使用-lpthread，g ++编译器错误，“未定义引用到”信号量调用，如`sem_open' [英] with -lpthread, g++ compiler error, "undefined reference to " semaphore calls such as `sem_open'

问题描述

  g ++  -  posix线程库我是posix线程库的新手，我试图从教程中编译示例代码： lpthread agreement.cpp -o agreement 
  

但是我无法编译代码并得到以下错误message：

  a3q2.cpp :(。text + 0x7e）：未定义引用`sem_open'
 a3q2.cpp （。text + 0xab）：未定义引用`sem_wait'
 a3q2.cpp :(。text + 0x290）：未定义引用`sem_post'
 a3q2.cpp :(。未定义引用`sem_close'
 a3q2.cpp :(。text + 0x2bb）：未定义引用`sem_unlink'
 collect2：ld返回1退出状态
 make：*** [a3q2_exe]错误1 
  

我知道-lpthread是编译工作所需要的，我可能需要解决问题？如果没有，我如何安装正确的pthread库？

感谢您的帮助！

解决方案

你想要编译选项 -pthread （如果你真的使用pthreads）。如果你只需要那些函数，他们在 librt 所以使用 -lrt

I am new to posix thread library, and I tried to compile a sample code from a tutorial with:

g++ -lpthread agreement.cpp -o agreement

however I was not able to compile the code and got the following error message:

a3q2.cpp:(.text+0x7e): undefined reference to `sem_open'
a3q2.cpp:(.text+0xab): undefined reference to `sem_wait'
a3q2.cpp:(.text+0x290): undefined reference to `sem_post'
a3q2.cpp:(.text+0x2af): undefined reference to `sem_close'
a3q2.cpp:(.text+0x2bb): undefined reference to `sem_unlink'
collect2: ld returned 1 exit status
make: *** [a3q2_exe] Error 1

I am aware that -lpthread is needed for compilation to work, but is there any other options i might need to solve the problem? if not how do I have to install the "proper" pthread library?

Thanks for your help!

解决方案

You want the compile option -pthread (if you are really using pthreads). If you just need those functions they are in librt so use -lrt

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