strange behaviour

From: Nicolai Hansen (nic_at_aub.dk)
Date: 10/24/03 

Date: 24 Oct 2003 00:51:26 -0700

Hi guys,

In an application I need to get the folder in which Windows are
installed.

My first attempt was:

var
 p: PChar;
 s: String;
begin
 GetWindowsDirectory(p, 256);
 s:=p;
 Showmessage(s); <---
 Showmessage('done');
end;

which crashed on the marked line (need to say that both s and p got
the right values, c:\winnt)

Second attempt:

var
 p: PChar;
 s: String;
begin
 GetWindowsDirectory(p, 256);
 s:=p;
 Showmessage('done'); <---
end;

weird.. Third attempt:

var
 p: PChar;
 s: String;
begin
 new(p);
 GetWindowsDirectory(p, 256);
 s:=p;
 Showmessage('done');
 dispose(p);
end;

which works! I thought, 'great!' and did:

var
 p: PChar;
 s: String;
begin
 new(p);
 GetWindowsDirectory(p, 256);
 s:=p;
 Showmessage(s); <---
 Showmessage('done');
 dispose(p);
end;

Crash again. I then tried

var
 p: PChar;
 s: String;
 i: Integer;
begin
 i:=GetWindowsDirectory(p, 256);
 s:=copy(p, 1, i);
 Showmessage(s); <---
 Showmessage('done');
end;

but nope. I changed it back to the working, with a little
modification:

var
 p: PChar;
 s: String;
begin
 new(p);
 GetWindowsDirectory(p, 256);
 s:=p;
 dispose(p);
 Showmessage('done'); <---
end;

In the end I made it work by declaring the pchar global and
new/dispose in oncreate/ondestroy. But why, oh why, does it behave
like this?

/Nic

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