On Apr 25, 2011, at 3:01 PM, Michael Tüxen wrote:
> dup_list = (guint32 *)((char *)sack_header + 16 + (nr * sizeof(struct gaps)))
Clang likes something that doesn't involve casting a "char *", which is not guaranteed to contain an address that's 4-byte aligned, to a "guint32 *", which is a pointer that's supposed to be 4-byte aligned...
...and that, on at least some architectures, *MUST* be 4-byte aligned in order for dereferences of it to work!
One such architecture is SPARC, which traps on unaligned references. I think at least some versions of ARM are other such architectures; I don't think it traps on unaligned accesses, but it might, for example, just act as if the lower 2 bits of the address are 0.
Unless sack_header is *guaranteed* to be aligned on a 4-byte boundary, that code is unsafe.
