英文:
CMake option default value is ignored
问题
给定以下的CMake代码：
cmake_minimum_required(VERSION 3.25)
project(foo)
option(XXX "List of things" "a;b;c")
message(STATUS "XXX is ${XXX}")
在一个完全干净的构建目录中执行cmake ..会打印：
-- XXX is OFF
为什么默认值不起作用？请注意，这个问题特指在构建目录干净的情况下默认值不起作用，因此这个问题不是重复。
英文:
Given the following CMake
cmake_minimum_required(VERSION 3.25)
project(foo)
option(XXX "List of things" "a;b;c")
message(STATUS "XXX is ${XXX}")
cmake .. with a completely clean build directory prints
-- XXX is OFF
Why doesn't the default value work? Note that this question is specifically about it not working when the build directory is clean so this question is not a duplicate.
答案1
得分: 2
option()仅用于布尔值。默认值只能是TRUE或FALSE（或它们的许多别名）。
对于非布尔选项，您需要执行以下操作：
set(var_name "默认值" CACHE STRING "帮助文本")
英文:
Ah option() is only intended to be used for booleans. The default value can only be TRUE or FALSE (or their many aliases).
For non-boolean options you need to do:
set(var_name "Default value" CACHE STRING "Help text")
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