如何在C中的可变参数函数中将结构指针作为参数传递

Question

I need to pass a struct pointer in my function which takes variable arguments. What is the correct way to do that. I tried this following code.Just pasting the code snippet, and not the full code.

struct node {
int label,
bool visited} vertex;

//My arguments in this function should be variable/unknown at runtime. It should take n number of streuct pointer arguments
int and_gate(struct vertex * v1, )
{
  va_list valist;
  va_start(valist, num) //not sure
  int out=0;

  for(int i=0;i<num,i++)
    out = va_args(valist, v1);
}

int main()
{
   struct vertex a,b,c;
   and_gate(3, &a,&b,&c)
}

Answer 1

Use dynamic array

int and_gate(int n, struct vertex *v1)
{
  for(int i = 0; i < n; ++i)
    printf("%d", v1[0].label);
}

int main()
{
   int n=3;
   struct vertex *a;
   a = malloc(n * sizeof(struct vertex));
   and_gate(n, a);
}

Answer 2

First of all, there is no declaration of struct vertex in your code. This:

struct node {
int label,
bool visited} vertex;

is just a definition of global variable named vertex , that has type struct node . Declaration of required type looks next:

struct vertex {
    int label,
    bool visited
};

Then and_gate() must be declared properly. According to way how you use it, it probably should look like this:

int and_gate(int vert_num, ...)
{
  va_list valist;
  va_start(valist, vert_num);
  struct vertex *vert;

  for(int i=0; i < vert_num; i++) {
    vert = va_arg(valist, struct vertex *);
    /* do what you want with `vert` */
  }
}

But anyway - using of stdargs here smells like overdesigned solution. Since passed data are homogeneous - it is better and more clear to pass array of struct vertex . It may be both static or dynamic array, depending on context. Eg:

int and_gate(struct vertex * data, int num)
{
  struct vertex *vert;

  for(int i=0; i < num; i++) {
      vert = data[i];
      /* do what you want with `vert` */
  } 
}

int main()
{
   struct vertex data[3] = { /* init array members */ };
   and_gate(data, 3)
}