setjmp / longjmp在发行和调试中的不同行为

Question

This question comes from SetJmp/LongJmp: Why is this throwing a segfault?

When I use debug mode run the code it did crash as expect. But if I use release it will output like this:

1 setjmping a_buf
2 calling b                // loop start
3 entering b_helper
4 longjmping to a_buf
5 longjmping to b_buf
6 returning from b_helper  // loop
2 calling b
3 entering b_helper
4 longjmping to a_buf
5 longjmping to b_buf
6 returning from b_helper
...

As my understanding, longjmp can be considered as return so the stack memory of b_helper will be erased and accessing become illegal. that make the program crash become reasonable. But why it gives different behaviour in release ? Looks like return behave as longjmp . So the result in release shall be the right and my understanding is wrong.

Mingw: 5.3

Answer 1

The code in question causes undefined behaviour . The program is incorrect, there is no expected behaviour. You should not expect nor be surprised by any particular output or other behaviour.

Answer 2

Which compiler do you use? If you use g++ compiler, ie the programming language is C++, the functions b_helper is inlined into the function b , and the function b is inlined into the function a in the release mode with enabled optimizations. In this case there are no more routings left that call setjmp and return.