freepascal.compiler/docs/user.tex

%
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%   This file is part of the FPC documentation.
%   Copyright (C) 1997, by Michael Van Canneyt
%
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%   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
%   Boston, MA 02111-1307, USA. 
%
\documentclass{report}
\usepackage{a4}
\usepackage{html}
\makeindex
\latex{\usepackage{multicol}}
\latex{\usepackage{fpcman}}
\latex{\usepackage{epsfig}}
\html{\input{fpc-html.tex}}
\usepackage{fancyheadings}
\pagestyle{fancy}
\renewcommand{\chaptermark}[1]{\markboth{#1}{}}
\newcommand{\remark}[1]{\par$\rightarrow$\textbf{#1}\par}
\newcommand{\olabel}[1]{\label{option:#1}}
% We should change this to something better. See \seef etc.
\newcommand{\seeo}[1]{See \ref{option:#1}}
\begin{document}
\title{Free Pascal :\\ Users' manual}
\docdescription{Users' manual for \fpc, version \fpcversion}
\docversion{1.2}
\input{date.inc}
\author{Micha\"el Van Canneyt\\Florian Kl\"ampfl}
\maketitle
\tableofcontents
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Introduction
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\chapter{Introduction}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% About this document
\section{About this document}
This is the user's manual for \fpc . It describes the installation and use of
the \fpc compiler on the different supported platforms. 
It does not attempt to give an exhaustive list of all supported commands,
nor a definition of the Pascal language. Look at the
\refref for these things. 
For a description of the
possibilities and the inner workings of the compiler, see the
\progref. In the appendices of this document you will find lists of 
reserved words and compiler error messages (with descriptions).

This document describes the compiler as it is/functions at the time of 
writing. Since the compiler is under continuous development, some of the
things described here may be outdated. In case of doubt, consult the
\file{README} files, distributed with the compiler. 
The \file{README} files are, in case of conflict with this manual,
 authoritative.


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% About the compiler
\section{About the compiler}
\fpc is a 32-bit compiler for the i386 and m68k processors\footnote{Work is being done
on a port to ALPHA Architecture}. Currently, it supports 3 operating systems:
\begin{itemize}
\item \dos
\item \linux
\item \windowsnt
\end{itemize}
and work is in progress to port it to other platforms (notably, \ostwo and
).

\fpc is designed to be, as much as possible, source compatible with 
Turbo Pascal 7.0 and Delphi 4 (although this goal is not yet attained), 
but it also enhances these languages with elements like function overloading.
And, unlike these ancestors, it supports multiple platforms.

It also differs from them in the sense that you cannot use compiled units
from one system for the other.

Also, at the time of writing, there is no Integrated Development Environment
(IDE) available for \fpc. This gap will, hopefully, be filled in the future.

\fpc consists of three parts :
\begin{enumerate}
\item The compiler program itself.
\item The Run-Time Library (RTL).
\item Utility programs and units.
\end{enumerate}

Of these you only need the first two, in order to be able to use the compiler.
In this document, we describe the use of the compiler. The RTL is described in the
\refref.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Getting more information.
\section{Getting more information.}
If the documentation doesn't give an answer to your questions, 
you can obtain more information on the Internet, on the following addresses:
\begin{itemize}
\item
\htmladdnormallink{http://tfdec1.fys.kuleuven.ac.be/\~{}michael/fpc/fpc.html}
{http://tfdec1.fys.kuleuven.ac.be/\~{}michael/fpc/fpc.html} is the main
site. It contains also useful mail addresses and
links to other places. 
It also contains the instructions for inscribing to the
\textit{mailing-list}.

\item
\htmladdnormallink{http://www.brain.uni-freiburg.de/\~{}klaus/fpc/fpc.html}
{http://www.brain.uni-freiburg.de/\~{}klaus/fpc/fpc.html} is a mirror
of the main \fpc information site.  
\end{itemize}
Both places can be used to download the \fpc distribution, although you can 
probably find them on other places also.

Finally, if you think something should be added to this manual 
(entirely possible), please do not hesitate and contact me at 
\htmladdnormallink{[email protected]}{mailto:[email protected]}
.

Let's get on with something useful.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Installation
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\chapter{Installing the compiler}
\label{ch:Installation}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Before Installation : Requirements
\section{Before Installation : Requirements}

%
% System requirements
%
\subsection{System requirements}
The compiler needs at least the following hardware:
\begin{enumerate}
\item An I386 or higher processor. A coprocessor is not required, although it
will slow down your program's performance if you do floating point calculations.
\item 2 Mb of free memory. Under \dos, if you use DPMI memory management,
such as under Windows, you will need at least 16 Mb.
\item At least 500 Kb. free disk space.
\end{enumerate}

%
%

% Software requirements
\subsection{Software requirements}

\subsubsection{Under DOS}
The \dos distribution contains all the files you need to run the compiler
and compile pascal programs.

