warning: function returns addresss of local variable

[gunitinug]

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

char* test(char* s) {
  char ret[]="";
  strcpy(ret, s);
  return ret;
}

int main() {
  puts(test("hello"));
}

I get error:
putstest.c: In function ‘test’:
putstest.c:7:3: warning: function returns address of local variable

Could someone explain what's gone wrong please. Thanks.

[GReaper]

It's a warning, not an error, and it says it all by itself.

EDIT: Also, your code is subject to undefined behaviour, as you're writing to stack memory you haven't allocated and return a pointer to the array which has expired, as the warning says.

[gunitinug]

It's a warning, not an error, and it says it all by itself.

Output gives blank line instead of "hello".

[GReaper]

Output gives blank line instead of "hello".

As I said, "Undefined behaviour".

[gunitinug]

As I said, "Undefined behaviour".

ok thanks

[CommonTater]

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

char* test(char* s) {
  char ret[]="";
  strcpy(ret, s);
  return ret;
}

int main() {
  puts(test("hello"));
}

I get error:
putstest.c: In function ‘test’:
putstest.c:7:3: warning: function returns address of local variable

Could someone explain what's gone wrong please. Thanks.

Simplest explanation.... C does not know how to return arrays from functions.
It just plain can't do that.