[Bug sanitizer/63564] New: -fsanitize=address obscures access to free memory

["bernd.edlinger at hotmail dot de" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63564

            Bug ID: 63564
           Summary: -fsanitize=address obscures access to free memory
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: sanitizer
          Assignee: unassigned at gcc dot gnu.org
          Reporter: bernd.edlinger at hotmail dot de
                CC: dodji at gcc dot gnu.org, dvyukov at gcc dot gnu.org,
                    jakub at gcc dot gnu.org, kcc at gcc dot gnu.org

Created attachment 33737
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33737&action=edit
test example with sem_post to free memory

Hi,

apparently the address sanitizer does not check the sem_post, sem_wait
and similar if the memory is free or the semaphore already deleted.

what makes this worse, is that the attached example crashes
in the following malloc but "works" with -fsanitize=address.

gcc -pthread test.c
./a.out
Segmentation fault (core dumped)

=> app crashes in malloc, not in sem_post!

gcc -pthread -fsanitize=address test.c
./a.out

=> works, and sanitizer "fixes" the malloc!