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author | Adhemerval Zanella <adhemerval.zanella@linaro.org> | 2020-10-05 17:30:05 -0300 |
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committer | Adhemerval Zanella <adhemerval.zanella@linaro.org> | 2020-10-06 15:29:35 -0300 |
commit | 7a887dd537cd00fe3cdf42b788b3f0e3b430b0ed (patch) | |
tree | 2ce82095bd3f24a54af4980703cbb69cd5b7d155 /sysdeps/unix/sysv/linux/x86_64/timer_gettime.c | |
parent | 862897d2addfacc2af85b571ebf5a82659455e8c (diff) | |
download | glibc-7a887dd537cd00fe3cdf42b788b3f0e3b430b0ed.tar.gz glibc-7a887dd537cd00fe3cdf42b788b3f0e3b430b0ed.tar.xz glibc-7a887dd537cd00fe3cdf42b788b3f0e3b430b0ed.zip |
posix: Fix -Warray-bounds instances building timer_create [BZ #26687]
GCC 11 -Warray-bounds triggers invalid warnings when building Linux timer_create.c: ../sysdeps/unix/sysv/linux/timer_create.c: In function '__timer_create_new': ../sysdeps/unix/sysv/linux/timer_create.c:83:17: warning: array subscript 'struct timer[0]' is partly outside array bounds of 'unsigned char[8]' [-Warray-bounds] 83 | newp->sigev_notify = (evp != NULL | ^~ ../sysdeps/unix/sysv/linux/timer_create.c:59:47: note: referencing an object of size 8 allocated by 'malloc' 59 | struct timer *newp = (struct timer *) malloc (offsetof (struct timer, | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 60 | thrfunc)); | ~~~~~~~~~ The struct allocated for !SIGEV_THREAD timers only requires two 'int' fields (sigev_notify and ktimerid) and the offsetof trick tries minimize the memory usage by only allocation the required size. However, although the resulting size is suffice for !SIGEV_THREAD time, accessing the partially allocated object is error-prone and UB. This patch fixes both issues by embedding the information whether the timer if a SIGEV_THREAD in the returned 'timer_t'. For !SIGEV_THREAD, the resulting 'timer_t' is the returned kernel timer identifer (kernel_timer_t), while for SIGEV_THREAD it uses the fact malloc returns at least _Alignof (max_align_t) pointers plus that valid kernel_timer_t are always positive to set MSB bit of the returned 'timer_t' to indicate the timer handles a SIGEV_THREAD. It allows to remove the memory allocation for !SIGEV_THREAD and also remove the 'sigev_notify' field from 'struct timer'. Checked on x86_64-linux-gnu and i686-linux-gnu.
Diffstat (limited to 'sysdeps/unix/sysv/linux/x86_64/timer_gettime.c')
-rw-r--r-- | sysdeps/unix/sysv/linux/x86_64/timer_gettime.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/sysdeps/unix/sysv/linux/x86_64/timer_gettime.c b/sysdeps/unix/sysv/linux/x86_64/timer_gettime.c index 89002c7243..0e4213d7aa 100644 --- a/sysdeps/unix/sysv/linux/x86_64/timer_gettime.c +++ b/sysdeps/unix/sysv/linux/x86_64/timer_gettime.c @@ -24,9 +24,9 @@ int __timer_gettime_new (timer_t timerid, struct itimerspec *value) { - struct timer *kt = (struct timer *) timerid; + kernel_timer_t ktimerid = timerid_to_kernel_timer (timerid); - return INLINE_SYSCALL_CALL (timer_gettime, kt->ktimerid, value); + return INLINE_SYSCALL_CALL (timer_gettime, ktimerid, value); } versioned_symbol (librt, __timer_gettime_new, timer_gettime, GLIBC_2_3_3); |