Add `qt_host` Option to Enable Cross-Platform Qt Builds Using Host SDK Tools #6097

Doekin · 2025-01-19T05:22:37Z

This update introduces an option, qt_host, to facilitate cross-building of Qt desktop applications.

Example Usage

Build a Qt Widgets app for MinGW on Linux
Using an SDK downloaded by aqt:

xmake f -c -p mingw --qt=../sdk/6.9.0/llvm-mingw_64 --qt_host=../sdk/6.9.0/gcc_64

Build a Qt Widgets app for Linux on Windows
Using an SDK downloaded by aqt and the Zig toolchain:

xmake f -c -p linux --toolchain=zig --qt=../sdk/6.9.0/gcc_64 --qt_host=../sdk/6.9.0/llvm-mingw_64

Caution

Ensure the host Qt version matches the target version.
The rules qt.deploy and qt.install might cause cross-platform issues, as windeployqt and macdeployqt need to run on their native platforms.

Tested Configurations

Cross-Builds:
- Qt 6.9.0 for Linux built on Windows with the Zig toolchain
- Qt 6.9.0 for MinGW built on Linux
- Qt 6.8.0 for Android built on Windows
Native Builds (Regression Tests):
- Qt 6.8.1 for Linux (system-installed)
- Qt 5.15.16 for Linux (system-installed)
- Qt 6.9.0 for Linux (downloaded via aqt)
- Qt 6.9.0 for MinGW

Doekin · 2025-01-19T05:38:35Z

The -qtconf argument is valid for both qmake5 and qmake6.

Help message for qmake-qt5

$ qmake-qt5 -v
QMake version 3.1
Using Qt version 5.15.16 in /usr/lib

$ qmake-qt5 -help
Usage: qmake-qt5 [mode] [options] [files]

QMake has two modes, one mode for generating project files based on
some heuristics, and the other for generating makefiles. Normally you
shouldn't need to specify a mode, as makefile generation is the default
mode for qmake, but you may use this to test qmake on an existing project

Mode:
  -project       Put qmake into project file generation mode
                 In this mode qmake interprets [files] as files to
                 be added to the .pro file. By default, all files with
                 known source extensions are added.
                 Note: The created .pro file probably will 
                 need to be edited. For example add the QT variable to 
                 specify what modules are required.
  -makefile      Put qmake into makefile generation mode (default)
                 In this mode qmake interprets files as project files to
                 be processed, if skipped qmake will try to find a project
                 file in your current working directory

Warnings Options:
  -Wnone         Turn off all warnings; specific ones may be re-enabled by
                 later -W options
  -Wall          Turn on all warnings
  -Wparser       Turn on parser warnings
  -Wlogic        Turn on logic warnings (on by default)
  -Wdeprecated   Turn on deprecation warnings (on by default)

Options:
   * You can place any variable assignment in options and it will be *
   * processed as if it was in [files]. These assignments will be    *
   * processed before [files] by default.                            *
  -o file        Write output to file
  -d             Increase debug level
  -t templ       Overrides TEMPLATE as templ
  -tp prefix     Overrides TEMPLATE so that prefix is prefixed into the value
  -help          This help
  -v             Version information
  -early         All subsequent variable assignments will be
                 parsed right before default_pre.prf
  -before        All subsequent variable assignments will be
                 parsed right before [files] (the default)
  -after         All subsequent variable assignments will be
                 parsed after [files]
  -late          All subsequent variable assignments will be
                 parsed right after default_post.prf
  -norecursive   Don't do a recursive search
  -recursive     Do a recursive search
  -set <prop> <value> Set persistent property
  -unset <prop>  Unset persistent property
  -query <prop>  Query persistent property. Show all if <prop> is empty.
  -qtconf file   Use file instead of looking for qt.conf
  -cache file    Use file as cache           [makefile mode only]
  -spec spec     Use spec as QMAKESPEC       [makefile mode only]
  -nocache       Don't use a cache file      [makefile mode only]
  -nodepend      Don't generate dependencies [makefile mode only]
  -nomoc         Don't generate moc targets  [makefile mode only]
  -nopwd         Don't look for files in pwd [project mode only]

Doekin · 2025-01-19T05:51:52Z

It's important to note that qmake reports its own version instead of the SDK version specified by -qtconf. For example, when running:

qmake -query -qtconf ../sdk/6.9.0/llvm-mingw_64/bin/qt.conf

The output shows:

