• d-bugmail puremagic.com (24/24) Nov 15 2006 http://d.puremagic.com/issues/show_bug.cgi?id=523
• Jarrett Billingsley (9/21) Nov 15 2006 You'll get the same thing in C or C++, because in D, as in those languag...
• d-bugmail puremagic.com (15/15) Dec 01 2006 http://d.puremagic.com/issues/show_bug.cgi?id=523

d-bugmail puremagic.com writes:

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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"Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:

<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. 

d-bugmail puremagic.com writes:

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


bugzilla digitalmars.com changed:

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





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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