November 1999 - Gpc

Unit behaviour
by Marc van Woerkom 24 Nov '99

24 Nov '99

Hi! I have a question concerning the use of units. Consider this example: (*****************) (** Queue.pas **) (*****************) unit Queue; interface function isEmpty : boolean; {..} implementation {..} begin {..} end. { Queue } (**************) (* Test.pas *) (**************) uses Queue; begin {..} if Queue.empty then writeln('Queue is empty!'); {..} end. { Test } I expected to be able to use a "Queue." qualifier in front of the empty call in the test routine. But the compiler complains about an undeclared symbol Queue. Is this a bug or a feature? If the latter, how am I supposed to differentiate between the empty function of an Queue and a Stack, if not by using Queue.empty / Stack.empty? Regards, Marc

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FreeBSD port
by Marc van Woerkom 24 Nov '99

24 Nov '99

As posted earlier, I am working on a FreeBSD port of gpc. So far I managed to create these two versions together with gcc 2.8.1: Reading specs from /usr/ports/lang/gpc/inst/lib/gcc-lib/i386-unknown-freebsd4.0/2.8.1/specs gpc version 19990118, based on gcc-2.8.1 Reading specs from /usr/ports/lang/gpc/inst2/lib/gcc-lib/i386-unknown-freebsd4.0/2.8.1/specs gpc version 19991030, based on gcc-2.8.1 I agreed with our primary compiler maintainer to first finish a clean gcc 2.8.1 based port and then move on to the latest gcc (2.96) we have ported. This is mostly because gpc is easier to integrate with the gcc-2.8.1 port. A major problem is how to distinguish errors due to plattform issues from bugs in the compiler (modulo my limited experience with the gpc dialect of Pascal :) Using a test suite would be very helpful. Something like that is mentioned in the gpc info documentation. Can you point me to a set of test programs (with a statement what is supposed to work and what not)? I would also like to know roughly how dependent gpc is on the gcc backend, do you have something like a reference version of gcc, one to test against? Regards, Marc

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Re: Warnings?
by Frank Heckenbach 23 Nov '99

23 Nov '99

Marc van Woerkom wrote: > > This is indeed only detected when the compiler is tracking > > each variable carefully enough - which is the case only with > > optimization. BTW, global variables are never considered > > uninitialized because they are initialized to zero (or Nil or > > false or empty string or ...) at the beginning of the program. > > I have no problems with it, as a TP and C++ vet, but the Pascal > purists do .. > > When I used gpc for a problem in a programming course recently, > I got some points deducted, because of an unitialized variable > (FeldMax in the example below), the use of the 'Ã¶' Umlaut > in the comment at the beginning and (this gpc is not supposed > to check :) the waste of an array for determing the maximum. Don't get this wrong, but... Better don't rely too much on the compiler's checks and warnings in a programming course, to train yourself to be more careful. It's better to learn programming without so much compiler assistance and later use all the compiler's features for production compiling, than relying on the checks and perhaps sometime later having to do some work in an environment without so many checks available... 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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Calling C functions in DLL from a Pascal program (Windows 9X environment)
by GiDeSa 23 Nov '99

23 Nov '99

Hello, I have this problem: I want to call some functions in a Windows DLL, the functions are C ones, then I know the list and type of C parameters to pass. Have anyone some suggestions? What are the correspondence from GPC Pascal types to C types? Thank you

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Re: Problem with strings in record imported/exported from/to modules
by Frank Heckenbach 23 Nov '99

