GNU Pascal Frequently-Asked Questions List, Edition 0.4, for GPC
version 2.0, November 1996

   by J.J. van der Heijden <j.j.vanderheijden@student.utwente.nl>

Please note that this FAQ list is somewhat outdated.  Some of
the things marked "not possible" are possible meanwhile. :-)
For up-to-date information, ask the GPC mailing list (see below).


What is GNU Pascal?
*******************

   The purpose of the GNU Pascal project is to produce a Pascal compiler
(called GNU Pascal or GPC) which

   * combines the clarity of Pascal with powerful tools suitable for
     real-life programming,

   * supports both the Pascal standard and the Extended Pascal standard
     as defined by ISO, ANSI and IEEE. (ISO 7185:1990, ISO/IEC
     10206:1991, ANSI/IEEE 770X3.160-1989)

   * supports other Pascal standards (UCSD Pascal, Borland Pascal,
     Pascal-SC) in so far as this serves the goal of clarity and
     usability,

   * may be distributed under GNU license conditions

   * can generate code and run on any computer for which the GNU C
     compiler can generate code and run.

   Pascal was originally designed for teaching.  GNU Pascal provides a
smooth way to proceed to challenging programming tasks without learning
a completely different language.

What is the current version of GNU Pascal?
==========================================

   The official release is GPC 2.0, based on GCC version 2.7.2.1.  The
previous official release was GPC 1.1, based on GCC 2.6.3, and there
was a patched version `turbo-alpha-1.1' with extensions related to
Borland Pascal (R).  Version 2.0 integrates these `turbo-alpha-1.1'
extensions, plus numerous new features and bugfixes.

Where is the GNU Pascal FTP site? WWW?
======================================

   The master FTP site for GNU Pascal is `kampi.hut.fi'. GNU Pascal
related files can be found in:

     ftp://ftp.kampi.hut.fi/jtv/gnu-pascal/

   This site is mirrored on:

     ftp://sunsite.doc.ic.ac.uk/gnu/pascal/

   The latest developer releases can be downloaded from:

     ftp://agnes.dida.physik.uni-essen.de/gnu-pascal/

   Also, we have a homepage on the web:

     http://agnes.dida.physik.uni-essen.de/~gnu-pascal/

Is it compatible with Turbo Pascal (R) ?
========================================

   GPC is currently *not* a drop-in replacement for Borland's Turbo
Pascal (R).  It supports a number, but not all of the Borland
extensions to the Pascal language. There is no replacement for most of
the Borland runtime library functions. GNU Pascal is part of the GNU
project, so portability is one of its primary goals.  For this reason,
non-portable features of Borland Pascal will probably not be included
into GNU Pascal. More information can be found in the section "Borland
Pascal" of the GPC manual.

Installation related questions
******************************

   This section discusses some common problems with the installation of
GNU Pascal.

Which platforms are supported by GNU Pascal?
============================================

   GPC uses the GCC backend, so it should run on any system that is
supported by GNU CC. This includes a large variety of Unix systems,
MS-DOS, OS/2 and Win32. A full list of platforms supported by GCC can
be found in the file `INSTALL' of the GCC distribution. Not all of
these have actually been tested, but the `gpc-1.2' pre-release is know
to run on these platforms:

          i486-linux         (Linux 2.x, ELF)
          i486-linuxaout
          i486-linuxoldld
          i386-freebsd1.2.0
          djgpp V2           (msdos)
          emx 0.9B           (OS/2, msdos)
          cygwin32 beta16    (Windows95, Windows NT)
          mips-sgi-irix5.3
          sun-sparc-sunos4.1.4

   >>> Ok people - send us your success stories, with canonical machine
name! <<<

Which components do I need to compile Pascal source code?
=========================================================

   A complete Pascal compiler system should at least have:

  1. The actual compiler, GPC.

  2. Assembler, linker, librarian and friends.

  3. A C library.

  4. A debugger, if you want to debug your programs.

   You don't need a C compiler to compile your Pascal programs, but you
do need it to build the GNU Pascal compiler itself.  GNU Pascal version
2.0 is based on GCC 2.7.2.1. Any attempt to build GPC with the wrong
version of GCC is bound to fail.

   For most people, the GNU binutils and GNU debugger (gdb) are a good
choice, although some may prefer to use vendor specific tools.

