proto-FAQ -- reactions please!
Tue, 15 Oct 96 14:48:30 CST
Hello,
I gathered some of the recently asked questions, together with some usefull
information from various readmes etc. and called it a 'FAQ'. It needs some
expanding, especially about the differences between various dialects of the
Pascal language. Also, I'm not a native english speaker so there are
probably lots of errors. Any feedback is appreciated.
It will be texified in the future, so it can be put on a www page.
JanJaap
===========================================================================
This is the GNU Pascal Frequently-Asked Questions List.
Author: J.J. van der Heijden
Revision: 0.1, Oct 14, 1996
1 What is GNU Pascal?
1.1 What is the current version of GNU Pascal?
1.2 Where is the GNU Pascal FTP site? WWW?
1.3 Is it compatible with Turbo Pascal (R) ?
2 Installation related questions
2.1 Which platforms are supported by GNU Pascal?
2.2 Which components, other than the GNU Pascal compiler do I need to
compile Pascal source code?
2.3 Help! linking gpc1 fails: _emit_string_move undefined (and more)
2.4 When I build libgpc.a, rts-rt0.c says: SIGXCPU undefined (and more)
2.5 I do I debug my Pascal programs?
2.6 Can you recommend an IDE?
2.7 Do we have a binary for you?
3 GNU Pascal and your system libraries
3.1 How do I use from the C library?
3.2 What's this confusion about Pascal and C style strings?
3.3 Are GNU Pascal objects compatible with GNU C++ classes ?
3.4 Where are the Turbo pascal (R) replacement units?
3.5 How do I build/use a shared library?
4 GNU Pascal on the djgpp (MS-DOS) platform
4.1 If you need more information
4.2 What do I download?
4.3 How do I install the compiler?
4.4 GPC says: no DPMI
4.5 I cannot read the info pages!
4.6 I have troubles with inline assembly
4.7 Tell me how to do DPMI, BIOS and other DOS related things.
4.8 I'm accessing an "array[1..4000000] of byte" and I got an exception.
5 Getting Help
5.1 Help! the compiler crashed!
5.2 I think I found a bug -- now what?
5.3 Which newsgroup(s) are suited for GPC related problems?
5.2 How to post to the mailing list
5.3 How to become a subscriber to the mailing list
5.4 How to unsubscribe from the mailing list
6 Miscellany
6.1 I want to contribute, where do I start?
6.2 About this FAQ.
1 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.
1.1 What is the current version of GNU Pascal?
==============================================
The last official release is GPC 1.1, based on GNU CC version 2.6.3.
GPC version 1.2, based on GCC 2.7.2 is currently in beta testing.
1.2 Where is the GNU Pascal FTP site? WWW?
==========================================
The master FTP site for GNU Pascal is kampi.hu.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/
Also, we have a homepage on the web:
http://home.pages.de/~GNU-Pascal/
1.3 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 file "bpqstart.txt"
2 Installation related questions
********************************
This section discusses some common problems with the installation of
GNU Pascal.
2.1 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
i486-freebsd2.1
i386-cygwin32 (Windows95/Windows NT)
i386-djgppv2 (MS-DOS)
i386-emx (OS/2, MS-DOS)
mips-sgi-irix5.3
>>> Ok people - send us your success stories, with canonical machine name! <<<
2.2 Which components, other than the GNU Pascal compiler do I need to
compile Pascal source code?
=====================================================================
A complete Pascal compiler system should at least have:
* The actual compiler, GPC.
* Assembler, linker, librarian and friends.
* A C library.
* 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 1.1 is
based on GCC 2.6.3, GPC v1.2 is based on GCC v2.7.2
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.
2.3 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:
* Get a recent version of GNU make. Version 3.74 or better is known to
work.
* Build GCC in a seperate directory instead of using the GCC source
directory.
* 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'.
2.4 When I build libgpc.a, rts-rt0.c says: SIGXCPU undefined (and more)
========================================================================
Compilation of the runtime system may fail in rts-rt0.c with a message
simular to this:
rts-rt0.c: `SIGXCPU' undeclared (first use this function)
or:
rts-rt0.c: storage size of `sv' isn't known
rts-rt0.c: storage size of `osv' isn't known
If this happens to you, you have to edit the rts/rts-config.h file and
comment out the last line to:
/* #undef HAVE_SIGSYS */
This will be fixed in a future release.
2.5 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.
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.
* XWPE
XWPE is an immitation of the Borland IDE, so users of Borland Pascal may
find it a good alternative.
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 usefull 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/
2.7 Do we have a binary for you?
================================
Currently, we have binaries for these platforms:
i486-linux (ELF)
i486-linuxaout
i486-linuxoldld
djgpp V2 (msdos)
emx 0.9B (OS/2, msdos)
cygwin32 beta16 (Windows95, Windows NT)
mips-sgi-irix5.3
3 GNU Pascal and your system libraries
**************************************
This section discusses common problems people have when they try to access
their system's libraries.
3.1 How do I use 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
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;
function sleep(seconds: word): word; external;
var
result : word;
begin
result := sleep(10);
end.
