http://d.puremagic.com/issues/show_bug.cgi?id=523

           Summary: I think this is  a GC bug
           Product: D
           Version: 0.175
          Platform: PC
        OS/Version: Windows
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: bugzilla@digitalmars.com
        ReportedBy: theos@list.ru


I think that this is a bug in gc/compiler

char [] foo() {
  char [10] arr = "hello, wor";
  return arr[0..4]; // or return arr;
}

void main() {
  printf(foo());
}

doesn`t work - it prints some rubbish, so, as i guess, arr is collected when function 'foo' returns. if I use char [] instead of char[10] all works fine.


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<d-bugmail@puremagic.com> wrote in message news:bug-523-3@http.d.puremagic.com/issues/...

> I think that this is a bug in gc/compiler
>
> char [] foo() {
>  char [10] arr = "hello, wor";
>  return arr[0..4]; // or return arr;
> }
>
> void main() {
>  printf(foo());
> }
>
> doesn`t work - it prints some rubbish, so, as i guess, arr is collected
> when function 'foo' returns. if I use char [] instead of char[10] all
> works
> fine.

You'll get the same thing in C or C++, because in D, as in those languages, statically-sized arrays are on the stack.  When you return the slice of that data, you're hiding from the compiler the fact that you're returning a pointer to a stack variable.  You can fix this by using "return arr[0 .. 4].dup;", as that'll copy the data from the stack onto the heap.

When you use dynamic arrays, though, they're always allocated on the heap, so it works fine.

http://d.puremagic.com/issues/show_bug.cgi?id=523


bugzilla@digitalmars.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |INVALID




------- Comment #1 from bugzilla@digitalmars.com  2006-12-01 02:52 -------
char[10] arr;
allocates arr on the stack. Returning a pointer to the stack will result in
corrupted data.
char[] arr = "string";
will make arr a reference to the static data literal "string", which is in the
static data segment and so remains valid when the function exits.

Not a compiler or gc bug.


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