Fix #68: gif: buffer underflow reported by AddressSanitizer

The buffer underflow happens at the start of the bitstream and after
each clear code, where the wrap-around is actually unnecessary. To
avoid the buffer underflow we simply initialize scd->last_byte to 2,
instead of adding further control logic to skip the relevant
assignments altogether.

We do not add a regression test, because the buffer underflow could
only be detected with ASAN or a similar memory-checker (or debugging),
and it happens for all proper GIFs anyway, so other tests (such as
tests/gif/gif_im2im) already exhibited the behavior.

0 files changed, 0 insertions, 0 deletions