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.<p>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.<p>So -Werror is fine if you are shipping binaries, but if you are shipping source code, it&#x27;s probably a good idea to not use it in the public build system.