\subsubsection{Under Linux}
Under \linux you need to have the following programs installed :
\begin{enumerate}
\item \gnu \file{as}, the \gnu assembler.
\item \gnu \file{ld}, the \gnu linker.
\item Optionally (but highly recommended) : \gnu \file{make}. For easy
recompiling of the compiler and Run-Time Library, this is needed.
\end{enumerate}
Other than that, \fpc should run on almost any I386 \linux system.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Installing the compiler.
\section{Installing the compiler.}
The installation of \fpc is easy, but is platform-dependent.
We discuss the process for each platform separately.

% Installing under DOS
\subsection{Installing under DOS}
\subsubsection{Mandatory installation steps.}
First, you must get the latest distribution files of \fpc. They come as zip
files, which you must unzip first, or you can download the compiler as a
series of separate files. This is especially useful if you have a slow 
connection, but it is also nice if you want to install only some pats of the
compiler distribution.  The distribution zip file contains an
installation program \file{INSTALL.EXE}. You must run this program to install
the compiler. 

\begin{htmlonly}
The screen of the installation program looks like this:
\htmladdimg{../pics/install.gif}
\end{htmlonly}
\begin{latexonly}
The screen of the installation program looks like figure \ref{fig:install}.
\begin{figure}
\caption{The \dos install program screen.}
\label{fig:install}
\epsfig{file=pics/install.eps,width=\textwidth}
\end{figure}
\end{latexonly}

The program allows you to select:
\begin{itemize}
\item What components you wish to install. e.g do you want the sources or
not, do you want docs or not. Items that you didn't download when
downloading as separate files, will not be enabled, i.e. you can't 
select them.

\item Where you want to install (the default location is \verb|C:\PP|).
\end{itemize}

In order to run \fpc from any directory on your system, you must extend 
your path variable to contain the \verb|C:\PP\BIN| directory.
Usually this is done in the \file{AUTOEXEC.BAT} file.
It should look something like this : 
\begin{verbatim}
  SET PATH=%PATH%;C:\PP\BIN
\end{verbatim}
(Again, assuming that you installed in the default location).
 
If you want to use the graphic drivers you must modify the
environment variable \var{GO32}. Instructions for doing this can be found
in the documentation of the Graph unit, at the \var{InitGraph} procedure.

\subsubsection{Optional Installation: The coprocessor emulation}
For people who have an older CPU type, without math coprocessor (i387)
it is necessary to install a coprocessor emulation, since \fpc uses the
coprocessor to do all floating point operations.

The installation of the coprocessor emulation is handled by the 
installation program (\file{INSTALL.EXE}). However,

%
% Installing under Linux
%
\subsection{Installing under Linux}
\subsubsection{Mandatory installation steps.}
The \linux distribution of \fpc comes in three forms:
\begin{itemize}
\item a \file{tar.gz} version, also available as seperate files.
\item a \file{.rpm} (Red Hat Package Manager) version, and
\item a \file{.deb} (debian) version.
\end{itemize}
All of these packages contain a \var{ELF} version of the compiler binaries and
units. the older \var{aout} binaries are no longer distributed, although you
still can use the comiler on an \var{aout} system if you recompile it.

If you use the \file{.rpm} format, installation is limited to
\begin{verbatim}
rpm -i fpc-pascal-XXX.rpm
\end{verbatim}
(\var{XXX} is the version number of the \file{.rpm} file)

If you use debian, installation is limited to 
\begin{verbatim}
dpkg -i fpc-XXX.deb
\end{verbatim}
Here again, \var{XXX} is the version number of the \file{.deb} file.

You need root access to install these packages. The \file{.tar} file
allows you to do an installation if you don't have root permissions.

When downloading the \var{.tar} file, or the separate files,
 installation is more interactive.

I nCAse you downloaded the \file{.tar} file, you should first untar 
the file, in some directory where 
you have write permission, using the following command:
\begin{verbatim}
tar -xvf fpc.tar
\end{verbatim}
We supposed here that you downloaded the file \file{fpc.tar} somewhere
from the Internet. (The real filename will have some version number in it, 
which we omit here for clarity.)

When the file is untarred, you will be left with more archive files, and
an install program: an installation shell script. 

If you downloaded the files as separate files, you should at least download
the \file{install.sh} script, and the libraries (in \file{libs.tar.gz}). 

To install \fpc, all that you need to do now is give the following command:
\begin{verbatim}
./install.sh
\end{verbatim}
And then you must answer some questions. They're very simple, they're
mainly concerned with 2 things :
\begin{enumerate}
\item Places where you can install different things.
\item Deciding if you want to install certain components (such as sources
and demo programs). 
\end{enumerate}
The script will automatically detect which components are present and can be
installed. It will only offer to install what has been found.
because of this feature, you must keep the original names when downloading,
since the script expects this.
 