Help! linking `gpc1' fails: `_emit_string_move' undefined (and more)
====================================================================

   If linking `gpc1' bombs out with an error message that looks like
this:

              ld: Undefined symbol
                 _emit_string_move
                 _emit_string_pad
                 _maybe_find_function_data
                 _dbxout_set_type_status
                 _version_flag
              *** Error code 1
              make: Fatal error: Command failed for target `gpc1'

   you probably suffer from a VPATH make problem. A few GPC source
files have counterparts with identical name in the GCC source
directory. When you have built GCC in the GCC source directory and you
are not using a recent version of GNU make this problem may occur.
There are three solutions:

  1. Get a recent version of GNU make. Version 3.74 or better is known
     to work.

  2. Build GCC in a seperate directory instead of using the GCC source
     directory.

  3. Manually delete these files from the GCC object directory:

     `stor-layout.o' `dbxout.o' `expr.o' `fold-const.o' `optabs.o'
     `convert.o' `function.o' `setop.o' `toplev.o'

     then resume `make'.

When I build `libgpc.a', `rt0.c' says: SIGXCPU undefined (and more)
=======================================================================

   Compilation of the runtime system may fail in `rt0.c' with a
message simular to this:

     rt0.c: `SIGXCPU' undeclared (first use this function)
   or:
     rt0.c: storage size of `sv' isn't known
     rt0.c: storage size of `osv' isn't known

   If this happens to you, you probably have run the `configure' script
with the `--with-bsdrts' option while your Unix is not fully BSD
compliant.  The solution is to rerun `configure' without the
`--with-bsdrts' switch.

I'm using Unix, and all my Pascal programs have linking problems.
=================================================================

   A number of Unix configurations use their system's linker instead of
GNU `ld'. Usually, GPC and GCC need a program called `collect2' before
calling the system's `ld'. `collect2' is installed by GCC, and if you
only install GPC, it will not find `collect2', and use the system
linker directly, which will result in various linker errors. The
solution is to copy `collect2' by hand from the GCC directory to the
location where `gpc1' lives.

I do I debug my Pascal programs?
================================

   To debug your programs, (a) GNU Pascal must be able to generate
executables with debug info for your platform, and (b) you must have a
debugger which understands this.

   * If `gpc -g -o hello hello.p' says: `gpc: -g not supported for this
     platform', then GPC is unable to generate debug info. Usually,
     installing GAS instead of your system's assembler can overcome
     this.  When you configure the GCC used for GPC, specify
     `-with-gnu-as', and possibly `-with-gnu-ld' and/or `-with-stabs'.
     More information can be found in `INSTALL' file in the GNU CC
     source directory.

   * Your system's debugger may not understand the debug info generated
     by GNU tools. In this case, installing GDB may help.

   The bottom line: if you can debug GCC compiled programs, you should
be able to do this with GPC too.

   The GNU debugger (GDB) currently does not have a "Pascal" mode, so
it is unable to display certain Pascal structures etc. When debugging,
please note that the Initial Letter In Each Identifier Is In Upper Case
And The Rest Are In Lower Case. If you want to display variable `foo'
in the debugger, type `show Foo' or `display Foo' instead.

Can you recommend an IDE?
=========================

   Users of Borland Pascal may wonder if there's a replacement for the
IDE (Integrated Development Environment). Here's a few suggestions:

   * (X)Emacs. Some people think it's the answer to the question of
     Life, the Universe and Everything, others decide it's uGNUsable.
     Available from your friendly GNU mirror.

   * XWPE is an imitation of the Borland IDE, so users of Borland
     Pascal may find it a good alternative.

   * RHIDE. djgpp users should definately try RHIDE. The latest (beta)
     release is compatible with GNU Pascal and allows stepping, tracing
     and watching like Borland's IDE. RHIDE v0.6 beta can be downloaded
     from:
          http://www.tu-chemnitz.de/~rho/rhidetest.html

   Although GDB is an excellent debugger, it's user interface is not
very attractive. Refer to the comp.windows.x FAQ: "Where can I get an
X-based debugger?" at:

     http://www.cis.ohio-state.edu/hypertext/faq/usenet/x-faq/part6/faq-doc-2.html

   Some useful frontends include: XXGDB, tGDB and XWPE. see:

     http://www.ee.ryerson.ca:8080/~elf/xapps/Q-IV.html

   Very nice, but resource consuming is the Motif based DDD:

     http://sol.ibr.cs.tu-bs.de/softech/ddd/

Do you have a binary for me?
============================

   Currently, we have binaries for these platforms:

          i486-linux         (ELF)
          i486-linuxaout
          i486-linuxoldld
          i386-freebsd1.2.0
          djgpp V2           (msdos)
          emx 0.9B           (OS/2, msdos)
          cygwin32 beta16    (Windows95, Windows NT)
          mips-sgi-irix5.3
          sun-sparc-sunos4.1.4

   New binaries may have been added after the release of this FAQ.

