设置带有缓存的变量强制缓存不会更新cmake变量

Question

我正在尝试根据 env 变量的值（如果预设）更新 cmake 变量。我也在缓存这个变量。但是，它在 cmake 中没有正确更新，但在缓存中我可以看到更新的值。

这里是我的测试 CMakeLists.txt 文件

我已经设置了环境变量

compiler_verion=clang15

cmake_minimum_required(VERSION 3.26)
project(test)

if(NOT compiler_version)
    set(compiler_version "gcc")
    message("++++++++++++++++++++++++++++++ default ${compiler_version}")
endif()

if(NOT "$ENV{compiler_version}" STREQUAL "")
    set(compiler_version $ENV{compiler_version} CACHE STRING "which compiler to use..." FORCE)
    message("++++++++++++++++++++++++++ env compiler_version : $ENV{compiler_version} cmake_compiler_version  ${compiler_version} ++++++++++++++++++++++++++++")
elseif(NOT compiler_version)
    set(compiler_version "gcc" CACHE STRING "which compiler to use..." FORCE)
    message("++++++++++++++++++++++++++++++ else if ${compiler_version}")
else()
    set(compiler_version ${compiler_version} CACHE STRING "which compiler to use..." FORCE)
    message("++++++++++++++++++++++++++++++ else ${compiler_version}")
endif()

我正在运行命令

cmake ..

来自构建文件夹。

这是实际输出。

-- The C compiler identification is GNU 8.5.0
-- The CXX compiler identification is GNU 8.5.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
++++++++++++++++++++++++++++++ default gcc
++++++++++++++++++++++++++ env compiler_verion : clang15 cmake_compiler_version  gcc ++++++++++++++++++++++++++++
-- Configuring done (0.6s)
-- Generating done (0.0s)
-- Build files have been written to: /test/buil

我的问题与此有关。

++++++++++++++++++++++++++ env compiler_version : clang15 cmake_compiler_version  gcc 

为什么不将

compiler_version

设置为

clang15

？

如果我在缓存文件已经可用时重新运行它，它会按预期工作。

++++++++++++++++++++++++++ env compiler_verion : clang15 cmake_compiler_version  clang15 ++++++++++++++++++++++++++++
-- Configuring done (0.0s)
-- Generating done (0.0s)

我错过了什么吗？ 我在linux平台上使用cmake版本3.26。

Answer 1

也许你应该导出环境

export compiler_version=clang15

或使用

compiler_version=clang15 cmake ...

运行cmake