23 Nov '99

David James wrote: > I converted my previous test from extended Pascal modules to units. > This is unit dajunit3 and program daj3u, attached. This case works. > daj3u makes the record using new(). So this bug is somehow module-specific. Peter is investigating it, but I don't know the current status... > However what I really want to do is to put this record into shared > memory, so I moved to daj4u and dajunit4, attached. This fails. > > Eventually, I tried setting the string's capacity before trying to > assign a value to it, and, of course, then the program works. > > My question is really what is the recommended way to do this: is it > to set the string's capacity, or should I be calling some other > function to initialise the record proerly after I shmat the shared > memory? I assume that new(record_pointer) is initialising string > capacities within the record, somehow. Oh, I see. That's a completely new thing, something which hasn't been tried with GPC yet. So, let's see, what would be a good solution here... - We could implement a routine that will initialize any data structure, just like `New' does. Technically, this might not be too difficult (Peter?), but OTOH, such a routine could be easily abused when applied to structures already initialized. (In the case of string or schema fields, this would not do much harm, but in the case of files, it could...) - You could use some lower-level hooks into GPC's memory manager. These hooks already exist in the gpc unit (originally introduced to implement some BP compatible stuff in the system unit). They allow you to redirect any raw memory de-/allocations to user-defined routines, while GPC will still do all the initializations of strings, schemata, files, objects, etc. I'm appending a crude example of this below. You might want to move the connect_shared_memory call into ShmGetMem, but it basically works. If you ever Dispose of this record, you will have to provide a similar FreeMem routine, because otherwise the memory would be given to free() which might not know what to do with it (and might segfault or whatever)... program daj4u(output); uses gpc, dajunit4; var size:integer; shmflg1:integer; shmflg2:integer; base_key:integer; shmid:integer; shmaddr:pointer; err:integer; OldGetMem : GetMemType; function ShmGetMem (Size : SizeType) : Pointer; begin (* we probably should check Size here, but that's just a simple demo... *) ShmGetMem := shmaddr end; begin base_key:=16; size:=sizeof(ty_shared_data); shmflg1:=IPC_CREAT + 8#666; shmflg2:=0; writeln('Calling shmget with key ',base_key:1,' for size ',size:1, ' with flags ',shmflg1:1,' and ',shmflg2:1); connect_shared_memory(base_key,size,shmflg1,shmflg2,shmid,shmaddr,err); writeln('returned from connect_shared_memory for main shared memory ', shmid:1,' ',integer(shmaddr):1); if shmid=-1 then begin writeln('Failed to get main shared memory, reason ',err:1); halt; end; if integer(shmaddr)=-1 then begin writeln('Failed to attach main shared memory, reason ',err:1); halt; end; OldGetMem := GetMemPtr; GetMemPtr := @ShmGetMem; New (shared_data); GetMemPtr := OldGetMem; with shared_data^ do begin sanity:=4567; writeln('sanity is ',sanity); prefix:='ABCD'; if (prefix='ABCD') then writeln('OK') else writeln('failed ',prefix,'|'); end; end. 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: Problem with strings in record imported/exported from/to modules
by david＠tcs01.demon.co.uk 22 Nov '99

