| Message ID | 20180619201458.4559-2-paul.burton@mips.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi. 2018-06-20 5:14 GMT+09:00 Paul Burton <paul.burton@mips.com>: > From: Arnd Bergmann <arnd@arndb.de> > > I have occasionally run into a situation where it would make sense to > control a compiler warning from a source file rather than doing so from > a Makefile using the $(cc-disable-warning, ...) or $(cc-option, ...) > helpers. > > The approach here is similar to what glibc uses, using __diag() and > related macros to encapsulate a _Pragma("GCC diagnostic ...") statement > that gets turned into the respective "#pragma GCC diagnostic ..." by > the preprocessor when the macro gets expanded. > > Like glibc, I also have an argument to pass the affected compiler > version, but decided to actually evaluate that one. For now, this > supports GCC_4_6, GCC_4_7, GCC_4_8, GCC_4_9, GCC_5, GCC_6, GCC_7, > GCC_8 and GCC_9. Adding support for CLANG_5 and other interesting > versions is straightforward here. GNU compilers starting with gcc-4.2 > could support it in principle, but "#pragma GCC diagnostic push" > was only added in gcc-4.6, so it seems simpler to not deal with those > at all. The same versions show a large number of warnings already, > so it seems easier to just leave it at that and not do a more > fine-grained control for them. > > The use cases I found so far include: > > - turning off the gcc-8 -Wattribute-alias warning inside of the > SYSCALL_DEFINEx() macro without having to do it globally. > > - Reducing the build time for a simple re-make after a change, > once we move the warnings from ./Makefile and > ./scripts/Makefile.extrawarn into linux/compiler.h > > - More control over the warnings based on other configurations, > using preprocessor syntax instead of Makefile syntax. This should make > it easier for the average developer to understand and change things. > > - Adding an easy way to turn the W=1 option on unconditionally > for a subdirectory or a specific file. This has been requested > by several developers in the past that want to have their subsystems > W=1 clean. > > - Integrating clang better into the build systems. Clang supports > more warnings than GCC, and we probably want to classify them > as default, W=1, W=2 etc, but there are cases in which the > warnings should be classified differently due to excessive false > positives from one or the other compiler. > > - Adding a way to turn the default warnings into errors (e.g. using > a new "make E=0" tag) while not also turning the W=1 warnings into > errors. > > This patch for now just adds the minimal infrastructure in order to > do the first of the list above. As the #pragma GCC diagnostic > takes precedence over command line options, the next step would be > to convert a lot of the individual Makefiles that set nonstandard > options to use __diag() instead. > > [paul.burton@mips.com: > - Rebase atop current master. > - Add __diag_GCC, or more generally __diag_<compiler>, abstraction to > avoid code outside of linux/compiler-gcc.h needing to duplicate > knowledge about different GCC versions. > - Add a comment argument to __diag_{ignore,warn,error} which isn't > used in the expansion of the macros but serves to push people to > document the reason for using them - per feedback from Kees Cook. > - Translate severity to GCC-specific pragmas in linux/compiler-gcc.h > rather than using GCC-specific in linux/compiler_types.h. > - Drop all but GCC 8 macros, since we only need to define macros for > versions that we need to introduce pragmas for, and as of this > series that's just GCC 8. > - Capitalize comments in linux/compiler-gcc.h to match the style of > the rest of the file. > - Line up macro definitions with tabs in linux/compiler-gcc.h.] > > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > Signed-off-by: Paul Burton <paul.burton@mips.com> > Tested-by: Christophe Leroy <christophe.leroy@c-s.fr> > Tested-by: Stafford Horne <shorne@gmail.com> > Cc: Michal Marek <michal.lkml@markovi.net> > Cc: Masahiro Yamada <yamada.masahiro@socionext.com> > Cc: Douglas Anderson <dianders@chromium.org> > Cc: Al Viro <viro@zeniv.linux.org.uk> > Cc: Heiko Carstens <heiko.carstens@de.ibm.com> > Cc: Mauro Carvalho Chehab <mchehab@kernel.org> > Cc: Matthew Wilcox <matthew@wil.cx> > Cc: Matthias Kaehlcke <mka@chromium.org> > Cc: Arnd Bergmann <arnd@arndb.de> > Cc: Ingo Molnar <mingo@kernel.org> > Cc: Josh Poimboeuf <jpoimboe@redhat.com> > Cc: Kees Cook <keescook@chromium.org> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Gideon Israel Dsouza <gidisrael@gmail.com> > Cc: Christophe Leroy <christophe.leroy@c-s.fr> > Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> > Cc: Paul Mackerras <paulus@samba.org> > Cc: Michael Ellerman <mpe@ellerman.id.au> > Cc: Stafford Horne <shorne@gmail.com> > Cc: Khem Raj <raj.khem@gmail.com> > Cc: He Zhe <zhe.he@windriver.com> > Cc: