Thread: Memory for Char*[x] - How to get the proper amount?

Hi,

I've got an array like this:

tmparr char*[some number]

Since number must be constant, I thought I just declare the array somehow and I reallocate the necessary space for it later using malloc, or calloc.

However I don't know how to do this, because void* cannot be converted to char*[]! Calloc would be cool, as it allocates space for an array of x elements, so it's just what I need (I guess -.

Or is there any other (better) method?

Also please somebody tell me what is difference between char** and char[]*! The latter is an array of pointers to strings, right? Then the first one would be the array of strings? Probably it's a stupid question, but I'm still very new to this C stuff.


Thanks for any help!

You have to cast it:

Code:

int Size = 12345;
char* Array;

Array = (char*)malloc(Size * sizeof(char));

if(Array != NULL)
{

   ...

   free(Array);
}
else
{
   printf("Not enough memory!");
}

Hi,

Thanks for the answer.

Yes, I knew that it is possbile to cast char* to void* and vice-versa, however my array is a char*[x]!

If I type in:

char *tmparr[] = (char*[]) malloc(some size + 1);

or

char *tmparr[] = (char*[]) calloc(count, count * somesize);

then the compiler (Borland C++ 6) will scream! -

I also tried to use char** instead of char*[num]. That is better, because I was able to cast it to void*, but in this case the size of the array will be always 4 (at least that's what sizeof says...)

What am I doing wrong?

>char *string_array [NR_OF_STRINGS];
>string_array [i] = malloc (STRING_LENGTH);
Two things:
- string_array is a reserved name, so don't use it in your real code.
- STRING_LENGTH would imply strlen(myvar) would do the job. But it wouldn't, you must remember to include +1 for the null terminator.

Here's a working example:

Code:

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

#define COUNT 5

int main(void)
{
    char *my_ary[COUNT];
    char buf[BUFSIZ];
    int i;
    
    for (i = 0; i < COUNT; i++)
    {
        /* You'd normally do error checking with this lot */
        fgets(buf, sizeof buf, stdin);
        my_ary[i] = malloc(strlen(buf)+1);
        strcpy(my_ary[i], buf);
    }
	
    for (i = 0; i < COUNT; i++)
    {
        printf("%s", my_ary[i]);
        free(my_ary[i]);
    }
	
    return 0;
}

Originally posted by Shiro
According to my copy of the C standard, there is no such as string_array. Where did you get this from?

It's in the "Future library directions" section (7.26 in c99). More explicitly, sections 7.26.10 and 7.26.11. It isn't mentioned by name, only that anything starting str followed by a lowercase letter is reserved.

whaaa? So it isn't "right" to name a variable strike, strong_man, strength, stripes and such?

It's been discussed a few times before.

Hi!

Ok I see, now it's clear. Thank you very much for your help!