Does unaligned memory access always cause bus errors?

Question

According to the Wikipedia page Segmentation fault, a bus error can be caused by unaligned memory access. The article gives an example about how to trigger a bus er

Answer 1

1. It may be significantly slower to access unaligned memory (as in, several times slower).

2. Not all platforms even support unaligned access - x86 and x64 do, but ia64 (Itanium) does not, for example.

3. A compiler can emulate unaligned access (VC++ does that for pointers declared as __unaligned on ia64, for example) - by inserting additional checks to detect the unaligned case, and loading/storing parts of the object that straddle the alignment boundary separately. That is even slower than unaligned access on platforms which natively support it, however.