Question

这是我的线程子例程...... 在这里，我创建了4个线程并将结构作为参数传递给线程子例程。

我正在尝试使用getid()函数打印线程ID，

我收到错误说＆＃34;对gettid（）＆＃34;未定义的引用。

我添加了必要的头文件......

#include <pthread.h>
#include <stdio.h>
#include <sys/types.h>
#define ARRAYSIZE 17
#define NUMTHREADS 4

struct ThreadData {
        int start, stop;
        int* array; 
};

void* squarer(void* td) 
{
     struct ThreadData* data=(struct ThreadData*) td;

     int start=data->start;
     int stop=data->stop;
     int* array=data->array;
     int i;
     pid_t tid1;

     tid1 = gettid(); //error at this statement//`
     printf("tid : %d\n",tid1);

     for (i=start; i<stop; i++) {
         sleep(1);
         array[i]=i*i;
         printf("arr[%d] = [%d]\n",i,array[i]);
     } 
   return NULL;
}

int main(void) {
    int array[ARRAYSIZE];
    pthread_t thread[NUMTHREADS];
    struct ThreadData data[NUMTHREADS];
    int i;

    int tasksPerThread=(ARRAYSIZE+NUMTHREADS-1)/NUMTHREADS;

    for (i=0; i<NUMTHREADS; i++) {
            data[i].start=i*tasksPerThread;
            data[i].stop=(i+1)*tasksPerThread;
            data[i].array=array;
    }

    data[NUMTHREADS-1].stop=ARRAYSIZE;

    for (i=0; i<NUMTHREADS; i++) {
            pthread_create(&thread[i], NULL, squarer, &data[i]);
    }

    for (i=0; i<NUMTHREADS; i++) {
            pthread_join(thread[i], NULL);
    }

    for (i=0; i<ARRAYSIZE; i++) {
            printf("%d ", array[i]);
    }
    printf("\n");

    return 0;
}

Answer 1

尝试

#include <unistd.h>
#include <sys/syscall.h>

#ifdef SYS_gettid
pid_t tid = syscall(SYS_gettid);
#else
#error "SYS_gettid unavailable on this system"
#endif

Answer 2

我已按照错误提供的建议并更正了源 * 下面是无错代码*

#include <pthread.h>
#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/syscall.h>

#define ARRAYSIZE 17
#define NUMTHREADS 4

struct ThreadData {
    int start, stop;
    int* array; 
};

void* squarer(void* td) 
{
 struct ThreadData* data=(struct ThreadData*) td;

 int start=data->start;
 int stop=data->stop;
 int* array=data->array;
 int i;
 pid_t tid1;

 tid1 = syscall(SYS_gettid); // here is the correct statement //
 printf("tid : %d\n",tid1);

 for (i=start; i<stop; i++) {
         sleep(1);
         array[i]=i*i;
         printf("arr[%d] = [%d]\n",i,array[i]);
 } 
 return NULL;
}

int main(void) {
    int array[ARRAYSIZE];
    pthread_t thread[NUMTHREADS];
    struct ThreadData data[NUMTHREADS];
    int i;

    int tasksPerThread=(ARRAYSIZE+NUMTHREADS-1)/NUMTHREADS;

    for (i=0; i<NUMTHREADS; i++) {
        data[i].start=i*tasksPerThread;
        data[i].stop=(i+1)*tasksPerThread;
        data[i].array=array;
    }

    data[NUMTHREADS-1].stop=ARRAYSIZE;

    for (i=0; i<NUMTHREADS; i++) {
            pthread_create(&thread[i], NULL, squarer, &data[i]);
    }

    for (i=0; i<NUMTHREADS; i++) {
            pthread_join(thread[i], NULL);
    }

    for (i=0; i<ARRAYSIZE; i++) {
            printf("%d ", array[i]);
    }
    printf("\n");

    return 0;
}

Answer 3

要粘贴的宏（相对于先前的答案有所改进）：

#include <unistd.h>
#include <sys/syscall.h>

#ifndef SYS_gettid
#error "SYS_gettid unavailable on this system"
#endif

#define gettid() ((pid_t)syscall(SYS_gettid))

示例：

#include <unistd.h>
#include <sys/syscall.h>

#ifndef SYS_gettid
#error "SYS_gettid unavailable on this system"
#endif

#define gettid() ((pid_t)syscall(SYS_gettid))

#include <stdio.h>

void main()
{
        printf("tid is %d\n", gettid());
}

Answer 4

如果您使用 glibc 或 musl，请定义 _GNU_SOURCE 以让 unistd.h 定义此符号。

在c程序中获取错误“对gettid的未定义引用”

4 个答案: