ROSE Compiler Framework/How to fix a bug
If you are trying to fix a bug ( your own or a bug assigned to you to fix). Here are high level steps to do the work
Reproduce the bug
You can only fix a bug when you can reproduce it. This step may be more difficult than it sounds. In order to reproduce a bug, you have to
- find a proper input file
- find a proper translator: a translator shipped with ROSE is easy to find. But be patient and sincere when you ask for a translator written by users.
- find a similar/identical software and hardware environment: a bug may only appear on a specific platform when a specific software configuration is used
Possible results for this step:
- You can reproduce the bug reliably. Bingo! Go to the next step.
- You cannot reproduce the bug. Either the bug report is invalid or you have to keep trying.
- You can reproduce the bug once a while (random errors). Oops. This is kind of difficult situation.
Find causes of the bug
Once you can reproduce the bug. You have to identify the root cause of the bug using a debugger like gdb.
Common steps involved
- simplify the input code as much as possible: It can be very hard to debug a problem with a huge input. Always try to prepare the simplest possible code which can just trigger the bug.
- Often, you have to use a binary search approach to narrow down the input code: only use half of the input at a time to try. Recursively cut the input file into two parts until no further cut is possible while you can still trigger the bug.
- forward tracking: for the translator, it usually takes input and generate intermediate results before the final output is generated. Using a debugger to set break points at each critical stages of the code to check if the intermediate results are what you expect.
- backwards tracking: similar to the previous techniques. But you just back tracking the problem.
Fix the bug
Any bug fix commit should contain
- a regression test: so make check rules can make sure the bug is actually fixed and no further code changes will make the bug relapse.