c – 对’pthread_key_create’的未定义引用(链接器错误)

https://code.google.com/p/googletest/downloads/list

并在ubuntu 13.10上构建gtest .a文件(lib文件)：

Linux ubuntu 3.11.0-15-generic #23-Ubuntu SMP Mon Dec 9 18:17:04 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux

并生成lib：libgtest.a.在我的main.cpp文件中有：

#include <iostream>
#include "gtest/gtest.h"

int main(){
    std::cout << "Test n";
    int argc = 2;
    char* cp01;
    char* cp02;
    char* argv[] = {cp01,cp02};
    testing::InitGoogleTest(&argc,argv);
    return 0;
}

从我建立的终端：

g++ main.cpp -I/home/user/gtest-1.7.0/include -L/home/user/gtest-1.7.0/lib/.libs -lpthread -lgtest

这给出了以下错误：

/home/user/gtest-1.7.0/lib/.libs/libgtest.so: undefined reference to `pthread_key_create'
/home/user/gtest-1.7.0/lib/.libs/libgtest.so: undefined reference to `pthread_getspecific'
/home/user/gtest-1.7.0/lib/.libs/libgtest.so: undefined reference to `pthread_key_delete'
/home/user/gtest-1.7.0/lib/.libs/libgtest.so: undefined reference to `pthread_setspecific'
collect2: error: ld returned 1 exit status

基于此：
error during making GTest

我也试过-pthread而不是-lpthread但是给出了同样的错误：

g++ main.cpp -I/home/user/gtest-1.7.0/include -L/home/user/gtest-1.7.0/lib/.libs -pthread -lgtest

编辑：我也尝试将-pthread指定为最后一个参数：

g++ main.cpp -I/home/user/gtest-1.7.0/include -L/home/user/gtest-1.7.0/lib/.libs -lgtest -pthread

同样的错误
我究竟做错了什么？