This file was generated automatically from faq.texi.
DO NOT CHANGE THIS FILE MANUALLY!

The GNU Pascal Frequently Asked Questions List
**********************************************

This document is a part of the GPC documentation. To make, copy and
distribute modified versions of this document please see the GPC
documentation.

   This is the Frequently Asked Questions List (FAQ) for GNU Pascal. If
the FAQ and the documentation do not help you, you have detected a
*bug* in it which should be reported, *Note Mailing List::.  Please
really do it, so we can improve the documentation.

1 GNU Pascal
************

1.1 What and why?
=================

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,
     parts of Borland Delphi, Mac Pascal and Pascal-SC) in so far as
     this serves the goal of clarity and usability,

   * may be distributed under GNU license conditions, and

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

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

   The current release implements Standard Pascal (ISO 7185, levels 0
and 1), most of Extended Pascal (ISO 10206, aiming for full
compliance), is highly compatible to Borland Pascal (version 7.0), has
some features for compatibility to other compilers (such as VAX Pascal,
Sun Pascal, Mac Pascal, Borland Delphi and Pascal-SC).

   It provides a lot of useful GNU extensions not found in other Pascal
compilers, e.g. to ease the interfacing with C and other languages in a
portable way, and to work with files, directories, dates and more,
mostly independent of the underlying operating system.

   Included units provide support for regular expressions, arithmetic
with integer, rational and real numbers of unlimited size,
internationalization, inter-process communication, message digests and
more. Demo programs show the usage of these units and of many compiler
features.

1.2 What is the current version?
================================

Prior to July 2000 releases were several months apart. Since then there
has been a new release every few days, available as a source archive
from the GPC web site, `http://www.gnu-pascal.de'.

   For details about new features, see the section `News' on the web
site. On bugs fixed recently, see the `Done' section of the To-Do list
(on the same web site).

   GPC uses GCC as a back-end. Patches for GCC 2.8.1 and GCC 2.95.x are
provided but it is recommended that you use GCC 2.95.x.

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

GPC is not a drop-in replacement for Borland's Turbo Pascal (R).
Almost all BP language features are supported. Notable exceptions are
the string format (as discussed below), or the `Mem' and `Port' pseudo
arrays, though replacement functions for the latter on IA32 platforms
exist in the `Ports' unit.

   Almost all of BP's run time library is supported in GPC, either by
built-in compiler features or in units with the same names as their BP
counterparts.

   For details about the compatibility, the few remaining
incompatibilities and some useful alternatives to BP features, see the
`Borland Pascal' chapter in the GPC Manual.

1.4 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 it is known to run on these
platforms:

ix86-gnu                      (GNU Hurd)
ix86-linux                    (Linux 2.x, ELF)
i486-linuxaout                
i486-linuxoldld               
i386-freebsd1.2.0             
AIX 4.2.1                     
AIX 4.3                       
DJGPP V2                      (Dos)
EMX 0.9B                      (OS/2, Dos)
Cygwin32 beta20 and higher    (MS-Windows95/98, MS-Windows NT)
mingw32                       (MS-Windows95/98, MS-Windows NT)
MSYS                          (MS-Windows)
mips-sgi-irix5.3              
mips-sgi-irix6.5              
sun-sparc-sunos4.1.4          
sparc-sun-solaris2.x          
sun-sparc-solaris 2.5.1       
sun-sparc-solaris 2.6         
sun-sparc-solaris 7           
sun-sparc-solaris 8           
alpha-unknown-linux           
alpha-dec-osf4.0b             
s390-ibm-linux-gnu            

   *OK people - send us your success stories, with canonical machine
name!*

2 Installing GPC
****************

You find the most up-to-date installation instructions in the GPC
Manual or the file `INSTALL' in source distributions, or on the GPC web
site.

   The following sections describe things you might need or want to
install besides GPC itself.

2.1 What to read next
=====================

After installing GPC, please check the files in the directory
`/usr/local/doc/gpc':

`README'           General Information about GPC
`FAQ'              This FAQ :-)
`NEWS'             Changes since the last release
`BUGS'             How to report bugs, about the Test Suite
`AUTHORS'          List of GPC authors
`COPYING'          The GNU General Public License
`COPYING.LIB'      The GNU Lesser General Public License

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

A complete Pascal compiler system should at least have:

  1. The actual compiler, GPC.

  2. An editor, assembler, linker, librarian and friends.

  3. A C library. If you have a working C compiler, you already have
     this.

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

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

2.3 How 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 debugging info. Usually, installing
     `gas' (part of GNU binutils) 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 the `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.

