C - array of pointers to struct, syntax

Question

I've got a struct A and an array of pointers to instances of that struct
I'm trying to access a member directly from the array but I don't know what's the right syntax to do it :

struct A  
{  
  int a;  
  void** b;  
}

A* p = (A*) malloc(sizeof(A));  
p->b = (A**) malloc(sizeof(A*) * 3);

//
// something is done
//

int c;

A* test = p->b[0];
c = test->a;

Basically what I'm asking is how do I get rid of the intermediate A* test so I can assign the value of c in one line ?

That's irrelevent. I just need a void for what I'm doing but not showing here. The problem lies in the two last lines — user3548298
– user3548298, Commented Apr 7, 2016 at 15:34
p->b = (A**) malloc(sizeof(A*) * 3); is ill-formed, the compiler should complain — M.M
– M.M, Commented Apr 8, 2016 at 8:03

alk · Accepted Answer · 2016-04-07 15:42:17Z

2

Just do

int c = ((struct A*) (p->b[0]))->a;

Defining

struct A  
{  
  int a;  
  struct A ** b;  
}

this would do

int c = p->b[0]->a;

edited Apr 7, 2016 at 15:42

answered Apr 7, 2016 at 15:38

alk

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2 Comments

user3548298 Over a year ago

That works, you rock ! So that void was kinda relevent after all ?

alk Over a year ago

@user3548298: That's why I asked. ;-)

embedded · Accepted Answer · 2016-04-08 08:00:46Z

-1

You can do :

c = ((A*) (p->b[0]))->a;

answered Apr 8, 2016 at 8:00

embedded

111 bronze badge

1 Comment

alk Over a year ago

You cannot, as A is not a type in C.

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