[Bug sanitizer/61422] False Asan positive in libopus

["jakub at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61422

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Comment on attachment 32896
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=32896
Proposed patch

Can't reproduce it, are you sure you don't have extra patches in the tree
(stringops currently don't use the the real_size_in_bytes != size_in_bytes
accesses).

The fix is good, except for the bogus whitespace after [ and incorrect testcase
(you should be really using "+m" instead of "=m", otherwise the compiler could
optimize away the stores of 1 or 3.  Also, please don't add * sizeof (char)
there, that is * 1 by definition.  And please use __builtin_memcpy instead of
unprototyped memcpy.  And copying around uninitialized bytes probably isn't a
good idea either, so you should first memset it or fill in or something.