Gpc

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by hantschr＠hantsch.co.at 02 Jun '98

02 Jun '98

--note----------------------------------------------------------------- Username: [rainer] Use the above line in your e-Mail body to reach me in our company. You may use [rainer] at the beginning of the SUBJECT line (with higher priority) instead. -- This will allow us "Automatic Mail Forwarding". Our human "postmaster" may be reached with [rainer]. DO NOT USE OTHER FILE-ENCODING THAN UUENCODE, IT CANNOT BE PROCESSED!!! --note----------------------------------------------------------------- Received: from Hantsch-Message_Server by hantsch.co.at with WordPerfect_Office; Tue, 02 Jun 1998 08:43:34 +0100 Message-Id: <s573bb36.001(a)hantsch.co.at> X-Mailer: WordPerfect Office 4.0 Date: Tue, 02 Jun 1998 08:42:31 +0100 From: hantschr(a)hantsch.co.at To: gpc(a)hut.fi Subject: FPK-Area: Where? Item Type: Note ** PRIVATE ** Hello to everybody! Please, be so kind and let me know if there exists a special area (like this GPC area) for FPK users. I would like to subcribe to it but I couldn't locate one! Thanks in advance, Rainer Hantsch ---------------------------------------------------------------------- | Office address: | You may reach us by: | |--------------------------|-------------------------------------------| | ING. RAINER HANTSCH | Phone : +43 1 7988538 0 | | Khunngasse 21/1 | Fax : +43 1 7988538 18 | | A-1030 Wien/Vienna | BBS : +43 1 7988538 17 | | | e-Mail: hantschr(a)hantsch.co.at | | *** A U S T R I A *** | www : http://members.eunet.at/hantschr/ | ----------------------------------------------------------------------

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GPC MANUAL: Schemata, Pointer arithmetics
by Peter Gerwinski 01 Jun '98

01 Jun '98

Hello, folks! here are three new sections for the "programmer's guide to GPC" (see `info -f gpc -n programming'). Comments/improvements/etc. welcome. Greetings, Peter -- Peter Gerwinski, Essen, Germany, http://home.pages.de/~Peter.Gerwinski/ Maintainer GNU Pascal - http://home.pages.de/~GNU-Pascal/ - gpc-980511 PGP key on request - 6C 94 45 BE 28 A4 96 - 0E CC E9 12 47 25 82 75 Fight the SPAM and UBE! - http://spam.abuse.net/ - http://maps.vix.com/ @c ============================================================================ @node Schemata @section Schema Types @cindex schemata @cindex types, schema Schemata are types that depend on a variable, called ``discriminant''. They are an ISO-10206 Extended Pascal extension. @smallexample Type RealArray ( n: Integer ) = array [ 1..n ] of Real; @end smallexample The type @samp{RealArray} in this example is called a Schema with the discriminant @samp{n}. To declare a variable of such a type, write @cindex Foo @smallexample Var Foo: RealArray ( 42 ); @end smallexample Schema-typed variables ``know'' about their discriminants. They can be accessed just like record fields: @smallexample writeln ( Foo.n ); (* yields 42 *) @end smallexample While types of variables must always have specified discriminants (which may be other variables), @emph{pointers} to schema variables may be without a discriminant: @cindex Bar @smallexample Type RealArrayPtr = ^RealArray; Var Bar: RealArrayPtr; @end smallexample When applying @samp{New} to such a pointer, you must specify the intended value of the discriminant as a parameter: @smallexample New ( Bar, 137 ); @end smallexample As a GNU extension, the above can also be written as @smallexample Bar:= New ( RealArrayPtr, 137 ); @end smallexample Schemata are not limited to arrays. They can be of any type that normally requires constant values in its definition, for instance subrange types, or records containing arrays etc. (Sets do not yet work.) To finish this section, here is a somewhat exotic example: @smallexample Type ColorType = ( red, green, blue ); ColoredInteger ( Color: ColorType ) = Integer; @end smallexample A @samp{ColoredInteger} behaves just like an ordinary integer, but it has an additional property @samp{Color} which can be accessed like a record field. @smallexample Var Foo: ColoredInteger ( green ); [...] Foo:= 7; if Foo.Color = red then inc ( Foo, 2 ) else Foo:= Foo div 3; @end smallexample @c ============================================================================ @node Pointer arithmetics @section Pointer Arithmetics @cindex pointer arithmetics GPC allows to increment, decrement, compare, and subtract pointers or to use them in @samp{for} loops just like the C language. @smallexample Var A: array [ 1..7 ] of Char; p, q: ^Char; i: Integer; [...] for p:= @@A [ 1 ] to @@A [ 7 ] do p^:= 'x'; q:= @@A [ 3 ]; while p > q do begin p^:= 'y'; dec ( p ); end (* while *); i:= q - p; @end smallexample Incrementing a pointer by one means to increment the address it contains by the size of the variable it is pointing to. For typeless pointers (@samp{Pointer}), the address is incremented by one instead. Similar things hold when decrementing a pointer. Subtracting two pointers yields the number of variables pointed to between both pointers, i.e.@: the difference of the addresses divided by the size of the variables pointed to. The pointers must be of the same type. @c ============================================================================ @node Type casts @section Type Casts @cindex type casts In some cases, especially when interfacing with other languages, Pascal's strong typing can be an obstacle. To temporarily circumvent this, GPC (and other Pascal compilers) defines explicit ``type casts''. To convert a value of one data type to another type, use the target type as a ``function'': @cindex Foo @cindex Bar @smallexample Type CharPtr = ^Char; CharArray = array [ 0..99 ] of Char; CharArrayPtr = ^CharArray; Var Foo: CharPtr; Bar: CharArrayPtr; [...] Foo:= CharPtr ( Bar ); @end smallexample Beware: Explicit type casts might have unexpected effects on different platforms since you cannot rely on a specific way the data is stored. If it is possible to avoid type casts (which holds for most cases), you should do that. For instance in the example above, you can make @samp{Foo} point to the first char in the array @samp{Bar^}: @smallexample Foo:= @@Bar^ [ 0 ]; @end smallexample When dealing with objects (see @ref{OOP}), it is often necessary---and safe---to cast a pointer to an object to a pointer of a ``bigger'' (derivated) object. In future releases, GPC will provide an operator @samp{as} for a safer approach to this problem. See also: @ref{absolute}. @c ============================================================================

