brew tries to install incorrect dependencies

[jacktose]

When I install or upgrade various formulae, brew tries to install glibc, gmp, [email protected], mpfr, libmpc, and gcc@5 as dependencies, even though they are not dependencies for the formula in question.

There's a full example in my gist, but here's the interesting part:

$ brew deps --include-build --include-optional --include-test --include-requirements gh
go
$ brew upgrade gh
==> Upgrading 1 outdated package:
gh 1.7.0 -> 1.8.1
==> Upgrading gh 1.7.0 -> 1.8.1 
... (warnings and downloads) ...
==> Installing dependencies for gh: glibc, gmp, [email protected], mpfr, libmpc and gcc@5
==> Installing gh dependency: glibc
^C
One sec, cleaning up...

This happens with various formulae, with different parameters. Here's vim, which does have other dependencies, and builds from source:

$ brew upgrade vim
==> Upgrading 1 outdated package:
vim 8.2.2725_1
==> Upgrading vim -> 8.2.2725_1 
...
==> Installing dependencies for vim: glibc, gmp, [email protected], mpfr, libmpc, gcc@5, lua, expat, sqlite, [email protected] and ruby
==> Installing vim dependency: glibc
^C
One sec, cleaning up...

I'm aware that my setup is nonstandard (see gist), which is why I didn't go straight to an issue for this, but I'd appreciate any help finding the cause and/or solution, and I'll happily submit a patch for it if appropriate.

[alebcay]

My guess is that Homebrew deems your system's compiler setup to be too old or non-existent, which is why it's installing gcc@5 (and dependencies of gcc@5: gmp, [email protected], libmpc, mpfr). I believe the glibc installation is also happening because your system's glibc is either too old or non-existent.

According to our docs here, your system should be new enough that Homebrew should not be installing these things, but I would suspect that this is the general direction to investigate towards.

[Bo98]

/usr/bin/gcc: 4.8.5

Homebrew for Linux requires GCC 5 to be installed (but is able to install its own if you have GCC 4.7.0 or later). This is a runtime dependency because of the linkage to libstdc++ etc.

[jacktose]

Oh, that makes more sense. Before this, I uninstalled gcc@5 etc. because I was trying to get the new, cleaner gcc setup to work.

So it's a legit installation, but a dependency of homebrew, not of the formula I'm installing directly. Seems like more of a UX issue then. Could it say something like

Homebrew requires `gcc@5` etc. on your system because your system gcc is <5.

or

==> Installing dependencies for Homebrew: glibc, gmp, [email protected], mpfr, libmpc and gcc@5
...
==> Installing dependencies for vim: lua, expat, sqlite, [email protected] and ruby

[SMillerDev]

Homebrew requires gcc@5 etc. on your system because your system gcc is <5.

I believe it did this when you installed homebrew. If you uninstall it we don't keep track of the reasons anymore. We just know there is a dependency.