[starspangled]

Compilers runs enormous regression suites, and CI/git/bisect/etc style of development has made bugs harder to check in and quicker to squash in a lot of cases I would say.

I have found a number of compiler bugs in GCC and LLVM (and GAS and LLMV AS). Almost without fail they have been in the use of new features (certain new instructions, new ABI / addresing model) or esoteric things (linker script trickery, unusual use of extended inline asm) etc where the compilers had probably no or very little "real" code to test against other than presumably some simple things and basic unit tests when they check in said features.

Unless you're doing _really_ unusual things, or exercising new paths that don't just get picked up when compiling existing code (e.g., like many/most optimizations would), it's just not that likely you'll write code that triggers some unique path / state that has a noticeable bug.

To identify the bug is a compiler bug that is silent bad code generation, you basically assume the compiler is correct until you start to narrow the problem down to a state which should be impossible. After you put in enough assertions and breakpoints and logging (some of which might make the problem mysteriously go away) and reach the point of banging your head on the table, you start side-eyeing the compiler. If you know assembly you might start looking at some assembly output. Or you would start trying to make an reduced reproducer case. E.g., take the suspect function out on its own and make some unit tests for it. A tool like C-reduce can sometimes help if it's not a relatively simple small function.

How quickly you reach that point where you can actually start to narrow down on a possible compiler bug entirely depends on the problem. If it's causing some memory ordering or race condition or silent memory corruption that is only detected later or can only be reproduced at a customer sporadically, then who knows? Could be months, if ever. Others could be an almost immediate assert or error log or obvious bad result that you could debug and file a bug report in a day.