Build failure: dbus-cplusplus aarch64

[andrewbaxter]

Steps To Reproduce

Steps to reproduce the behavior:

1. cross compile dbus-cplusplus from x86_64 to aarch64.

Build log

https://gist.github.com/andrewbaxter/22b065690b56b4ed5442a24cb9dd15b9

Additional context

I'm not familiar with automake conventions, but is this caused by

CXX = $(CXX_FOR_BUILD)

in tools/Makefile.am? If I understood correctly, CXX_FOR_BUILD is the cross compiler, so the tools are built for the target arch. However these tools are used on the build system for other parts of the build, so need to be executable on the build system.

I looked around for other patches but couldn't find distros packaging this for arch. The SF patches list had one patch that went even further here, overriding CXXFLAGS + co in a similar manner.

Notify maintainers

@cillianderoiste

Metadata

$ nix-shell -p nix-info --run "nix-info -m"
this path will be fetched (0.00 MiB download, 0.00 MiB unpacked):
  /nix/store/kajzlkh8kydmflf8ir8iid9ig0zrd90n-nix-info
copying path '/nix/store/kajzlkh8kydmflf8ir8iid9ig0zrd90n-nix-info' from 'https://cache.nixos.org'...
 - system: `"x86_64-linux"`
 - host os: `Linux 6.5.5-arch1-1, Arch Linux, noversion, rolling`
 - multi-user?: `no`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.11.1`
 - channels(...): `"nixpkgs"`
 - nixpkgs: `/home/.../.nix-defexpr/channels/nixpkgs`
 - ```

[andrewbaxter]

Apparently it also sets CXX_FOR_BUILD to CXX maybe? I found a patch that deletes both of those (remove_CXX_FOR_BUILD_stuff) https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl-demo/+/10455

[andrewbaxter]

CXX_FOR_BUILD is actually what it should be using I guess, but it looks like somewhere else sets CXX_FOR_BUILD to CXX, hence why the later CXX = CXX_FOR_BUILD doesn't help.

I tried adding the autoconf-archive ax_prog_cxx_for_build.m4 macro like

          (final: prev: {
            dbus_cplusplus = prev.dbus_cplusplus.overrideAttrs (old: {
              nativeBuildInputs = old.nativeBuildInputs ++ [
                pkgs.autoreconfHook
              ];
              patches = old.patches ++ [
                ./dbus-cplusplus-tools-cxx.patch
              ];
              preAutoreconf = ''
                cp ${./ax_prog_cxx_for_build.m4} m4/
              '';
            });
          })

with

diff -Naur libdbus-c++-0.9.0.ori/configure.ac libdbus-c++-0.9.0/configure.ac
--- libdbus-c++-0.9.0.ori/configure.ac  2016-11-15 14:25:36.085882774 +0100
+++ libdbus-c++-0.9.0/configure.ac  2016-11-15 14:27:08.814568717 +0100
@@ -64,9 +64,8 @@
 AC_PROG_CC
 AC_PROG_CXX

-CXX_FOR_BUILD=${CXX_FOR_BUILD-${CXX}}
-AC_SUBST(CXX_FOR_BUILD)
+AC_PROG_CXX_FOR_BUILD

 AM_PROG_LIBTOOL

 PKG_PROG_PKG_CONFIG
diff -Naur libdbus-c++-0.9.0.ori/tools/Makefile.am libdbus-c++-0.9.0/tools/Makefile.am
--- libdbus-c++-0.9.0.ori/tools/Makefile.am 2016-11-15 14:25:36.089882803 +0100
+++ libdbus-c++-0.9.0/tools/Makefile.am 2016-11-15 14:26:19.454203583 +0100
@@ -1,7 +1,5 @@
 # hacky, but ...

-CXX = $(CXX_FOR_BUILD)
-
 AM_CPPFLAGS = \
    $(dbus_CFLAGS) \
    $(xml_CFLAGS) \

but getting

./configure: line 6474: AX_PROG_CC_FOR_BUILD: command not found
checking how to run the C++ preprocessor... aarch64-unknown-linux-gnu-g++ -E
checking for x86_64-unknown-linux-gnu-g++... no
checking for x86_64-unknown-linux-gnu-c++... no
...
checking for g++... no
checking for c++... no
...
configure: error: C++ preprocessor "/lib/cpp" fails sanity check

Not sure about the AX_PROG_CC_FOR_BUILD thing when it's apparently running it, it seems like I just need some more native inputs here.

[andrewbaxter]

Ah... I guess both buildInputs and nativeBuildInputs use the host arch, not build arch. depsBuildBuild seems to work. Some progress with

          (final: prev: {
            dbus_cplusplus = prev.dbus_cplusplus.overrideAttrs (old: {
              # https://github.com/NixOS/nixpkgs/issues/268533
              depsBuildBuild = [
                pkgs.autoreconfHook
                pkgs.gcc
                pkgs.pkg-config
                pkgs.expat
                pkgs.dbus
              ];
              patches = old.patches ++ [
                ./dbus-cplusplus-tools-cxx.patch
              ];
              preAutoreconf = ''
                cp ${./ax_prog_cc_for_build.m4} m4/
                cp ${./ax_prog_cxx_for_build.m4} m4/
              '';
            });
          })

but it's now using aarch64 headers and libs for linking the tool. I modified the patch to overload CXXFLAGS and LDFLAGS but it looks like the issue is actually pkgconfig is finding aarch64 packages.

There's no AC_CHECK_LIB_FOR_BUILD afaict and I'm not excited to set forth on the adventure of writing it myself.

I wonder if it would be easier to split this into two packages... actually maybe I can just patch uses of dbusxx-* with the binaries from the build-arch package (are they distributed?)

[andrewbaxter]

This worked

let
  buildPkgs = (import
    (nixpkgs_path + /nixos/lib/eval-config.nix)
    {
      system = builtins.currentSystem;
      modules = [{ }];
    }).pkgs;
in
...
          (final: prev: {
            dbus_cplusplus = prev.dbus_cplusplus.overrideAttrs (old: {
              # https://github.com/NixOS/nixpkgs/issues/268533
              postConfigure = ''
                ${buildPkgs.findutils}/bin/find . -type f -exec ${buildPkgs.gnused}/bin/sed -i -e 's^..top_builddir..tools.dbusxx-xml2cpp^${buildPkgs.dbus_cplusplus}/bin/dbusxx-xml2cpp^' {} \;
              '';
            });
          })

No patches, etc, just replacing the calls to -xml2cpp.

I'm sure there's a better way to refer to non-host packages though, but google and discord failed me.