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GPC REFERENCE: SetLength
by Peter Gerwinski 01 Jun '98

01 Jun '98

Hello, folks! Here is a sketch for a `SetLength' reference section. Dose somebody know whether this > @samp{SetLength} is a Borland Delphi 1.0 extension. is really true? Yours, Peter -- Peter Gerwinski, Essen, Germany, http://home.pages.de/~Peter.Gerwinski/ Maintainer GNU Pascal - http://home.pages.de/~GNU-Pascal/ - gpc-980511 PGP key on request - 6C 94 45 BE 28 A4 96 - 0E CC E9 12 47 25 82 75 Fight the SPAM and UBE! - http://spam.abuse.net/ - http://maps.vix.com/ @c ---------------------------------------------------------------------------- @node SetLength @unnumberedsec SetLength @cindex SetLength @unnumberedsubsec Syntax @smallexample Procedure SetLength ( Var S: String; NewLength: Integer ); @end smallexample @unnumberedsubsec Description @samp{SetLength} explicitly assigns a new length @samp{NewLength} to the string parameter @code{S}. The contents of the string is @emph{not} changed; if the operation increases the length of the string, the characters appended at the end are @emph{undefined}. If you want to use @samp{SetLength}, please enable ``extended syntax'' (@samp{--extended-syntax} or @samp{(*$X+*)}). @unnumberedsubsec Standards @samp{SetLength} is a Borland Delphi 1.0 extension. @unnumberedsubsec Example @example Program TestSetLength; (*$X+*) (* Enable "dangerous" features *) Var S: String ( 26 ); begin S:= 'Hello, world!'; SetLength ( S, length ( 'Hello' ) ); writeln ( S ); (* 'Hello' *) SetLength ( S, 26 ); writeln ( S ); (* 'Hello, world!(%$@Â§"!"Â§$Â§"$' *) (* undefined characters ^^^^^^^^^^^^^ *) SetLength ( S, 42 ); (* The overflow is *not* (yet) detected *) writeln ( S ); (* This might cause a runtime error. *) end. @end example @unnumberedsubsec See also @ref{@ref{length}, @ref{String}, @ref{SetType}. @c ----------------------------------------------------------------------------

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[Off-topic?] Req: Code snippet...
by Orlando Llanes 31 May '98

31 May '98

Hey all! Hopefully I'm not out of place by asking so, but here goes anyway. I'm looking for a snippet of *working* Pascal code using Tim Kientzle's algorithm for Approximate Inverse Color Mapping. If nobody has this, does someone out there at least have a snippet of code that uses Inverse Color Mapping in Pascal to reduce a 24-bit image to an 8-bit image? Thanks in advance! See ya! Orlando Llanes "Meine Damen und Herren, Elvis hat soeben das Gebaeude verlassen!" "Look out fo' flyeeng feet" O__/ a010111t(a)bc.seflin.org \/|____. O <__. \/\> / \ ____________|___\______ http://ourworld.compuserve.com/homepages/Monkey414