If you run the installation script as the \var{root} user, you can just accept all installation
defaults. If you don't run as \var{root}, you must take care to supply the
installation program with directory names where you have write permission,
as it will attempt to create the directories you specify.
In principle, you can install it wherever you want, though.

At the end of installation, the installation program will generate a
configuration file for the \fpc compiler which reflects the settings
that you chose. It will install this file in the \file{/etc} directory, (if
you are not installing as \var{root}, this will fail), and in the
directory where you installed the libraries.

If you want the \fpc compiler to use this configuration file, it must be
present in \file{/etc}, or you can set the environment variable
\var{PPC\_CONFIG\_PATH}. Under \file{csh}, you can do this by adding  a 
\begin{verbatim}
setenv PPC_CONFIG_PATH /usr/lib/ppc/0.99.1
\end{verbatim}
line to your \file{.login} file in your home directory. 
(see also the next section) 

\section{Optional configuration steps}
You may wish to set some environment variables. The \fpc compiler
recognizes the following variables :
\begin{itemize}
\item \verb|PPC_EXEC_PATH| contains the directory where '\file{as}' and
'\file{ld}' are. (default \file{/usr/bin})
\item \verb|PPC_GCCLIB_PATH| contains the directory where \file{libgcc.a} 
is (no default). This if for \linux only.
\item \verb|PPC_CONFIG_PATH| specifies an alternate path to find
\file{ppc386.cfg} (default under \linux is \file{/etc})
\item \verb|PPC_ERROR_FILE|  specifies the path and name of the error-definition file. 
                  (default \file{/usr/lib/fpc/errorE.msg})
\end{itemize}

These locations are, however, set in the sample configuration file which is 
built at the end of the installation process, except for the
\verb|PPC_CONFIG_PATH| variable, which you must set if you didn't install
things in the default places.
\subsubsection{finally}
Also distributed in \fpc is a README file. It contains the latest
instructions for installing \fpc, and should always be read first.


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Testing the compiler
\section{Testing the compiler}
After the installation is completed and the environment variables are
set as described above, your first program can be compiled. 

Included in the \fpc distribution are some demonstration programs, 
showing what the compiler can do. 
You can test if the compiler functions correctly by trying to compile 
these programs.

The compiler is called
\begin{itemize}
\item \file{PPC386.EXE} under \dos, and 
\item \file{ppc386} under \linux
\end{itemize}
To compile a program (e.g \verb|demo\hello.pp|) simply type :
\begin{verbatim}
  ppc386 hello
\end{verbatim}
at the command prompt. If you don't have a configuretion file, then you may
need to tell the compiler where it can find the units, for instance as
follows:
\begin{verbatim}
ppc386 -Upc:\pp\rtl\dos\go32v2 hello
\end{verbatim}
under \dos, and under\linux you could type
\begin{verbatim}
ppc386 -Up/usr/lib/fpc/0.99.7/linuxunits hello
\end{verbatim}
This is, of course, assuming that you installed under \verb|C:\PP| or
\file{/usr/lib/fpc/0.99.7}, respectively.

If you got no error messages, the compiler has generated an executable 
called \file{hello} (no extension) under \linux, and a file \file{hello.exe}
under \dos. 

To execute the program, simply type :
\begin{verbatim}
  hello
\end{verbatim}
If all went well, you should see the following friendly greeting:
\begin{verbatim}
Hello world
\end{verbatim}
In the \dos case, this friendly greeting may be preceded by some ugly
message from the \file{GO32} extender program. This unfriendly behavior can 
be switched off by setting the \file{GO32} environment variable.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Usage
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\chapter{Compiler usage}
\label{ch:Usage}

Here we describe the essentials to compile a program and a unit. 
We also describe how to make a stand-alone executable of the 
compiled program under \dos. For more advanced uses of the compiler, 
see the section on configuring the compiler, and the 
\progref.

The examples in this section suppose that you have a \file{ppc386.cfg} which
is set up correctly, and which contains at least the path setting for the
RTL units. In principle this file is generated by the installation program.
You may have to check that it is in the correct place (see section
\ref{se:config_file} for more information on this).

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Where the compiler looks for its files.
\section{File searching}
Before you start compiling a program or a series of units, it is 
important to know where the compiler looks for its source files and other
files. In this section we discuss this, and we indicate how to influence
this.

{\em Remark:}
The use of slashes (/) and backslashes (\verb+\+) as directory separators 
is irrelevant, the compiler will convert to whatever character is used on
the current operating system. Examples will be given using slashes, since
this avoids problems on \linux. 

