Em Fri, Dec 20, 2019 at 05:52:36AM +0300, Vitaly Chikunov escreveu: > Arnaldo, > > On Tue, Dec 17, 2019 at 05:04:20PM -0300, Arnaldo Carvalho de Melo wrote: > > Em Tue, Dec 17, 2019 at 03:23:32PM +0300, Vitaly Chikunov escreveu: > > > Arnaldo, > > (Btw, you didn't include me into the To: of your reply). > > > > Ping. Can you accept or comment on this patch? There is further > > > explanations of it: > > > > Will this work when building with clang > > Clang doesn't produce this warning: > > https://clang.llvm.org/docs/DiagnosticsReference.html#wredundant-decls > "-Wredundant-decls > This diagnostic flag exists for GCC compatibility, and has no effect > in Clang." > > Thus, this change doesn't affect clang. (When building the kernel objtool > compiles OK). > > But, compilation with clang fails compiling perf with: > > CC util/string.o > ../lib/string.c:99:8: error: attribute declaration must precede definition [-Werror,-Wignored-attributes] > size_t __weak strlcpy(char *dest, const char *src, size_t size) > ^ > ../../tools/include/linux/compiler.h:66:34: note: expanded from macro '__weak' > # define __weak __attribute__((weak)) > ^ > /usr/include/bits/string_fortified.h:151:8: note: previous definition is here > __NTH (strlcpy (char *__restrict __dest, const char *__restrict __src, > ^ > 1 error generated. > > This warning could be disabled with this: > > diff --git tools/lib/string.c tools/lib/string.c > index f2ae1b87c719..65b569014446 100644 > --- tools/lib/string.c > +++ tools/lib/string.c > @@ -96,6 +96,8 @@ int strtobool(const char *s, bool *res) > * If libc has strlcpy() then that version will override this > * implementation: > */ > +#pragma GCC diagnostic push > +#pragma GCC diagnostic ignored "-Wignored-attributes" > size_t __weak strlcpy(char *dest, const char *src, size_t size) > { > size_t ret = strlen(src); > @@ -107,6 +109,7 @@ size_t __weak strlcpy(char *dest, const char *src, size_t size) > } > return ret; > } > +#pragma GCC diagnostic pop > > /** > * skip_spaces - Removes leading whitespace from @str. > > If this is acceptable I will resend v2 with this. Go ahead, and please let me know if there is any container image for Altlinux, as I test with clang on all the distros I have container images for, and this hasn't appeared on my radar, i.e. clang + strlcpy warnings :-) - Arnaldo > Thanks, > > > > > - Arnaldo > > > > > 1. It seems that people putting strlcpy() into the tools was already aware of > > > the problems it causes and tried to solve them. Probably, that's why they put > > > `__weak` attribute on it (so it would be linkable in the presence of another > > > strlcpy). Then `#ifndef __UCLIBC__`ed and later `#if defined(__GLIBC__) && > > > !defined(__UCLIBC__)` its declaration. But, solution was incomplete and could > > > be improved to make kernel buildable on more systems (where libc contains > > > strlcpy). > > > > > > There is not need to make `redundant redeclaration` warning an error in > > > this case. > > > > > > 2. `#pragma GCC diagnostic ignored` trick is already used multiple times > > > in the kernel: > > > > > > $ git grep '#pragma GCC diagnostic ignored' > > > arch/arm/lib/xor-neon.c:#pragma GCC diagnostic ignored "-Wunused-variable" > > > tools/build/feature/test-gtk2-infobar.c:#pragma GCC diagnostic ignored "-Wstrict-prototypes" > > > tools/build/feature/test-gtk2.c:#pragma GCC diagnostic ignored "-Wstrict-prototypes" > > > tools/include/linux/string.h:#pragma GCC diagnostic ignored "-Wredundant-decls" > > > tools/lib/bpf/libbpf.c:#pragma GCC diagnostic ignored "-Wformat-nonliteral" > > > tools/perf/ui/gtk/gtk.h:#pragma GCC diagnostic ignored "-Wstrict-prototypes" > > > tools/testing/selftests/kvm/lib/assert.c:#pragma GCC diagnostic ignored "-Wunused-result" > > > tools/usb/ffs-test.c:#pragma GCC diagnostic ignored "-Wdeprecated-declarations" > > > > > > So the solution does not seem alien in the kernel and should be acceptable. > > > > > > (I also send this to another of your emails in case I used wrong one before.) > > > > > > Thanks, > > > > > > > > > On Mon, Dec 09, 2019 at 12:46:07AM +0300, Vitaly Chikunov wrote: > > > > Disable `redundant-decls' error for strlcpy declaration and solve build > > > > error allowing users to compile vanilla kernels. > > > > > > > > When glibc have strlcpy (such as in ALT linux since 2004) objtool and > > > > perf build fails with something like: > > > > > > > > In file included from exec-cmd.c:3: > > > > tools/include/linux/string.h:20:15: error: redundant redeclaration of ‘strlcpy’ [-Werror=redundant-decls] > > > > 20 | extern size_t strlcpy(char *dest, const char *src, size_t size); > > > > | ^~~~~~~ > > > > > > > > It's very hard to produce a perfect fix for that since it is a header > > > > file indirectly pulled from many sources from different Makefile builds. > > > > > > > > Fixes: ce99091 ("perf tools: Move strlcpy() from perf to tools/lib/string.c") > > > > Fixes: 0215d59 ("tools lib: Reinstate strlcpy() header guard with __UCLIBC__") > > > > Signed-off-by: Vitaly Chikunov <vt@xxxxxxxxxxxx> > > > > Cc: Dmitry V. Levin <ldv@xxxxxxxxxxxx> > > > > Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> > > > > Cc: Vineet Gupta <Vineet.Gupta1@xxxxxxxxxxxx> > > > > Cc: stable@xxxxxxxxxxxxxxx > > > > --- > > > > tools/include/linux/string.h | 3 +++ > > > > 1 file changed, 3 insertions(+) > > > > > > > > diff --git a/tools/include/linux/string.h b/tools/include/linux/string.h > > > > index 980cb9266718..99ede7f5dfb8 100644 > > > > --- a/tools/include/linux/string.h > > > > +++ b/tools/include/linux/string.h > > > > @@ -17,7 +17,10 @@ int strtobool(const char *s, bool *res); > > > > * However uClibc headers also define __GLIBC__ hence the hack below > > > > */ > > > > #if defined(__GLIBC__) && !defined(__UCLIBC__) > > > > +#pragma GCC diagnostic push > > > > +#pragma GCC diagnostic ignored "-Wredundant-decls" > > > > extern size_t strlcpy(char *dest, const char *src, size_t size); > > > > +#pragma GCC diagnostic pop > > > > #endif > > > > > > > > char *str_error_r(int errnum, char *buf, size_t buflen); > > -- - Arnaldo