   Although `gdb' is an excellent debugger, it's user interface is not
everybody's preference. If you like to debug under X11, please 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/'

   Furthermore, RHIDE (*note IDE::) contains built-in debugging suport,
similar to the IDE of BP.

2.4 What additional libraries should I have?
============================================

You will need certain additional libraries when you compile some of the
units. These can be found in the directory
`http://www.gnu-pascal.de/libs/'.

   Currently, there are the following libraries:

gmp
     Arithmetic for integers, rationals and real numbers with arbitrary
     size and precision. Used by the GMP unit.

rx
     Regular expression matching and substitution. Used by the RegEx
     unit.

ncurses
PDCurses
     Screen handling. Used by the CRT unit. Depending on your system,
     you have the following choices:

     Unix: You can compile terminal applications with ncurses and
     applications that run in an X11 window with PDCurses (though
     terminal applications can, of course, also run in an xterm under
     X11). ncurses is used by default. If you want to use PDCurses
     (a.k.a. XCurses), give the option `-DX11' when compiling CRT.

     Dos with DJGPP and MS-Windows with mingw: Only PDCurses is
     available and will be used by default.

     MS-Windows with Cygwin: PDCurses and ncurses are available.
     PDCurses is used by default. If you want to use ncurses, give the
     option `-DUSE_NCURSES' when compiling CRT.

     Other systems: Please see the `README's and installation
     instructions of PDCurses and ncurses to find out which one(s) can
     be built on your system. See the conditionals at the end of
     crt.inc and crtc.h (and change them if necessary) on which library
     is used by default.

intl
     Internationalization. Used by the Intl unit. On some systems, it is
     part of the system library (libc).

ElectricFence
     This library is not used by any GPC unit. It is a debugging tool to
     assist you in finding memory allocation bugs. To use it, just link
     it to your program, either on the command line (`-lefence') or in
     the source code (`{$L efence}') which you might want to put into
     an `{$ifdef DEBUG}' or similar since using libefence is only
     recommended for debugging.

   The source code of the libraries is available in the main `libs'
directory. Most libraries come with one or several patches which should
be applied before compiling them.

   Binaries for some platforms are available in the `binary/PLATFORM'
subdirectories. If you compile the libraries for other platforms, be
invited to make the binaries available to us for distribution on the
web site.

   There are also the following files:

`terminfo-linux.tar.gz'
     This is a patch to enable ncurses programs to make use of the
     ability of Linux 2.2 and newer kernels to produce a block cursor
     when needed. The present patch can be installed without recompiling
     anything, just by copying some files into place. More details can
     be found in the `README' file included in this archive. The patch
     will not do any harm on older kernels. Please note that *not* only
     on Linux machines it is useful to install the patch. Installing
     them on any other machine will allow users who telnet in from a
     Linux console to profit from the block cursor capability. Besides,
     some Unix systems have installed older Linux terminfo entries or
     none at all, so it's a good thing, anyway, to give them a current
     version. The patch is included in the terminfo database of ncurses
     5.0, so if you install ncurses 5.0 (source or binary), you don't
     need to get the patch separately. But you can install it on a
     system with an older ncurses version if you don't feel like
     upgrading ncurses altogether.

`tsort-2.9i.zip'
     A little utility (extracted from util-linux-2.9i, but not Linux
     specific), needed for the configuration of the rx library. You
     need it only if you compile rx yourself (and if it's not already
     present on your system), not when using a rx binary.

2.5 Contributed units
=====================

Several people have contributed units for GPC. They are usually
announced on the mailing list, *Note Mailing List::. Most of them can
be found in `http://www.gnu-pascal.de/contrib/'.

2.6 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 and most distributions.

   * PENG. It's not free software, but it was written with GPC.  It's
     very similar to Borland's IDE, but with many extensions.  Binaries
     for DJGPP, Linux and Solaris can be downloaded from
     `http://fjf.gnu.de/peng/'.

   * RHIDE. DJGPP users might want to try RHIDE. The latest (beta)
     release is compatible with GNU Pascal and allows stepping, tracing
     and watching like Borland's IDE. It can be downloaded from
     `http://www.rhide.com'.

