c - 将结构数组作为参数输入 pthread_create 时出现问题

Question

我正在编写一个小型步进电机控制程序，我需要一个单独的线程来检查是否有任何电机需要更新。

我一直陷入将数据结构传递到 pthread_create() 并修改 test_motor2 的状态值的过程中。下面的代码应该可以让我了解我想要完成的任务:

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>

typedef struct motor{
    int motor_status; 
} motor;

typedef struct argstruct{
    int *vect;
    struct motor *allmotors;
} args;

void *test(void *arg){

    struct argstruct *arguments = arg;
    int *a_array = arguments->vect;
    a_array[0] = 80;

    // HERE I GET STUCK
    struct motor *motors = arguments->allmotors;
    // set test_motor2 status to 1

}

int main(){

    pthread_t sidethread;

    struct motor test_motor;
    struct motor test_motor2;
    test_motor.motor_status = 0;
    test_motor2.motor_status = 0;

    int a[3];
    a[0] = 8; a[1] = 3; a[2] = 2;

    struct motor *all_motors[2];
    all_motors[0] = &test_motor;
    all_motors[1] = &test_motor2;

    struct argstruct motors_and_a;
    motors_and_a.allmotors = all_motors;
    motors_and_a.vect = a;

    if (pthread_create(&sidethread, NULL, test, (void *)&motors_and_a)){
        printf("Thread could not be started\n");
    }

    pthread_join(sidethread, NULL);

    // Check that a[0] has been set to 80
    printf("a[0]: %d\n", a[0]);
    // Check that test_motor2 status is now 1
    printf("Status of test_motor2: %d\n", test_motor2.motor_status);

}

该示例适用于数组 a，但我无法使其适用于电机。

您能帮我找到解决方案吗？

谢谢!

最大

Answer 1

警告作业

 motors_and_a.allmotors = all_motors;

无效，因为 all_motors 是 motor* [2] ，而不是 motor* 预期的 motors_and_a.allmotors ，因此之后的使用具有未定义的行为。

您必须只给出一个motor*，而不是一组motor*，或者将argstruct的定义更改为struct motor **allmotors;当然还有它的用途

因为

// HERE I GET STUCK
struct motor *motors = arguments->allmotors;
// set test_motor2 status to 1

我想你想要:

typedef struct argstruct{
    int *vect;
    struct motor ** allmotors; /* MODIFIED */
} args;

void *test(void *arg){

    struct argstruct *arguments = arg;
    int *a_array = arguments->vect;
    a_array[0] = 80;

    struct motor ** motors = arguments->allmotors; /* MODIFIED */

    motors[1]->motor_status = 1; /* MODIFIED */

    return 0;
}

其余不变。

编译和执行:

pi@raspberrypi:~ $ gcc -g -pedantic -Wextra -Wall m.c -lpthread
pi@raspberrypi:~ $ ./a.out
a[0]: 80
Status of test_motor2: 1

在valgrind下执行:

pi@raspberrypi:~ $ valgrind ./a.out
==4083== Memcheck, a memory error detector
==4083== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==4083== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info
==4083== Command: ./a.out
==4083== 
a[0]: 80
Status of test_motor2: 1
==4083== 
==4083== HEAP SUMMARY:
==4083==     in use at exit: 0 bytes in 0 blocks
==4083==   total heap usage: 2 allocs, 2 frees, 1,160 bytes allocated
==4083== 
==4083== All heap blocks were freed -- no leaks are possible
==4083== 
==4083== For counts of detected and suppressed errors, rerun with: -v
==4083== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 6 from 3)

<小时/>

测试中也缺少返回