| Message ID | 20240410232637.4135564-2-jstultz@google.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [1/3] selftests: timers: Fix posix_timers ksft_print_msg warning | expand |
On Wed, Apr 10, 2024 at 04:26:29PM -0700, John Stultz wrote: > Building with clang, I see the following warning: > > In file included from posix_timers.c:17: > ./../kselftest.h:398:6: warning: variable 'major' is used uninitialized whenever '||' condition is true [-Wsometimes-uninitialized] > if (uname(&info) || sscanf(info.release, "%u.%u.", &major, &minor) != 2) > ^~~~~~~~~~~~ > ./../kselftest.h:401:9: note: uninitialized use occurs here > return major > min_major || (major == min_major && minor >= min_minor); > ^~~~~ > > This is a bit of a red-herring as if the uname() call did fail, > we would hit ksft_exit_fail_msg() which should exit. Correct, although we have not really conveyed that to the compiler, right? exit() is noreturn, which means all functions that call exit() unconditionally are also noreturn, such as ksft_exit_fail_msg(). LLVM will figure this out once it performs inlining and such but that happens after clang's static analysis phase that this warning occurs in. I think a better solution would be to add __noreturn to the functions in tools/testing/selftests/kselftest.h that call exit(), so that the compiler is aware of this through all pipeline phases, maybe something like this? It resolves the wawrning for me. diff --git a/tools/testing/selftests/kselftest.h b/tools/testing/selftests/kselftest.h index 050c5fd01840..29364c9f3332 100644 --- a/tools/testing/selftests/kselftest.h +++ b/tools/testing/selftests/kselftest.h @@ -83,6 +83,7 @@ #define KSFT_XPASS 3 #define KSFT_SKIP 4 +#define __noreturn __attribute__((__noreturn__)) #define __printf(a, b) __attribute__((format(printf, a, b))) /* counters */ @@ -324,13 +325,13 @@ void ksft_test_result_code(int exit_code, const char *test_name, break; \ } } while (0) -static inline int ksft_exit_pass(void) +static inline __noreturn int ksft_exit_pass(void) { ksft_print_cnts(); exit(KSFT_PASS); } -static inline int ksft_exit_fail(void) +static inline __noreturn int ksft_exit_fail(void) { ksft_print_cnts(); exit(KSFT_FAIL); @@ -357,7 +358,7 @@ static inline int ksft_exit_fail(void) ksft_cnt.ksft_xfail + \ ksft_cnt.ksft_xskip) -static inline __printf(1, 2) int ksft_exit_fail_msg(const char *msg, ...) +static inline __noreturn __printf(1, 2) int ksft_exit_fail_msg(const char *msg, ...) { int saved_errno = errno; va_list args; @@ -372,7 +373,7 @@ static inline __printf(1, 2) int ksft_exit_fail_msg(const char *msg, ...) exit(KSFT_FAIL); } -static inline void ksft_exit_fail_perror(const char *msg) +static inline __noreturn void ksft_exit_fail_perror(const char *msg) { #ifndef NOLIBC ksft_exit_fail_msg("%s: %s (%d)\n", msg, strerror(errno), errno); @@ -385,19 +386,19 @@ static inline void ksft_exit_fail_perror(const char *msg) #endif } -static inline int ksft_exit_xfail(void) +static inline __noreturn int ksft_exit_xfail(void) { ksft_print_cnts(); exit(KSFT_XFAIL); } -static inline int ksft_exit_xpass(void) +static inline __noreturn int ksft_exit_xpass(void) { ksft_print_cnts(); exit(KSFT_XPASS); } -static inline __printf(1, 2) int ksft_exit_skip(const char *msg, ...) +static inline __noreturn __printf(1, 2) int ksft_exit_skip(const char *msg, ...) { int saved_errno = errno; va_list args;
On Thu, Apr 11, 2024 at 8:39 AM Nathan Chancellor <nathan@kernel.org> wrote: > On Wed, Apr 10, 2024 at 04:26:29PM -0700, John Stultz wrote: > > Building with clang, I see the following warning: > > > > In file included from posix_timers.c:17: > > ./../kselftest.h:398:6: warning: variable 'major' is used uninitialized whenever '||' condition is true [-Wsometimes-uninitialized] > > if (uname(&info) || sscanf(info.release, "%u.%u.", &major, &minor) != 2) > > ^~~~~~~~~~~~ > > ./../kselftest.h:401:9: note: uninitialized use occurs here > > return major > min_major || (major == min_major && minor >= min_minor); > > ^~~~~ > > > > This is a bit of a red-herring as if the uname() call did fail, > > we would hit ksft_exit_fail_msg() which should exit. > > Correct, although we have not really conveyed that to the compiler, > right? exit() is noreturn, which means all functions that call exit() > unconditionally are also noreturn, such as ksft_exit_fail_msg(). LLVM > will figure this out once it performs inlining and such but that happens > after clang's static analysis phase that this warning occurs in. I think > a better solution would be to add __noreturn to the functions in > tools/testing/selftests/kselftest.h that call exit(), so that the > compiler is aware of this through all pipeline phases, maybe something > like this? It resolves the wawrning for me. No objection from me if this is the better approach. Would you send that patch out? thanks -john
