CODEWITHSUNDEEP
csemaphoresymbols
user3372128
user3372128

Reputation: 13

Semaphore symbols not found (c)

So I have made a method using semaphores.

My program opens with

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

And my make file is

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

EDIT: added -lrt....no change

However when I make the file it finds can't find the symbols for

sem_destroy sem_getvalue sem_init sem_post sem_wait

why is this?

Edit: output from "make officeHours"

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

Upvotes: 1

Views: 788

Answers (1)

Eugene S
Eugene S

Reputation: 3122

You need to link with the librt library.

This library contains POSIX realtime extensions.

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

If you look at the man page for sem_init(3RT):

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

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

Upvotes: 1

Related Questions