What prevents ghc@8.8 from using a bottle (with a non-default prefix)?

[kthchew]

I have the non-default Homebrew prefix, ~/.brew. I understand that with this configuration, some formulae that are not relocatable will need to be built from source.

One such formula is ghc@8.8. When installing it without any additional flags, I get this message:

❯ brew install ghc@8.8
Warning: Building ghc@8.8 from source as the bottle needs:
- HOMEBREW_CELLAR: /usr/local/Cellar (yours is /Users/kenneth/.brew/Cellar)
- HOMEBREW_PREFIX: /usr/local (yours is /Users/kenneth/.brew)

I was wondering whether this was something that I could try to resolve, so first I used brew install --build-bottle ghc@8.8, which (after more than 2 hours) was successful. Then, I used brew bottle --verbose ghc@8.8 to see if I could fix any errors I saw. This was the output I got:

❯ brew bottle --verbose ghc@8.8
git config --replace-all homebrew.devcmdrun true
==> Determining ghc@8.8 bottle rebuild...
==> Bottling ghc@8.8--8.8.4_1.big_sur.bottle.1.tar.gz...
tar cf /Users/kenneth/.brew/Library/Taps/homebrew/homebrew-cask-versions/ghc@8.8--8.8.4_1.big_sur.bottle.1.tar ghc@8.8/8.8.4_1
gzip -f ghc@8.8-bottle.tar
==> Detecting if ghc@8.8--8.8.4_1.big_sur.bottle.1.tar.gz is relocatable...
./ghc@8.8--8.8.4_1.big_sur.bottle.1.tar.gz
  bottle do
    rebuild 1
    sha256 cellar: :any, big_sur: "c758212d48edb54296c40066ae545b15d988443f4c211061f0321160c91f55f9"
  end

Strangely enough, I don't see any errors; in fact, it looks like it decided that it was, in fact, relocatable (am I interpreting this output correctly?).

I'm not here to ask for it to be fixed, but I was wondering why Homebrew decided to build ghc@8.8 from source. If ghc@8.8 is, in fact, relocatable, then what other criteria decides whether Homebrew builds from source or tries to use a bottle when a non-default prefix is used?

Note: I'm asking specifically about ghc@8.8 because it's what I tested; ghc also decides to build from source, and I assume it would be the same, but I haven't tried it myself due to the long build times.

[jonchang]

Try running brew bottle --verbose --debug FORMULA. The logs for building ghc@8.8 have unfortunately expired so we can't find the original reasoning why it's not relocatable. We only recently permitted formulae to have different relocatable status for macOS versions, so it's possible that it's relocatable on e.g. Big Sur but not on Catalina.

[kthchew]

I tried that, and the logs are at https://gist.github.com/kthchew/deb962a3d3b0fb0b5aebb188392a5dc2. I'm not completely sure, but I don't think I see anything of interest there.

We only recently permitted formulae to have different relocatable status for macOS versions, so it's possible that it's relocatable on e.g. Big Sur but not on Catalina.

Ah, makes sense, thank you. I'm on Big Sur. If this is indeed the case, would this be automatically resolved the next time the formula updates?

[danielnachun]

That log indicates the bottle is relocatable, and my understanding of the way ghc is works is that it should always be relocatable. ghc takes a very long time to build, and it's possible that this has something to do with why it was not given the proper cellar. It looks like all versions of ghc lost their relocatable status, so there may need to be more investigation here.

[kthchew]

It looks like all versions of ghc lost their relocatable status, so there may need to be more investigation here.

In this case, should I make an issue to track this outside of just this discussion?