接觸了Linux系統編程中的線程編程模塊,可gcc sample.c(習慣把書上的sample代碼寫進sample.c文件中)出現“undefined reference to ‘pthread_create’”,所有關於線程的函數都會有此錯誤,導致無法編譯通過。
問題的原因:pthread不是Linux下的默認的庫,也就是在鏈接的時候,無法找到phread庫中各函數的入口地址,於是鏈接會失敗。
解決:在gcc編譯的時候,附加要加 -lpthread參數即可解決。
#include <stdio.h> #include <pthread.h> #include <unistd.h> pthread_t ntid; void printids(const char * s) { pid_t pid; pthread_t tid; pid = getpid(); tid = pthread_self(); printf("%s pid %u tid %u (0x%x)\n",s,(unsigned int)pid, (unsigned int)tid,(unsigned int)tid); } void * thr_fn(void * arg) { printids("new thread:"); return ((void *)0); } int main(void) { int err; err = pthread_create(&ntid,NULL,thr_fn,NULL); if(err != 0) printf("pthread_create error \n"); printids("main thread:"); sleep(1); return 0; }
root@daoluan:/code/pthreadid# gcc sample.c /tmp/cc1WztL9.o: In function `main’: sample.c:(.text+0×83): undefined reference to `pthread_create’ collect2: ld returned 1 exit status
root@daoluan:/code/pthreadid# gcc -lpthread sample.c root@daoluan:/code/pthreadid# ./a.out main thread: pid 7059 tid 3078141632 (0xb778b6c0) new thread: pid 7059 tid 3078138736 (0xb778ab70)