linux-kbuild@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > Cc: linux-mips@linux-mips.org > Cc: linuxppc-dev@lists.ozlabs.org > > --- > > Changes in v2: > - Add version argument to fallback __diag_GCC definition. > - Translate severity from generic ignore,warn,error to GCC-specific > pragma content ignored,warning,error in linux/compiler-gcc.h in order > to keep linux/compiler_types.h generic per feedback from Masahiro > Yamada. > - Drop all but GCC 8 macros, since we only need to define macros for > versions that we need to introduce pragmas for, and as of this series > that's just GCC 8. > - Capitalize comments in linux/compiler-gcc.h to match the style of the > rest of the file. > - Line up macro definitions with tabs in linux/compiler-gcc.h. > > include/linux/compiler-gcc.h | 27 +++++++++++++++++++++++++++ > include/linux/compiler_types.h | 18 ++++++++++++++++++ > 2 files changed, 45 insertions(+) > > diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h > index f1a7492a5cc8..5067a90af9c3 100644 > --- a/include/linux/compiler-gcc.h > +++ b/include/linux/compiler-gcc.h > @@ -347,3 +347,30 @@ > #if GCC_VERSION >= 50100 > #define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1 > #endif > + > +/* > + * Turn individual warnings and errors on and off locally, depending > + * on version. > + */ > +#define __diag_GCC(version, severity, s) \ > + __diag_GCC_ ## version(__diag_GCC_ ## severity s) > + > +/* Severity used in pragma directives */ > +#define __diag_GCC_ignore ignored > +#define __diag_GCC_warn warning > +#define __diag_GCC_error error > + > +/* Compilers before gcc-4.6 do not understand "#pragma GCC diagnostic push" */ > +#if GCC_VERSION >= 40600 > +#define __diag_str1(s) #s > +#define __diag_str(s) __diag_str1(s) > +#define __diag(s) _Pragma(__diag_str(GCC diagnostic s)) > +#else > +#define __diag(s) You can omit the #else here because it is covered by compiler_types.h > +#endif > + > +#if GCC_VERSION >= 80000 > +#define __diag_GCC_8(s) __diag(s) > +#else > +#define __diag_GCC_8(s) > +#endif > diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h > index 6b79a9bba9a7..a8ba6b04152c 100644 > --- a/include/linux/compiler_types.h > +++ b/include/linux/compiler_types.h > @@ -271,4 +271,22 @@ struct ftrace_likely_data { > # define __native_word(t) (sizeof(t) == sizeof(char) || sizeof(t) == sizeof(short) || sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long)) > #endif > > +#ifndef __diag > +#define __diag(string) > +#endif > + > +#ifndef __diag_GCC > +#define __diag_GCC(version, severity, string) > +#endif > + > +#define __diag_push() __diag(push) > +#define __diag_pop() __diag(pop) > + > +#define __diag_ignore(compiler, version, option, comment) \ > + __diag_ ## compiler(version, ignore, option) > +#define __diag_warn(compiler, version, option, comment) \ > + __diag_ ## compiler(version, warn, option) > +#define __diag_error(compiler, version, option, comment) \ > + __diag_ ## compiler(version, error, option) > + > #endif /* __LINUX_COMPILER_TYPES_H */ > -- > 2.17.1 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h index f1a7492a5cc8..5067a90af9c3 100644 --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -347,3 +347,30 @@ #if GCC_VERSION >= 50100 #define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1 #endif + +/* + * Turn individual warnings and errors on and off locally, depending + * on version. + */ +#define __diag_GCC(version, severity, s) \ + __diag_GCC_ ## version(__diag_GCC_ ## severity s) + +/* Severity used in pragma directives */ +#define __diag_GCC_ignore ignored +#define __diag_GCC_warn warning +#define __diag_GCC_error error + +/* Compilers before gcc-4.6 do not understand "#pragma GCC diagnostic push" */ +#if GCC_VERSION >= 40600 +#define __diag_str1(s) #s +#define __diag_str(s) __diag_str1(s) +#define __diag(s) _Pragma(__diag_str(GCC diagnostic s)) +#else +#define __diag(s) +#endif + +#if GCC_VERSION >= 80000 +#define __diag_GCC_8(s) __diag(s) +#else +#define __diag_GCC_8(s) +#endif diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h index 6b79a9bba9a7..a8ba6b04152c 100644 --- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h @@ -271,4 +271,22 @@ struct ftrace_likely_data { # define __native_word(t) (sizeof(t) == sizeof(char) || sizeof(t) == sizeof(short) || sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long)) #endif +#ifndef __diag +#define __diag(string) +#endif + +#ifndef __diag_GCC +#define __diag_GCC(version, severity, string) +#endif + +#define __diag_push() __diag(push) +#define __diag_pop() __diag(pop) + +#define __diag_ignore(compiler, version, option, comment) \ + __diag_ ## compiler(version, ignore, option) +#define __diag_warn(compiler, version, option, comment) \ + __diag_ ## compiler(version, warn, option) +#define __diag_error(compiler, version, option, comment) \ + __diag_ ## compiler(version, error, option) + #endif /* __LINUX_COMPILER_TYPES_H */