[tbirdz]

The problem with -Werror in open source projects is that it can produce errors for users building your code on different compilers or compiler versions than the one you originally developed it for.

As compilers change they can end up adding new warnings to the defaults, or for or example -Wall, or -Weverything. And different compilers might throw different warnings on the same code with the same options involved. Using -Werror will force an error, which can end up terminating the build for users, even when the code compiles cleanly on your version of your compiler.

So -Werror is fine if you are shipping binaries, but if you are shipping source code, it's probably a good idea to not use it in the public build system.