Gpc May 2000

gpc@gnu.de

34 participants
63 discussions

Re: possible bug question...
by Russ Whitaker 25 May '00

25 May '00

Hi Sounds like someone tried to define Pascal by using a Flow Chart and someone else converted the Flow Chart itself into english :-) Does the Standards Committiee still exist? It would be nice to start the ball rolling tward a rewrite, even if nothing more than a conversion into real english. In the meanwhile, just for fun patched the original program that started this thread: program prime1; {find prime numbers up to 100} var i,j,k: integer; begin for i := 2 to 100 do begin k := 0; for j := 2 to i do if i mod j = 0 then begin k := j; break; end; if k = i then writeln( k ); end; end. It prints out 25 prime numbers 2,3,5, ... ,97 useing 1158 passes through the inner loop. program prime2; {find prime numbers up to 100} var i,j: integer; k: boolean; begin for i := 2 to 100 do begin k := false; j := 1; repeat inc( j ); if i mod j = 0 then k := true; until( k or ( j > sqrt( i ))); if not k or ( j = i ) then writeln( i ); end; end. It prints out the same list useing 261 passes Russ <russwhit(a)mind.net>

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Re: posible bug question...
by Frank Heckenbach 24 May '00

24 May '00

J. David Bryan wrote: > On 20 May 2000, at 9:31, Russ Whitaker wrote: > > > So what does the Pascal specs say? > > The Extended Pascal standard, section 6.9.3.9.1, says: > > "After a for-statement is executed, other than being left by a > goto-statement, the control-variable shall be undefined." > > That's remarkably clear. :-) That means that variable "b" in the code > below isn't guaranteed to be true: In fact, i = 10 in the current GPC version (but don't rely on it :-). > procedure p; > var i : integer; > b : Boolean; > begin > for i := 1 to 10 do ; > b := (i > 10); > end; > The next part of the standard is a bit less clear: > > "Neither a for-statement nor any procedure-and-function-declaration-part > of the block that closest-contains a for-statement shall contain a > statement threatening (see 6.9.4) a variable-access denoting the > variable denoted by the control-variable of the for-statement." > > I believe that says that you can't modify the control variable of a for- > statement (a "threat" is defined in the standard as one of ten ways that a > variable may be assigned a value). Including a `for' statement (item g :-). Therefore I conclude that a `for' statement by itself is illegal in Pascal. Alright, we'll take it out of the next GPC release. Just kidding... > So this would clearly be illegal: > > procedure p; > var i : integer; > begin > for i := 1 to 10 do > i := 11; > end; > > However, it also says that a block containing a for-statement cannot > contain a threat to the control variable. In other words, this would be > illegal too: > > procedure p; > var i : integer; > begin > i := 0; > for i := 1 to 10 do > end; > > I suppose the reason is to disallow something like this: > > procedure p; > var i : integer; > label 1, 2, 3; > begin > goto 1; > 2: i := 11; > goto 3; > > 1: for i := 1 to 10 do > begin > goto 2; > 3: > end > end; > > ...which is functionally equivalent to the second code example. Yes, but is a goto into a loop legal at all (the last sentence of 6.9.2.4 seems to indicate not to me, but I'm not completely sure)? If it is legal, what should the following code do? procedure p; var i : integer = 42; label 1; begin goto 1; for i := 1 to 10 do begin 1: Writeln (i) end end; > So it would seem that to comply with the EP standard, GPC must prohibit any > threat (i.e., variable assignment) to a for-statement control variable > anywhere within the scope of that variable, and not just within the for- > statement itself. This would mean that the loop variable could practically not be used outside of the for loop. If this is really true, I'd really favour a syntax that makes this clear (like `for i : Integer = 1 to 10 do ...'), so i has only the corresponding scope. Frank -- Frank Heckenbach, frank(a)g-n-u.de, http://fjf.gnu.de/ GPC To-Do list, latest features, fixed bugs: http://agnes.dida.physik.uni-essen.de/~gnu-pascal/todo.html

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Re: posible bug question...
by Frank Heckenbach 24 May '00

