Thread: possible to return a string ?

I'm not used at all to the fact that strings aren't supported in C like they are in other languages. I have a 2 dimensionnal array with words and I want to return one of the array's word and it doesn't work. I have compiler errors like "return makes integer from pointer without a cast" and "function returns address of local variable" so my guess is that it's returning the addess of the local variable :P

What confuses me is that I can print the word but not return it. I know this could be done with a pointer but I'm wondering if it's possible to do it without.

Code:

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

char getWord() {
	char a_words[5][20];
	
	strcpy (a_words[0],"nucleaire");
	strcpy (a_words[1],"patate");
	strcpy (a_words[2],"verre d'eau");
	strcpy (a_words[3],"table");
	strcpy (a_words[4],"compagnon");

	printf("%s", a_words[2]);
	
	return a_words[2];
}

int main() {
	char word[20];
	strcpy(word ,getWord());
	printf("%s", word);
        return 0;
}

thanks

Variables declared in functions are local to that function. The space for them is allocated on the stack and when the function returns that stack space is freed automagically which means that anything that was stored there is no longer valid. That's what the compiler is warning you about.

There's a few ways to get around this:
1) Pass a buffer to the function for it to store the word in.
2) Use malloc() to allocate the space for the words. This uses memory in the heap instead of the stack. Just be sure to free() the memory when you're done with it.
3) Declare your variable as static (e.g. static char a_words[5][20];). Variables declared as static live for as long as the program is running.

Originally Posted by Tonto

Also, in regards to the above, the way he is doing it is "pretty" safe. He used strcpy to copy the buffer returned from the function to a local one in main, which is fine. If he had directly been accessing the char* returned from his function, then it would mostly likely be overwritten with stupid stuff from another function call, but he didn't.

It's not safe in any way. It's undefined and that's never safe. Don't you think strcpy() uses the stack? strcpy() expects two pointers to be passed to it (dest and src) and those get stored on the stack (not to mention any other local variables strcpy() uses.) Blamo, there goes whatever was in that part of the stack in the getWord() function.

Please don't make it sound like it's sometimes okay to use already-freed memory because it's not. Ever. The C standard says its use is undefined which means that you may or may not be able to get away from it but you should never ever depend on it being okay. A conforming compiler could even zero-out stack space as it's freeing up that memory if it wanted to and still be compliant with the standard.

Never ever use memory contents that may or may not exist anymore.