检查工具链文件中的 CMake 缓存变量 [英] Check CMake Cache Variable in Toolchain File

问题描述

我在通过命令行设置配置变量时遇到问题.我无法从系统中确定它，所以我希望用户指定:

I'm having trouble setting a configuration variable via the command line. I can't determine it from the system, so I expect the user to specify:

cmake -DCMAKE_TOOLCHAIN_FILE=../android.toolchain -DANDROID_ABI:STRING="arm64" ..

在我的 android.toolchain 中，我有以下内容:

Inside my android.toolchain, I have the following:

message(STATUS "Android ABI: ${ANDROID_ABI}")
if( "${ANDROID_ABI}" STREQUAL "" )
   message(FATAL_ERROR "Please specifiy ABI at cmake call -DANDROID_ABI:STRING=armeabi or -DANDROID_ABI:STRING=arm64")
endif()

无论如何，即使它打印出正确的 arm64，它也会在这一行失败:

No matter what, it fails at this line EVEN THOUGH it prints out the correct arm64:

 -- Android ABI: arm64
CMake Error at yaml-cpp/android.toolchain:45 (message):
Please specifiy ABI at cmake call -DANDROID_ABI:STRING=armeabi or -DANDROID_ABI:STRING=arm64

谁能告诉我我做错了什么?

Could anyone direct me to what I'm doing wrong?

我认为这与:

• -D 添加缓存变量而不是普通变量
• 这是在一个工具链文件中...它似乎忽略了缓存变量

有什么想法或建议吗?

推荐答案

我并不假装完全了解幕后发生的事情，但这里有一个对我有用的解决方法:

I don't pretend to fully understand what's going on behind the scenes, but here's a workaround that works for me:

# Problem: CMake runs toolchain files multiple times, but can't read cache variables on some runs.
# Workaround: On first run (in which cache variables are always accessible), set an intermediary environment variable.

if (FOO)
    # Environment variables are always preserved.
    set(ENV{_FOO} "${FOO}")
else ()
    set(FOO "$ENV{_FOO}")
endif ()

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