Copyright (C) 1996 J.J. van der Heijden
This FAQ list may be freely distributed with GNU Pascal, provided this copyright notice is left intact on all copies.
The purpose of the GNU Pascal project is to produce a Pascal compiler (called GNU Pascal or GPC) which
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 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.
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/
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.
This section discusses some common problems with the installation of 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! <<<
A complete Pascal compiler system should at least have:
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.
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:
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 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.
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.
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.
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.
Users of Borland Pascal may wonder if there's a replacement for the IDE (Integrated Development Environment). Here's a few suggestions:
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/
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.
This section discusses common problems people have when they try to access their system's libraries.
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.
----------------------------------------------------------
It is important not to confuse Pascal and C string types.
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;
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); { Pascal string schema }
CString = __cstring__; { C style string }
{ Convert a "C" string to a "Pascal" string }
function StrPas(Src: CString): 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;
{ Convert a "Pascal" string to a "C" string }
function StrPCopy(Dest: CString; Src: String): CString;
var
c: integer;
p : CString;
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':
---------------------------------------------------------
Program EnvDemo;
{ include the above StrPas() and StrPCopy() snippet here }
{ C library function prototype: char *getenv(const char *name); }
function GetEnv(name : CString): CString; C;
var
pName: CString;
begin
getmem(pName, 256);
pName := StrPCopy(pName, 'PATH');
writeln('Your PATH is: ', StrPas(GetEnv(pName)));
freemem(pName, 256);
end.
---------------------------------------------------------
And this is how you access the `system()' call in your C library:
---------------------------------------------------------
program SysCall;
{ include the above StrPas() and StrPCopy() snippet here }
function system(name : CString): integer; C;
var
pName: CString;
result : integer;
begin
getmem(pName, 256);
pName := StrPCopy(pName, 'ls -l');
result := system(pName);
writeln('system() call returned : ', result);
freemem(pName, 256);
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!
No. (This may change in a future version)
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.
(topic under construction)
This chapter discusses some potential problems with GNU Pascal on MS-DOS, using djgpp.
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/
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
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.
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*'
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.
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".
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.
---------------------------------------------------------
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.
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.
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.
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.
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.
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.
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.
To leave the mailing list, send a message to <gpc-request@hut.fi>.
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.
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.