-Werror can be useful for CI, but elsewhere it is obnoxious. Warnings should be warnings, errors should be errors. If you always turn warnings into errors then

-Werror can be useful for CI, but elsewhere it is obnoxious. Warnings should be warnings, errors should be errors. If you always turn warnings into errors then you remove a useful tool. Warnings do not mean the program is incorrect, and lack of warnings do not mean the program is correct. It is just heuristics, and changes between major versions and different implementations, even while the program execution behavior is exactly the same. OpenBSD cares about portability. A well implemented program should work correctly with a good range of different reasonable compilers, and -Werror really throws a wrench in that. Imagine you want to update the compiler to a new major version that has some corner-case correctness improvement or some security mitigation feature - but it also has a new warning. Can't do that! Unless you change the source of a bunch of libraries and applications which you didn't write. Mistakes have been made fixing warnings, like the infamous Debian openssl fix that removed most of the entropy from generated ssh keys. If you care about correctness, you pay attention to and fix warnings where appropriate, without forcing yourself by making all your builds on different compiler versions/implementations just fail. There was a time that CPython wanted to add a deprecation warning, but some popular libraries ran tests with the equivalent of -Werror during a regular build/install (trying to be super-correct best-practices etc), so adding a warning would break compatibility with most of the ecosystem, so CPython couldn't just add the warning using the long-established system. Instead they had to come up with a new system for warnings shown in some circumstances and not others, to effectively trick these super-best-practices projects into still working.