CMakeLists引入Qt5::QML失败，编译报错求助

问题详情 #

编译ROS包osm_map时，Qt的Widgets模块可正常识别，但Qt5::Qml目标找不到。已确认系统中Qt QML模块的头文件存在于/usr/include/x86_64-linux-gnu/qt5/QtQml路径下。

我的CMakeLists.txt代码 #

cmake_minimum_required(VERSION 3.0.2)
project(osm_map)
find_package(catkin REQUIRED COMPONENTS rviz)

find_package(Qt5 COMPONENTS Widgets REQUIRED)
set(QT_LIBRARIES Qt5::Widgets Qt5::Qml)

set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTORCC ON)
set(CMAKE_AUTOUIC ON)

set(SRC_FILES
  src/core.cpp
)

add_library(${PROJECT_NAME} ${SRC_FILES})
target_link_libraries(${PROJECT_NAME} ${QT_LIBRARIES} ${catkin_LIBRARIES})

编译命令 #

catkin_make -Wno-dev --only-pkg-with-deps osm_map

报错信息 #

CMake Error at osm_map/CMakeLists.txt:53 (target_link_libraries):
  Target "osm_map" links to:

    Qt5::Qml

  but the target was not found.  Possible reasons include:

    * There is a typo in the target name.
    * A find_package call is missing for an IMPORTED target.
    * An ALIAS target is missing.

原因分析 #

问题出在find_package(Qt5)的调用上：CMake的Qt5查找机制要求必须在COMPONENTS列表中明确声明需要的模块，才会生成对应模块的导入目标（如Qt5::Qml）。即便系统已安装QML模块，只要find_package没指定该模块，CMake就不会自动识别并生成这个目标。

解决方法 #

1. 修改find_package调用，添加Qml模块 #

将find_package(Qt5)的行修改为：

find_package(Qt5 COMPONENTS Widgets Qml REQUIRED)

2. 优化库链接变量（可选） #

find_package(Qt5)会自动生成Qt5_LIBRARIES变量，包含所有指定模块的库目标，可直接用这个变量替代手动拼接的QT_LIBRARIES，简化代码。

修改后的完整CMakeLists.txt #

cmake_minimum_required(VERSION 3.0.2)
project(osm_map)
find_package(catkin REQUIRED COMPONENTS rviz)

find_package(Qt5 COMPONENTS Widgets Qml REQUIRED)

set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTORCC ON)
set(CMAKE_AUTOUIC ON)

set(SRC_FILES
  src/core.cpp
)

add_library(${PROJECT_NAME} ${SRC_FILES})
target_link_libraries(${PROJECT_NAME} ${Qt5_LIBRARIES} ${catkin_LIBRARIES})

修改后重新执行编译命令，即可正常找到Qt5::Qml目标。

内容的提问来源于stack exchange，提问作者cmosig