{$IFDEF MSWINDOWS}
function currentStackUsage: NativeUInt;
//NB: Win32 uses FS, Win64 uses GS as base for Thread Information Block.
asm
  {$IFDEF WIN32}
  mov eax, fs:[4]  // TIB: base of the stack
  sub eax, esp     // compute difference in EAX (=Result)
  {$ENDIF}
  {$IFDEF WIN64}
  mov rax, gs:[8]  // TIB: base of the stack
  sub rax, rsp     // compute difference in RAX (=Result)
  {$ENDIF}
{$ENDIF}
end;