C Dynamic Array of void pointers

Question

OK, so I've got the following C code:

//for malloc
#include <stdlib.h>

//to define the bool type
#if __STDC_VERSION__ >= 199901L
#include <stdbool.h>
#else
typedef int bool;
#endif

//define structs
typedef struct A{
   int integerValue;
    char characterValue;
} A;

typedef struct B{
    float floatValue;
    bool booleanValue;
} B;

int main(int argc, const char * argv[])
{
    //allocate a void pointer array
    void* myArray[3];

    //fill the array with values of different struct types
    myArray[0] = malloc(sizeof(A));
    myArray[1] = malloc(sizeof(B));
    myArray[2] = malloc(sizeof(A));
}

but I want to be able to dynamically resize the array. I know that you can dynamically resize an array containing just one type like this:

int* myArray;
myArray = malloc(3*sizeof(int));
myArray[0] = 3;

myArray = realloc(myArray,4*sizeof(int));
printf("%i",myArray[0]);

but how would you do this in the upper situation (it needs to be able to handle a virtually infinite number of types). Would it work to reallocate the array with realloc(myArray,newNumberOfIndices*sizeof(ElementWithBiggestSize)), or is there a more elegant way to achieve this?

vanomart · Accepted Answer · 2013-11-05 17:45:03Z

1

B* b_pointer = (B*) malloc (sizeof(B*));
void** arr = (void**) malloc (3 * sizeof(void*));
arr[0] = b_pointer;

void** new_arr = (void**) malloc (6 * sizeof(A*));
memcpy(new_arr, arr, 3 * sizeof(A*));
// now arr[0] == new_arr[0] == b_pointer;

free(arr);
// now new_arr[0] == b_pointer;

Note that if you're allocating pointers, it doesn't really matter which struct or array (or i don't know what) you want to point to.

PS: happy debugging using void pointer array with different structs

edit: renaming "b_instance to b_pointer", just trying to make it less confusing

edited Nov 5, 2013 at 17:45

answered Nov 5, 2013 at 17:37

vanomart

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