Does unaligned memory access always cause bus errors?
c, memory-alignment
Solution
It may be significantly slower to access unaligned memory (as in, several times slower).
Not all platforms even support unaligned access - x86 and x64 do, but ia64 (Itanium) does not, for example.
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.
Problem
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 error. In the example, we have to enable alignment checking to see the bus error. What if we disable such alignment checking? The program seems to work properly. I have a program access unaligned memory frequently, and it is used by quite a few people, but no one reports bus errors or other weird results to me. If we disable alignment checking, what is the side effect of unaligned memory? Platforms: I am working on x86/x86-64. I also tried my program by compiling it with "gcc -arch ppc" on a Mac and it works properly.