24 May '00

J. David Bryan wrote: > Hello Marco, > > I have copied my reply to the list. > > > On 21 May 2000, at 15:56, Marco van de Voort wrote: > > > Or do they mean: > > > > procedure x; > > > > var i : integer; > > > > procedure nestedx; > > > > begin > > i:=5; > > end; > > > > begin > > for i:=1 to 5 do nestedx; > > end; > > I believe you are correct, and my original reading that: > > i := 0; > for i := 1 to 10 do ; > > was incorrect is itself incorrect. The key part of the statement in the > standard is that the "...procedure-and-function-definition part of the > block that closest-contains a for-statement..." cannot threaten the control > variable. In your example, the "procedure x" block (the second begin-end > block) is the "block that closest-contains a for-statement." Therefore, > your first block, that of "procedure nestedx", forms the "procedure-and- > function-definition-part of the block...." > > So your example breaks the requirement listed in the standard, meaning your > interpretation is correct. In my example, the threat ("i := 0") is not in > either the for-statement nor the procedure-and-function-definition part, so > it is legal. I see. So `for' statement are not illegal by themselves in Pascal, I'm relieved. ;-) Checking all this seems quite difficult, but at least in principle possible... Frank -- Frank Heckenbach, frank(a)g-n-u.de, http://fjf.gnu.de/ GPC To-Do list, latest features, fixed bugs: http://agnes.dida.physik.uni-essen.de/~gnu-pascal/todo.html

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PPC
by f.c. kuechmann 24 May '00

24 May '00

Has anyone compiled gpc to run on PowerPC platforms under LinuxPPC? I'd hate to go to the trouble if somebody already did it. Cheers fk

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Re: revised faq
by Frank Heckenbach 23 May '00

23 May '00

Russ Whitaker wrote: > Attached is a .gz file. It should look ok. Yep. > > (Note: The syntax given here is valid for GPC releases of May 2000 > > and newer.) > > > ok entered change > visited agnes earlier today - No May releases yet. I didn't claim there were any. ;-) (Which means that the syntax doesn't yet work with the existing releases, but since I expect Peter to make the next release soon, I think we can put this forward-looking information in the FAQ already.) Since there were no more comments (besides the ones by The Chief and mine which you've integrated), I'm putting this version of the FAQ into the GPC distribution now. In the future, you will be able to put updates into the distribution yourself via CVS. (Please contact Peter after he's announced the CVS server.) Frank -- Frank Heckenbach, frank(a)g-n-u.de, http://fjf.gnu.de/ GPC To-Do list, latest features, fixed bugs: http://agnes.dida.physik.uni-essen.de/~gnu-pascal/todo.html

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Re: revised faq
by Russ Whitaker 23 May '00

23 May '00

Hi Andreas Jaeger writes> > >>>>> Russ Whitaker writes: > > Mandrake is NOT compatible with RedHat despite claims - you need less > > manual tweaks then in case with SuSE or Debian but ONLY RedHat is > Why do you need manual tweaks at all with SuSE? SuSE 6.4 ships with: > rpm -q -f /usr/bin/gpc > gpc-2.95.2-19 > (Version from October 1999) > Any given binary should install easily on the target it was intended for. Any other target you may have problems. For instance, SuSE 5.1, 5.2, 6.1, 6.2 did not have GPC, so you might run into problems trying to install the SuSE 6.4 package into a 5.1 box. Russ <russwhit(a)mind.net>

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Re: revised faq
by Frank Heckenbach 23 May '00

23 May '00

Khimenko Victor wrote: > > {$ifdef DJGPP} > > var > > MinStackSize : Cardinal = $200000; asmname '_stklen'; > > {$endif} > > Hmm. If here we said about DJGPP's stack handling perhaps setrlimit(2) and > ulimit from bash(1) should be mentioned as well ? In SVr4 and BSD 4.3-based > systems (including Linux) you can raise stack size limit via setrlimit(2) in > run-time or from bash's command line BEFORE starting program with ulimit -s ... > Of course in Linux you'll need not `array[1..4000000] of byte' but > `array[1..10000000] of byte' to get exception (with default 8MiB limit) but > anyway ... That's one difference. The main difference, of course, is that a Linux user can set the stack size on the command line (and if s/he or the admin limits it, they might have their reasons, so a program probably should not usually override it) while under DJGPP the stack size has to be written into the executable (and the whole stack has to be allocated in physical memory at program startup due to a weakness of the DPMI specification), so one cannot just set it to some large value without problems. Finally, the method of setting the stack size is quite different (DJGPP: declare a constant(*) with a certain asmname; Unix: call a function at any time), so these are almost completely different matters, IMHO. Now, I wouldn't object to putting the information for Unix into the FAQ, but since the DJGPP information is in the DJGPP specific section, one would have to find a suitable place for it... (*) I wrote `var', but it should rather be `const'. Russ, can you please change it in the FAQ? Frank -- Frank Heckenbach, frank(a)g-n-u.de, http://fjf.gnu.de/ GPC To-Do list, latest features, fixed bugs: http://agnes.dida.physik.uni-essen.de/~gnu-pascal/todo.html

