Unable to install conf-gmp on Arch Linux with Homebrew

[pm5]

Hello. I have Homebrew installed on a custom location at /home/linuxbrew/.linuxbrew. When trying to install conf-gmp using gmp provided by Homebrew, I encoutered the folowing errors:

$ env CFLAGS="-I$(brew --prefix)/include" opam install conf-gmp
The following actions will be performed:
  ∗ install conf-gmp 4

<><> Processing actions <><><><><><><><><><><><><><><><><><><><><><><><><><><><>
[ERROR] The compilation of conf-gmp.4 failed at "sh -exc cc -c $CFLAGS -I/usr/local/include test.c".

#=== ERROR while compiling conf-gmp.4 =========================================#
# context     2.1.5 | linux/x86_64 | ocaml-base-compiler.4.14.1 | https://opam.ocaml.org#a2d9de3b
# path        ~/.opam/stdlib/.opam-switch/build/conf-gmp.4
# command     ~/.opam/opam-init/hooks/sandbox.sh build sh -exc cc -c $CFLAGS -I/usr/local/include test.c
# exit-code   1
# env-file    ~/.opam/log/conf-gmp-178822-403927.env
# output-file ~/.opam/log/conf-gmp-178822-403927.out
### output ###
# + cc -c -I/home/linuxbrew/.linuxbrew/include -I/usr/local/include test.c
# test.c:1:10: fatal error: gmp.h: No such file or directory
#     1 | #include <gmp.h>
#       |          ^~~~~~~
# compilation terminated.



<><> Error report <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
┌─ The following actions failed
│ λ build conf-gmp 4
└─ 
╶─ No changes have been performed

This looks suspiciously like #6958, except that I've already set the CFLAGS to where the header file should be and indeed was:

$ ls $(brew --prefix)/include/gmp.h
/home/linuxbrew/.linuxbrew/include/gmp.h

What's more baffling for me is that if I run the build command manually, it works. If I do:

$ opam source conf-gmp
$ cd conf-gmp.4/
$ export CFLAGS="-I$(brew --prefix)/include" 

then this works:

$ sh -exc "cc -c $CFLAGS -I/usr/local/include test.c"
+ cc -c -I/home/linuxbrew/.linuxbrew/include -I/usr/local/include test.c

but this doesn't:

$ opam pin add .
...
<> Processing actions <><><><><><><><><><><><><><><><><><><><><><><><><><><><>
⬇ retrieved conf-gmp.4  (file:///run/media/deck/7964a95d-ebb5-4dc2-9346-f59577499d65/pm5/src/slacko/conf-gmp.4)
[ERROR] The compilation of conf-gmp.4 failed at "sh -exc cc -c $CFLAGS -I/usr/local/include test.c".

#=== ERROR while compiling conf-gmp.4 =========================================#
# context     2.1.5 | linux/x86_64 | ocaml-base-compiler.4.14.1 | pinned(file:///run/media/deck/7964a95d-ebb5-4dc2-9346-f59577499d65/pm5/src/slacko/conf-gmp.4)
# path        ~/.opam/stdlib/.opam-switch/build/conf-gmp.4
# command     ~/.opam/opam-init/hooks/sandbox.sh build sh -exc cc -c $CFLAGS -I/usr/local/include test.c
# exit-code   1
# env-file    ~/.opam/log/conf-gmp-179328-e15062.env
# output-file ~/.opam/log/conf-gmp-179328-e15062.out
### output ###
# + cc -c -I/home/linuxbrew/.linuxbrew/include -I/usr/local/include test.c
# test.c:1:10: fatal error: gmp.h: No such file or directory
#     1 | #include <gmp.h>
#       |          ^~~~~~~
# compilation terminated.



<><> Error report <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
┌─ The following actions failed
│ λ build conf-gmp 4
└─ 
╶─ No changes have been performed
[NOTE] Pinning command successful, but your installed packages may be out of sync.

This there anything I missed or I can try?

[arbipher]

I tried doing some experiments but did not find the reason yet. It may not be totally useless so let me share it here.

I don't know a good way to set custom homebrew prefix for experimenting, given I just use the default prefix (and it costs too much to totally re-install it).

I have a brew installed gmp and I did

/usr/local/Cellar/gmp/6.3.0$ mv include include-hack

The header file in the prefix path is just a soft link /usr/local/includegmp.h -> /usr/local/Cellar/gmp/6.3.0/include/gmp.h.

Now both opam install conf-gmp and opam pin add . fail and complain on cannot find <gmp.h>. The default CFLAGS is empty.

Then after export CFLAGS=-I/usr/local/Cellar/gmp/6.3.0/include-hack, both opam install conf-gmp and opam pin add . work.

I cannot reproduce your problem but would you like to check if the custom prefix in your machine does soft-links to the correct gmp/include path?

You can also add export $CFLAGS in the build section in the local opam's file (after opam source conf-gmp) to see if the $CFLAGS is passed correctly when running opam pin add . -vv (not sure if -vv is necessary).

[pm5]

Thanks for spending time with me on this. I checked the soft-link and it appears to be correct.

lrwxrwxrwx 1 deck deck 33 Feb 15 09:36 /home/linuxbrew/.linuxbrew/include/gmp.h -> ../Cellar/gmp/6.3.0/include/gmp.h

(Yes, I'm going through the trouble because I want to build OCaml programs on Steam Deck, whose SteamOS is Arch-based.)

I can also see the content of the header file with cat $(brew --prefix)/include/gmp.h.

Also tried adding the following as the first line in the build section of the local opam file:

["sh" "-exc" "export CFLAGS=/home/linuxbrew/.linuxbrew/include"]

but it didn't change the result. Plus, I think the compilation command (the line immediately before the failure on test.c) already says it got the CFLAGS argument, no?

# + cc -c -I/home/linuxbrew/.linuxbrew/include -I/usr/local/include test.c

[arbipher]

Maybe the reason is opam (sh -exc) cannot keep the environment across the actions inside the build.
Exported environment variables can only live with one shell process if I remember correctly.

If you add the debug commands in it

build: [
  ["sh" "-exc" "export FOO=/home/linuxbrew/.linuxbrew/include"]
  ["sh" "-exc" "echo $FOO"]
  ...

the log (opam install . --verbose) will have

+ /home/me/.opam/opam-init/hooks/sandbox.sh "build" "sh" "-exc" "export FOO=/home/linuxbrew/.linuxbrew/include" (CWD=/home/me/.opam/5.1.1/.opam-switch/build/conf-gmp.4)
- + export FOO=/home/linuxbrew/.linuxbrew/include
+ /home/me/.opam/opam-init/hooks/sandbox.sh "build" "sh" "-exc" "echo $FOO" (CWD=/home/me/.opam/5.1.1/.opam-switch/build/conf-gmp.4)
- + echo

This can also explain why your experiment works because a child process (sh -exc) can inherit environment variables from the parent shells.

$ export CFLAGS="-I$(brew --prefix)/include" 
sh -exc "cc -c $CFLAGS -I/usr/local/include test.c"