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crtf.o
by Bendersky 31 May '98

31 May '98

Hi, I've just upgraded to the last alpha. When trying to compile a program I got this: ****************************** C:\UTILS\GPC\Ariel\Mandel>...\bin\gpc -v --automake=-v mandel1.pas Reading specs from c:/utils/gpc/lib/specs gpc driver version 2.81 executing gpc version 2.8.1 c:/utils/gpc/bin/gpc-cpp.exe -lang-pascal -v -nocharescape -undef -D__GNUC__=2 -D__GPC__=2 -D__GNUC_MINOR__=8 -Dunix -Di386 -DGO32 -DMSDOS -DDJGPP=2 -DDJGPP_MI NOR=1 -D__unix__ -D__i386__ -D__GO32__ -D__MSDOS__ -D__DJGPP__=2 -D__DJGPP_MINOR __=1 -D__unix -D__i386 -D__GO32 -D__MSDOS -D__DJGPP=2 -D__DJGPP_MINOR=1 -D__BITS _LITTLE_ENDIAN__=1 -D__BYTES_LITTLE_ENDIAN__=1 -D__WORDS_LITTLE_ENDIAN__=1 mande l1.pas c:/utils/gpc/tmp/ccbywrgj GNU CPP version 2.81 (80386, BSD syntax) #include "..." search starts here: #include <...> search starts here: c:/utils/gpc/include c:/utils/gpc/lang/pascal c:/utils/gpc/contrib/grx22/include /usr/local/include JDIR/djgpp/include JDIR/lib/gcc-lib/djgpp/2.81/include $DJDIR/include End of search list. c:/utils/gpc/bin/gpc1.exe c:/utils/gpc/tmp/ccbywrgj -quiet -dumpbase mandel1.pa s -version -famtmpfile=mandel1.gpc -fautomake=-v -o c:/utils/gpc/tmp/cccywrgj GNU Pascal version 2.81 (djgpp) compiled by GNU C version 2.8.1. c:/utils/gpc/bin/as.exe -o c:/utils/gpc/tmp/ccdywrgj c:/utils/gpc/tmp/cccywrgj c:/utils/gpc/bin/ld.exe crtf.o c:/utils/gpc/lib/crt0.o -Lc:/utils/gpc/lib -Lc:/ utils/gpc/contrib/grx22/lib -Lc:/utils/gpc/lib/gcc-lib/djgpp/2.81 -Lc:/utils/gpc /lib c:/utils/gpc/tmp/ccdywrgj -lgpc -lm -lgcc -lc -lgcc -Tdjgpp.djl c:/utils/gpc/bin/ld.exe: cannot open crtf.o: No such file or directory (ENOENT) ************************************ I've already compiled the grx20, and that program used to work with gpc 2.0 Also, when trying to compile it under rhide I always get (with every program)" cannot open crtf.o: No such file or directory (ENOENT)" Why is that? Am I doing something wrong? Thanks, Ariel --- Ariel Bendersky bender(a)einstein.com.ar

2 7

Mailing list addition
by Richard Earl Green 30 May '98

30 May '98

Please add me to your mailing list addition. You may have me at 'pslmsngr(a)ix.netcom.com'; please remove this as this is nolonger an open account. My current e-mail account is 'pslmsngr(a)inr.net'. Thanks. Richard Green.

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Re: Executing external programs
by Frank Heckenbach 28 May '98

28 May '98

Geoffrey Arnold wrote: > I have GPC version 2.0 compiled for a 486 running linux. > > How do I execute a external shell script from a pascal program? You can use the system(3) function from libc. The first program passes a Pascal string to a CString parameter which is only supported by very recent (alpha) GPC versions. The second program does the conversion explicitly, and therefore works with older GPC versions as well. I'm not sure if it works with 2.0 since I don't have that here for testing. Anyway, it might be a good idea to get a newer version, which, though alpha, is already more stable than 2.0 was. program Exec_Demo; function System (cmd: CString): Integer; C; var s: String (1000); i: Integer; begin Write ('Enter a system command: '); Readln (s); i := System (s); Writeln ('The returned status of the executed command was ', i, '.') end. program Exec_Demo; function System (cmd: CString): Integer; C; function Str2CStrRO (var s: String): CString; begin s[Length(s)+1] := #0; Str2CStrRo := @s[1] end; var s: String (1000); i: Integer; begin Write ('Enter a system command: '); Readln (s); i := System (Str2CStrRO (s)); Writeln ('The returned status of the executed command was ', i, '.') end. Frank -- Frank Heckenbach, frank(a)pascal.gnu.de http://fjf.gnu.de/ PGP keys: http://pgp5.ai.mit.edu/pks/lookup?op=index&search=Frank+Heckenbach

