auto-patchelf: doesn't use existing RPATHs from executables

[corngood]

Nixpkgs version

• Unstable (25.05)

Describe the bug

According to auto-patchelf --help:

  --ignore-existing     Do not add the existing rpaths of the patched files to the list of directories to search for
                        dependencies.

This option was added in 62b6336 (Cc: @Pandapip1)

This implies that the existing RPATHs of patched files will be searched for dependencies. However, populate_cache limits itself to *.so*, so the RPATH of executables without an extension always ignored.

Steps to reproduce

$ nix build --impure --expr 'with import ./. {}; stdenvNoCC.mkDerivation { name = "test"; nativeBuildInputs = [ autoPatchelfHook ]; unpackPhase = ":"; installPhase = "install -Dm 755 ${perl}/bin/perl $out/bin/perl"; }'
error: builder for '/nix/store/qrvzl3fv0i2saaivfkyppjx93hya4jsc-test.drv' failed with exit code 1;
       last 25 log lines:
       >           PosixPath('/nix/store/h9lc1dpi14z7is86ffhl3ld569138595-audit-tmpdir.sh/lib'),
       >           PosixPath('/nix/store/m54bmrhj6fqz8nds5zcj97w9s9bckc9v-compress-man-pages.sh/lib'),
       >           PosixPath('/nix/store/wgrbkkaldkrlrni33ccvm3b6vbxzb656-make-symlinks-relative.sh/lib'),
       >           PosixPath('/nix/store/5yzw0vhkyszf2d179m0qfkgxmp5wjjx4-move-docs.sh/lib'),
       >           PosixPath('/nix/store/fyaryjvghbkpfnsyw97hb3lyb37s1pd6-move-lib64.sh/lib'),
       >           PosixPath('/nix/store/kd4xwxjpjxi71jkm6ka0np72if9rm3y0-move-sbin.sh/lib'),
       >           PosixPath('/nix/store/pag6l61paj1dc9sv15l7bm5c17xn5kyk-move-systemd-user-units.sh/lib'),
       >           PosixPath('/nix/store/cmzya9irvxzlkh7lfy6i82gbp0saxqj3-multiple-outputs.sh/lib'),
       >           PosixPath('/nix/store/hxv896faph0rqxjq2ycxpcrbnngc95sz-patch-shebangs.sh/lib'),
       >           PosixPath('/nix/store/cickvswrvann041nqxb0rxilc46svw1n-prune-libtool-files.sh/lib'),
       >           PosixPath('/nix/store/xyff06pkhki3qy1ls77w10s0v79c9il0-reproducible-builds.sh/lib'),
       >           PosixPath('/nix/store/z7k98578dfzi6l3hsvbivzm7hfqlk0zc-set-source-date-epoch-to-latest.sh/lib'),
       >           PosixPath('/nix/store/pilsssjjdxvdphlg2h19p0bfx5q0jzkn-strip.sh/lib')],
       >  'paths': [PosixPath('/nix/store/fb94vsj0lyk5xqd5wb7450m32j047ia4-test')],
       >  'recursive': True,
       >  'runtime_dependencies': []}
       > setting interpreter of /nix/store/fb94vsj0lyk5xqd5wb7450m32j047ia4-test/bin/perl
       > searching for dependencies of /nix/store/fb94vsj0lyk5xqd5wb7450m32j047ia4-test/bin/perl
       >     libperl.so -> not found!
       >     libcrypt.so.2 -> not found!
       > auto-patchelf: 2 dependencies could not be satisfied
       > error: auto-patchelf could not satisfy dependency libperl.so wanted by /nix/store/fb94vsj0lyk5xqd5wb7450m32j047ia4-test/bin/perl
       > error: auto-patchelf could not satisfy dependency libcrypt.so.2 wanted by /nix/store/fb94vsj0lyk5xqd5wb7450m32j047ia4-test/bin/perl
       > auto-patchelf failed to find all the required dependencies.
       > Add the missing dependencies to --libs or use `--ignore-missing="foo.so.1 bar.so etc.so"`.
       For full logs, run 'nix log /nix/store/qrvzl3fv0i2saaivfkyppjx93hya4jsc-test.drv'.

Expected behaviour

auto-patchelf should leave an executable unchanged if it's RPATH satisfies all dependencies.

Screenshots

No response

Relevant log output

Additional context

No response

System metadata

• system: "x86_64-linux"
• host os: Linux 6.14.0-rc7, NixOS, 25.05 (Warbler), 25.05.20250319.a84ebe2
• multi-user?: no
• sandbox: yes
• version: nix-env (Nix) 2.24.12
• channels(root): ""
• nixpkgs: not found

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[corngood]

Note that changing the file extension in the test script causes it to work:

$ nix build --impure --expr 'with import ./. {}; stdenvNoCC.mkDerivation { name = "test"; nativeBuildInputs = [ autoPatchelfHook ]; unpackPhase = ":"; installPhase = "install -Dm 755 ${perl}/bin/perl $out/bin/perl.so"; }'

[corngood]

Changing the glob in populate_cache to * does fix the problem, but I'm not sure if that's the right approach.

populate_cache currently does two things:

• add all .so files being patched to the cache (so they are preferred)

    # Add all shared objects of the current output path to the cache,
    # before lib_dirs, so that they are chosen first in find_dependency.

• recursively add all .so files in all rpaths to the cache

I'm not sure the latter is a good idea. Should we perhaps limit existing RPATHs to have an effect only on the ELF containing them?

populate_cache is also used on the lib dirs, where it probably does make sense to limit it to .so files, and to recurse (though maybe it should be optional?).