内螺纹打印参数 [英] Print arguments inside thread

问题描述

 无效* consumer_child（无效*参数）{
    范围RNG = *（（范围*）参数）;
    //使用很容易地确定每个线程的范围prinnting
    的printf（consumer_child [％D-％D]。开始的\\ n，rng.start，rng.end）;    了pthread_exit（0）;
}
 

当我打印出来，它打印内存位置，而不是价值。我需要打印的价值。

在主线程中开始和结束的值是否设置正确。我检查了他们。

在主我设置参数如下

 范围* RNG =的malloc（sizeof的（* RNG））;
        RNG-GT＆;启动= I * numbersPerChild;
        RNG-＆GT;端=（numbersPerChild *第（i + 1））-1;
        的printf（范围线程％d为％d到％d \\ n，我，RNG-GT＆;启动，RNG-GT＆端）;
        的printf（测试打印％d个\\ N，RNG-GT＆;启动）;
在pthread_create（安培; TID [Ⅰ]，NULL，consumer_child，（无效*）及RNG）;
 

范围是一个结构

  typedef结构
{
    INT开始;
    INT结束;
} 范围;
 

解决方案

您需要修改：

 在pthread_create（安培; TID [I]，NULL，consumer_child，（无效*）及RNG）;
 

到

 在pthread_create（安培; TID [I]，NULL，consumer_child，RNG）;
 

因为 RNG 已经是一个指针，你想传递的，而不是它的地址。你并不需要一个对象指针转换为无效* 在C，除非你有期望一个可变参数函数之一，你想传递一种不同的对象的指针。

void * consumer_child(void *arguments){
    Range rng = *((Range *) arguments);
    //prinnting with the range to easily identify each thread
    printf("consumer_child[%d-%d] started\n", rng.start, rng.end );

    pthread_exit(0);
}

When I print it, it prints memory location, not the value. I need to print the value.

In main thread start and end values are set properly. I have checked them.

in main I have set the argument as following

Range *rng = malloc(sizeof(*rng));
        rng->start = i * numbersPerChild;
        rng->end = (numbersPerChild * (i + 1)) -1 ;
        printf("Range for thread %d is %d to %d\n", i, rng->start, rng->end );
        printf("test print %d\n",rng->start);
pthread_create(&tid[i], NULL, consumer_child, (void *)&rng );

Range is a struct

typedef struct
{
    int start;
    int end;
} Range;

解决方案

You need to change:

pthread_create(&tid[i], NULL, consumer_child, (void *)&rng );

to:

pthread_create(&tid[i], NULL, consumer_child, rng);

since rng is already a pointer, and you want to pass that, not its address. You don't need to cast an object pointer to void * in C, unless you have a variadic function that expects one and you're trying to pass it a different kind of object pointer.

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