CMake:错误的构建目标目录 [英] CMake: wrong build target directory

问题描述

系统:

Linux anon-S 3.19.0-31-generic #36~14.04.1-Ubuntu SMP Thu Oct 8 10:21:08 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

CMake版本:

anon@anon-S:~/$ cmake --version
cmake version 3.2.2

主要CMakeLists.txt:

Main CMakeLists.txt :

cmake_minimum_required(VERSION 3.0)

set(CMAKE_CXX_STANDARD 11)

add_subdirectory(${PROJECT_SOURCE_DIR}/src)
add_subdirectory(${PROJECT_SOURCE_DIR}/test)

但是

anon@anon-S:/home/anon/project/build$ cmake ..
-- Configuring done
-- Generating done
-- Build files have been written to: /home/anon/project/

构建文件已写入:/home/anon/project/而不是/home/anon/project/build/

Build files have been written to: /home/anon/project/ instead /home/anon/project/build/

我在使用cmake 3.4.1的Debian jessie上没有这个问题:

I haven't this problem on my Debian jessie with cmake 3.4.1 :

anon@anon-S:/home/anon/project/build$ cmake ..
-- The C compiler identification is GNU 5.2.1
-- The CXX compiler identification is GNU 5.2.1
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found Doxygen: /usr/bin/doxygen (found version "1.8.11") 
-- Configuring done
-- Generating done
-- Build files have been written to: /home/anon/project/build/

推荐答案

要澄清此处发生的情况:

To clarify what happened here:

运行 cmake< directory> 时，它会执行以下两项操作之一:

When running cmake <directory> it does one of two things:

• 如果< directory> 是源目录(即其中包含 CMakeLists.txt )，它将在该源上运行CMake并使用当前的工作方式目录作为构建目录.
• 如果< directory> 是构建目录(即其中包含 CMakeCache.txt )，它将在用于创建的任何源目录上运行CMake.构建目录.

• If <directory> is a source directory (ie. has a CMakeLists.txt in it), it will run CMake on that source and use the current working directory as the build directory.
• If <directory> is a build directory (ie. has a CMakeCache.txt in it), it will run CMake on whatever source directory was used to create the build directory.

请注意，后一种情况优先于第一种情况.也就是说，如果您执行以下操作:

Note that the latter case takes precedence over the first one. That is, if you do the following:

cd <src_dir>
cmake .
 *oops, wrong directory, i didn't mean that*
cd build
cmake ..

您可能希望这将以< src_dir> 作为源，而 build 作为构建目录运行CMake.但是由于第一次偶然的CMake运行，< src_dir> 现在也是源代码构建的构建目录！因此，第二次运行将忽略 build 中的所有内容，而是将 src_dir 用作源目录和构建目录.

You might expect that this will run CMake with <src_dir> as the source and build as the build directory. But because of the first accidental CMake run, <src_dir> is now also a build directory for an in-source build! Hence the second run will ignore everything that is in build and instead use src_dir as both the source and build directory.

这确实是一个非常令人讨厌的问题，但是幸运的是，一旦您意识到发生了什么，就可以很快解决:只需从< src_dir> 中删除 CMakeCache.txt

This is indeed a very nasty issue, but fortunately it can be solved very quickly once you realize what's happening: Simply remove the CMakeCache.txt from <src_dir>.

请注意，在较新的CMake版本(3.13及更高版本)中，可以使用 -S 和 -B 命令行选项，用于消除目录参数的含义:

Note that in newer CMake versions (3.13 and up), you can use the -S and -B command line options to disambiguate the meaning of the directory argument:

-S<到源的路径>

到CMake项目的根目录的路径构建.

Path to root directory of the CMake project to build.

-B<构建路径>

CMake将用作目录的路径构建目录的根.

Path to directory which CMake will use as the root of build directory.

如果该目录尚不存在，CMake将创建该目录.

If the directory doesn’t already exist CMake will make it.

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