% Command-line files.
\subsection{Command line files}
The file that you specify on the command line, such as in
\begin{verbatim}
ppc386 foo.pp
\end{verbatim}
will be looked for ONLY in the current directory. If you specify a directory
in the filename, then the compiler will look in that directory:
\begin{verbatim}
ppc386 subdir/foo.pp
\end{verbatim}
will look for \file{foo.pp} in the subdirectory \file{subdir} of the current
directory.

Under \linux, the name of this file is case sensitive, under other operating 
systems (\dos, \windowsnt, \ostwo) this is not the case.

% Unit files.
\subsection{Unit files}

When you compile a unit or program that needs other units, the compiler will
look for compiled versions of these units in the following way:
\begin{enumerate}
\item It will look in the current directory.
\item It will look in the directory where the compiler binary is. 
(not under \linux)
\item It will look in all the directories specified in the unit search path.
\end{enumerate}
You can add a directory to the unit search path with the \var{-Up} or 
\var{-Fu} options (\seeo{Up}, \seeo{Fu}). Every occurrence of one of
those options will append a directory to the unit search path.

On \linux, the compiler will first convert the filename of a unit to
all-lowercase. This is necessary, since Pascal is case-independent, and
the statements \var{Uses Unit1;} or \var{uses unit1;} should have the same
effect.
Also, unit names that are longer than 8 characters will first be looked for
with their full length. If the unit is not found with this name, the name
will be truncated to 8 characters, and the compiler will look again in the
same directories, but with the truncated name.

For instance, suppose that the file \file{foo.pp} needs the unit
\file{bar}. Then the command 
\begin{verbatim}
ppc386 -Up.. -Upunits foo.pp
\end{verbatim}
will tell the compiler to look for the unit \file{bar} in the following 
places:
\begin{enumerate}
\item In the current directory.
\item In the directory where the compile binary is (not under \linux).
\item In the parent directory of the current directory. 
\item In the subdirectory \file{units} of the current directory
\end{enumerate}

If the compiler finds the unit it needs, it will look for the source file of
this unit in the same directory where it found the unit. 
If it finds the source of the unit, then it will compare the file times. 
If the source file was modified more recent than the unit file, the
compiler will attempt to recompile the unit with this source file. 

If the compiler doesn't find a compiled version of the unit, or when the
\var{-B} option is specified, then the compiler will look in the same
manner for the unit source file, and attempt to recompile it.

It is recommended to set the unit search path in the configuration file
\file{ppc386.cfg}. If you do this, you don't need to specify the unit search
path on the command-line every time you want to compile something.

% Include files.
\section{Include files}
If you include files in your source with the \var{\{\$I filename\}}
directive, the compiler will look for it in the following places:

\begin{enumerate}
\item It will look in the path specified in the incude file name. 
\item It will look in the directory where the current source file is.
\item it will look in all directories specified in the include file search
path.
\end{enumerate}
You can add files to the include file search
 path with the \var{-I} (\seeo{I})
option.

As an example, consider the following include statement in a file
\file{units/foo.pp}:
\begin{verbatim}

{$i ../bar.inc}

\end{verbatim}
Then the following command :
\begin{verbatim}
ppc386 -Iincfiles units/foo.pp
\end{verbatim}
will cause the compiler to look in the following directories for
\file{bar.inc}:
\begin{enumerate}
\item the parent directory of the current directory
\item the \file{units} subdirectory of the current directory
\item the \file{incfiles} directory of the current directory.
\end{enumerate}

% Object files.
\section{Object files}
When you link to object files (using the \var{\{\$L file.o\}} directive,
the compiler will look for this file in the same way as it looks for include
files:

\begin{enumerate}
\item It will look in the path specified in the object file name. 
\item It will look in the directory where the current source file is.
\item it will look in all directories specified in the object file search path.
\end{enumerate}
You can add files to the object file search path with the \var{-Fo} (\seeo{Fo})
option.

% Configuration file
\subsection{Configuration file}
Unless you specify the \var{-n} (\seeo{n}) option, the compiler will look 
for a configuration file \file{ppc386.cfg} in the following places:

\begin{itemize} 
\item Under \linux
\begin{enumerate}
\item The current directory.
\item In your home directory, it looks for \file{.ppc386.cfg}.
\item The directory specified in the environment variable 
\var{PPC\_CONFIG\_PATH}, and if it's not set under \file{/etc}.
\end{enumerate}
\item Under all other OSes:
\begin{enumerate}
\item The current directory.
\item If it is set, the directory specified in the environment variable.
\var{PPC\_CONFIG\_PATH}.
\item The directory where the compiler is. 
\end{enumerate}
\end{itemize}


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Compiling a program
\section{Compiling a program}
Compiling a program is very simple. Assuming that you have a program source
in the file \file{prog.pp}, you can compile this with the following command:
\begin{verbatim}
  ppc386 [options] prog.pp
\end{verbatim}
The square brackets \var{[\ ]} indicate that what is between them is optional. 

