Dynamically grown array of strings

Question

I\'m trying to build a dynamically grown array of strings. Neither the number of strings nor the length of each string is known at compile time. Here\'s the code I came up w

Answer 1

The following statement makes both result[0] and temp point to the same memory address:

result[0]=temp;

Having performed the above assignment, you then free(temp) and try to access result[0]:

free(temp);
printf ("%s \n", result[0]);

This is undefined behaviour, since you're accessing the memory that's just been deallocated.

The same goes for the identical code you have for result[1].

Answer 2

• In the first example you are using a string after freeing it
• In the second example you are strcating to unallocated memory (plus the uneducated realloc(result[0] makes no sense)

You could try this:

char **result = NULL;
result = realloc(result, sizeof(char *) * 1);

result[0] = strdup("hello");

/* ... */

result = realloc(result, sizeof(char *) * 2);
result[1] = strdup(" world");

Now strdup isn't standard but it's not hard to steal it / fake it. Here's one attempt:

char *strdup2(const char *str)
{
    size_t len;
    char *rval = NULL;

    len = strlen(str);        /* We should probably check this. */
    rval = malloc(len + 1);   /* And this. */

    memcpy(rval, str, len);
    rval[len] = 0;

    return rval;
}

EDIT

I was under the (possibly wrong) impression you want to later modify the strings. If that is not the case, simply storing them (without strdup) is adequate:

result[0] = "hello";