Allows to share CMake variables in multi-ABI builds
This variable was introduced in Qt 6.4.2.
Note: This variable is in technology preview and may change in future releases.
Note: This variable is used only if targeting the Android platform.
QT_ANDROID_MULTI_ABI_FORWARD_VARS variable allows specifying the list of CMake variables that need to be forwarded from the main ABI project to ABI-specific subprojects. Due to the specifics of the Multi-ABI project build process, there is no generic way to forward the CMake cache variables that are specified either in the command line or in another similar way.
A typical use case for the variable is propagating CMake cache variables specified in the command line. For example, a project has two variables
PROJECT_WIDE_VARIABLE2 that affect the project configuration:
cmake_minimum_required(VERSION 3.18) project(MyProject LANGUAGES CXX) find_package(Qt6 REQUIRED COMPONENTS Core) qt_add_executable(MyApp main.cpp) if(PROJECT_WIDE_VARIABLE1) target_sources(MyApp PRIVATE sourcefile1.cpp) endif() if(PROJECT_WIDE_VARIABLE2) target_sources(MyApp PRIVATE sourcefile2.cpp) endif()
The above contents of
CMakeLists.txt enable you to control how
MyApp is built by setting the corresponding CMake variables from the command line:
qt-cmake -S<source directory> -B<build directory> \ -DPROJECT_WIDE_VARIABLE1=ON \ -DPROJECT_WIDE_VARIABLE2=ON \ -DQT_ANDROID_MULTI_ABI_FORWARD_VARS="PROJECT_WIDE_VARIABLE1;PROJECT_WIDE_VARIABLE2"
When configuring the application for desktop,
PROJECT_WIDE_VARIABLE2 are visible in CMake listings and scripts as global cache variables. This doesn't work for Android Multi-ABI builds because ABI-specific subprojects do not inherit the cache variables from the main-ABI project. This issue can be solved by passing the list of required variables to the
QT_ANDROID_MULTI_ABI_FORWARD_VARS variable, so both
PROJECT_WIDE_VARIABLE2 values will be propagated to the ABI-specific builds.
The variable can be also defined in the project's CMakeLists.txt:
... qt_add_executable(MyApp main.cpp) ... if(ANDROID) set(QT_ANDROID_MULTI_ABI_FORWARD_VARS "PROJECT_WIDE_VARIABLE1;PROJECT_WIDE_VARIABLE2") endif() ...
Setting the variable in this way allows you to have a predefined set of variables that will always be forwarded to abi-specific projects.
Note: The forwarding is done in the target finalizer, which is implicitly called when qt_add_executable() is used. The finalization occurs automatically when using CMake 3.19 or later.
See also qt_finalize_target() and qt_add_executable().
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