[fpc-pascal] PChar -> AnsiString -> PChar = memory leak?

[Mattias Gaertner]

On Thu, 29 Oct 2009 15:44:09 +0200
Graeme Geldenhuys <graemeg.lists at gmail.com> wrote:

> On 29/10/2009, Mattias Gaertner <nc-gaertnma at netcologne.de> wrote:
> >
> >
> > Text:=strnew(PChar(s));
> 
> You read my mind. I was going to ask if it's ok to cast a PString to
> a PChar.

Yes.
But it will not change the reference count.
 
> Trying what you suggested, I get the following compiler error.
> 
> project1.lpr(20,11) Error: Incompatible types: got "PString" expected
> "PChar"

It compiles here. Probably you use some special units.

 
> Changing my test code to the following solves the compiler error, but
> now heaptrc reports that I have two memory leaks.
> 
> --------------------------
> var
>   Text: PChar;
> 
> procedure AppendText(const AText: string);
> var
>   s: string;
> begin
>   s := Text + AText;
>   StrDispose(Text);
>   Text := PChar(NewStr(s));

ok
Not very fast, but ok.

> end;
> 
> var
>   t: string;
> begin
>   t := 'hello';
>   writeln('t=', t);
>   Text := PChar(t);
>   writeln('Text=', Text);
>   AppendText(' world');
>   writeln('Text=', Text);
> end.

Graeme, why don't you just change the type of 'Text' to string?


This does not change the reference count:
Text := PChar(t);
The string is not duplicated. And StrDispose can not free that.
And 'Text' is not freed at the end.

Mattias