Dynamic allocation of string array using void pointer

Question

The problem is as follows. I have a void pointer and I want to allocate string array with that. Is it possible to cast void* to char** like this:

void* ptr = (char**)calloc(size, sizeof(char*))

and then allocate each row of that table? I'm currently running out of ideas.

(1) I guess you didn't intend to make ptr have the type void. (2) There is a missing ). — user202729
– user202729, Commented Mar 11, 2018 at 13:12
yes, you can. You do not need the (char**) cast.void* just points to any arbitrary chunk of memory. — Serge
– Serge, Commented Mar 11, 2018 at 13:14
If you want to allocate a "string array", if you want to allocate memory for the array and then for each row, it will be much easier if you work with a char **. Why do you want to use void * instead? Yu can do it, but it will be harder. Every time you do anything with ptr, you'll have to cast it back to char **. — Steve Summit
– Steve Summit, Commented Mar 11, 2018 at 13:15
I'd like to use that as a pointer to a dynamic array as well as a static array, depending on a value of a specific flag. — PatrykTraveler
– PatrykTraveler, Commented Mar 11, 2018 at 13:16

0x51ba · Accepted Answer · 2018-03-11 13:51:43Z

1

Psuedo Code that should get you what you need.

char **ptr = NULL;    
// Allocates an array of pointers
ptr = malloc(sizeof(char *) * (NUM_OF_STRINGS_IN_ARRAY));
If (ptr == NULL)
    return; // Do error handling here
for (int i =0; i < NUM_OF_STRINGS_IN_ARRAY; i++)
{
    // Allocates each string in the array.
    ptr[i] = malloc(strlen(STRING));
    if (ptr[i] == NULL)
    {
        return; // Do error handling here
    }
}

edited Mar 11, 2018 at 13:51

0x51ba

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answered Mar 11, 2018 at 13:17

Jim Gorski

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2 Comments

Steve Summit Over a year ago

He said he wanted ptr to be void *.

PatrykTraveler Over a year ago

Actually, that's what I needed.

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