How to return the array of strings?

Question

I have to return the array b to the main program as char **. How do I do it? If I give

return b;

it gives me an error.

In main() if I give

char **c;
c=GetRandomStrings(2,10,10);

I will get the first string. How to obtain the remaining strings?

char b[10][20];

char**  GetRandomStrings(int minimumLengthOfString, int maximumLengthOfString, int numOfStrings)
{
    static const char alphanum[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
    char s[maximumLengthOfString];
    int num =0,length;

    srand((unsigned int)time(NULL));

    for (int j=0;j<numOfStrings;j++)
    {
        length = randomLength (minimumLengthOfString,maximumLengthOfString);
        for (int i = 0; i < length; ++i)
        {
            num = rand() % (sizeof(alphanum) - 1);
            s[i] = alphanum[num];
        }

       s[length] = '\0';
       strcpy(b[j],s);
    }

    for (int j=0;j<numOfStrings;j++)
    {
       printf("\n\n%s",b[j]);
    }
    return b;
}

int randomLength(int minimumLength, int maximumLength)
{
    return (rand()%(maximumLength - minimumLength) + minimumLength);
}

Besides that, if you intend to return b, then consider that you will return a pointer to a local variable, which leads to undefined behavior, and also that b is an array of arrays of characters, which is not the same as a pointer to a pointer to character. — Some programmer dude
– Some programmer dude, Commented Sep 3, 2014 at 7:43
b should not be global, you should malloc it within GetRandomStrings() — n0p
– n0p, Commented Sep 3, 2014 at 9:27
type of b is char (*)[20], not char**. but There is no need to return a global variable. — BLUEPIXY
– BLUEPIXY, Commented Sep 3, 2014 at 10:05

Sathish · Accepted Answer · 2014-09-03 07:50:37Z

1

When you try to return b from your function you will get warning such as-

warning: return from incompatible pointer type [enabled by default]
warning: function returns address of local variable [enabled by default]

Which leads to undefined behavior!

Try to make b as a pointer to pointer to character and allocate memory for it, Get the strings and return the address of b. This time when you leave the function b wont get affected.

And finally don't forget to free the allocated memory!

answered Sep 3, 2014 at 7:50

Sathish

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