C++ 如何让 CMake 在 Ubuntu 上识别 pthread？
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How to get CMake to recognize pthread on Ubuntu?
提问by Stéphane
If I compile on the command-line with g++ directly, I can see everything I need is there:
如果我直接在命令行上用 g++ 编译，我可以看到我需要的一切都在那里：
$ g++ -pthread test.cpp
$ ldd a.out
linux-vdso.so.1 => (0x00007fffd05b3000)
libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f4a1ba8d000)
libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f4a1b870000)
...more...
Then I try to create a simple cmake file for this 5-line test app:
然后我尝试为这个 5 行测试应用程序创建一个简单的 cmake 文件：
$ cat CMakeLists.txt
PROJECT ( Test CXX )
CMAKE_MINIMUM_REQUIRED ( VERSION 2.8 )
FIND_PACKAGE ( Threads REQUIRED )
ADD_EXECUTABLE ( test test.cpp )
TARGET_LINK_LIBRARIES ( test ${CMAKE_THREAD_LIBS_INIT} )
However, I cannot figure out why CMake doesn't find what it needs to use for Threads:
但是，我无法弄清楚为什么 CMake 找不到它需要用于的内容Threads：
$ cd build/
$ cmake ..
CMake Error at /usr/share/cmake-2.8/Modules/FindPackageHandleStandardArgs.cmake:97 (MESSAGE):
Could NOT find Threads (missing: Threads_FOUND)
Call Stack (most recent call first):
/usr/share/cmake-2.8/Modules/FindPackageHandleStandardArgs.cmake:288 (_FPHSA_FAILURE_MESSAGE)
/usr/share/cmake-2.8/Modules/FindThreads.cmake:166 (FIND_PACKAGE_HANDLE_STANDARD_ARGS)
CMakeLists.txt:4 (FIND_PACKAGE)
-- Configuring incomplete, errors occurred!
回答by Stéphane
Oh, this was was a pain! I probably lost 2 hours on this. Here is the solution:
哦，这是一种痛苦！我可能为此浪费了 2 个小时。这是解决方案：
CMake uses short 'C' applications to test/try things. If the CMakeLists.txt states that C++ is used for the project, without also listing C, then some of those shorts tests incorrectly fail, and cmake then thinks those things aren't found.
CMake 使用简短的“C”应用程序来测试/尝试。如果 CMakeLists.txt 声明项目使用了 C++，而没有列出 C，那么其中一些 shorts 测试错误地失败了，然后 cmake 认为没有找到这些东西。
The solution was to change the first line of CMakeLists from this:
解决方案是从此更改 CMakeLists 的第一行：
PROJECT ( Test CXX )
...to include C as a language:
...将 C 作为一种语言包括在内：
PROJECT ( Test C CXX )
Then delete build, recreate it, and everything then works:
然后删除build，重新创建它，然后一切正常：
rm -rf build
mkdir build
cd build
cmake ..