QT_SYSROOT:
QT_INSTALL_PREFIX:/run/media/leemu/D8C48579C4855B20/projects/qt/sdk/6.9.0/llvm-mingw_64
...
QT_VERSION:5.15.16

Notice that QT_VERSION is 5.15.16, not 6.9.0 as expected. This discrepancy may lead to XMake incorrectly identifying the Qt SDK version:

$ xmake f -c -vD --qt=../sdk/6.9.0/llvm-mingw_64 --qt_host=../sdk/6.8.1/gcc_64 -p mingw

The output shows:

checking for Qt SDK version ... 6.8.1

The Qt SDK version should be 6.9.0

Doekin · 2025-01-19T08:35:20Z

This discrepancy may lead to XMake incorrectly identifying the Qt SDK version

It is fixed now.

waruqi · 2025-01-19T13:59:11Z

Why is an additional qt_host needed? I remember that cross-compilation was also supported now.

It can do cross-compilation for ios/android.

xmake/xmake/modules/detect/sdks/find_qt.lua

Lines 244 to 262 in 1ea11f3

    
           local bindir_host = qtenvs.QT_HOST_BINS 
        
           if not bindir_host and libexecdir and is_plat("android", "iphoneos") then 
        
               local rootdir = path.directory(path.directory(bindir)) 
        
               if is_host("macosx") then 
        
                   bindir_host = path.join(rootdir, "macos", "bin") 
        
               else 
        
                   -- TODO 
        
               end 
        
           end 
        
           local libexecdir_host = qtenvs.QT_HOST_LIBEXECS 
        
           if not libexecdir_host and libexecdir and is_plat("android", "iphoneos") then 
        
               local rootdir = path.directory(path.directory(libexecdir)) 
        
               if is_host("macosx") then 
        
                   libexecdir_host = path.join(rootdir, "macos", "libexec") 
        
               else 
        
                   -- TODO 
        
               end 
        
           end 
        
           return {sdkdir = sdkdir, bindir = bindir, bindir_host = bindir_host, libexecdir = libexecdir, libexecdir_host = libexecdir_host, libdir = libdir, includedir = includedir, qmldir = qmldir, pluginsdir = pluginsdir, mkspecsdir = mkspecsdir, sdkver = sdkver}

and did you test qt5base/qt6base packages? it also supports cross-compilation without extra qt_host sdk.

https://github.com/xmake-io/xmake-repo/blob/a266c2344972fd8d7cce4301b1a02500db9afa1c/packages/q/qtbase/xmake.lua#L153

Doekin · 2025-01-19T14:22:07Z

The current setup doesn't support building Qt applications for Linux on Windows, or vice versa.

Regarding the qt6base package, I've encountered issues where it fails to function properly, with errors like:

$ xmake f -c -vD -p linux -a x86_64 --toolchain=zig
.........
checking for qt6widgets ... no
note: install or modify (m) these packages (pass -y to skip confirm)?
in myrepo:
  -> qt6base 6.8.0 [from:qt6gui,qt6core,qt6widgets, license:LGPL-3]
  -> qt6core 6.8.0 [toolchains:"zig", from:qt6gui,qt6widgets, license:LGPL-3]
  -> zlib v1.3.1 [toolchains:"zig", from:freetype, license:zlib]
  -> freetype 2.13.1 [toolchains:"zig", from:fontconfig,qt6gui, license:BSD]
  -> meson 1.6.1 [host, from:wayland,libxkbcommon,fontconfig, license:Apache-2.0]
  -> expat 2.6.4 [toolchains:"zig", from:fontconfig,wayland, license:MIT]
  -> gperf 3.1 [host, from:fontconfig, license:GPL-3.0-or-later]
  -> fontconfig 2.14.2 [toolchains:"zig", from:qt6gui]
  -> libxml2 v2.13.4 [toolchains:"zig", from:wayland, license:MIT]
  -> libffi 3.4.6 [toolchains:"zig", from:wayland, license:MIT]
  -> wayland 1.23.0 [toolchains:"zig", from:libxkbcommon, license:MIT]
  -> libxkbcommon 1.0.3 [toolchains:"zig", from:qt6gui, license:MIT]
  -> qt6gui 6.8.0 [toolchains:"zig", from:qt6widgets, license:LGPL-3]
  -> qt6widgets 6.8.0 [toolchains:"zig", license:LGPL-3]
please input: y (y/n/m)

