[fpc-devel] Macro Processing

[Joerg Schuelke]

Am Mon, 16 May 2011 13:01:39 +0300
schrieb ik <idokan at gmail.com>:

> procedure toLog(const S : String); <------
> {$IFDEF DEBUG}                           |
>    ....                                  |
> {$ENDIF}                                 |
> end;                                     |
                                           |
What do you think, is my debug thing? It is this. What you write, but in
an unit and an included file, so I never have to think about again. But
approved to vanish completely.

> 
> It's not a hack but a choice to insert things to log.
> I can also create something like this:
> 
> procedure toLog(debug_level : TDebugLevel; const S : String);
> {$IFDEF DEBUG}
>    if debug_level <= current_debug_level then
>     writeln(debug_to_str(debug_level), ' [', DateTimeToStr(now) ,']
> ', s); {$ENDIF}
> end;

OK, this is a starting point, I think many programmers start with
something like this. After they have done writeln and commenting out a
bit.
What my debug system does, is exactly this, what your example code
does. A little more. 
-You can not use the compile time information %LINE% %FILE% ... in your
 procedure because they would expand to the information from your
 procedure.
-You are forced this way to use run-time information
-Where go the units in the uses clause. Some writing of ifdefs? OK.
-Is the code really vanishing if you switch debug off? In this simple
 example, maybe, if inlined. 
-How do you retrieve the function name, line number, file name and how
 do you give it to the procedure? Really Much Writing?? Not done
 therefor.

A macro has the possibility to expand where used, and this way you can
circumvent the Really Much Writing. Thats all.

	Jörg