22 Nov '99

In message <214E52CA.19991120140550.FOO-4F71.frank(a)g-n-u.de> Frank Heckenbach writes: > David James wrote: > > > I'm having problems with a string in a record that is exported > > from one module and imported into another. I *hope* I am doing > > something stupid! > > > > The maodule (dajmod3.pas) and main program (daj3.pas) below > > should illustrate the problem. > > > > [...] > > This seems to be another innstance of a known bug with string types. > Thanks for the report and the test program which I'm adding to the > test suite. I converted my previous test from extended Pascal modules to units. This is unit dajunit3 and program daj3u, attached. This case works. daj3u makes the record using new(). However what I really want to do is to put this record into shared memory, so I moved to daj4u and dajunit4, attached. This fails. Eventually, I tried setting the string's capacity before trying to assign a value to it, and, of course, then the program works. My question is really what is the recommended way to do this: is it to set the string's capacity, or should I be calling some other function to initialise the record proerly after I shmat the shared memory? I assume that new(record_pointer) is initialising string capacities within the record, somehow. ===== program daj3u(output); uses dajunit3; begin new(shared_data); with shared_data^ do begin sanity:=4567; writeln('sanity is ',sanity); prefix:='ABCD'; if (prefix='ABCD') then writeln('OK') else writeln('failed ',prefix,'|'); end; end. ===== unit dajunit3; interface TYPE astring=string(255); tshared_data = record sanity:integer; prefix:astring; end; VAR shared_data : ^tshared_data; implementation end. {of unit implentation} ===== program daj4u(output); uses dajunit4; var size:integer; shmflg1:integer; shmflg2:integer; base_key:integer; shmid:integer; shmaddr:pointer; err:integer; begin base_key:=16; size:=sizeof(ty_shared_data); shmflg1:=IPC_CREAT + 8#666; shmflg2:=0; writeln('Calling shmget with key ',base_key:1,' for size ',size:1, ' with flags ',shmflg1:1,' and ',shmflg2:1); connect_shared_memory(base_key,size,shmflg1,shmflg2,shmid,shmaddr,err); writeln('returned from connect_shared_memory for main shared memory ', shmid:1,' ',integer(shmaddr):1); if shmid=-1 then begin writeln('Failed to get main shared memory, reason ',err:1); halt; end; if integer(shmaddr)=-1 then begin writeln('Failed to attach main shared memory, reason ',err:1); halt; end; shared_data:=shmaddr; with shared_data^ do begin sanity:=4567; writeln('sanity is ',sanity); (*if we set the string capacity here, everything works prefix.capacity:=255; *) prefix:='ABCD'; if (prefix='ABCD') then writeln('OK') else writeln('failed ',prefix,'|'); end; end. ===== unit dajunit4; interface const IPC_CREAT = 8#0001000; (* create entry if key doesn't exist *) TYPE astring=string(255); ty_shared_data = record sanity:integer; prefix:astring; end; VAR shared_data : ^ty_shared_data; procedure connect_shared_memory(key,size,shmflg1,shmflg2:integer; var shmid:integer; var shmaddr:pointer; var err:integer); implementation var errno: asmname 'errno' integer; function shmget(key:integer; size, shmflg:integer):integer; C_language; function shmat (shmid:integer;shmaddr:integer; shmflg:integer):pointer; C_language; procedure connect_shared_memory; var retval:pointer; inshmaddr:integer; begin shmid:=-1; inshmaddr:=-1; shmid:=shmget(key,size,shmflg1); if shmid=-1 then begin err:=errno; end else begin inshmaddr:=0; retval:=shmat(shmid,inshmaddr,shmflg2); if integer(retval)=-1 then begin integer(shmaddr):=-1; err:=errno; end else begin shmaddr:=retval; end; end; end; end. {of unit implentation} ===== -- David James mailto:david@tcs01.demon.co.uk Special Stage Rally results archive <URL:http://www.tcs01.demon.co.uk/>

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Re: Prototypes translations
by Frank Heckenbach 21 Nov '99

21 Nov '99

Nicola Girardi wrote: > i'm translating svgalib header file (vga.h) under pascal > to make it simply available by using vga.gpi. > > i have some troubles in translating some things, and i ask > you for help... > > these are things i can't translate (they are part of a struct/record) > > {FIXME void *extensions;} Extensions : Pointer; > {FIXME char *linear_aperture;} type TBytes = array [0 .. MaxInt] of Byte; PBytes = ^TBytes; LinearAperture : PBytes; (Most of the time, char * is CString, but here, this is clearly not a C string, but rather a pointer to a 0-based array of Byte (Byte in Pascal is unsigned char in C), so the above is probably the best approximation...) > {FIXME void (*set_aperture_page) (int page);} SetAperturePage : ^procedure (Page : Integer); > {FIXME unsigned char *colors)} Colors : PBytes; 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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Prototypes translations
by Nicola Girardi 21 Nov '99

21 Nov '99

i'm translating svgalib header file (vga.h) under pascal to make it simply available by using vga.gpi. i have some troubles in translating some things, and i ask you for help... these are things i can't translate (they are part of a struct/record) {FIXME void *extensions;} {FIXME char *linear_aperture;} {FIXME void (*set_aperture_page) (int page);} {FIXME unsigned char *colors)} thanks in advance -- Nicola Girardi aka nikke <girardi(a)keycomm.it>

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Free Vision
by Pablo Bendersky 21 Nov '99

21 Nov '99

Hi ! Does anyone know where can I get free vision ? (For GPC, or better GCC) Thanks !

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Warnings?
by Marc van Woerkom 21 Nov '99

21 Nov '99

What Warnings are supposed to work right now? I have the impression that -Wall, -pedantic do have not much effect. E.g. detecting uninitialized variables seems to be a problem (did not work too when using -O, -O2..) Regards, Marc

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