cmake - 供应商项目中的静音 CMP0048 警告

Question

我有带有 CMakeLists.txt 的 git 子模块由于 CMP0048 导致警告的文件。警告如下所示:

CMake Warning (dev) at submodule_directory/CMakeLists.txt:24 (project):
  Policy CMP0048 is not set: project() command manages VERSION variables.
  Run "cmake --help-policy CMP0048" for policy details.  Use the cmake_policy
  command to set the policy and suppress this warning.

  The following variable(s) would be set to empty:

    PROJECT_VERSION
    PROJECT_VERSION_MAJOR
    PROJECT_VERSION_MINOR
    PROJECT_VERSION_PATCH
This warning is for project developers.  Use -Wno-dev to suppress it.

我不控制这些 CMakeLists.txt文件，我不想 fork ，所以对此没有什么可做的，我只想让 CMake 闭嘴。使用 cmake_policy(SET CMP0048 OLD)在添加子模块目录之前不能解决这个问题。 (我猜 project() 重置 cmake 策略？)。

对此我能做些什么吗？

Answer 1

如果您不关心启用策略，最简单的解决方案就是设置 CMAKE_POLICY_DEFAULT_CMP0048 至NEW 在 CMake 命令行。以下答案显示了一种替代方法，可让您采取更零碎的方法。

在 CMake 3.15+ 中有一个更灵活的解决方案，使用 CMAKE_PROJECT_INCLUDE_BEFORE 多变的。在此处查看我的示例:

$ tree
.
├── CMakeLists.txt
├── cmake
│   └── EnableCMP0048.cmake
└── subproj
    └── CMakeLists.txt

我假设 subproj/CMakeLists.txt包含这个:

cmake_minimum_required(VERSION 2.8.12) # Never do this
project(subproj)

在 cmake/EnableCMP0048.cmake ， 放:

cmake_policy(SET CMP0048 NEW)

在 ./CMakeLists.txt ， 放:

cmake_minimum_required(VERSION 3.15)
project(test VERSION 1.0.0)

set(CMAKE_PROJECT_INCLUDE_BEFORE "${CMAKE_CURRENT_SOURCE_DIR}/cmake/EnableCMP0048.cmake")
add_subdirectory(subproj)
unset(CMAKE_PROJECT_INCLUDE_BEFORE)  # if you don't want to affect subsequent add_subdirectory calls.

现在这将启用 CMP0048并将清除子项目中提到的变量。鉴于在您的问题中，您尝试通过修改策略来解决此问题，我认为这没关系。但如果没有，您可以添加另一个脚本， cmake/RestoreProjectVars.cmake :

# Recall the top-level CMakeLists.txt had project(test).
set(PROJECT_VERSION "${test_VERSION}")
set(PROJECT_VERSION_MAJOR "${test_VERSION_MAJOR}")
set(PROJECT_VERSION_MINOR "${test_VERSION_MINOR}")
set(PROJECT_VERSION_PATCH "${test_VERSION_PATCH}")

然后 set(CMAKE_PROJECT_INCLUDE "${CMAKE_CURRENT_SOURCE_DIR}/cmake/RestoreProjectVars.cmake")在调用 add_subdirectory 之前在调用后恢复这些变量。