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Re: posible bug question...
by Frank Heckenbach 23 May '00

23 May '00

Maurice Lombardi wrote: > Frank Heckenbach a Ã©crit : > > This would mean that the loop variable could practically not be used > > outside of the for loop. If this is really true, I'd really favour a > > syntax that makes this clear (like `for i : Integer = 1 to 10 do ...'), > > so i has only the corresponding scope. > > In fact this very syntax was used in one of the intermediate Wirth > languages between algol and pascal (we used at Grenoble an algolW > compiler implementing it at that time). It was done so exactly to forbid > any use of the for control variable outside of the loop, because in many > CPU for control variables are maintained in registers (CX in 16 bit 386 > CPU for example) and need not at any time to be affected into memory (at > least the for control variable of the innermost loop). > So a good idea was lost in going into EP. > But who may update the standard ? The commitees... ;-) But we could perhaps implement it in GPC (like we've already implemented a lot of other non-standard extensions)... Frank -- Frank Heckenbach, frank(a)g-n-u.de, http://fjf.gnu.de/ GPC To-Do list, latest features, fixed bugs: http://agnes.dida.physik.uni-essen.de/~gnu-pascal/todo.html

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Re: revised faq
by Russ Whitaker 22 May '00

22 May '00

Hi Frank wrote: > Russ Whitaker wrote: > > > COPYING.LIB GNU Library Public License > > The precise name is "GNU Library General Public License". > ok > > http://www.cis.ohio-state.edu/hypertext/faq/usenet/x-faq/part6/faq-doc-2.htm > > l > > Bad line break. > Have 2 computers on my desk - the old one runs Windows 95 and it is used strictly for email. When I insert a .txt file it breaks lines where it wants to. Attached is a .gz file. It should look ok. > > Another way is to add the following code to your program to define a > minimum stack size (here: 2 MB). This value will be honored even if > a user sets a lower value by using stubedit, so this method might be > a little safer. > > (Note: The syntax given here is valid for GPC releases of May 2000 > and newer.) > ok entered change visited agnes earlier today - No May releases yet. Did find version 0.4 of the FAQ Russ <russwhit(a)mind.net>

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Re: revised faq
by Frank Heckenbach 22 May '00

22 May '00

Russ Whitaker wrote: > hi > here's the monthly :-) revised faq > > > COPYING.LIB GNU Library Public License The precise name is "GNU Library General Public License". > http://www.cis.ohio-state.edu/hypertext/faq/usenet/x-faq/part6/faq-doc-2.htm > l Bad line break. > I'm accessing an `array[1..4000000] of byte' and I got an exception. > ==================================================================== > > Per default, the maximum stack size of a djgpp application is 256K. > If you need more, you have to adjust it with the stubedit program, i.e.: > > stubedit your_app.exe minstack=5000K Another way is to add the following code to your program to define a minimum stack size (here: 2 MB). This value will be honored even if a user sets a lower value by using stubedit, so this method might be a little safer. (Note: The syntax given here is valid for GPC releases of May 2000 and newer.) {$ifdef DJGPP} var MinStackSize : Cardinal = $200000; asmname '_stklen'; {$endif} Frank -- Frank Heckenbach, frank(a)g-n-u.de, http://fjf.gnu.de/ GPC To-Do list, latest features, fixed bugs: http://agnes.dida.physik.uni-essen.de/~gnu-pascal/todo.html

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Gpc May 2000