Question

I know that I can check the current state of Delphi’s switch directives using this construct:

{$IFOPT R+}
      Writeln('Compiled with range-checking');
{$ENDIF}

Since I’m lacking of in-depth sources on how the Delphi backend compiler works, I’m not sure wether there is a way of changing the behaviour of a function depending on the state of a switch directive at the code line calling it. It’ll look something like this:

procedure P1;
begin  
    {$I+}
    P3; 
    {$I-}
end;

// ** state of I unknown

procedure P2;
begin
    {$I-}   
    P3; 
    {$I+}
end;

// ** state of I unknown

procedure P3;
begin       
    // Something like {$IFOPT I+}, but at the state P3 is called
    DoThis;
    {$ELSE}
    DoThat
    {$ENDIF}
end; 

I’m writing adapters for legacy code which I’d urgently like to be untouched.
P3 doesn’t need to use directives, but I figured this to be the way to go.

Answer 1

Change your Programm like this

procedure P1;
begin  
    {$I+}
    P3(true); 
    {$I-}
end;

procedure P2;
begin
    {$I-}       
    P3(false); 
    {$I+}
end;

// ** state of I unknown, but the parameter know the state

procedure P3(WIthRangeCheck: Boolean);
begin       
    if WIthRangeCheck then
       DoThis
    else
       DoThat;
end;