[syslinux] chain.c32 memcmp bug

[Szymon H]

Hello,

I've noticed that finding disks by guid using chain.c32 from both 4.03
and latest 4.04 pre12 doesn't work as expected (unable to find
requested GPT disk/partition). The entered guid is correct according
to gdisk and chain.c32 debug information but still chain.c32 claims it
can't find the drive.

The bug is located in function find_by_guid, line 991. It is
is_me = !memcmp(&header->disk_guid, &gpt_guid, sizeof(*gpt_guid));
but should be
is_me = !memcmp(&header->disk_guid, gpt_guid, sizeof(*gpt_guid));
as memcmp takes two void pointers and gpt_guid is already a pointer to
struct guid.

I've recompiled chain.c32 with this tiny fix (using gcc 4.4.3) and now
it finds disks by guid fine.

Best regards,
Simon