Question

I tried to replace Delphi build-in function with my own version on-the-fly.

function ShortCutToTextOverride(ShortCut: TShortCut): string;
begin
  if SomeCondition then
    Result := Menus.ShortCutToText // after patching the pointer equals ShortCutToTextOverride
  else
  begin
    // My own code goes here
  end;
end;

FastcodeAddressPatch(@Menus.ShortCutToText, @ShortCutToTextOverride);

After patching, the original function is no longer accessible.
It is possible access it anyway?

Answer 1

I’m afraid not: the first bytes are overwritten by a jump to the new function.

You can use KOLDetours.pas: it returns the pointer to the trampoline (original first few bytes that are overwritten by the detour).
http://code.google.com/p/asmprofiler/source/browse/trunk/SRC/KOLDetours.pas

For example:

type
  TNowFunction = function:TDatetime;
var
  OrgNow: TNowFunction;
function NowExact: TDatetime;
begin
  //exact time using QueryPerformanceCounter
end; 

initialization
  OrgNow := KOLDetours.InterceptCreate(@Now, @NowExact);
  Now()     -> executes NowExact() 
  OrgNow()  -> executes original Now() before the hook