CMake如何查找包

31moq8wy 于 2023-11-19 发布在其他

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我有一个CMake，可以将OpenCV添加到项目中。
我使用以下代码将OpenCV添加到我的项目中：

if (MSVC)
    file(TO_CMAKE_PATH $ENV{OPENCV_ROOT} OpenCV_DIR)
    IF(NOT OpenCV_DIR)
        MESSAGE( FATAL_ERROR "Please point the environment variable OpenCV_ROOT to the root directory of OpenCV installation. required openCv V 4.2.x as minimum")
    ENDIF()
    set(BUILD_SHARED_LIBS OFF)
    find_package(OpenCV 4.2.0 REQUIRED)
else (MSVC)
    set(BUILD_SHARED_LIBS ON)
    find_package(OpenCV COMPONENTS core highgui imgproc imgcodecs videoio photo stitching flann ml features2d calib3d objdetect REQUIRED)
endif(MSVC)

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如果我没有定义OpenCV_root环境变量，CMake找不到OpenCV。但是如果我定义了它，我会得到这样的警告：

CMake Warning (dev) at CMakeLists.txt:36 (find_package):
  Policy CMP0074 is not set: find_package uses <PackageName>_ROOT variables.
  Run "cmake --help-policy CMP0074" for policy details.  Use the cmake_policy
  command to set the policy and suppress this warning.

  Environment variable OpenCV_ROOT is set to:

    D:\local\opencv

  For compatibility, CMake is ignoring the variable.
This warning is for project developers.  Use -Wno-dev to suppress it.

型
那么，如果我没有定义openCV_root环境变量，CMake如何找到OpenCV呢？
同样的问题也适用于其他软件包（比如boost，我得到了同样的警告），我们应该定义一个env变量吗？
如果我没有定义一个env变量，OpenCV如何找到这个包？

cmake

来源：https://stackoverflow.com/questions/60453531/how-cmake-finds-packages

1条答案

按热度按时间

y0u0uwnf1#

CMP 0074策略的description说明：
在CMake 3.12及更高版本中，find_package(<PackageName>)命令现在搜索由<PackageName>_ROOT CMake变量和<PackageName>_ROOT环境变量指定的前缀.此策略提供了与尚未更新的项目的兼容性，以避免将<PackageName>_ROOT变量用于其他目的。
也就是说，在你的项目中，你需要消除使用OPENCV_ROOT变量的目的，而不是直接影响find_package(OpenCV)行为。
在较新的CMake中，此变量被自动使用：

# This sets CMP0074 to NEW.
cmake_minimum_required(VERSION 3.12) # Or bigger version
set(BUILD_SHARED_LIBS OFF)
# If `OPENCV_ROOT` variable is set, it will be used in the next call without a warning.
find_package(OpenCV 4.2.0 REQUIRED)

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如果你想让你的项目有一个关于OpenCV安装的提示用于其他目的，请使用不同名称的变量。

# We want to support old CMake versions too!
cmake_minimum_required(VERSION 3.11) # Or lower version

# Use `OPENCV_INSTALL_PREFIX` environment variable for set `OpenCV_DIR`, which helps CMake to find OpenCV.
# This setting works for both new and old CMake versions.
file(TO_CMAKE_PATH $ENV{OPENCV_INSTALL_PREFIX} OpenCV_DIR)
IF(NOT OpenCV_DIR)
    MESSAGE( FATAL_ERROR "Please point the environment variable OPENCV_INSTALL_PREFIX to the root directory of OpenCV installation. required openCv V 4.2.x as minimum")
ENDIF()
set(BUILD_SHARED_LIBS OFF)
find_package(OpenCV 4.2.0 REQUIRED)

型
或者，您也可以禁用CMP0074策略，使用OPENCV_ROOT变量来实现您的目的。但不推荐：

# 'find_package' won't use `_ROOT` variable. This suppress the corresponding warning. 
cmake_policy(SET CMP0074 OLD)
file(TO_CMAKE_PATH $ENV{OPENCV_ROOT} OpenCV_DIR)
IF(NOT OpenCV_DIR)
    MESSAGE( FATAL_ERROR "Please point the environment variable OpenCV_ROOT to the root directory of OpenCV installation. required openCv V 4.2.x as minimum")
ENDIF()
set(BUILD_SHARED_LIBS OFF)
find_package(OpenCV 4.2.0 REQUIRED)

型

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CMake如何查找包

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