Linux下pthread问题

Linux下 undefined reference to "pthread_*" 问题

  (2010-05-30 20:29:14)

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分类： Linux

  tried to use pthread_create in RedHat Linux AS4, both in Eclipse+CDT and KDevelop.

KDevelop:
When you build a project by KDevelop, you'd better add a '-pthread' to the link option if your project includes <pthread.h>. Without that option, KDevelop would report an link error : '/root/kde/oop/src/oop.c:23: undefined reference to `pthread_create'

After rebuild, the program works well.

Eclipse + CDT:
When you use pthread_create in your project, it will compile and link ok. But when you execute the program, the thread will receive a signal SIGSEGV that said: Execution is suspended because of error. Cannot find bounds of current function

I tried to add '-pthread' to the link option of the Eclipse CDT, but it's helpless. I don't know how to correct this.

Linux上编译pthread程序，默认会出错。如题。原因如下。

             -pthread
                     Add support for multithreading using the POSIX threads library.
                     This option sets flags for both the preprocessor and linker. It
                     does not affect the thread safety of object code produced by the
                     compiler or that of libraries supplied with it. These are HP-UX
                     specific flags.
     
       所以如果在gcc的编译中（更准确的说是链接中）没有启动pthread的话，就会出现如下的链接错误。
       pthread_test.c:(.text+0x8a): undefined reference to `pthread_create'
       collect2: ld returned 1 exit status

       另外一个参数-lpthread也能起到同样的作用。所以可以看出-pthread的本质应当时引入了thread对应的library。默认情况下，pthread对应的library在gcc编译链接中是不会被引入的。

所以 gcc -o backupfile backupfiles.c -pthread

出现如下错误：
undefined reference to 'pthread_create'
undefined reference to 'pthread_join'

问题原因：
pthread 库不是 Linux 系统默认的库，连接时需要使用静态库 libpthread.a，所以在使用pthread_create()创建线程，以及调用 pthread_atfork()函数建立fork处理程序时，需要链接该库。

问题解决：
在编译中要加 -lpthread参数
gcc thread.c -o thread -lpthread
thread.c为你些的源文件，不要忘了加上头文件#include<pthread.h>