While working interpreters (PaxCompiler and DECLAN), I realized we use SizeOf(type) very often. Recently, while migrating to other compilers and operating systems, we had to address FPC's Integer 16bit vs FPC's Integer 32bit. So, I had to touch all of the code for LongInt to enforce 32bit for consistancy. Anyway, I became curious if all of these SizeOf() calls were slower that having predefined constants. In short, no... here is my test code:
    Download sizeof.pas source

Uses
   dxutil_environment;// contains TimeCounter for Windows, Linux and Mac

const
   LongWordSize = SizeOf(LongWord);
   LongWordSizeX2 = SizeOf(LongWord)*2;

Var
   Loop:LongWord;
   StartTime:Comp;
   X:Longint;

Begin
   StartTime:=Trunc(TimeCounter);
   For Loop:=1 to 100000000 do X:=SizeOf(LongWord);
   System.Writeln(Trunc(Trunc(TimeCounter)-StartTime));
   StartTime:=Trunc(TimeCounter);
   For Loop:=1 to 100000000 do X:=LongWordSize;
   System.Writeln(Trunc(Trunc(TimeCounter)-StartTime));
   StartTime:=Trunc(TimeCounter);
   For Loop:=1 to 100000000 do X:=SizeOf(LongWord)*2;
   System.Writeln(Trunc(Trunc(TimeCounter)-StartTime));
   StartTime:=Trunc(TimeCounter);
   For Loop:=1 to 100000000 do X:=LongWordSizeX2;
   System.Writeln(Trunc(Trunc(TimeCounter)-StartTime));
end.

    Oddly, the SizeOf() code is actually a millisecond or two faster (over 100 million calls).

G.E. Ozz Nixon Jr.

Ian Wright
Codemasters