Returning a const string from a function in C

Question

I have the following code:

const char * func_journey ()
{
    const char * manner = "Hello";

    manner = "World";

    return manner;

 }

 int main()
 {

     const char * Temp;

     Temp = func_journey();

     return 0;
 }

I ran it in debug just to see what happens, somehow manner changed from "Hello" to "World" and also the pointer changed even due I have declared it a const.

Another thing is that at the end of the run Temp was "World", now how can it be? manner was an automate variable inside func_journey, shouldn't it get destroyed at the end?

Thanks a lot.

`manner` is a pointer to `const char`, if you want the pointer to also be `const` pointer you need `const char * const`. — Shafik Yaghmour, Jun 18 '13 at 19:07
from the FAQ: http://stackoverflow.com/questions/890535/what-is-the-difference-between-char-const-and-const-char — Brian Cain, Jun 18 '13 at 19:07
(not pretty sure)Strings in c are arrays with a reference at the first char .. at all initialisations you change the reference (pointer) to another .. — Alexander Sidikov Pfeif, Jun 18 '13 at 19:15
Yeah, that is exactly what happened, the pointer was to changed to already a pre initialized string ("World"). — Assaf Malki, Jun 18 '13 at 19:20

score 6 · Answer 1 · answered Jun 18 '13 at 19:07

6

I ran it in debug just to see what happens, somehow manner changed from "Hello" to "World"

That's precisely what your code told it to do, so there's no surprise that it did what you asked for.

and also the pointer changed even due I have declared it a const.

You declared it a pointer to const, not a const pointer (I know, this may sound confusing). When you write const char *, it means that what's pointed to is const. If you want to say that the pointer itself is const, you need

char * const manner = "Hello";

answered Jun 18 '13 at 19:07

Sergey Kalinichenko

714,442
84
1,110
1,523

oh... you beat me by 20 seconds. – ruben2020 Jun 18 '13 at 19:08
1

Also, you should read this, very informative: http://stackoverflow.com/questions/16021454/difference-between-declared-string-and-allocated-string/16021546#16021546 – Cloud Jun 18 '13 at 19:26

score 1 · Answer 2 · answered Jun 18 '13 at 19:23

The answer to your questions are two part: 1) you have declared pointer to a "const" and not a "const" pointer (which you wanted I guess). 2) The memory allocated for both "Hello" and "World" is not in function func_journey local stack but in a global read-only memory location (look into how string literals are allocated). If you declare using char array then "World" would not be copied back to Temp.

Returning a const string from a function in C

2 Answers2