Errors and warnings in C

I want to come up with a good strategy for error and warning handing in my C code.

Right now I validate any action that may potentially fail or require a warning.

If an error is detected, I use fprintf to stderr to print an informative error message starting with big fat “ERROR:” and continuing with details about failure and what function it happen in (using __func__).

I then use exit(1) to crash and burn fast. 1 is to be replaced by a more meaningful error code if software gets stable and mature and I start polishing code. I don’t bother with cleanup (memory freeing, file closing etc.) since exit() should take care of it I think.

For warnings it’s the same, but message starts with “WARNING:” and there is no exit().

This mostly works but I feel it could be done better:

• messages shouldn’t be baked into the code, it’s bad for internationalization;
• may be I should start doing some cleanup before exit(), such as deleting unfinished output files;
• for warnings, think of recovery strategy that avoids excess of nested if / else conditions. Perhaps start using goto in some limited way. This would trigger Dijkstra’s zealots, but would improve code readability, which would improve my ability to reason about it;
• consider using perror() instead of fprintf(stderr, ...) where apropriate;

It is obvious I should read through some popular code bases to see how other people handle errors. May be read through OpenBSD or Linux kernel code.

Meanwhile I did some searching and found some interesting materials:

• sensible error handling: part 1, part 2, part 3;
• exceptions are hard;
• using longjmp() / setjmp() for error recovery;

To be continued…