What's the best way to get a c++ executable on the PATH?

[colindean]

I'm working on some Homebrew formulae. When I went to do a brew audit/brew test cycle, Homebrew couldn't install one of the relevant development dependencies because c++ is not on the PATH.

I opened a discussion about it, and the result is basically that Homebrew's gcc package doesn't create a c++ symlink to c++-15, etc., but Homebrew itself sets its portable-ruby runtime to look for c++ on the path when a Gem needs to compile C++ code. portable-ruby doesn't depend on a Homebrew-provided compiler: it expects one already to exist in the OS, IIRC one of the few Homebrew formuale with that assumption given its foundational nature to Homebrew distribution.

So, Homebrew expects a /usr/bin/c++ or similar path to exist and be provided by the OS/distro repos, but it seems like Bluefin expects Homebrew to provide it. A lovely impasse.

The obvious quick solution is to symlink it to c++-${gcc_version} provided by Homebrew, e.g.

ln -s $(brew --prefix gcc)/bin/c++-$( brew info gcc --json | jq -r '.[0].linked_keg | split(".") | first') /usr/local/bin/c++

This seems safe, but would break when Homebrew moves to GCC 16, etc, so I'm thinking some kind script that dynamically looks at the gcc versions installed would be appropriate, caching the output of brew --prefix and brew info to keep c++ invocation fast.

I'd love to hear thoughts on alternative ways to resolve this.

[repires]

Give a try in ask.projectbluefin.io :

This is a real gap. Bluefin's base image installs gcc but not gcc-c++ [1], so there's no /usr/bin/c++ or /usr/bin/g++ on the system. Homebrew's portable-ruby expects the OS to provide c++ when it needs to compile native gems — and Homebrew's own gcc formula doesn't create a bare c++ symlink either. Classic impasse.

A few options in order of "cleanness":

1. Add gcc-c++ to the Bluefin base image — This is the most correct fix if Homebrew is a first-class citizen in Bluefin and expects a system C++ compiler. It's a single package addition to build_files/base/04-packages.sh. Given that gcc and make are already there, gcc-c++ seems like a reasonable addition. Worth opening a PR/issue on the bluefin repo for this.

2. Symlink via a Homebrew post-install hook or shell profile — The dynamic symlink approach colindean described works but is fragile across GCC major version bumps. A slightly more robust variant using ls:

   ln -sf "$(ls $(brew --prefix)/bin/c++-* | sort -V | tail -1)" /usr/local/bin/c++

3. Do the brew audit/brew test work inside a Distrobox — This aligns with Bluefin's container-first philosophy. An Ubuntu or Fedora toolbox will have g++ readily available. But this is awkward for Homebrew formula development specifically since you need Homebrew's own environment.

My take: option 1 is the right answer. Bluefin already ships gcc and make in the base image precisely to support Homebrew's compilation needs — gcc-c++ is the missing piece of that same story. It's a small package and would resolve this for all users without workarounds.

[colindean]

Thank you for the prompt response! I've opened a PR #4586 that will add gcc-c++.

I can do № 3 if the PR ends closed non-merged, as that's more "the Bluefin way" and building inside of ghcr.io/homebrew/brew:latest ought to be sufficient for formulae development.