为什么地址清理程序有时会忽略段错误？

Question

Been using fsanitize=address while compiling C programs, in order to track seg faults for about a year now. Every now and then I encounter a strange behavior, my program would be seg faulting if compiled without fsanitize=address but when I compile with fsanitize=address this seg fault disappears. I have looked around the web but haven't been able to figure out exactly why this might be happening. I know that address sanitizer is not a perfect program but just don't know exactly why it has this behavior.

Answer 1

A part of AddressSanitizer algorithm intersperses all local and global variables (and heap allocations) with 32-byte gaps to detect overflow. Thus off-by-one overflows which used to corrupt other variables (and likely cause crashes if those variables were pointers or offsets) may no longer do this and corresponding faults will disappear.

Asan should still report errors for such overflows which apparently it does not in your case. This may be uncovering some issue in Asan or (more likely) the way you run it (eg not combining it with -U_FORTIFY_SOURCE or -fno-common as explained in FAQ )