If your program file has the \file{.pp} or \file{.pas} extension, 
you can omit this on the command line, e.g. in the previous example you 
could have typed:
\begin{verbatim}
  ppc386 [options] prog
\end{verbatim}

If all went well, the compiler will produce an executable, or, for version 1
of the \dos extender, a file which can be converted to an executable.

Unless you are using \dos and version 1 of the \dos extender, 
the file you obtained is the executable. 
You can execute it straight away, you don't need to do 
anything else. Under version 1 of the \dos extender,
additional processing is required. See section \ref{go32v1} on how to
create an executable in this case.

You will notice that there is also another file in your directory, with
extensions \file{.o}. This contains the object file for your program. 
If you compiled a program, you can delete the object file (\file{.o}), 
but not if you compiled a unit. 
Then the object file contains the code of the unit, and will be
linked in any program that uses the unit you compiled, so you shouldn't
remove it.


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Compiling a unit
\section{Compiling a unit}

Compiling a unit is not essentially different from compiling a program.
The difference is mainly that the linker isn't called in this case.

To compile a unit in the file \file{foo.pp}, just type :
\begin{verbatim}
  ppc386  foo
\end{verbatim}
Recall the remark about file extensions in the previous section.

When all went well, you will be left with 2 (two) unit files:
\begin{enumerate}
\item \file{foo.ppu} This is the file describing the unit you just
compiled.
\item \file{foo.o} This file contains the actual code of the unit.
This file will eventually end up in the executables.
\end{enumerate}
Both files are needed if you plan to use the unit for some programs. 
So don't delete them. If you want to distribute the unit, you must
provide both the \file{.ppu} and \file{.o} file. One is useless without the
other.

{\em Remark:}
Under \linux, a unit source file {\em must} have a lowercase filename.
Since Pascal is case independent, you can specify the names of units in the
\var{uses} clause in either case. To get a unique filename, the \fpc compiler
changes the name of the unit to all lowercase when looking for unit files.

The compiler produces lowercase files, so your unit will be found, even if
your source file has uppercase letters in it. Only when the compiler tries to
recompile the unit, it will not find your source because of the uppercase
letters. 

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Creating an executable for GO32V1, PMODE/DJ targets
\section{Creating an executable for GO32V1 and PMODE/DJ targets}
\label{go32v1}

The GO32V1 platform is officially no longer supported, so this section
is of interest only to people who wish to make go32V1 binaries anyway. 

%
% GO32V1
%
\subsection{GO32V1}
When compiling under \dos, GO32V2 is the default target. However, if you use
go32V1 (using the \var{-TGO32V1} switch), the 
compilation process leaves you with a file which you cannot execute right away.
There are 2 things you can do when compiling has finished.

The first thing is to use the \dos extender from D.J. Delorie to execute
your program :
\begin{verbatim}
  go32 prog
\end{verbatim}
This is fine for testing, but if you want to use a program regularly, it
would be easier if you could just type the program name, i.e.
\begin{verbatim}
  prog
\end{verbatim}
This can be accomplished by making a \dos executable of your compiled program.
 
There two ways to create a \dos executable (under \dos only): 
\begin{enumerate}
\item if the \file{GO32.EXE} is already
installed on the computers where the program should run, you must
only copy a program called \file{STUB.EXE} at the begin of
the AOUT file. This is accomplished with the \file{AOUT2EXE.EXE} program. 
which comes with the compiler:
\begin{verbatim}
AOUT2EXE PROG
\end{verbatim}
and you get a \dos executable which loads the \file{GO32.EXE} automatically. 
the \file{GO32.EXE} executable must be in current directory or be 
in a directory in the \var{PATH} variable.
\item
The second way to create a \dos executable is to put 
\file{GO32.EXE} at the beginning of the \file{AOUT} file. To do this, at the
command prompt, type :
\begin{verbatim}
COPY /B GO32.EXE+PROG PROG.EXE
\end{verbatim}
(assuming \fpc created a file called \file{PROG}, of course.)
This becomes then a stand-alone executable for \dos, which doesn't need the
\file{GO32.EXE} on the machine where it should run.
\end{enumerate}

%
%

% PMODE/DJ
\subsection{PMODE/DJ}
You can also use the PMODE/DJ extender to run your \fpc applications.
To make an executable which works with the PMODE extender, you can simply
create an GO32V2 executable (the default), and then convert it to a PMODE
executable with the following two extra commands:
\begin{enumerate}
\item First, strip the GO32V2 header of the executable:
\begin{verbatim}
EXE2COFF PROG.EXE
\end{verbatim}
(we suppose that \file{PROG.EXE} is the program generated by the compilation
process.
\item Secondly, add the PMODE stub:
\begin{verbatim}
COPY /B PMODSTUB.EXE+PROG PROG.EXE
\end{verbatim}
If the \file{PMODSTUB.EXE} file isn't in your local directory, you need to
supply the whole path to it.
\end{enumerate}

That's it. No additional steps are needed to create a PMODE extender
executable.