On Thu, Apr 11, 2024 at 11:11:59AM -0700, John Stultz wrote: > On Thu, Apr 11, 2024 at 8:39 AM Nathan Chancellor <nathan@kernel.org> wrote: > > On Wed, Apr 10, 2024 at 04:26:29PM -0700, John Stultz wrote: > > > Building with clang, I see the following warning: > > > > > > In file included from posix_timers.c:17: > > > ./../kselftest.h:398:6: warning: variable 'major' is used uninitialized whenever '||' condition is true [-Wsometimes-uninitialized] > > > if (uname(&info) || sscanf(info.release, "%u.%u.", &major, &minor) != 2) > > > ^~~~~~~~~~~~ > > > ./../kselftest.h:401:9: note: uninitialized use occurs here > > > return major > min_major || (major == min_major && minor >= min_minor); > > > ^~~~~ > > > > > > This is a bit of a red-herring as if the uname() call did fail, > > > we would hit ksft_exit_fail_msg() which should exit. > > > > Correct, although we have not really conveyed that to the compiler, > > right? exit() is noreturn, which means all functions that call exit() > > unconditionally are also noreturn, such as ksft_exit_fail_msg(). LLVM > > will figure this out once it performs inlining and such but that happens > > after clang's static analysis phase that this warning occurs in. I think > > a better solution would be to add __noreturn to the functions in > > tools/testing/selftests/kselftest.h that call exit(), so that the > > compiler is aware of this through all pipeline phases, maybe something > > like this? It resolves the wawrning for me. > > No objection from me if this is the better approach. > > Would you send that patch out? Done: https://lore.kernel.org/20240411-mark-kselftest-exit-funcs-noreturn-v1-1-b027c948f586@kernel.org/ If you have to respin this series for some reason, feel free to include that change so that they go together, up to you though. Cheers, nathan
diff --git a/tools/testing/selftests/kselftest.h b/tools/testing/selftests/kselftest.h index 973b18e156b2..12e2f3ab8b13 100644 --- a/tools/testing/selftests/kselftest.h +++ b/tools/testing/selftests/kselftest.h @@ -392,7 +392,7 @@ static inline __printf(1, 2) int ksft_exit_skip(const char *msg, ...) static inline int ksft_min_kernel_version(unsigned int min_major, unsigned int min_minor) { - unsigned int major, minor; + unsigned int major = 0, minor = 0; struct utsname info; if (uname(&info) || sscanf(info.release, "%u.%u.", &major, &minor) != 2)
Building with clang, I see the following warning: In file included from posix_timers.c:17: ./../kselftest.h:398:6: warning: variable 'major' is used uninitialized whenever '||' condition is true [-Wsometimes-uninitialized] if (uname(&info) || sscanf(info.release, "%u.%u.", &major, &minor) != 2) ^~~~~~~~~~~~ ./../kselftest.h:401:9: note: uninitialized use occurs here return major > min_major || (major == min_major && minor >= min_minor); ^~~~~ This is a bit of a red-herring as if the uname() call did fail, we would hit ksft_exit_fail_msg() which should exit. But to make clang happpy, lets initialize the major/minor values to zero. Cc: Shuah Khan <shuah@kernel.org> Cc: Anna-Maria Behnsen <anna-maria@linutronix.de> Cc: Frederic Weisbecker <frederic@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Stephen Boyd <sboyd@kernel.org> Cc: Nathan Chancellor <nathan@kernel.org> Cc: Nick Desaulniers <ndesaulniers@google.com> Cc: Bill Wendling <morbo@google.com> Cc: Justin Stitt <justinstitt@google.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Edward Liaw <edliaw@google.com> Cc: Carlos Llamas <cmllamas@google.com> Cc: kernel-team@android.com Cc: linux-kselftest@vger.kernel.org Fixes: 6d029c25b71f ("selftests/timers/posix_timers: Reimplement check_timer_distribution()") Signed-off-by: John Stultz <jstultz@google.com> --- tools/testing/selftests/kselftest.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)