未找到信号量符号 (c)

Question

所以我做了一个使用信号量的方法。

我的程序打开

#include <pthread.h>
#include <semaphore.h>

我的make文件是

officeHours: officeHours.c
    gcc -o officeHours officeHours.c -lpthread -lrt

编辑：添加 -lrt....没有变化

但是，当我制作它找到的文件时，找不到符号

sem_destroy sem_getvalue sem_init sem_post sem_wait

这是为什么？

编辑：“make officeHours”的输出

cc -o officeHours officeHours.c
"officeHours.c", line 4: warning: invalid white space character in directive
"officeHours.c", line 5: warning: invalid white space character in directive
"officeHours.c", line 41: warning: argument #3 is incompatible with prototype:
    prototype: pointer to function(pointer to void) returning pointer to void : "/usr/include/pthread.h", line 197
    argument: pointer to void
"officeHours.c", line 68: warning: argument #3 is incompatible with prototype:
    prototype: pointer to function(pointer to void) returning pointer to void : "/usr/include/pthread.h", line 197
    argument: pointer to void
Undefined symbol            first referenced in file
sem_destroy                 officeHours.o
sem_getvalue                officeHours.o
sem_init                    officeHours.o
sem_post                    officeHours.o
sem_wait                    officeHours.o

Answer 1

您需要链接到librt 库。

此库包含 POSIX 实时扩展。

officeHours: officeHours.c
    gcc -o officeHours officeHours.c -lpthread -lrt

如果您查看 sem_init(3RT) 的手册页：

cc [ flag... ] file... -lrt [ library... ]
#include <semaphore.h>

int sem_init(sem_t *sem, int pshared, unsigned int value);