Thread: Returning the Address of a Local Variable (Array)

It did what you wanted, but what's your point?

If you put a single bullet in a revolver, put it to your head, pulled the trigger, and lived, would you conclude that such an activity is therefore safe?

Originally Posted by Jesdisciple

No, but my point is whether there really is a bullet in the revolver. Is that result portable? If so, I don't see any difference between the effects of the two approaches.

The result is not portable. It is simply wrong code. Usually it will not crash but there are circumstances where it might.

And what does this main do for you?

Code:

int main(){
    char* input;
    char* input2;
    input = readLine("Please enter a number: ", 256, 1);
    input2 = readLine("Please enter a number: ", 256, 1);
    printf( "You entered %s.\n", input);
    printf( "You entered %s.\n", input2);
    return 0;
}

Edit: Of course it doesn't have to be a call to the same function to reuse the memory; try this:

Code:

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

char* readLine(char* message, int maxSize, short pad){
    char string[maxSize];
    int i;
    printf(message);
    fgets(string, maxSize, stdin);
    for (i = 0; i < maxSize; i++ ){
        if ( string[i] == '\n' ){
            string[i] = '\0';
            if(pad){
                return string;
            }else{
                char temp[i + 1];
                strcpy(temp, string);
                return temp;
            }
        }
    }
    return string;
}

int silly(void) {
    int bob[64] = {0x41424344, 0x45464748, 0x49000000};
    return bob[2];
}


int main(){
    char* input;
    int foo;
    input = readLine("Please enter a number: ", 256, 1);
    foo = silly();
    printf( "You entered %s.\n", input);
    printf( "I entered %d.\n", foo);
    return 0;
}

Originally Posted by mike_g

Like tabstop said, in C you will usually pass a refernce to you array in as a parameter so the changes made in your function persist.

Another approach would be to allocate space using malloc inside the function and return the pointer. This issue with that is that you have to remember to free the memory when you are done.

Or, if you are absolutely sure that a case like tabstops first example, you can use a static variable (essentially a global that isn't visible outside of the function). This however does mean that you will have exactly the same problem as tabstops example - if you call readline twice it will overwrite the previous answer.

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Mats