   * DevPascal. DevPascal is a Free Software IDE for mingw32. It can be
     downloaded from `http://www.gnu-pascal.de/contrib/chief/' or
     `http://www.bloodshed.net/devpascal.html'

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

3 GNU Pascal on the DJGPP (MS-DOS) platform
*******************************************

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

3.1 What is DJGPP?
==================

The following paragraph is from the site
`http://www.delorie.com/djgpp/':

   DJGPP is a complete 32-bit C/C++ development system for Intel 80386
(and higher) PCs running DOS. It includes ports of many GNU development
utilities. The development tools require a 80386 or newer computer to
run, as do the programs they produce. In most cases, the programs it
produces can be sold commercially without license or royalties.

3.2 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/230b.zip'

   Another place to look for DJGPP documentation is the DJGPP Knowledge
Base, at this URL: `http://www.delorie.com/djgpp/doc/kb/'

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

As discussed in *Note Components::, other than GPC itself, you need an
assembler, linker and friends, a C library and possibly a debugger.
The site `http://www.delorie.com/djgpp/' recommended the following
files and they will help you find a mirror:

`v2/djdev203.zip'       (C library)
`v2gnu/bnu2951b.zip'    (assembler, ...)
`v2gnu/gcc2952b.zip'    (gcc)
`v2gnu/gdb418b.zip'     (debugger)
`v2gnu/mak379b.zip'     (make)
`v2gnu/txi40b.zip'      (texi)

   This list is about 10 MB not counting GPC. You can use a binary
version of GPC from the web site.

3.4 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:

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

   The GPC online documentation is in GNU info format; you need the
Info reader (`txi390b.zip') to read it, or use the built-in Info reader
of the RHIDE or PENG IDE. 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.

3.5 I cannot read the Info documentation!
=========================================

To read the Info documentation, you need the `info' program from
`txi390b.zip' or an IDE like RHIDE or PENG.

3.6 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 MS-Windows) or download and install CWSDPMI
(`csdpmi3b.zip') which is a free DPMI server written for DJGPP.

3.7 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.delorie.com/djgpp/doc/brennan/brennan_att_inline_djgpp.html'

   There's also a GPC assembler tutorial at
`http://www.gnu-pascal.de/contrib/misc/gpcasm.zip'

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

   However, please note that assembler code is unportable, i.e. it will
work on IA32 ("x86") and compatible processors if written for them, but
will not even compile for other processors. So by writing assembler
code in your programs, you will limit their usefulness substantially.

   If you think you "need" assembler code for speed - and you've
checked that your assembler code actually runs faster than Pascal code
compiled with suitable optimizations - you might want to put both
Pascal and assembler versions of the critical sections in your program,
and let, e.g., an `{$ifdef i386}' decide which one to use. This way,
your program will at least compile on all processors.

3.8 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 the GPC Manual on 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 DPMIDemo;
     
     { Only for DJGPP }
     
     {$X+}
     
     { `Byte' is `unsigned char' in C,
       `ShortCard' is `unsigned short' in C,
       `MedCard' is `unsigned long' in C,
       `Word' is `unsigned' in C,
       etc. (all these types are built-in). }
     
     type
       TDpmiVersionRet = record
         Major     : Byte;
         Minor     : Byte;
         Flags     : ShortCard;
         CPU       : Byte;
         Master_PIC: Byte;
         Slave_PIC : Byte;
       end;
     
     type
       TDpmiFreeMemInfo = record
         LargestAvailableFreeBlockInBytes,
         MaximumUnlockedPageAllocationInPages,
         MaximumLockedPageAllocationInPages,
         LinearAddressSpaceSizeInPages,
         TotalNumberOfUnlockedPages,
         TotalNumberOfFreePages,
         TotalNumberOfPhysicalPages,
         FreeLinearAddressSpaceInPages,
         SizeOfPagingFilePartitionInPages,
         Reserved1,
         Reserved2,
         Reserved3: MedCard;
       end;
     
     function DpmiGetVersion (var Version: TDpmiVersionRet): Integer;
              external name '__dpmi_get_version';
     
     function DpmiGetFreeMemoryInformation
              (var MemInfo: TDpmiFreeMemInfo): Integer;
              external name '__dpmi_get_free_memory_information';
     
     var
       Version: TDpmiVersionRet;
       MemInfo: TDpmiFreeMemInfo;
     
     begin
       if DpmiGetVersion (Version) = 0 then
         begin
           WriteLn ('CPU type:       ', Version.CPU, '86');
           WriteLn ('DPMI major:       ', Version.Major);
           WriteLn ('DPMI minor:       ', Version.Minor);
         end
       else
         WriteLn ('Error in DpmiGetVersion');
       if DpmiGetFreeMemoryInformation (MemInfo) = 0 then
         WriteLn ('Free DPMI memory: ',
                  MemInfo.TotalNumberOfFreePages, ' pages.')
       else
         WriteLn ('Error in DpmiGetMemoryInformation');
     end.

