---- Delphi-Talk Discussion List <delphi-talk@elists.org> wrote: > > Hello, > > Subject maybe not technically correct, but there is something where > I have no explanation for it: > > procedure Test(const S: string); > begin > WriteLn(Length(S)); > end; > > procedure TForm1.FormCreate(Sender: TObject); > var > P: PChar; > begin > AllocConsole; > GetMem(P, 512); > FillChar(P^, 511, ' '); > P[511] := #0; > Test(P + ^Z); // displays 256 > Test(string(P) + ^Z); // displays 512 wich is correct > FreeMem(P); > end; > > Wy is the length of the first string only 256 ? > I try this in Delphi 7.
First off I was surprized that you could pass a "naked" PChar as a parameter to a routine taking a string parameter like that, it seems to me a bad choice as a permissable type coercion. In any case, in the absence of proper string identification information to the contrary (which a naked PChar would lack) the compiler evidently assumes you're passing an old style Borlandish short string, which is limited to 255 characters (as mentioned by another poster). If you explicitly define the parameter as a Delphi32 long string like so: procedure Test(const S: AnsiString); You get the result you expect. It's arguable that coercion to short string is a poor assumption in 32-bit Delphi, but I think it's also a more conservative assumption and more likely to avoid memory overruns or other grief. Expecting the compiler to second guess what you meant in this case is IMO a bad idea. If it were me I wouldn't permit it in the first place. I'd say the moral of the story is to be explicit about what you mean when converting between string representations like this. Stephen Posey [EMAIL PROTECTED] __________________________________________________ Delphi-Talk mailing list -> Delphi-Talk@elists.org http://www.elists.org/mailman/listinfo/delphi-talk
