[fpc-devel] Performance of string handling in trunk

[Sven Barth]

Am 26.06.2013 09:41, schrieb Michael Schnell:
> On 06/25/2013 01:20 PM, Hans-Peter Diettrich wrote:
>> Michael Schnell schrieb:
>>> Supposedly the length and encoding number and code-bytecount is 
>>> copied, too.
>>
>> Please understand reference counted memory objects :-]
> Please check this program I tested with a pre-Unicode Delphi.
>
> It shows that (of course) the string length gets copied when assigning 
> a string variable to another and how it is done.
>
You do know that s2 will point to the same record of s1 after the 
assignment? The contents of the string record are not copied, only the 
pointer of s2 will change. See this example:

=== code begin ===

program tstrassign;

{$apptype console}
{$ifdef fpc}
   {$H+}
{$endif}

{$ifndef fpc}
uses
   SysUtils;

function hexstr(ptr: Pointer): String;
begin
   Result := IntToHex(Integer(ptr), 8);
end;
{$endif}

var
   s1, s2: String;
begin
   s1 := 'Test';
   Writeln(hexstr(Pointer(s1)), ' ', hexstr(Pointer(s2)));
   s2 := s1;
   Writeln(hexstr(Pointer(s1)), ' ', hexstr(Pointer(s2)));
end.

=== code end ===

Regards,
Sven