[Sirened]

My favorite is when the codebase is so deeply buried in macros and headers that send you on a wild goose chase to find any actual code that it becomes much easier to just dump the binary in ida/binja. The source code can lie but at least the compiled binary directly does what it says

[hinkley]

That feeling when you finally, finally find the bit of code you’ve been looking for… and you can no longer remember why you were looking for it, because you’ve completely purged your short term memory.

[matheusmoreira]

Having to track down macros across several files really annoys me as well. When I write macros in C, I place them just above the code where they are used and undefine them immediately after.

[cultureswitch]

Using #undef is a big one that wasn't mentioned but oh god it is the ideal way to hide things. If you use it sparingly but in critical places of header files, especially to undef something potentially defined in three other headers, it becomes impossible to find the real substitution without reading the cc output