GNU Pascal and your system libraries
************************************

   This section discusses common problems people have when they try to
access their system's libraries.

How do I use <insert_your_function_here> from the C library?
============================================================

   GNU Pascal can use every function of your C library, but it may be
up to you to write declaration of an external function, before you can
use it.  Consider the function `sleep'. `man(3) sleep' reveals:

     ---------------------------------------------------------
     NAME
        sleep - Sleep for the specified number of seconds
     
     SYNOPSIS
        #include <unistd.h>
     
        unsigned int sleep(unsigned int seconds);
     ---------------------------------------------------------

   This small demo program shows how to use `sleep' in a Pascal program:

     ---------------------------------------------------------
     program SleepDemo;
     
     type
       word = __unsigned__ integer;
     
     function sleep(seconds: word): word; C;
     
     var
       result : word;
     
     begin
       result := sleep(10);
     end.
     ----------------------------------------------------------

What's this confusion about Pascal and C style strings?
=======================================================

   It is important not to confuse Pascal and C string types.

  1. The Pascal string schema, as defined in section 6.4.3.3.3 of the
     ISO-10206:1990 Extended Pascal standard, is a record:

          type string = record
                          Capacity : integer;
                          length   : integer;
                          string   : packed array [ 1..Capacity ] of char;
                        end;

     `string' is not `string(256)', unlike Turbo Pascal. The capacity
     must be declared:

          type
            MyString = string(256);

     before it can be used, i.e.:

          function MyFunction: MyString;

  2. A C string (`char *') is an array of char, terminated with a
     `NULL' char.

   C library functions require C, not Pascal style string arguments.
However, Pascal style strings are automatically converted to C style
strings when passed to a routine that expects C style strings. This
works only if the routine reads from the string, not if it modifies it.

   E.g., this is how you access the `system()' call in your C library
(which is not necessary any more, since `Execute' is already built-in):

     ---------------------------------------------------------
     program SysCall;
     
     function system(name : CString): integer; C;
     
     var
       result : integer;
     
     begin
       result := system ('ls -l');
       writeln('system() call returned : ', result);
     end.
     ---------------------------------------------------------

   There may be other ways to do the same thing; you could declare a
type `PChar' instead of `CString':

     type
       PChar = ^char;

   and replace all references to `CString' with `PChar'. Do *NOT* pass
a "C" style string as a var-argument if the C prototype says `const
char *' or you will get a coredump.

   You are right if you think this stuff belongs in a library, to be
distributed with GPC. Have patience, or start coding!

Are GNU Pascal objects compatible with GNU C++ classes ?
========================================================

   No. (This may change in a future version)

Where are the Turbo Pascal (R) replacement units?
=================================================

   They don't exist (yet). Most of their fuctionality can easily be
implemented, some things are very x86/msdos dependent and would be
meaningless on any other platform.

How do I build/use a shared library?
====================================

   (topic under construction)

GNU Pascal on the djgpp (MS-DOS) platform
*****************************************

   This chapter discusses some potential problems with GNU Pascal on
MS-DOS, using djgpp.

If you need more information
============================

   GPC/djgpp is a djgpp V2 application, and most of the djgpp
documentation applies for GPC too. A great source of information is the
djgpp FAQ:

     http://www.delorie.com/djgpp/v2faq/faq202b.zip

   Another place to look for DJGPP documentation is the DJGPP Knowledge
Base, at this URL:

     http://www.delorie.com/djgpp/doc/kb/

What do I download?
===================

   As discussed in section 2.2, other than GPC itself, you need an
assembler, linker and friends, a C library and possibly a debugger.
From your local djgpp mirror, you can get these as:

     v2/djdev201.zip         (C library)
     v2gnu/bnu270b.zip       (assembler, ....)
     v2gnu/gdb416b.zip       (debugger)

