checks.
Having such code in scripts/Makefile.build results in the same flags
being added to KBUILD_CFLAGS multiple times becuase
scripts/Makefile.build is invoked every time Kbuild descends into
the subdirectories.
Since the top Makefile is already too cluttered, this commit moves
all of extra gcc check stuff to a new file scripts/Makefile.extrawarn,
which is included from the top Makefile.
Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
CC: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Michal Marek <mmarek@suse.cz>
