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I am a student in Computer Science, and I am learning programming with Pascal.

I have found an interesting Pascal compiler, P4 (http://homepages.cwi.nl/~steven/pascal/).

To know more about Pascal, I am trying to compile their source code, but I failed.

In this web page, they said:

  1. Compile pcom.p and pint.p with a Pascal compiler. You obviously have to have a Pascal compiler already. This gives you a Pascal compiler (pcom) that produces P4 code, and an interpreter (pint) that runs P4 code.
  2. To use the compiler, run pcom with the Pascal program as standard input. This produces any diagnostics on standard output, and its code on a Pascal file that is called prr. Check with your Pascal compiler how this gets assigned to a file in the filestore. You may have to change the lines 'rewrite(prr)' in pcom.p and pint.p and 'reset(prd)' in pint.p for your compiler, for instance to "rewrite(prr, 'prr')" etc.
  3. To run the resulting code, run pint with the prr output produced by pcom as input for the file 'prd', and input for the compiled Pascal program on standard input.

I have compiled it with Free Pascal (on https://ideone.com/), but failed too.

Free Pascal Compiler version 2.6.4+dfsg-4 [2014/10/14] for i386
Copyright (c) 1993-2014 by Florian Klaempfl and others
Target OS: Linux for i386
Compiling pcom.p
pcom.p(1,3) Warning: Unsupported switch "$L"
pcom.p(88,23) Fatal: Syntax error, ":" expected but ")" found
Fatal: Compilation aborted
Error: /usr/bin/ppc386 returned an error exitcode (normal if you did not specify a source file to be compiled)

I don't know how to compile this source code in Windows machine, because I know Pascal language only.

Can I compile it with Turbo Pascal (without any requirement) on Windows XP? Can you remove some part of script for Pascal compiling only?

fpj
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    Seems like P4's source is not supported by Free Pascal, the same way you can't compile GCC from source using Visual Studio. Try compiling it with P4 itself - download the binary, and use that to compile the source. – sashoalm Apr 28 '15 at 08:11
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    Unmodified versions will not compile with Turbo Pascal since P4/P5 are "the other" dialect family, not Borland but more J&W/ISO like. In the past there were versions adapted to P4 on the web though. In general resurrecting things in TP is painful, Free Pascal is a much better bet. It supports more, is native Windows, and doesn't have painful 16-bit memory limitations – Marco van de Voort Apr 28 '15 at 08:53

2 Answers2

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Free Pascal's Florian has been working getting Scott Moore's P5 compiler (which is a P4 compiler accepting a larger subset of Pascal) to work with FPC's ISO mode for old sources. However it will work (mostly) only in development versions (including the upcoming "stable" branch 3.0.x).

I tried last summer and it compiled and generally worked with FPC 3.x and the -Miso parameter (to select ISO style dialects). IIRC the last thing fixed was ISO style parameter transfer.

I quickly tried the referenced P4 compiler version and it seems to stumble on a few spots with "comment this" comments related to switching back and fro from ISO Mode. If I comment those files, pint compiles. (and then you could run the original bytecode if necessary)

pcom then still stumbles on taking the ord() of a pointer, which is obviously not very portable either, but unfortunately with 20+ occurrences that have to be replaced with ord(ptrint()).

pcom still doesn't compile then, FPC doesn't like passing union fields to VAR parameters. Working around that with a variable and the source compiles, 15 minutes total.

The fixed sourcecode with extra mode statements is at http://www.stack.nl/~marcov/files/p4fixed.zip but requires (as yet unreleased) FPC 3.0 or newer.

The resulting EXE binary can compile the original pcom source to bootstrap itself to bytecode.

Marco van de Voort
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  • Small nitpick: Pascal-p5 does not compile a "larger subset of Pascal", it compiles (all) of ISO 7185 Pascal, not a subset. Pascal-P4 was a subset compiler by definition: it was never designed to compile all of pascal, but only the minimum necessary to self compile. – Scott Franco Dec 13 '16 at 00:31
  • If I say Pascal I mean Pascal. If I mean to say "ISO Pascal", I say "ISO Pascal" or better even "ISO-xxxx" Pascal, see http://www.stack.nl/~marcov/ansiiso.txt Fourth Q&A – Marco van de Voort Jan 19 '17 at 11:36
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You want to get an ISO 7185 compliant compiler to compile that. It is true that Pascal-P4 (the proper name) was written prior to the ISO 7185 standard. However, the adaption to the standard is generally less of a change set than adaption to a dielect.

You will find that work already done and documented at:

http://sourceforge.net/projects/pascalp4/

It specifies use of GPC. However, as Marco said, it is possible with more work to adapt to FPC, and I believe the FPC folks are improving the ISO 7185 capability of their compiler.

Having said that, I'm not sure why Pascal-P4 would be an interesting target. Pascal-P4 was a subset compiler, meaning an incomplete implementation of Pascal. You will find a complete implementation as Pascal-P5:

http://sourceforge.net/projects/pascalp5/

And I believe it has less portability issues as well.

Good luck.

Scott Franco
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