3.9 I got an exception when accessing an `array [1 .. 4000000] of Byte'.
========================================================================

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. (The linker name `_stklen' is essential; the Pascal
identifier doesn't matter. The constant doesn't have to be used
anywhere in the program. It is recommended to put this declaration in
the main program file, not in any unit/module, so programs using a
unit/module can set whatever limit they need.)

     {$ifdef __GO32__}
     const
       MinStackSize: Cardinal = $200000; attribute (name = '_stklen');
     {$endif}

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

   DJGPP has to allocate the stack in physical memory at program
startup, so one might have to be careful with too large stack limits.
Most other systems allocate stack pages on demand, so the only reason
to set a limit at all might be to prevent a runaway recursion from
eating up all memory ...

   On Unix-like systems, you can set a resource limit, but you usually
don't do it in normal programs, but rather in the shell settings (bash:
`ulimit'; csh: `limit'; syscall: `setrlimit'(2)).

4 Strings
*********

4.1 What's this confusion about strings?
========================================

Turbo Pascal strings have a length byte in front. Since a byte has the
range 0 .. 255, this limits a string to 255 characters. However, the
Pascal string schema, as defined in section 6.4.3.3.3 of the ISO 10206
Extended Pascal standard, is a schema record:

     type
       String (Capacity: Integer) = record
         Length: 0 .. Capacity;
         String: packed array [1 .. Capacity + 1] of Char
       end;

   The `+ 1' is a GPC extension to make it feasible to automatically
add the `#0' terminator when passing or assigning them to CStrings.
Thus at the expense of a little added complexity (must declare
capacity, don't use `GetMem' without explicit initialization of the
`Capacity' field, and the additional space requirement) you can now
have very long strings.

4.2 Overlaying strings in variant records
=========================================

Q: Should the different variants in a variant record overlay in the
same memory? Previous Pascals I have used have guaranteed this, and
I've got low-level code that relies on this. The variants are not the
same length, and they are intended not to be.

   A: No, this is intentional so that the discriminants are not
overwritten, and they can be properly initialized in the first place.
Consider:

     record
     case Boolean of
       False: (s1: String (42));
       True:  (s2: String (99));
     end;

   If the strings would overlay, in particular their discriminants
would occupy the same place in memory. How should it be initialized?
Either way, it would be wrong for at least one of the variants ...

   So, after a discussion in the ISO Pascal newsgroup
(news:comp.lang.pascal.ansi-iso) where this topic came up concerning
file variables (which also require some automatic initialization and
finalization), we decided to do this in GPC for all types with
automatic initialization and finalization (currently files, objects and
schemata, including strings, in the future this might also be Delphi
compatible classes and user-defined initialized and finalized types),
since the standard does not guarantee variants to overlay, anyway ...

   There are two ways in GPC to get guaranteed overlaying (both
non-standard, of course, since the standard does not assume anything
about internal representations; both BP compatible), `absolute'
declarations and variable type casts. E.g., in order to overlay a byte
array `b' to a variable `v':

     var
       b: array [1 .. SizeOf (v)] of Byte absolute v;

   Or you can use type-casting:

     type
       t = array [1 .. SizeOf (v)] of Byte;

   then `t (v)' can be used as a byte array overlayed to `v'.

4.3 Why does `s[0]' not contain the length?
===========================================

Q: In standard Pascal you expect `s[1]' to align with the first
character position of `s' and thus one character to the left is the
length of `s'. Thus `s[0]' is the length of `s'.  True?

   A: This holds for UCSD/BP strings (which GPC does not yet implement,
but that's planned). The only strings Standard Pascal knows are arrays
of char without any length field.

   GPC also supports Extended Pascal string schemata (*note String
schema::), but they also don't have a length byte at "position 0", but
rather a `Length' field (which is larger than one byte).

