如果未在命令行上明确指定，则将安装前缀自动设置为自定义路径 [英] Set installation prefix automatically to custom path if not explicitly specified on the command line

问题描述

对于某些内部测试，除非用户明确覆盖，否则我希望将安装前缀默认为构建目录的子目录。我知道用户可以通过以下方式指定安装前缀：

For some internal tests, I would like the install prefix to default to a subdirectory of the build directory, unless explicitly overridden by the user. I know the user can specify a install prefix by:

$ cmake -DCMAKE_INSTALL_PREFIX=/foo/bar ..

但是如果用户未指定 ，则默认为 $ {PWD} /已安装。

But if the user does not specify this, it should default to, e.g. ${PWD}/installed.

变量 CMAKE_INSTALL_PREFIX 已设置为 / usr / local ，所以我不能在设置它之前先检查它是否未设置/为空。

The variable CMAKE_INSTALL_PREFIX is already set to /usr/local, so I cannot just check to see if it unset/empty before setting it.

我当前的解决方案是添加一个用户必须调用的自定义开关，以指定要尊重 CMAKE_INSTALL_PREFIX 变量：

My current solution is to add a custom switch that the user has to invoke to specify that the CMAKE_INSTALL_PREFIX variable gets respected:

option(ENABLE_INSTALL_PREFIX "Install build targets to system (path given by '-DCMAKE_INSTALL_PREFIX' or '${CMAKE_INSTALL_PREFIX}' if not specified)." OFF)
if ( ENABLE_INSTALL_PREFIX )
    set (CMAKE_INSTALL_PREFIX installed CACHE PATH "Installation root")
else()
    set (CMAKE_INSTALL_PREFIX installed CACHE PATH "Installation root" FORCE)
endif()

我的问题是：

（a ）除了需要传递给CMake以获得 CMAKE_INSTALL_PREFIX 的额外标志的麻烦之外，上述内容是否还有其他问题？有效果吗？

(a) Are there any issues with the above, beyond the annoyance of the extra flag needing to be passed to CMake to get CMAKE_INSTALL_PREFIX to have an effect?

（b）是否有更好，更清洁，更强大，更惯用和/或更讨厌的方式来实现上述目标？

(b) Is there a better, cleaner, more robust, more idiomatic and/or less annoying way to achieve the above?

谢谢。

推荐答案

CMake设置布尔变量 CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT 如果未明确指定 CMAKE_INSTALL_PREFIX 且已初始化为默认设置。您可以通过以下方式覆盖它：

CMake sets the boolean variable CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT if CMAKE_INSTALL_PREFIX has not been explicitly specified and is initialized to its default setting. You can override it in the following way:

if (CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT)
    set (CMAKE_INSTALL_PREFIX "${CMAKE_BINARY_DIR}/installed" CACHE PATH "default install path" FORCE )
endif()

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