Problem with Qt6 Xdg plugin's RPATH in deployment

Grit Clef

Hello,
Using Arch Linux ARM aarch64, Kernel: Linux 6.17.0, Qt: 6.10.2, Desktop: LXQt 2.3.0.
When I had tried to use Qt CMake deployment functions to deploy my application, like this:

qt_add_executable(FreePictureSplitter xxx.cpp)
qt_generate_deploy_app_script(
    TARGET FreePictureSplitter
    OUTPUT_SCRIPT deploy_script
    NO_UNSUPPORTED_PLATFORM_ERROR
)
install(SCRIPT ${deploy_script})

I encountered an error which halted the deployment process:

-- Installing: /opt/FreePictureSplitter/lib/qt6/plugins/iconengines/libQt6XdgIconPlugin.so
CMake Error at /usr/lib/cmake/Qt6Core/Qt6CoreDeploySupport.cmake:139 (file):
  file RPATH_SET could not write new RPATH:

    $ORIGIN/../../../

  to the file:

    /opt/FreePictureSplitter/lib/qt6/plugins/iconengines/libQt6XdgIconPlugin.so

  No valid ELF RPATH or RUNPATH entry exists in the file;
Call Stack (most recent call first):
  /usr/lib/cmake/Qt6Core/Qt6CoreDeploySupport.cmake:597 (_qt_internal_set_rpath)
  /usr/lib/cmake/Qt6Core/Qt6CoreDeploySupport.cmake:852 (_qt_internal_generic_deployqt)
  .qt/deploy_FreePictureSplitter_843d65e738.cmake:5 (qt6_deploy_runtime_dependencies)
  src/cmake_install.cmake:105 (include)
  cmake_install.cmake:47 (include)

The command

readelf -d /usr/lib/qt6/plugins/iconengines/libQt6XdgIconPlugin.so

printed

Dynamic section at offset 0xfcd8 contains 30 entries:
  Tag        Type                        Name/Value
 0x0000000000000001 (NEEDED)             Shared library：[libQt6XdgIconLoader.so.4]
 0x0000000000000001 (NEEDED)             Shared library：[libQt6Gui.so.6]
 0x0000000000000001 (NEEDED)             Shared library：[libQt6Core.so.6]
 0x0000000000000001 (NEEDED)             Shared library：[libstdc++.so.6]
 0x0000000000000001 (NEEDED)             Shared library：[libc.so.6]
 0x000000000000000c (INIT)               0x10e8
 0x000000000000000d (FINI)               0x16ac
 0x0000000000000019 (INIT_ARRAY)         0x1fbf0
 0x000000000000001b (INIT_ARRAYSZ)       16 (bytes)
 0x000000000000001a (FINI_ARRAY)         0x1fc00
 0x000000000000001c (FINI_ARRAYSZ)       8 (bytes)
 0x000000006ffffef5 (GNU_HASH)           0x2a8
 0x0000000000000005 (STRTAB)             0x618
 0x0000000000000006 (SYMTAB)             0x2d0
 0x000000000000000a (STRSZ)              1102 (bytes)
 0x000000000000000b (SYMENT)             24 (bytes)
 0x0000000000000003 (PLTGOT)             0x1ff08
 0x0000000000000002 (PLTRELSZ)           192 (bytes)
 0x0000000000000014 (PLTREL)             RELA
 0x0000000000000017 (JMPREL)             0x1028
 0x0000000000000007 (RELA)               0xb60
 0x0000000000000008 (RELASZ)             1224 (bytes)
 0x0000000000000009 (RELAENT)            24 (bytes)
 0x000000000000001e (FLAGS)              BIND_NOW
 0x000000006ffffffb (FLAGS_1)            Flags： NOW
 0x000000006ffffffe (VERNEED)            0xab0
 0x000000006fffffff (VERNEEDNUM)         4
 0x000000006ffffff0 (VERSYM)             0xa66
 0x000000006ffffff9 (RELACOUNT)          21
 0x0000000000000000 (NULL)               0x0

There's no rpath info. What should I do?

Christian Ehrlicher

You should it report to your distro packager or the author: https://github.com/lxqt/libqtxdg
This is not a plugin shipped directly with Qt.

Grit Clef

Reported, thanks.

Grit Clef

However I continuously received that error on libraries not belonging to Qt itself. For example, /usr/lib/qt6/plugins/platforminputcontexts/libfcitx5platforminputcontextplugin.so doesn't have RPATH information, either. I'd like to ask if there's a way to limit the generic Qt deploy tool to certain Qt libraries?

yan12125

Hi, LXQt co-maintainer here. I suspect there is something wrong in Qt's CMake files. As discussed at https://github.com/lxqt/libqtxdg/issues/329, RPATH_SET is an undocumented CMake command as mentioned at https://code.qt.io/cgit/qt/qtbase.git/commit/?id=5430fb22439db9fc1ad1df4cbf0319b63346b0a5. Moreover, the fallback patchelf approach (-DQT_DEPLOY_USE_PATCHELF=ON), works without an error. Maybe Qt should always use patchelf.

kevin009

The problem is that RPATH_SET can't set a RUNPATH if it doesn't already exist. It will only overwrite an existing value.

patchelf, however, will do this. So, as @yan12125 says, QT_DEPLOY_USE_PATCHELF=ON should work.