   The rest is up to you; `make' (v2gnu/mak375b.zip) can be useful, The
latest RHIDE test release (an IDE with Borland-look) has support for
GNU Pascal, and can be downloaded from:
     http://www.tu-chemnitz.de/~rho/rhidetest.html

How do I install the compiler?
==============================

   If you don't have djgpp installed on your harddisk, create a
directory for GNU pascal (`c:\gpc'), and unzip the archives. Make sure
you preserve the directory structure (use `pkunzip -d'). Now, add the
directory where `gpc.exe' lives (`c:\gpc\bin') to your path and set the
DJGPP environment variable to point to your `djgpp.env' file:

     set DJGPP=c:\gpc\djgpp.env

   Then, add this to your `djgpp.env' file:

     ---------------------------------------------------------
     [gpc-cpp]
     C_INCLUDE_PATH=%/>;C_INCLUDE_PATH%%DJDIR%/lang/pascal;%DJDIR%/include;%DJDIR%/contrib/grx20/include
     
     [gpc]
     COMPILER_PATH=%/>;COMPILER_PATH%%DJDIR%/bin
     LIBRARY_PATH=%/>;LIBRARY_PATH%%DJDIR%/lib;%DJDIR%/contrib/grx20/lib
     ---------------------------------------------------------

   The binary distribution should come with a `djgpp.env' which is
already modified, so you may not have to do this.

   The GPC online documentation is in GNU info format; you need the info
reader (`txi390b.zip') to read it. To add the GPC documentation to the
info directory file, edit the `c:\gpc\info\dir' file, and locate this
section:

     ---------------------------------------------------------
     * GCC: (gcc.inf).
             The GNU C, C++, and Objective-C Compiler
     
     * GDB: (gdb.inf).
             The GNU Debugger (gdb and gdb-dpmi).
     
     ---------------------------------------------------------

   To add GPC, change it to look like this:

     ---------------------------------------------------------
     * GCC: (gcc.inf).
             The GNU C, C++, and Objective-C Compiler
     
     * GPC: (gpc.inf).
             The GNU Pascal Compiler
     
     * GDB: (gdb.inf).
             The GNU Debugger (gdb and gdb-dpmi).
     
     ---------------------------------------------------------

   Specific information for low-memory conditions and more can be found
in the djgpp FAQ and documentation.

I cannot read the info pages!
=============================

   To read the info pages, you need the `info' program from
`txi390b.zip'. At least for some of the pre-releases of `gpc-1.2', the
`gpc.info' file is invalid: it refers to the `gpc.i*' sections as
`gpc.info-*'. This can be fixed by loading `gpc.inf' in an editor and
replacing `gpc.info-*' with `gpc.i*'

GPC says: no DPMI
=================

   You don't have a DPMI server installed, and DJGPP v2 requires it to
run.  You can either use one of the commercial DPMI servers (e.g., run
`gpc' in a DOS box under Windows) or download and install CWSDPMI
(`csdpmi3b.zip') which is a free DPMI server written for DJGPP.

I have troubles with assembly code
==================================

   The GNU Assembler (`as.exe'), or `gas', called by GCC accepts "AT&T"
syntax which is different from "Intel" syntax. Differences are
discussed in section 17.1 of the djgpp FAQ.

   A guide is available which was written by Brennan Mr. Wacko Underwood
<brennan@mack.rt66.com> and describes how to use inline assembly
programming with DJGPP, at this URL:

     http://www.rt66.com/~brennan/djgpp/djgpp_asm.html

   Section 17.3 of the djgpp FAQ discusses some methods to convert
"Intel" syntax to "AT&T".

Tell me how to do DPMI, BIOS and other DOS related things.
==========================================================

   DPMI, BIOS and other functions are no different than other system
functions. Refer to section 3.1 how to access your system's C-library.
This small example shows how to use DPMI, copying some structures and
function prototypes of `<dpmi.h>':

     ---------------------------------------------------------
     program dpmitest;
     