Be aware, though, that the PMODE extender doesn't support virtual memory, so
if you're short on memory, you may run unto trouble. Also, officially there
is not support for the PMODE/DJ extender. It just happens that the compiler
and some of the programs it generates, run under this extender too.


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Reducing the size of your program
\section{Reducing the size of your program}

When you created your program, it is possible to reduce its size. This
is possible, because the compiler leaves a lot of information in the
program which, strictly speaking, isn't required for the execution of
it. The surplus of information can be removed with a small program
called \file{strip}. It comes with the \var{GO32} development
environment under \dos, and is standard on \linux machines where you can
do development. The usage is simple. Just type
\begin{verbatim}
strip prog
\end{verbatim}
On the command line, and the \file{strip} program will remove all unnecessary
information from your program. This can lead to size reductions of up to
30 \%.

You can use the \var{-Xs} switch to let the compiler do this stripping
automatically at program compile time (the switch has no effect when
compiling units). 

Another technique to reduce the size of a program is to use smartlinking. 
Normally, units (including the system unit) are linked in as a whole.
It is however possible to compile units such that the can be smartlinked.
This means that only the functions and procedures are linked in your
program, leaving out any unnecessary code. This technique is described in
full in the programmers guide.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Problems
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\chapter{Compiling problems}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% General problems
\section{General problems}
\begin{itemize}
\item \textbf{IO-error -2 at ...} : Under \linux you can get this message at
compiler startup. It means typically that the compiler doesn't find the
error definitions file. You can correct this mistake with the \var{-Fr}
option under \linux. (\seeo{Fr})
\item \textbf {Error : File not found : xxx} or \textbf{Error: couldn't compile
unit xxx}: This typically happens when
your unit path isn't set correctly. Remember that the compiler looks for
units only in the current directory, and in the directory where the compiler
itself is. If you want it to look somewhere else too, you must explicitly
tell it to do so using the \var{-Up} option (\seeo{Up}). Or you must set op
a configuration file.
\end{itemize}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Problems you may encounter under DOS
\section{Problems you may encounter under DOS}
\begin{itemize}
\item \textbf{No space in environment}.\\
An error message like this can occur, if you call 
\verb|SET_PP.BAT| in the \file{AUTOEXEC.BAT}.\\
To solve this problem, you must extend your environment memory.
To do this, search a line in the \file{CONFIG.SYS} like
\begin{verbatim}
SHELL=C:\DOS\COMMAND.COM
\end{verbatim}
and change it to the following: 
\begin{verbatim}
SHELL=C:\DOS\COMMAND.COM /E:1024
\end{verbatim}
You may just need to specify a higher value, if this parameter is already set.
\item \textbf{ Coprocessor missing}\\ 
If the compiler writes
a message that there is no coprocessor, install
the coprocessor emulation.
\item \textbf{Not enough DPMI memory}\\ 
If you want to use the compiler with \var{DPMI} you must have at least
7-8 MB free \var{DPMI} memory, but 16 Mb is a more realistic amount.
\end{itemize}



%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Configuration.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\chapter{Compiler configuration}
\label{ch:CompilerConfiguration}

The output of the compiler can be controlled in many ways. This can be done
essentially in two distinct ways:
\begin{itemize}
\item Using command-line options.
\item Using the configuration file: \file{ppc386.cfg}.
\end{itemize}
The compiler first reads the configuration file. Only then the command line
options are checked. This creates the possibility to set some basic options
in the configuration file, and at the same time you can still set some
specific options when compiling some unit or program. First we list the
command line options, and then we explain how to specify the command
line options in the configuration file. When reading this, keep in mind
that the options are case sensitive. While this is customary for \linux, it
isn't under \dos.
  