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gpc-980511 build bug
by Klaus Espenlaub 28 May '98

28 May '98

Hi! just subscribed, so for now it's probably the best solution to send me a direct carbon copy, too. I downloaded gpc-980511.tar.gz, integrated it into gcc-2.8.1, ran configure and "make LANGUAGES=pascal", as suggested by the docs. The make run didn't manage to compile the runtime library, because it uses the --automake option. It tries to compile some dependent modules, but fails, because there is no executable on the system called gpc yet: ./../xgpc -B../../ --automake -c -DGPC -Wall -Wpointer-arith -Wmissing-prototypes -Wmissing-declarations -g -I. -I../.. -I/scratch/s_kespen/gcc-2.8.1/p/rts/../.. -I/scratch/s_kespen/gcc-2.8.1/p/rts/../../config rts-move.p gpc1: installation problem, cannot exec `gpc': No such file or directory gpc1: gpc exited with status 255 gpi-hash.c:329: failed assertion `rp == 0' xgpc: Internal compiler error: program gpc1 got fatal signal 6 make[1]: *** [rts-move.o] Error 1 make[1]: Leaving directory `/scratch/s_kespen/gcc-2.8.1/p/rts' make: *** [libgpc.a] Error 2 I worked around by just doing a "make install", giving me a half-working installed gpc. I reran the gpc build, this time with success. So currently if you start from scratch, you need good two runs to get gpc working. This isn't the ideal situation, but changing it would require a few substantial changes all over the place. You need some means of passing the name of the compiler driver down to the compiler. Then it would be easy to change the code in module.c to accommodate for the different location and name of xgpc. Generally it shouldn't be necessary for gpc to be in the PATH. There's no reason why /some/path/to/my/private/gpc should fail, while just gpc works. There has to be some means of keeping -B and -V options given to gpc initially, too. Otherwise it can be painful to use an different gpc version or a cross-compiler, like in this case a not installed compiler version. Anyway, to summarise all this - building gpc doesn't work correctly even if you have gpc installed previously. As long as some older gpc version is potentially used to compile some parts of the RTS, it's wrong. Older gpc versions may have bugs that are already fixed in the current release - this way they can pop up once more. The automake feature is quite useful as it is, but it needs to be polished a bit to make it robust enough for heavy duty work. Klaus

3 2

Executing external programs
by Geoffrey Arnold 27 May '98

27 May '98

I have GPC version 2.0 compiled for a 486 running linux. How do I execute a external shell script from a pascal program? ----------Geoffrey Arnold--------- ------garnold(a)cyberdrive.net------ http://www.cyberdrive.net/~garnold

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Re: RECORD bug?...
by Frank Heckenbach 23 May '98

23 May '98

Orlando Llanes wrote: > Well, I got GPC to run, but I still have the (null) record field error > :( As it turns out, I forgot to upload one of the files. I'm uploading the > one I forgot, if you need the rest, let me know and I'll e-mail them. > This file I'm sending is the one that caused the error, but the > Integer(32) declaration (as opposed to just plain Integer) seems to be the > root of the problem. Thanks in advance! I just reduced your files to the minimum showing the bug and put them in "test suite format" (sorry for the "abuse" of your identifiers ;-). Strangely, it does not depend on using Integer(32) or plain Integer -- it even shows the bug with a string type. But the record is necessary. Well, this bug seems to be a bit volatile, but since it takes two units to trigger it, it reminds me a bit of another bug I found some time ago that's listed as "pointer types do not properly survive transport through two interfaces" in the To-Do list. So hopefully it's not a new bug after all. But I listed your message there so it will be checked when the bug will be fixed. Frank -- Frank Heckenbach, frank(a)pascal.gnu.de http://fjf.gnu.de/ PGP keys: http://pgp5.ai.mit.edu/pks/lookup?op=index&search=Frank+Heckenbach UNIT Orlando1a; INTERFACE TYPE TWorldXY = String(2); TClipRect = RECORD MinX : TWorldXY; END; IMPLEMENTATION END. UNIT orlando1b; INTERFACE USES orlando1a; PROCEDURE PutImg( zClipRect : TClipRect ); IMPLEMENTATION PROCEDURE PutImg( zClipRect : TClipRect ); BEGIN Writeln (zClipRect.MinX) END; END. PROGRAM Orlando1; USES Orlando1a, Orlando1b; VAR ScrClip : TClipRect; BEGIN ScrClip.MinX := 'OK'; PutImg( ScrClip); END.

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