The issue really isn't with -Wall, it's with -Werror. If I release an open source package that compiles fine today with -Wall -Werror, and tomorrow there's a ne

The issue really isn't with -Wall, it's with -Werror. If I release an open source package that compiles fine today with -Wall -Werror, and tomorrow there's a new compiler release that adds a new warning to -Wall, then that adds a new error to my package, and users trying to compile it with a new compiler will fail and complain. They didn't ask for -Wall -Werror, they only asked for some program that produces a working executable with ./configure ; make. Like enabling assertions or not, this is (a matter of opinion, and) a difference between "development" and "release" compilations. Ideally we would consistently use something like ./configure --devel for one and ./configure --release for the other. Other languages' build systems have this built in, and building a tarball with autotools used to do something similar, but if you just pull something off GitHub it's not clear what mode you'll end up with.