Bus error vs Segmentation fault
On most architectures I've used, the distinction is that:
- a SEGV is caused when you access memory you're not meant to (e.g., outside of your address space).
- a SIGBUS is caused due to alignment issues with the CPU (e.g., trying to read a long from an address which isn't a multiple of 4).
SIGBUS will also be raised if you mmap() a file and attempt to access part of the mapped buffer that extends past the end of the file, as well as for error conditions such as out of space. If you register a signal handler using sigaction() and you set SA_SIGINFO, it may be possible to have your program examine the faulting memory address and handle only memory mapped file errors.
For instance, a bus error might be caused when your program tries to do something that the hardware bus doesn't support. On SPARCs, for instance, trying to read a multi-byte value (such as an int, 32-bits) from an odd address generated a bus error.
Segmentation faults happen for instance when you do an access that violate the segmentation rules, i.e. trying to read or write memory that you don't own.