4.4 Watch out when using strings as parameters
==============================================

Q: Any "gotchas" with string parameters?

   A: Be careful when passing string literals as parameters to routines
accepting the string as a value parameter and that internally modify
the value of the parameter. Inside the routine, the value parameter
gets a fixed capacity - the length of the string literal that was
passed to it. Any attempt to assign a longer value will not work.

   This only applies if the value parameter is declared as `String'. If
it is declared as a string with a given capacity (e.g., `String
(255)'), it gets this capacity within the routine.

4.5 Support for BP compatible short strings
===========================================

Q: Two different kinds of strings with the same name - `String' - does
make a bit of confusion. Perhaps the oldstyle strings could be renamed
`short string' ?

   A: When we implement the short strings, we'll have to do such a
distinction. Our current planning goes like this:

   `String (N)': string schema (EP compatible)

   `String [N]': short string (UCSD/BP compatible, where N must be <=
255)

   `String': dependent on flags, by default undiscriminated schema, but
in BP mode (or with a special switch) short string of capacity 255
(UCSD/BP compatible).

   Q: So when will these short strings be available?

   A: It's been planned for over a year. The delay has been caused by
more pressing problems.

4.6 What about C strings?
=========================

A C string (`char *') is an array of char, terminated with a `#0' 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 could access the `system()' call in your C
library (which is not necessary anymore, since `Execute' is already
built-in):

     program SysCall;
     
     function System (CmdLine: CString): Integer; external name 'system';
     
     var
       Result: Integer;
     
     begin
       Result := System ('ls -l');
       WriteLn ('system() call returned: ', Result)
     end.

   You could use the type `PChar' instead of `CString'. Both `CString'
and `PChar' are predefined as `^Char' - though we recommend `CString'
because it makes it clearer that we're talking about some kind of
string rather than a single character.

   A lot of library routines in Pascal for many applications exist in
the GPC unit and some other units. Where available, they should be
preferred (e.g. `Execute' rather than `system()', and then you won't
have to worry about `CString's.)

   Do *not* pass a C style string as a `const' or `var' argument if the
C prototype says `const char *' or you will probably get a segfault.

5 Getting Help
**************

Please read the GPC Manual (info files or other formats) as well as the
`README' and `BUGS' files that come with GPC (usually installed in
directory `/usr/local/doc/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.

   In particular, the `BUGS' file contains information on how to submit
bug reports in the most efficient way.

   The `Support' chapter of the GPC Manual tells you where to find more
information about GPC and how to contact the GPC developers.  The
following information is from this chapter.

5.1 The GPC Mailing List
========================

There is a mailing list devoted to GNU Pascal. You can write to the
mailing list, e.g. if you have problems installing GPC or if you found
a problem with GPC (please see *Note Reporting Bugs::). You can also
use it to discuss suggestions for improving GPC and, most welcome, to
offer your help or contribute code, documentation or other work. Mails
to the list should be in English.

   To subscribe to the mailing list, send the command
     subscribe gpc your@email.address
   in the body of a mail to <majordomo@gnu.de> (*not* to
`gpc@gnu.de'!). The subject is ignored. (Please replace
`your@email.address' with your real email address.) For more info, send
a line `help' to <majordomo@gnu.de>.

   After subscribing, you can send a message to the mailing list by
sending email to the list address <gpc@gnu.de> as if it were a person.

   To leave the mailing list, send the command
     unsubscribe gpc your@email.address
   to <majordomo@gnu.de>.

   You can reach a human moderator at _gpc-owner@gnu.de_.

   There is a separate mailing list for discussions about GPC
documentation, <gpc-doc@gnu.de>. To subscribe, send the command
     subscribe gpc-doc your@email.address
   to <majordomo@gnu.de>.

   There is also a (low-traffic) announce list, <gpc-announce@gnu.de>
that you can subscribe to stay up-to-date. To subscribe to the list,
write an email with
     subscribe gpc-announce your@email.address
   in the body to <majordomo@gnu.de>. If you like to announce a
contribution, a service or an event related to GPC, you are invited to
post to this list rather than `gpc@gnu.de', but please don't use the
announce list for questions or discussions. Please note that all mail
sent to the announce list is forwarded to the regular list, so you
won't have to subscribe to both lists if you don't want to miss
anything. For the same reason, please don't cross-post to both lists.