checking for ping ... ok
pinging the host(downloads.sourceforge.net) ... 65535 ms
pinging the host(github.com) ... 100 ms
pinging the host(gitlab.freedesktop.org) ... 65535 ms
pinging the host(www.freedesktop.org) ... 218 ms
pinging the host(download.savannah.gnu.org) ... 65535 ms
pinging the host(gitlab.gnome.org) ... 65535 ms
aqt install-qt -O C:\Users\leemu\AppData\Local\.xmake\packages\q\qt6base\6.8.0\c9e1ef6b685d43d6b38c1427181ac297 windows desktop 6.8.0 linux_gcc_64
INFO    : aqtinstall(aqt) v3.1.17 on Python 3.12.4 [CPython MSC v.1940 64 bit (AMD64)]
WARNING : Specified Qt version "6.8.0" did not exist when this version of aqtinstall was released. This may not install properly, but we will try our best.
WARNING : Specified target combination "windows desktop linux_gcc_64" did not exist when this version of aqtinstall was released. This may not install properly, but we will try our best.
ERROR   : The packages ['qt_base'] were not found while parsing XML of package information!
==============================Suggested follow-up:==============================
* Please use 'aqt list-qt windows desktop --arch 6.8.0' to show architectures available.
error: @programdir\core\sandbox\modules\os.lua:378: execv(aqt install-qt -O C:\Users\leemu\AppData\Local\.xmake\packages\q\qt6base\6.8.0\c9e1ef6b685d43d6b38c1427181ac297 windows desktop 6.8.0 linux_gcc_64) failed(1)
stack traceback:
    [C]: in function 'error'
    [@programdir\core\base\os.lua:1075]:
    [@programdir\core\sandbox\modules\os.lua:378]:
    [@programdir\core\sandbox\modules\os.lua:291]: in function 'vrunv'
    [D:\projects\xmake-repo\packages\q\qtbase\xmake.lua:147]:
    [D:\projects\xmake-repo\packages\q\qt6base\xmake.lua:26]: in function 'script'
    [...dir\modules\private\action\require\impl\utils\filter.lua:114]: in function 'call'
    [...\modules\private\action\require\impl\actions\install.lua:452]:

  => install qt6base 6.8.0 .. failed
error: @programdir\core\main.lua:329: @programdir\modules\async\runjobs.lua:325: ...\modules\private\action\require\impl\actions\install.lua:561: install failed!
stack traceback:
    [C]: in function 'error'
    [@programdir\core\base\os.lua:1075]:
    [...\modules\private\action\require\impl\actions\install.lua:561]: in function 'catch'
    [@programdir\core\sandbox\modules\try.lua:123]: in function 'try'
    [...\modules\private\action\require\impl\actions\install.lua:419]:
    [...modules\private\action\require\impl\install_packages.lua:510]: in function 'jobfunc'
    [@programdir\modules\async\runjobs.lua:241]:

Doekin · 2025-01-22T00:55:33Z

Additional Notes:

The Qt SDK consists of two main components: libraries and tools (e.g., qmake, moc, uic, etc.), where libraries are specific to the target platform.

Since Qt SDKs are not typically configured for cross-platform use, cross-compilation requires two separate SDKs:

Target-Dependent SDK: Includes the libraries the application links against, built for the target platform. It may also contain Qt tools that are incompatible with the build machine.
Host-Dependent SDK: Provides the tools needed for the build process, compatible with the build machine.

waruqi · 2025-01-22T01:35:03Z

xmake/rules/qt/moc/xmake.lua

-            moc = path.join(qt.libexecdir_host, is_host("windows") and "moc.exe" or "moc")
+        local moc
+        local moc_name = is_host("windows") and "moc.exe" or "moc"
+        for _, dir in ipairs({qt.bindir_host, qt.libexecdir_host, qt.bindir, qt.libexecdir}) do


we can use lib.detect.find_file

waruqi · 2025-01-22T01:35:13Z

xmake/rules/qt/qmltyperegistrar/xmake.lua

+        for _, dir in ipairs({qt.bindir_host, qt.libexecdir_host, qt.bindir, qt.libexecdir}) do
+            if dir then
+                qmltyperegistrar = path.join(dir, qmltyperegistrar_name)
+                if os.isexec(qmltyperegistrar) then


waruqi · 2025-01-22T01:35:24Z

xmake/rules/qt/ts/xmake.lua

+            for _, dir in ipairs({qt.bindir_host, qt.libexecdir_host, qt.bindir, qt.libexecdir}) do
+                if dir then
+                    lupdate = path.join(dir, lupdate_name)
+                    if os.isexec(lupdate) then


waruqi · 2025-01-22T01:36:37Z

Did you test for qt5base/qt6base packages?

