find_package() 忽略<PackageName>_ROOT

Question

在我的CMake脚本中，我将路径附加到包含<PackageName>Config.cmake到<PackageName>_ROOT的文件夹，然后调用find_package(<PackageName> REQUIRED)，但它找不到我的包。

当我使用CMAKE_FIND_DEBUG_MODE时，我看到我的文件夹在<PackageName>_ROOT CMake variable [CMAKE_FIND_USE_PACKAGE_ROOT_PATH]中列出(它实际上是那里唯一的文件夹)，但它没有在find_package considered the following locations for the Config module:之后列出。

为什么我得到这样的行为?我使用CMake 3.18.1从Android Studio。我想找到的包是OpenCV。

---

相对于我的CMakeLists.txt文件OpenCV安装在../../build/opencv-build<custom suffix>中，所以我的代码找到它是:

get_filename_component(OPENCV_BUILD_DIRS_ROOT ../../build REALPATH)
file(GLOB OPENCV_BUILD_DIRS ${OPENCV_BUILD_DIRS_ROOT}/opencv-build*)
list(APPEND OpenCV_ROOT ${OPENCV_BUILD_DIRS})
find_package(OpenCV ${OPENCV_VERSION} REQUIRED ${OPENCV_PUBLIC_LIBRARIES} ${OPENCV_PRIVATE_LIBRARIES})

当我在Linux上运行它时(实际上是WSL)，一切工作正常，CMake在../../build/opencv-build(或<project path>/build/opencv-build的绝对路径形式)中成功找到OpenCV。

但是当我试图从Android Studio构建项目时，它没有，我从CMAKE_FIND_DEBUG_MODE得到这个输出:

CMake Debug Log at external/opencv/CMakeLists.txt:12 (find_package):
find_package considered the following paths for OpenCV.cmake
C:/Users/<username>/AppData/Local/Android/Sdk/cmake/3.18.1/share/cmake-3.18/Modules/FindOpenCV.cmake
The file was not found.
<PackageName>_ROOT CMake variable [CMAKE_FIND_USE_PACKAGE_ROOT_PATH].
<project path>/build/opencv-build

CMAKE_PREFIX_PATH variable [CMAKE_FIND_USE_CMAKE_PATH].
C:/Users/<username>/AppData/Local/Android/Sdk/ndk/23.1.7779620/toolchains/llvm/prebuilt/windows-x86_64

CMAKE_FRAMEWORK_PATH and CMAKE_APPBUNDLE_PATH variables
[CMAKE_FIND_USE_CMAKE_PATH].

Env variable OpenCV_DIR [CMAKE_FIND_USE_CMAKE_ENVIRONMENT_PATH].
none
CMAKE_PREFIX_PATH env variable [CMAKE_FIND_USE_CMAKE_ENVIRONMENT_PATH].
none
CMAKE_FRAMEWORK_PATH and CMAKE_APPBUNDLE_PATH env variables
[CMAKE_FIND_USE_CMAKE_ENVIRONMENT_PATH].
none
Paths specified by the find_package HINTS option.
none
Standard system environment variables
[CMAKE_FIND_USE_SYSTEM_ENVIRONMENT_PATH].
<a lot of unrelated directories>

CMake User Package Registry [CMAKE_FIND_USE_PACKAGE_REGISTRY].
none
CMake variables defined in the Platform file
[CMAKE_FIND_USE_CMAKE_SYSTEM_PATH].
C:/Users/<username>/AppData/Local/Android/Sdk/cmake/3.18.1
<other unrelated directories>

CMake System Package Registry
[CMAKE_FIND_PACKAGE_NO_SYSTEM_PACKAGE_REGISTRY].
none
Paths specified by the find_package PATHS option.
none
find_package considered the following locations for the Config module:
C:/Users/<username>/AppData/Local/Android/Sdk/ndk/23.1.7779620/toolchains/llvm/prebuilt/windows-x86_64/OpenCVConfig.cmake
C:/Users/<username>/AppData/Local/Android/Sdk/ndk/23.1.7779620/toolchains/llvm/prebuilt/windows-x86_64/opencv-config.cmake
C:/Users/<username>/AppData/Local/Android/Sdk/ndk/23.1.7779620/OpenCVConfig.cmake
C:/Users/<username>/AppData/Local/Android/Sdk/ndk/23.1.7779620/opencv-config.cmake
C:/Users/<username>/AppData/Local/Android/Sdk/ndk/23.1.7779620/toolchains/llvm/prebuilt/windows-x86_64/sysroot/usr/lib/i686-linux-android/21/OpenCVConfig.cmake
C:/Users/<username>/AppData/Local/Android/Sdk/ndk/23.1.7779620/toolchains/llvm/prebuilt/windows-x86_64/sysroot/usr/lib/i686-linux-android/21/opencv-config.cmake
C:/Users/<username>/AppData/Local/Android/Sdk/ndk/23.1.7779620/toolchains/llvm/prebuilt/windows-x86_64/sysroot/usr/local/OpenCVConfig.cmake
C:/Users/<username>/AppData/Local/Android/Sdk/ndk/23.1.7779620/toolchains/llvm/prebuilt/windows-x86_64/sysroot/usr/local/opencv-config.cmake
C:/Users/<username>/AppData/Local/Android/Sdk/ndk/23.1.7779620/toolchains/llvm/prebuilt/windows-x86_64/sysroot/usr/OpenCVConfig.cmake
C:/Users/<username>/AppData/Local/Android/Sdk/ndk/23.1.7779620/toolchains/llvm/prebuilt/windows-x86_64/sysroot/usr/opencv-config.cmake
C:/Users/<username>/AppData/Local/Android/Sdk/ndk/23.1.7779620/toolchains/llvm/prebuilt/windows-x86_64/sysroot/OpenCVConfig.cmake
C:/Users/<username>/AppData/Local/Android/Sdk/ndk/23.1.7779620/toolchains/llvm/prebuilt/windows-x86_64/sysroot/opencv-config.cmake
The file was not found.

Answer 1

所以，问题实际上是，对于Android(和，可能，iOS) CMake设置CMAKE_FIND_ROOT_PATH_MODE_PACKAGE变量(和其他CMAKE_FIND_ROOT_PATH_MODE_*变量)到ONLY，这使得find_package(和其他find_*函数)前缀路径是在CMAKE_FIND_ROOT_PATH列表。

要覆盖此设置，可以执行以下操作:

• 设置CMAKE_FIND_ROOT_PATH_MODE_*为BOTH或NEVER
• 每个find_*呼叫使用CMAKE_FIND_ROOT_PATH_BOTH或NO_CMAKE_FIND_ROOT_PATH

它还应该修复CMake忽略HINTS,PATHS和其他前缀构建步骤的路径的问题。