#include <stdio.h>
#define _GNU_SOURCE
#include <sched.h>

static int cpu_is_available(cpu_set_t cpu_set, int cpu){
    return CPU_ISSET(cpu, &cpu_set);
}

int cpu_get_num(void){
    cpu_set_t cpus;
    int i;
    int num_procs = 0;
    if(!sched_getaffinity(0, sizeof(cpu_set_t), &cpus)){
        for(i = 0; i < sizeof(cpu_set_t); i++){
            num_procs += cpu_is_available(cpus, i);
        }
    }
    else{
        //error
    }
    return num_procs;
}



int main(int argc, char *argv[]){
    printf("Processor Number:\t%d\n", cpu_get_num());
    return 0;
}

编译报错：

/tmp/ccQ8TCmy.o: In function `cpu_is_available':
cpu.c:(.text+0x18): undefined reference to `CPU_ISSET'
collect2: ld returned 1 exit status

如何解决？