Doekin · 2025-01-22T01:46:42Z

qt5base/qt6base does not support cross-compilation well. Cross-compiling for desktop platforms is not supported, and Android targets are not enabled.

https://github.com/xmake-io/xmake-repo/blob/4fd9216b6d1bd108f9211849a4bfd3b1b6f96b3c/packages/q/qt6base/xmake.lua#L25-L27

waruqi · 2025-01-22T08:26:26Z

xmake/rules/qt/ui/xmake.lua

-        if not os.isexec(uic) and qt.libexecdir_host then
-            uic = path.join(qt.libexecdir_host, is_host("windows") and "uic.exe" or "uic")
-        end
+        local uic = find_file(is_host("windows") and "uic.exe" or "uic", {qt.bindir_host, qt.libexecdir_host, qt.bindir, qt.libexecdir})


if dir is nil, e.g. {dir1, nil, dir2, dir3}, find_file/ipairs will be broken.

local dirs = {} if dir then table.insert(dirs, dir) end

waruqi · 2025-01-22T08:27:10Z

xmake/modules/detect/sdks/find_qt.lua

+        return sdkver
+    end
+    -- Extract the actual SDK version from qconfig.pri
+    local actual_sdkver = io.readfile(qconfig_path):match("QT_VERSION%s*=%s*(%S+)") -- Expected format: QT_VERSION = x.y.z


readfile maybe return nil

waruqi · 2025-01-22T09:10:56Z

xmake/rules/qt/deploy/android.lua

-        androiddeployqt = path.join(qt.bindir_host, "androiddeployqt" .. (is_host("windows") and ".exe" or ""))
-    end
+    local search_dirs = {}
+    if qt.bindir_host       then table.insert(search_dirs, qt.bindir_host       ) end


remove spaces, we don't need alignment

…K tools

waruqi · 2025-01-22T14:25:45Z

Thanks, can you help to update docs here https://xmake.io/#/guide/project_examples?id=supported-qt-sdks

Doekin · 2025-01-22T14:28:51Z

OK, I'd be happy to help

Doekin marked this pull request as ready for review January 19, 2025 08:30

Doekin changed the title ~~Add cross-platform build support for Qt desktop applications~~ Add qt_host Option to Enable Cross-Platform Qt Builds Using Host SDK Tools Jan 19, 2025

Doekin marked this pull request as draft January 19, 2025 17:42

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Doekin force-pushed the cross-qt branch from 92ff817 to 3e16571 Compare January 21, 2025 13:26

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Add qt_host option to enable cross-platform Qt Builds using host SD…

bb89dfc

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Doekin force-pushed the cross-qt branch from cd5a5d1 to bb89dfc Compare January 22, 2025 09:25

waruqi added this to the v2.9.8 milestone Jan 22, 2025

waruqi merged commit 590cb76 into xmake-io:dev Jan 22, 2025
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交叉编译环境中，Qt找不到uic #4809

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Doekin mentioned this pull request Jan 25, 2025

docs: add qt_host option documentation xmake-io/xmake-docs#199

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Add `qt_host` Option to Enable Cross-Platform Qt Builds Using Host SDK Tools #6097

Add `qt_host` Option to Enable Cross-Platform Qt Builds Using Host SDK Tools #6097

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Add qt_host Option to Enable Cross-Platform Qt Builds Using Host SDK Tools #6097

Add qt_host Option to Enable Cross-Platform Qt Builds Using Host SDK Tools #6097

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Doekin commented Jan 19, 2025 • edited Loading

Example Usage

Caution

Tested Configurations

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Additional Notes:

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Add `qt_host` Option to Enable Cross-Platform Qt Builds Using Host SDK Tools #6097

Add `qt_host` Option to Enable Cross-Platform Qt Builds Using Host SDK Tools #6097

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