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From: Paul Robinson <p...@paul-robinson.us>
To: "fpc-devel@lists.freepascal.org" <fpc-devel@lists.freepascal.org>
Sent: Sunday, January 15, 2012 5:44 PM
Subject: Adding compiler directives?
I would like to ask whether there's a rule or policy on new compiler
directives. I'd like to see some directives added, to do with two features
which I think are sorely needed in the compiler. Since * I * think they are
needed, * I * will write the code for them, but I need to find out how to
submit them. I know where they have to go: scandir.pas (or quite possibly a
separate unit so as not to clutter that unit up with these routines), and I
know how to write them, but there's no point writing them if there is no desire
to allow them to be added. The new directives are first, for printing
capability:
$LIST
$LISTING
$PRINT
These are all the same (all three would be equivalent), and control the
generation of listings of source code. Currently the compiler does not do
listings, and I think it's an important feature (Pascal Compilers from
mainframe and minicomputer systems did do this, and I miss the functionality.)
There would be options, like $LISTING 55 (the default, a page is 55 lines long)
or
$LISTING PORTRAIT (Default, 55 lines and about 80 characters), or
$LISTING LANDSCAPE
$PRINT ON
$PRINT OFF - The default, would not generate a listing unless enabled
$PRINT INCLUDE - List include files inline as they are read
$PRINT NOINCLUDE - skip include file listing
$TITLE - Text here is printed at the top of the page
$SUBTITLE - Text here is printed at the second line
$EJECT - End page and start new page.
$SKIP 10 - put in 10 blank lines
$EJECT IF 10 - Eject if less than 10 lines are left on the page
And so on.
The listing would either be line printer formatted or it might be generated for
PDF formatting, with things like keyword highlighting and so forth; that's
later. But the main thing is getting the hooks in place so that this
capability is possible.
Then there is the second part of this inquiry which is:
$CROSS - various options I haven't decided yet
A most desperately missing feature - Cross Reference generation. I can always
write a cross-reference program, and in fact I'm working on one because I can't
find the nice one I had that was written about 20 years ago that did much of
what I'm thinking of now, but a cross-reference function should be part of the
compiler since the compiler "knows" which reference the person is referring to,
e.g. if I write
Var I:Integer; (*Line 1*)
R:real;
procedure Q;
var i,j: integer; (*Line 5*)
begin
i :=1; (*Line 8*)
j := 5;
writeln('Hello ',J);
...
end;
begin
I := 15; (*Line 13*)
J := I*12;
Q;
if (J=6) then
Q
else
I++;
...
end.
The Cross-reference listing can be something like this (it follows the source
code listing, which would include line numbers):
Identifier Defined Referenced
I 1 13, 14, 19
I 5 8
J 1 14, 16
... More items ...
Procedure Q
is defined by Main Program 4
is called by Main Program 15,16
and calls Writeln 10
While it might not be this slick - it might not reference local definitions -
at least at first, it is something I am thinking about because listing and
cross-reference capability were in compilers 20 years ago and while to get good
performance when PCs were slow, it was something that probably had to go,
there's no reason we can't restore the capability now.
So, again, I'm not asking for anyone else to do this, I can write the code
myself, I just have to know how I would submit changes for approval.
Paul Robinson <p...@paul-robinson.us>
The Lessons of history teach us - if they teach us anything - that no one
learns the lessons that history teaches us.
-- End of Message --
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