[lazarus] StrPCopy bug

[michael at tfdec1.fys.kuleuven.ac.be]

On Thu, 8 Jul 1999, Michael A. Hess wrote:

> Shane Miller wrote:
> > 
> > Could someone else try and get some example to Peter please.  If
> > needed, send him the Lazarus code and pinpoint the location.  I think
> > I may have found the other problem with the gtk_widget_show error and
> > I am stalking that.
> 
> I won't be back in my office for another 2 1/2 hours at the least so I
> can't do it until then. However, given what you have found so far with
> the DispatchStr('resize') crash I tend to think that we might be do some
> bad pointer passing or something and stomping on memory that is just
> plain messing everything up. StrPCopy was first and we by passed that
> only to find something else that got messed up. Since a smaller program
> StrPCopy does work I am leaning towards it being our problem. We are
> going to have to isolate parts of the code little by little until we
> find it.  :-\

Here is a test program I made:
-------------------------------------------------------
Program Example46;

{ This program demonstrates the StrBufSize function }
{$H+}

Uses heaptrc,sysutils;

Procedure DoTest;

Const S  = 'Some nice ansi string';

Var P : Pchar;
    SS : AnsiString;
Begin
   SS:=S+'!!!';
   P:=StrAlloc(Length(SS)+1);
   StrPCopy(P,SS);
   Write (P, ' has length ',length(SS));
   Writeln (' and  buffer size ',StrBufSize(P));
   StrDispose(P);
End;

Var L : longint;

begin
  L:=Memavail;
  Writeln('Mem :',L);
  DoTest;
  Writeln ('Mem : ',Memavail,' or lost ',L-Memavail,'bytes');
end.
------------------------------------------------------------

here is the output:

------------------------------------------------------------
home: >ex46
Mem :262016
Some nice ansi string!!! has length 24 and  buffer size 25
Mem : 262016 or lost 0bytes
Heap dump by heaptrc unit
7 memory blocks allocated : 125/144
5 memory blocks freed     : 101/112
2 unfreed memory blocks : 24
True heap size : 262144
True free heap : 262016
Should be : 262016
Call trace for block 0x08062600 size 12
  0x080592E2
  0x080551A0
  0x08053B09
  0x08053C04
  0x08058D65
  0x0805D49F
  0x080480A4
Call trace for block 0x080625C0 size 12
  0x080592E2
  0x080551A0
  0x08053AF1
  0x08053C04
  0x08058D65
  0x0805D49F
------------------------------------------------------------

Remark the '0 bytes lost.'

The 2 allocated blocks that heaptrc cmplains about are because 
2 exception objects that are allocated in iitialization code of
the sysutils unit are never freed (no finalization code yet), 
they have nothing to do with the StrPCopy.

Michael.