Subject: Re: bug#31970: epiphany: Strange "XXXXXXXXXXXXX..." entries in library RPATHs

From: [email-masked] (Ludovic Courtès)
Date: Tue, 26 Jun 2018 14:48:52 +0200

Hi Mark,

Mark H Weaver <[email-masked]> skribis:

> which also changed the build-system from 'glib-or-gtk-build-system' to
> 'meson-build-system', warnings started appearing in the build logs for
> epiphany complaining about "XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX"
> appearing in the RPATH of the built libraries.

I suspect the only way those XXX can end up here is if Meson adds them
through -Wl,-rpath.  And indeed, it does!  From compilers.py:

--8<---------------cut here---------------start------------->8---
    def build_unix_rpath_args(self, build_dir, from_dir, rpath_paths, build_rpath, install_rpath):
        if not rpath_paths and not install_rpath and not build_rpath:
            return []
        # The rpaths we write must be relative, because otherwise
        # they have different length depending on the build
        # directory. This breaks reproducible builds.
        rel_rpaths = []
        for p in rpath_paths:
            if p == from_dir:
                relative = '' # relpath errors out in this case
            else:
                relative = os.path.relpath(os.path.join(build_dir, p), os.path.join(build_dir, from_dir))
            rel_rpaths.append(relative)
        paths = ':'.join([os.path.join('$ORIGIN', p) for p in rel_rpaths])
        # Build_rpath is used as-is (it is usually absolute).
        if build_rpath != '':
            if paths != '':
                paths += ':'
            paths += build_rpath
        if len(paths) < len(install_rpath):
            padding = 'X' * (len(install_rpath) - len(paths))
            if not paths:
                paths = padding
            else:
                paths = paths + ':' + padding
--8<---------------cut here---------------end--------------->8---

So AIUI, those XXX are here precisely so we can overwrite the RUNPATH at
installation time with the final RUNPATH (this works around the fact
that Meson, unlike Libtool, doesn’t relink files upon install.)

We should take advantage of this in ‘meson-build-system’, or maybe we
don’t need to do anything?

> See below for the relevant excerpt of the build log.  Note also the
> RPATH entries preceeding "XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX",
> beginning with "$ORIGIN/".  I'm not sure if those are a problem or not.

Use of $ORIGIN is fine.

Thanks,
Ludo’.