---------------------------------------------------------
3.3 What's this confusion about Pascal and C style strings?
===========================================================
It is important not to confuse Pascal and C string types.
* The Pascal string schema is a record:
STRING = RECORD
Capacity : integer;
length : integer;
string : packed array [ 1..Capacity ] of char;
END;
'string' is not 'string(256)', unlike Turbo Pascal. The capacicty must be
declared:
type
MyString = string(256);
function MyFunction: MyString;
* A C string is an array of char, terminated with a NULL char.
C library functions require C, not Pascal style string arguments!
Consider this code snippet to convert Pascal style strings to C style and
vice versa:
---------------------------------------------------------
type
word = __unsigned__ integer;
TString = string[256];
PChar = ^char;
function StrPas(Src: PChar): TString;
var
S : TString;
begin
S := '';
if (Src <> NIL)
then while ( (Src^ <> chr(0)) AND (length(S) < S.capacity)) do
begin
S := S + Src^;
inc(Word(Src));
end;
StrPas := S;
end;
function StrPCopy(Dest: PChar; Src: String): PChar;
var
c: integer;
p : PChar;
begin
p := Dest;
for c:=1 to length(Src) do
begin
p^ := Src[c];
inc(word(p))
end;
p^ := chr(0);
StrPCopy := Dest;
end;
---------------------------------------------------------
Then this small example will print the PATH:
---------------------------------------------------------
function GetEnv(name : PChar): PChar; C;
function GetEnv(name : PChar): PChar; external;
var
pName: PChar;
begin
getmem(pName, 256);
pName := StrPCopy(pName, 'PATH');
writeln('PATH=', StrPas(GetEnv(pName)));
freemem(pName, 256);
end.
---------------------------------------------------------
And this is how you access the 'system()' call in you C library:
---------------------------------------------------------
program SysCall;
function system(name : PChar): integer; C;
function system(name : PChar): integer; external;
var
pName: PChar;
result : integer;
begin
getmem(pName, 256);
pName := StrPCopy(pName, 'ls -l');
result := system(pName);
writeln('system() call returned : ', result);
freemem(pName, 256);
end.
---------------------------------------------------------
3.4 Are GNU Pascal objects compatible with GNU C++ classes ?
============================================================
No.
3.5 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 dependant and would be
meaningless on any other platform.
3.6 How do I build/use a shared library?
========================================
(topic under construction)
4 GNU Pascal on the djgpp (MS-DOS) platform
*******************************************
This chapter discusses some potential problems with GNU Pascal on MS-DOS,
using djgpp.
4.1 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/faq201b.zip
Another place to look for DJGPP documentation is the DJGPP Knowledge Base,
at this URL:
http://www.delorie.com/djgpp/doc/kb/
4.2 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/djdev200.zip (C library)
v2gnu/bnu252b.zip (assembler, ....)
v2gnu/gdb412b.zip (debugger)
The rest is up to you; 'make' (v2gnu/mak372b.zip) can be usefull, RHIDE (an
IDE with Borland-look) is nice, but still under development. Future releases
of RHIDE may have better GPC support.
4.3 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
Specific information for low-memory conditions and mre can be found in the
djgpp FAQ and documentation.
4.4 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.
4.5 I cannot read the info pages!
=================================
To read the info pages, you need the `info' program from txi360b.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*"
4.6 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
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".
4.7 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 :
---------------------------------------------------------
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';
function DpmiGetVersion(ret: PDpmiVersionRet): integer; external;
function DpmiGetFreeMemoryInformation(info: PDpmiFreeMemInfo): integer; external;
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.
---------------------------------------------------------
4.8 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.
5 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.
5.1 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.
5.2 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.
5.3 Which newsgroup(s) are suited for GPC related problems?
===========================================================
There are several Pascal related newsgroups, but none is dedicated just to
GNU Pascal. These may be usefull:
comp.lang.pascal.ansi-iso Pascal according to ANSI and ISO standards.
comp.lang.pascal.misc Pascal in general and ungrouped Pascals.
5.2 How to post to the mailing list
===================================
You can send a message to the GPC mailing list by sending email to the list
address as if it were a person.
5.3 How to become a subscriber to the mailing list
==================================================
You can join the mailing list by sending a message to
(NOT !) with your request to be added to the list. Maintenance
is done by hand, so some delay is possible.
5.4 How to unsubscribe from the mailing list
============================================
To leave the mailing list, send a message to .
6 Miscellany
************
6.1 I want to contribute, where do I start?
===========================================
A list of jobs which should be done for GNU-Pascal can be found in the
file `how_to_contrib.txt'. 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.
6.2 About this FAQ.
==================
Maintainer: J.J. van der Heijden
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 this FAQ list was taken from the gpc mailing
list traffic, so you may have (unbeknownst to you) contributed to this
list.
EOF
---
"Nothing shocks me, I'm a scientist", Indiana Jones
J.J. van der Heijden (j.j.vanderheijden@student.utwente.nl)
HTML conversion by Lluís de Yzaguirre i Maura
Institut de Lingüística Aplicada -
Universitat "Pompeu Fabra"
e-mail: de_yza@upf.es