Question

Say, among other elements I want to parse a C structure, from file1.c :

typedef struct mynode{
   int* x;
   int length;
}node;

int callerFunction(int myLength){
  //memory space  
  node* n = (node*)malloc(sizeof(node));

  //dummy values for explanation purpose only
  double d = 3.14;
  int max  = 100;



//populate struct
  n->length = myLength;
  for(int i =0; i < n->length; i++)
     n->x[i]= i;

  //calling foo passing an structure  
   int result = foo(3,d,max,n);
}

and I want to pass this structure to another function via va_arg, in file2.c

int foo(int n,...){

int foo_max;
double foo_d;
node* foo_n;
va_list ap;

va_start(ap,n);  
 d = va_arg(ap,double);
 foo_d = va_arg(ap,int);
 foo_n = va_arg(ap,node*);
va_end(ap);
....
}

I thought I was doing the right thing, however if I include the structure, the data collected by foo is totally wrong (not the right data). What am I doing wrong here?

Answer 1

Inside callerFunction
seems like you have not allocated memory for n->x but using it.

 //populate struct
 n->length = myLength;

 n->x = malloc(n->lenght * sizeof(int));     //////////add this line

 for(int i =0; i < n->length; i++)
     n->x[i]= i;