Gpc July 2005

gpc@gnu.de

25 participants
67 discussions

Forward defined types (and object references)
by Peter N Lewis 05 Jul '05

05 Jul '05

What facilities does GPC have for forward defining types. In CW Pascal, I have some code that looks like this: type MyProc = procedure( browser: MyObjectA ); MyObjectA = object f: MyProc; b: MyObjectB; procedure Doit( proc: MyProc ); function GetB: MyObjectB; end; MyObjectB = object; f: MyObjectA; // other references to ObjectA end; Keep in mind all the "used before defined" types are pointer types (objects being implicitly pointers) and defined in the same "type" block. GPC is not happy with this. Needless to say, given the dual referential nature of the references, it is hard to see how I can cleanly untangle this. Is there any support in GPC or EP for these kinds of forward defined types? Any suggestions how I can untangle them within GPC? The best I can see is to turn all of them into explicit pointers and explicit dereferences, which is doable, but rather ugly. Any suggestions? Thanks, Peter. -- <http://www.stairways.com/> <http://download.stairways.com/>

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Re: Forward defined types (and object references)
by Peter N Lewis 05 Jul '05

05 Jul '05

At 13:09 +0200 5/7/05, Marco van de Voort wrote: >In gmane.comp.compilers.gpc, you wrote: >> What facilities does GPC have for forward defining types. >> >> In CW Pascal, I have some code that looks like this: >[...] >> MyObjectB = object; >> f: MyObjectA; >> // other references to ObjectA >> end; > >(btw Does this compile? Note the semi-colon after object) No, sorry, it was only meant as a basic idea, I didn't actually run it through the compiler to get out any silly syntax errors like that. >Delphi supports this: (remember its object model is similar) > >Type > MyObjectB = class; > MyObjectA = class; > MyProc = procedure( browser: MyObjectA ); > MyObjectA = class > f: MyProc; > b: MyObjectB; > procedure Doit( proc: MyProc ); > function GetB: MyObjectB; > end; > MyObjectB = class > f: MyObjectA; > // other references to ObjectA > end; > >Must be in one typeblock though, IOW, the same system as pointers. >For MacPascal mode object=class btw. Yes, that would be what I'd expect, although the EP definition of class .. end; is acceptable to. I'd suggest GPC accept either syntax to be compatible with Delph and EP (as well as allowing it with "object" when using reference objects for the Mac case). Enjoy, Peter. -- <http://www.stairways.com/> <http://download.stairways.com/>

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Re: Forward defined types (and object
by Frank Heckenbach 05 Jul '05

05 Jul '05

marcov(a)stack.nl wrote: > In gmane.comp.compilers.gpc, you wrote: > > What facilities does GPC have for forward defining types. > > > > In CW Pascal, I have some code that looks like this: > [...] > > MyObjectB = object; > > f: MyObjectA; > > // other references to ObjectA > > end; > > (btw Does this compile? Note the semi-colon after object) Yes, the semicolon seems wrong (at least in other dialects). > Delphi supports this: (remember its object model is similar) > > Type > MyObjectB = class; > MyObjectA = class; This seems to be what `class .. end' is in OOE. > Must be in one typeblock though, IOW, the same system as pointers. Yes, same in OOE. Frank -- Frank Heckenbach, frank(a)g-n-u.de http://fjf.gnu.de/ GnuPG and PGP keys: http://fjf.gnu.de/plan (7977168E)

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Download
by Silvio a Beccara 05 Jul '05

05 Jul '05

Good morning, it's a while now that the binaries and sources are not available from GPC's website. If one wants to download and install the latest stable version, how should he/she do? Thanks and regards Silvio a Beccara University of Trieste - Italy -- Email.it, the professional e-mail, gratis per te: http://www.email.it/f Sponsor: Scopri come proteggere dai virus il tuo computer e come eliminare * ogni tipo di virus! - clicca qui Clicca qui: http://adv.email.it/cgi-bin/foclick.cgi?mid=3212&d=5-7

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GPC on OS 10.4
by Aleck Brinkman 04 Jul '05

04 Jul '05

Has anybody successfully installed GPC on Mac OS 10.4 (Tiger)? Thanks. Aleck Brinkman Temple University

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$D directive
by Peter N Lewis 03 Jul '05

03 Jul '05

The warning message for $D is: ignoring BP directive `{$d-}' which is unnecessary in GPC CW Pascal uses $D to turn symbol generation on and off (typically used to disable around sensitive areas of code like password / serial number / authentication / etc). I don't know if there is any equivalent for the Mac directive, but the warning is a bit inaccurate for Mac. Perhaps it should just be the normal "unknown directive", or perhaps there should be a general scheme for setting ignored directives (which could include $D for BP, and could include $unused for Mac). Or perhaps the warning message should just be changed a little? Enjoy, Peter. -- <http://www.stairways.com/> <http://download.stairways.com/>

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Dropping some misfeatures in for-loops and `absolute' variables
by Frank Heckenbach 02 Jul '05

02 Jul '05

GPC accepts the following program, but produces quite silly results: program Foo; var a: array [1 .. 2] of Integer value (0, 0); i: Integer; begin i := 1; for a[i] := 1 to 10 do begin WriteLn (i, ' ', a[i]); if a[i] = 5 then i := 2 end end. The problem is that it evaluates the index i each time, not once before the loop. It would be possible to fix it, but do we really want that? Neither BP nor CP/EP allow it, they allow only identifiers in for-loops. Waldek and I see no need for such a feature. (If it made it possible to nest a compile-time-unknown number of `for' loops, I could see some point, but of course, it doesn't.) So, would anybody mind dropping this misfeature, and requiring an identifier in for-loop counters? The same (and probably a lot of other weird stuff) can be achieved with "extended" `absolute' variables, such as: program Foo; var a: array [1 .. 2] of Integer value (0, 0); i: Integer; {$local W-} c: Integer absolute a[i]; {$endlocal} begin i := 1; for c := 1 to 10 do begin WriteLn (i, ' ', c); if a[i] = 5 then i := 2 end end. We support `absolute' for BP compatibility, but IMHO then we should restrict it to what BP requires, i.e. really absolute addresses, or the address of entire variables or parameters. I suppose (hope) few users actually knew about the extended (mis)features GPC allowed, so I hope we can drop them. (If not, we probably should change semantics to evaluate the address once, and not on each usage, as is done now, so if you rely on this behaviour, you might have to change your code anyway -- if nothing else helps, you can always achieve the same effect with type-casting of pointers.) BP compatible code will not be affected. Any objections? Frank -- Frank Heckenbach, frank(a)g-n-u.de http://fjf.gnu.de/ GnuPG and PGP keys: http://fjf.gnu.de/plan (7977168E)

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Gpc July 2005