Thread: question about holding a structure in a char array

What are you ACTUALLY trying to do? It would probably be better to have a bigger picture of what you're trying to achieve, as that will give you better advice. [A bit like, "How do I loose a wheelnut", when you want to fix a puncture - you'd just come back with, how do I attach the jack to lift the car now, and so on - instead of saying "I've got a puncuture, how do I replace my wheel?"]

--
Mats

thanks for the advice matsp. the thing is that if I can find a way to address a member of a structure using a void pointer or something else would be a easy and clean aproach for me. The first code snippet is a way I can deal with it... I was looking for a more direct aproach.

Well, I still don't quite understand what problem you are trying to solve. If you want to, you could write your own malloc function that uses a array of char, like this:

Code:

#define SOMEBIGNUMBER 100000
void *mymalloc(size_t size)
{
   static char  bigarray[SOMEBIGNUMBER];
   static char *ptr = bigarray;

   void *res = NULL;

   if (size + ptr < &bigarray[SOMEBIGNUMBER]) {
      res = ptr;
      ptr += size;
   }
   return res;
}

This of course doesn't allow for data being freed, but it shows you how you can store some data in an array in a very flexible way - I just don't quite understand WHY you would want to do that.

--
Mats

Switch from this

Code:

t.a = (complex*)p->a;
t.b = (complex*)p->b;

to this

Code:

t.a = ((complex*)p)->a;
t.b = ((complex*)p)->b;

and it should work fine.

"->" operator has a highest preseance (duh, is this the right word?) than the cast operator.

Code:

typedef struct
{
        int a,b;
} myStruct;

int main()
{
	char test[sizeof(myStruct)];
	(*(myStruct*)test).a = 1;
	return 1;
}

( you're right foxman. stupid me for not realizing that.

Code:

#include<stdio.h>
#include<stdlib.h>

typedef struct complex
{
        int a,b;
} complex;

typedef struct complex2
{
        double f,g;
} complex2;

int main()
{
        complex a;
        complex2 b;
        void *p[20];

        p[0]=calloc(1,sizeof(a));
        p[1]=calloc(1,sizeof(b));

        ((complex*)p[0])->a=1;
        ((complex*)p[0])->b=2;

        ((complex2*)p[1])->f=3;
        ((complex2*)p[1])->g=4;


        printf("&#37;d+%di\t%lf+%lfi\n",((complex*)p[0])->a,((complex*)p[0])->b,((complex2*)p[1])->f,((complex2*)p[1])->g);

        return 0;
}

something like this I was trying to accomplish. I just post it for someone who would be interested in it in the future.

Thank you for your time!