为了测试获取线程id，所以用
#include <unistd.h>
pid_t tid = gettid();
cout << "now pid is:" << tid << endl;
但是每次编译都会报错：
[root@localhost cpp]# g++ test.cpp -o test -lpthread
test.cpp: 在函数‘void* say_hello(void*)’中:
test.cpp:16:20: 错误：‘gettid’在此作用域中尚未声明
pid_t tid = gettid();
解决办法：
加入以下，
#include <unistd.h>
#include <sys/syscall.h>
#define gettid() syscall(SYS_gettid)
贴完整测试代码：
#include <iostream>
#include <ctime>
#include <cstdlib>
#include <pthread.h>
#include <unistd.h>
#include <sys/syscall.h>
#define gettid() syscall(SYS_gettid)
using namespace std;
#define NUM_THREADS 5
void* say_hello(void* args)
{
cout << "Hello Runoob！" << endl;
pid_t tid = gettid();
cout << "now pid is:" << tid << endl;
return 0;
}
int main()
{
pthread_t tids[NUM_THREADS];
for (int i = 0; i < NUM_THREADS; ++i)
{
int ret = pthread_create(&tids[i], NULL, say_hello, NULL);
if (ret != 0)
{
cout << "pthread_create error: error_code=" << ret << endl;
}
else
{
cout << "tids:" << tids[i] << endl;
}
}
pthread_exit(NULL);
cin.get();
return 0;
}