     {$X+}
     
     type
       word  = __unsigned__ integer;
       short = __short__ integer;
       byte  = __byte__ integer;
     
     type
       PDpmiVersionRet = ^TDpmiVersionRet;
       TDpmiVersionRet = record
           major      : byte;
           minor      : byte;
           flags      : short;
           cpu        : byte;
           master_pic : byte;
           slave_pic  : byte;
       end;
     
     type
       PDpmiFreeMemInfo = ^TDpmiFreeMemInfo;
       TDpmiFreeMemInfo = record
           largest_available_free_block_in_bytes     : word;
           maximum_unlocked_page_allocation_in_pages : word;
           maximum_locked_page_allocation_in_pages   : word;
           linear_address_space_size_in_pages        : word;
           total_number_of_unlocked_pages            : word;
           total_number_of_free_pages                : word;
           total_number_of_physical_pages            : word;
           free_linear_address_space_in_pages        : word;
           size_of_paging_file_partition_in_pages    : word;
           reserved1 : byte;
           reserved2 : byte;
           reserved3 : byte;
       end;
     
     function DpmiGetVersion(ret: PDpmiVersionRet): integer;
                     asmname '__dpmi_get_version';
     function DpmiGetFreeMemoryInformation(info: PDpmiFreeMemInfo): integer;
                     asmname '__dpmi_get_free_memory_information';
     
     var
       version: TDpmiVersionRet;
       meminfo: TDpmiFreeMemInfo;
     
     begin
       DpmiGetVersion(@version);
       writeln('CPU type :       ', version.cpu, '86');
       writeln('DPMI major :       ', version.major);
       writeln('DPMI minor :       ', version.minor);
     
       DpmiGetFreeMemoryInformation(@meminfo);
       writeln('Free DPMI memory : ', meminfo.total_number_of_free_pages, ' pages.');
     end.
     ---------------------------------------------------------

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

   Still, it might be a good idea to use pointers for this kind of
structures, and allocate the memory at runtime.

Getting Help
************

   This section discusses ways to get help with GNU Pascal. Please read
the documentation (info files, readme's) that come with GPC, plus other
docs that might help (the djgpp FAQ if you use djgpp etc.) before you
send email to the maintainers or mailing list.

Help! The compiler crashed!
===========================

   If the compiler crashes, you have discovered a bug. A reliable
compiler never crashes. To help the maintainers fix this bug, it is
important that you send us a problem report.

I think I found a bug - now what?
=================================

   Bugs are best reported to the GPC mailinglist <gpc@hut.fi>.  That
way, they always reach the maintainers. Try to give as much information
as possible, plus a short code snippet that triggers the compiler bug.
If you're on Unix, you can find out where the compiler crashed if you
enable coredumps, then load the compiler (`gpc1') plus the core file in
the debugger (`gdb /your_path_here/gpc1 core'), then type `backtrace'
to get a stacktrace. Include this stacktrace in your bug report.

Which newsgroup(s) are suited for GPC related problems?
=======================================================

   There are several Pascal related newsgroups, but none is dedicated
just to GNU Pascal. This one may be useful:

     comp.lang.pascal.misc         Pascal in general and ungrouped Pascals.

   Pascal syntax related questions may be appropriate in:

     comp.lang.pascal.ansi-iso     Pascal according to ANSI and ISO standards.
     comp.lang.pascal.borland      Borland Pascal questions.

How to post to the mailing list
===============================

   You can send a message to the GPC mailing list by sending email to
the list address <gpc@hut.fi> as if it were a person.

How to become a subscriber to the mailing list
==============================================

   You can join the mailing list by sending a message to
<gpc-request@hut.fi> (NOT <gpc@hut.fi> !) with your request to be added
to the list.  Maintenance is done by hand, so some delay is possible.

How to unsubscribe from the mailing list
========================================

   To leave the mailing list, send a message to <gpc-request@hut.fi>.

Miscellaneous
*************

I want to contribute; where do I start?
=======================================

   A list of jobs which should be done for GNU-Pascal can be found in
the section "How to contribute" of the Texinfo deocumentation.  In cases
where somebody is already working on a topic, the name of that person is
written behind the job's description.

   This does not mean that you shouldn't do that but just that you
should get in contact with that person if you would like to contribute
to that field.

About this FAQ.
===============

   Maintainer: J.J. van der Heijden
<j.j.vanderheijden@student.utwente.nl>

   This is the first incarnation of the GNU Pascal FAQ list. Comments
about, suggestions for, or corrections to this FAQ list are welcome.

   Please make sure to include in your mail the version number of the
document to which your comments apply (you can find the version at the
beginning of this FAQ list).

   Much of the info in, and inspiration for this FAQ list was taken
from the gpc mailing list traffic, so you may have (unbeknownst to you)
contributed to this list.

