perl's TermReadKey fails to cross compile to armv7

[illegalprime]

First let me say that cross-compilation in Nix is awesome! Thank you everyone!

Issue description

Probably related to #34273.

Compiling this module (TermReadKey) for armv7l-hf-multiplatform fails, which leads to nix failing to compile other packages like git and ripgrep. The error is the following:

builder for '/nix/store/4s2r5jma26fkazlp1ingl2g2rvnijw8c-perl5.28.1-TermReadKey-2.37-armv7l-unknown-linux-gnueabihf.drv' failed with exit code 2; last 10 log lines:
   #   define WIDEST_UTYPE U64
   
  rm -f blib/arch/auto/Term/ReadKey/ReadKey.so
  armv7l-unknown-linux-gnueabihf-gcc  -shared  ReadKey.o  -o blib/arch/auto/Term/ReadKey/ReadKey.so  \
        \
    
  chmod 755 blib/arch/auto/Term/ReadKey/ReadKey.so
  "/nix/store/22w1n5jkpqa5yy7ks45xfqg5ygl18nsl-perl-5.28.1-armv7l-unknown-linux-gnueabihf/bin/perl" "-Iblib/arch" "-Iblib/lib" ReadKey_pm.PL ReadKey.pm
  /nix/store/vs6d2fjkl4kb3jb7rwibsd76k9v2n4xy-bash-4.4-p23/bin/bash: /nix/store/22w1n5jkpqa5yy7ks45xfqg5ygl18nsl-perl-5.28.1-armv7l-unknown-linux-gnueabihf/bin/perl: cannot execute binary file: Exec format error
  make: *** [Makefile:534: ReadKey.pm] Error 126
[0 built (1 failed), 0.0 MiB DL]
error: build of '/nix/store/4s2r5jma26fkazlp1ingl2g2rvnijw8c-perl5.28.1-TermReadKey-2.37-armv7l-unknown-linux-gnueabihf.drv' failed

After applying this diff:

diff --git a/pkgs/development/perl-modules/generic/default.nix b/pkgs/development/perl-modules/generic/default.nix
index a87e0c616fd..5b4d9ffa15c 100644
--- a/pkgs/development/perl-modules/generic/default.nix
+++ b/pkgs/development/perl-modules/generic/default.nix
@@ -1,4 +1,4 @@
-{ lib, stdenv, perl }:
+{ lib, stdenv, perl, buildPackages }:
 
 { nativeBuildInputs ? [], name, ... } @ attrs:
 
@@ -37,6 +37,6 @@ stdenv.mkDerivation (
     name = "perl${perl.version}-${name}";
     builder = ./builder.sh;
     nativeBuildInputs = nativeBuildInputs ++ [ (perl.dev or perl) ];
-    inherit perl;
+    perl = buildPackages.perl;
   }
 )

The error changes:

builder for '/nix/store/i52d724nqy0zw7kkxwvn4wqa47asw7qs-perl5.28.1-TermReadKey-2.37-armv7l-unknown-linux-gnueabihf.drv' failed with exit code 2; last 10 log lines:
        \
    
  chmod 755 blib/arch/auto/Term/ReadKey/ReadKey.so
  "/nix/store/9q11wzyadmm9nrx9nrmb7l2iwf52sprm-perl-5.28.1/bin/perl" "-Iblib/arch" "-Iblib/lib" ReadKey_pm.PL ReadKey.pm
  Can't load 'blib/arch/auto/Term/ReadKey/ReadKey.so' for module Term::ReadKey: blib/arch/auto/Term/ReadKey/ReadKey.so: wrong ELF class: ELFCLASS32 at /nix/store/9q11wzyadmm9nrx9nrmb7l2iwf52sprm-perl-5.28.1/lib/perl5/5.28.1/x86_64-linux-thread-multi/DynaLoader.pm line 193.
   at /nix/store/9q11wzyadmm9nrx9nrmb7l2iwf52sprm-perl-5.28.1/lib/perl5/5.28.1/x86_64-linux-thread-multi/DynaLoader.pm line 95.
        DynaLoader::croak("Can't load 'blib/arch/auto/Term/ReadKey/ReadKey.so' for modul"...) called at /nix/store/9q11wzyadmm9nrx9nrmb7l2iwf52sprm-perl-5.28.1/lib/perl5/5.28.1/x86_64-linux-thread-multi/DynaLoader.pm line 193
        DynaLoader::bootstrap("Term::ReadKey") called at ReadKey_pm.PL line 515
  Creating ReadKey.pm
  Bootstrapping the XS for blockoptions: make: *** [Makefile:534: ReadKey.pm] Error 255
[0 built (1 failed)]
error: build of '/nix/store/i52d724nqy0zw7kkxwvn4wqa47asw7qs-perl5.28.1-TermReadKey-2.37-armv7l-unknown-linux-gnueabihf.drv' failed

I can see that it's trying to load the wrong .so but I'm not sure how to debug beyond this point.

Steps to reproduce

1. clone nixpkgs and cd into it
2. nix build -f . pkgsCross.armv7l-hf-multiplatform.perlPackages.TermReadKey

Technical details

$ nix-shell -p nix-info --run "nix-info -m"
 - system: `"x86_64-linux"`
 - host os: `Linux 4.14.78, NixOS, 18.09.1185.9ea650bb5de (Jellyfish)`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.1.1`
 - channels(michael): `""`
 - channels(root): `"nixos-18.09"`
 - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixos`

[AlexLJordan]

I have the same problem with aarch64 right now. It's because as you can see here:

chmod 755 blib/arch/auto/Term/ReadKey/ReadKey.so
  "/nix/store/22w1n5jkpqa5yy7ks45xfqg5ygl18nsl-perl-5.28.1-armv7l-unknown-linux-gnueabihf/bin/perl" "-Iblib/arch" "-Iblib/lib" ReadKey_pm.PL ReadKey.pm
  /nix/store/vs6d2fjkl4kb3jb7rwibsd76k9v2n4xy-bash-4.4-p23/bin/bash: /nix/store/22w1n5jkpqa5yy7ks45xfqg5ygl18nsl-perl-5.28.1-armv7l-unknown-linux-gnueabihf/bin/perl: cannot execute binary file: Exec format error

It tries to execute /nix/store/.../bin/perl which of course fails because this binary is compiled for aarch64 (or armv7 in your case) not our current system ("x86_64-linux").

This is stopping me from compiling an aarch64 installation medium and I don't know how to fix this right now.

[illegalprime]

looks like yocto has to do a hack for this module as well:
http://cgit.openembedded.org/meta-openembedded/tree/meta-perl/recipes-perl/libterm/libterm-readkey-perl_2.37.bb?h=master

[illegalprime]

i think i have some kind of fix, will post later today

[illegalprime]

this was fixed by #56019