   There is also a German speaking mailing list, <gpc-de@gnu.de>. To
subscribe send the command
     subscribe gpc-de your@email.address
   in the body of a mail to <majordomo@gnu.de> (note the hints above).

5.2 The GPC Mailing List Archives
=================================

Perhaps your problem was already discussed on the list. There is a
searchable archive of the mailing list on the WWW. It can be browsed or
searched at
     `http://www.gnu-pascal.de/crystal/gpc/en/'

   The archive of the documentation list is at
     `http://www.gnu-pascal.de/crystal/gpc-doc/en/'

   The archive of the announce list is at
     `http://www.gnu-pascal.de/crystal/gpc-announce/en/'

   The archive of the German GPC list is at
     `http://www.gnu-pascal.de/crystal/gpc-de/de/'

5.3 Newsgroups relevant to GPC
==============================

To get support, you can also ask the Usenet newsgroups for help.  There
are several Pascal related newsgroups, but none is dedicated just to
GNU Pascal, so use the one which is most appropriate for your problem.
For general Pascal questions, we recommend the following one:

`news://comp.lang.pascal.misc'       Pascal in general and ungrouped
                                     Pascals.

   Pascal syntax related questions may be appropriate in:

`news://comp.lang.pascal.ansi-iso'   Pascal according to ANSI and ISO
                                     standards.

   The next newsgroup is a haven for beginners, answering questions
that would apply to almost any Pascal. However, if you have a
GPC-specific question don't post there - use the GPC mailing list.  And
when in doubt use the GPC mailing list.

`news://comp.lang.pascal.borland'    Borland Pascal questions.

   Don't forget to give back what you have obtained. None of us is
getting money for answering your questions (unless you pay us by
yourself). Please do your part by answering the questions of others
instead.

5.4 Where to get individual support for GPC
===========================================

GPC is free software and comes *without any warranty*.

   If you want to get professional support, you can hire an individual
or a company for providing such a service.

   G-N-U GmbH (http://www.g-n-u.de) is doing large parts of the
development of GNU Pascal. This company offers special support for GPC
and can be contacted at <info@g-n-u.de>.

   More generally, to find a company or an individual who offers
support and other consulting services for free software, look into the
GNU Service Directory (http://www.gnu.org/prep/service.html).

5.5 If the compiler crashes ...
===============================

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.

   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.

5.6 How to report GPC bugs
==========================

If you encounter a bug with GPC, please check whether it is one of the
known bugs. If not, please report it to the GNU Pascal mailing list
(*note Mailing List::). That way, they always reach the maintainers.
Please note the following points.

   * Please send a description of the problem. Try to give as much
     information as possible, with the full text of any error messages
     encountered, or a description of how some output varies from the
     expected output. Always specify the operating system type with
     version and the machine type (try `uname -a' if unsure) as well as
     the version of GPC which you get by typing `gpc -v'.

   * A good article on submitting bug reports can be found at either
     `http://www.chiark.greenend.org.uk/~sgtatham/bugs.html' or
     `http://freshmeat.net/news/2000/02/26/951627540.html'

     Another good article "How To Ask Questions The Smart Way" is
     available as `http://www.catb.org/~esr/faqs/smart-questions.html'


   If the problem is with the compiler itself, not an installation
problem or something like this, please provide a test program to
reproduce the problem, and note the following hints. You can also
contribute test programs for features that are working in GPC to ensure
they will not break in future releases.

   * The test program should be as short as possible, but *by all
     means*, please send a *complete* program and *make sure* that it
     still reproduces the problem before you send it. Too often, users
     have sent code which contained obvious syntax errors far before
     the actual problem, or just code fragments that we could only make
     wild guesses about. This is unproductive for us and doesn't help
     you get your problem solved.


6 Miscellaneous
***************

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

If you want to contribute, please write to the mailing list, *Note
Mailing List::.

6.2 Where is the GNU Pascal web site?
=====================================

The GPC homepage on the web, for information and downloads, is
`http://www.gnu-pascal.de'.

   The GPC To-Do list, listing the latest features and fixed bugs can
also be found there.

6.3 About this FAQ
==================

Current Maintainer: Russ Whitaker, <russ@ashlandhome.net>

   This is the second incarnation of the GNU Pascal FAQ list, based on
the previous FAQ by J.J. van der Heijden. 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).

   Many people have contributed to this FAQ, only some of them are
acknowledged above. 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.

