Hi, I'm writing because I will occasionally see messages like the following from CI systems (specifically GitHub Actions' macOS runners) when they attempt to run autoconf:
/Applications/Xcode_15.2.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/gm4: unrecognized option `--gnu' Try `/Applications/Xcode_15.2.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/gm4 --help' for more information. autom4te: error: gm4 failed with exit status: 1 My first attempt at fixing this was hacking in support for the `--gnu` flag for Apple's copy of gm4, but since the apple-oss-distributions organization has pull requests turned off, there isn't much I can really do there to get Apple to upstream it: https://github.com/apple-oss-distributions/gm4/compare/main...cooljeanius:apple-gm4:gnu_flag My second attempt at fixing this was to figure out why autoconf was passing the `--gnu` flag to m4 in the first place, and it seems that it comes from the AC_PROG_GNU_M4 macro in m4.m4 (which seems generally-useful, btw, and like something that autoconf should probably ship to users). I think what is happening here is that [g]m4's support for the `--gnu` flag gets detected at autoconf's configure time, but then when the user overrides the M4 variable to point to a different [g]m4, the M4_GNU variable stays set to whatever it was first detected as, which might not match up with what the new [g]m4 supports. I'm wondering if there's some way that autoconf could shift around the timing of these checks so that it doesn't try passing `--gnu` to an installation of [g]m4 that doesn't support it? Please let me know if there's a different mailing list I should send this request to instead. Thanks, Eric Gallager
