No, this is where "typecasting" is used. Typecasting allows you to fool the compiler into thinking that one type of variable is of another type for the ultimate in flexibility. The last parameter of the Windows API function SendMessage() is a good example. It is documented as requiring a long integer, but commonly requires a PChar for certain messages (i.e. WM_WININICHANGE). Generally, the variable you are typecasting from must be the same size as the variable type you are casting it to. In the SendMessage example, you could typecast a PChar as a longint, since both occupy 4 bytes of memory:

Example:

var s : array[0..64] of char; begin StrCopy(S, 'windows'); SendMessage(HWND_BROADCAST, WM_WININICHANGE, 0, LongInt(@S)); end;

Pointers are the easiest to typecast, and are the most flexible since you can pass anything to the called procedure. They are also the most dangerous for the same reason. You can also use untyped variable parameters for convenience, although var parameters are really pointers behind the scenes.

Example:

type PBigArray = ^TBigArray; TBigArray = Array[0..65000] of char;

procedure ZeroOutPointerVariable(P : pointer; size : integer); var i : integer;

begin for i := 0 to size - do PBigArray(p)^[i] := #0; end;

procedure ZeroOutUntypedVariable(var v, size : integer); var i : integer;

begin for i := 0 to size - do TBigArray(v)[i] := #0; end;

procedure TForm .Button Click(Sender: TObject); var s : string[255]; i : integer; l : longint;

begin s := 'Hello'; i := 0; l := 2000;

ZeroOutPointerVariable(@s, sizeof(s)); ZeroOutPointerVariable(@i, sizeof(i)); ZeroOutPointerVariable(@l, sizeof(l));

s := 'Hello'; i := 0; l := 2000;

ZeroOutUntypedVariable(s, sizeof(s)); ZeroOutUntypedVariable(i, sizeof(i)); ZeroOutUntypedVariable(l, sizeof(l)); end;

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