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Using the command-line options
\section{Using the command-line options}

The available options for version 0.99.10 of the compiler are listed by 
category (see appendix A for a listing as generated by the compiler):

%
% General options
%

\subsection{General options}
\begin{description}
\item[-h] if you specify this option, the compiler outputs a list of all options, 
and exits after that.
\olabel{h}
\item[-?] idem as \var{-h}, waiting after every screenfull for the enter key.
\item[-i] This option tells the compiler to print the copyright information.
\olabel{i} You can give it an option, as \var{-ixxx} where xxx can be one of the
following:
\begin{description}
\item[D] : Returns the compiler date.
\item[V] : Returns the compiler version.
\item[SO] : Returns the compiler OS.
\item[SP] : Returns the compiler processor.
\item[TO] : Returns the target OS.
\item[TP] : Returns the target Processor.
\end{description}
\item[-l] This option tells the compiler to print the \fpc logo on standard
output. It also gives you the \fpc version number.
\olabel{l}
\item [-n] Tells the compiler not to read the configuration file.
\olabel{n}
\end{description}

%
% Options for getting feedback
%
\subsection{Options for getting feedback}
\begin{description}
\item[-vxxx] Be verbose. \var{xxx} is a combination of the following :
\olabel{v}
\begin{itemize}
\item \var{e} : Tells the compiler to show only errors. This option is on by default.
\item \var{i} : Tells the compiler to show some general information.
\item \var{w} : Tells the compiler to issue warnings.
\item \var{n} : Tells the compiler to issue notes.
\item \var{h} : Tells the compiler to issue hints.
\item \var{l} : Tells the compiler to show the line numbers as it processes a
file. Numbers are shown per 100.
\item \var{u} : Tells the compiler to print the names of the files it opens.
\item \var{t} : Tells the compiler to print the names of the files it tries
to open. 
\item \var{p} : Tells the compiler to print the names of procedures and
functions as it is processing them.
\item \var{c} : Tells the compiler to warn you when it processes a
conditional.
\item \var{m} : Tells the compiler to write which macros are defined.
\item \var{d} : Tells the compiler to write other debugging info.
\item \var{a} : Tells the compiler to write all possible info. (this is the
same as specifying all options)
\item \var{0} : Tells the compiler to write no messages. This is useful when
you want to override the default setting in the configuration file.
\item \var{b} : Tells the compiler to show all procedure declarations if an
overloaded function error occurs.
\item \var{x} : Tells the compiler to output some executable info (for Win32
platform only).
\item \var{r} : Rhide/GCC compatibility mode: formats the errors
differently, so they are understood by RHIDE.
\end{itemize}
\end{description}

%
% Options concerning files and directories
%
\subsection{Options concerning files and directories}
\begin{description}
\item [-exxx] \file{xxx} specifies the directory where the 
compiler can find the executables \file{as} (the assembler) and \file{ld} (the
compiler).
\olabel{e}
\item [-FD] same as \var{-e}.
\item [-Fexxx] This option tells the compiler to write errors, etc. to 
the file in \file{xxx}.
\olabel{Fe} 
\item [-Fgxxx] (\linux only, obsolete) \file{xxx} specifies the path where the compiler
can find the \gnu C library. This is superseded by the \var{-Fl} option.
\olabel{Fg}
\item [-Fixxx] adds \var{xxx} to the path where the compiler searches for
its include files.
\olabel{Fi}
\item [-Flxxx] Adds \var{xxx} to the library searching path, and is passed
to the linker.
\olabel{Fl}
\item[-FLxxx] (\linux only) Tells the compiler to use \file{xxx} as the
dynamic linker. Default this is \file{/lib/ld-linux.so.2}, or
\file{lib/ld-linux.so.1}, depending on which one is found.
\olabel{FL}
\item[-Foxxx] Adds \file{xxx} to the object file path. This path is used
when looking for files that need to be linked in.
\olabel{Fo} 
\item [-Frxxx] \file{xxx} specifies the file which contain the compiler
messages. Default the compiler ahs built-in messages. Specifying this option
will override the default messages.
\olabel{Fr}
\item [-Fuxxx] Idem as \var{-Up}: Add \file{xxx} to the object path.
\olabel{Fu}
\item [-FUxxx] Tells the compiler to write units in directory \var{xxx}
instead of the current directory.
\item [-Ixxx] \olabel{I} Add \file{xxx} to the include file search path.
This path is used when looking for include files.
\item [-P] uses pipes instead of files when assembling. This may speed up
the compiler on \ostwo and \linux. Only with assemblers (such as \gnu
\file{as}) that support piping..
\item [-Upxxx] \olabel{Up} Tells the compiler to add \file{xxx} to the path where to find
units. \\
By default, the compiler only searches for units in the current directory 
and the directory where the compiler itself resides. This option tells the
compiler also to look in the directory \file{xxx}.
\end{description}

