C双指针结构 [英] C Double Pointer to Structure

问题描述

我正在努力找出C中的一个结构的双指针，不能弄清楚出了什么问题...简单的来源如下：

  typedef struct 
 {
 int member; 
} mystruct; 
 
 void myfunc（mystruct ** data）
 {
（* data） - > member = 1; 
} 
 
 void main（int argc，char * argv []）
 {
 mystruct ** data; 
 
 myfunc（data）; 
 
 printf（member =％d\\\
，（* data） - > member）; 
} 
  

在这里提到了一个类似的问题：如何使用指向C中结构的指针的指针如何通过双指针修改结构的成员。解决方案是语法（* data） - > member = 1; 这是有道理的。但是在这里我的小应用程序中，执行该行时，我收到一个seg错误。我究竟做错了什么？

谢谢

解决方案

如果你是去取消引用指针。尝试这样：

  void main（int argc，char * argv）{
 mystruct actualThing; 
 mystruct * pointer =& actualThing; 
 mystruct ** data =& pointer; 
 myfunc（data）; 
 
 printf（Member：％d，（* data） - > member）; 
} 
  

I am trying to work out a double pointer to a structure in C and cannot figure out what is going wrong... The simple source is below:

typedef struct
{
    int member;
} mystruct;

void myfunc(mystruct **data)
{
    (*data)->member = 1;
}

void main(int argc, char *argv[])
{
    mystruct **data;

    myfunc(data);

    printf("member = %d\n", (*data)->member);
}

A similar question was asked here: How to work with pointer to pointer to structure in C? on how to modify a member of a structure through a double pointer. The solution was the syntax (*data)->member = 1; which makes sense. But in my little application here, I receive a seg fault when executing that line. What am I doing wrong?

Thanks

解决方案

You need to point to something if you are going to dereference a pointer. Try this:

void main(int argc, char *argv) {
    mystruct actualThing;
    mystruct *pointer = &actualThing;
    mystruct **data = &pointer;
    myfunc(data);

    printf("Member: %d", (*data)->member);
}

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