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7a887dd537
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.
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|---|---|---|
| .. | ||
| 64 | ||
| x32 | ||
| ____longjmp_chk.S | ||
| __start_context.S | ||
| brk.c | ||
| clone.S | ||
| compat-timer.h | ||
| configure | ||
| configure.ac | ||
| dl-cache.h | ||
| dl-procinfo.c | ||
| dl-procinfo.h | ||
| getcontext.S | ||
| Implies | ||
| kernel_stat.h | ||
| kernel-features.h | ||
| ldconfig.h | ||
| ldd-rewrite.sed | ||
| libmvec.abilist | ||
| makecontext.c | ||
| Makefile | ||
| readelflib.c | ||
| register-dump.h | ||
| setcontext.S | ||
| sigaction.c | ||
| sigaltstack-offsets.sym | ||
| sigcontextinfo.h | ||
| swapcontext.S | ||
| syscall.S | ||
| syscalls.list | ||
| sysdep.h | ||
| sysdep.S | ||
| timer_create.c | ||
| timer_delete.c | ||
| timer_getoverr.c | ||
| timer_gettime.c | ||
| timer_settime.c | ||
| ucontext_i.sym | ||
| Versions | ||
| vfork.S | ||