% Options controlling the kind of output.
\subsection{Options controlling the kind of output.}
for more information on these options, see also \progref
\begin{description}
\item [-a] \olabel{a} Tells the compiler not to delete the assembler file.
This also counts for the (possibly) generated batch script.
\item [-al] \olabel{al} Tells the compiler to include the sourcecode lines
in the assembler file as comments. This feature is still experimental, and
should be used with caution.
\item [-Axxx] \olabel{A}specifies what kind of assembler should be generated . Here
\var{xxx} is one of the following :
\begin{itemize}
\item \textbf{o} : A unix .o (object) file, using \gnu \file{as}.
\item \textbf{nasmcoff} : a coff file using the \file{nasm} assembler.
\item \textbf{nasmelf} : a ELF32 file (\linux only) using the \file{nasm} assembler.
\item \textbf{nasmonj} : a obj file  using the \file{nasm} assembler.
\item \textbf{masm} : An obj file using the Microsoft \file{masm} assembler.
\item \textbf{tasm} : An obj file using the Borland \file{tasm} assembler.
\end{itemize}
\item [-CD] Create dynamic library.
\item [-Chxxx] \olabel {Ch} Reserves \var{xxx} bytes heap. \var{xxx} should
be between 1024 and 67107840.
\item [-Ci] \olabel{Ci} Generate Input/Output checking code.
\item [-Cn] \olabel{Cn} Omit the linking stage.
\item [-Co] \olabel{Co} Generate Integer overflow checking code.
\item [-Cr] \olabel{Cr} Generate Range checking code.
\item [-Csxxx] \olabel{Cs} Set stack size to \var{xxx}. 
\item [-CS] \olabel{CS} Create static library.
\item [-Ct] \olabel{Ct} generate stack checking code. 
\item [-Cx] \olabel{Cx} Use smartlinking when compiling and linking units.
\item [-dxxx] \olabel{d} Define the symbol name \var{xxx}. This can be used
to conditionally compile parts of your code.
\item {-E} \olabel{E} Same as \var{-Cn}.
\item [-g] \olabel{g} Generate debugging information for debugging with
\file{gdb}
\item [-gg] idem as \var{-g}.
\item [-gd] \olabel{gd} generate debugging info for \file{dbx}.
\item [-gh] use the heaptrc unit (see \unitsref).
\item[-Oxxx] \olabel{O} optimize the compiler's output; \var{xxx} can have one
of the following values :
\begin{description}
\item[g] optimize for size, try to generate smaller code.
\item[G] optimize for time, try to generate faster code (default).
\item[r] keep certain variables in registers (experimental, use with
caution).
\item[u] uncertain optimizations
\item[1] Level 1 optimizations (quick optimizations).
\item[2] Level 2 optimizations (\var{-O1} plus some slower optimizations).
\item[3] Level 2 optimizations (\var{-O2} plus \var{-Ou}).
\item[Pn] Specify processor: \var{n} can be one of 
\begin{description}
\item[1] optimize for 386/486
\item[2] optimize for Pentium/PentiumMMX (tm)
\item[3] optimizations for PentiumPro/PII/Cyrix 6x86/K6 (tm)
\end{description}
\end{description}
The exact effect of these effects can be found in the \progref.
\item [-oxxx] Tells the compiler to use \var{xxx} as the name of the output
file (executable). Only with programs.
\item [-pg] \olabel{gp} Generate profiler code for \file{gprof}.
\item [-s] \olabel{s} Tells the compiler not to call the assembler and linker.
Instead, the compiler writes a script, \file{PPAS.BAT} under \dos, or
\file{ppas.sh} under \linux, which can then be executed to produce an
executable.
\item[-Txxx] \olabel{T}Specifies the target operating system. \var{xxx} can be one of
the following:
\begin{itemize}
\item \textbf{GO32V1} : \dos and version 1 of the DJ DELORIE extender.
\item \textbf{GO32V2} : \dos and version 2 of the DJ DELORIE extender.
\item \textbf{LINUX} : \linux.
\item \textbf{OS2} : OS/2 (2.x) (this is still under development).
\item \textbf{WIN32} : Windows 32 bit (this is still under development).
\end{itemize}
\item [-uxxx] \olabel{u} undefine the symbol \var{xxx}. This is the opposite
of the \var{-d} option.
\item [-uxxx] \olabel{U} Undefine symbol \var{xxx}.

\item [-Xx] \olabel{X} executable options. This tells the compiler what
kind of executable should be generated. the parameter \var{x}
can be one of the following:
\begin{itemize}
% \item \textbf{e} : (\linux only) Create an \file{ELF} executable (default).
\item \textbf{c} : (\linux only) Link with the C library. You should only use this when
  you start to port \fpc to another operating system.
\item \textbf{D} : Link with dynamic libraries (defines the 
\var{FPC\_LINK\_DYNAMIC} symbol)
\item \textbf{s} : Strip the symbols from the executable.
\item \textbf{S} : Link with static libraries (defines the 
\var{FPC\_LINK\_STATIC} symbol)
\end{itemize}
\end{description}

%
%

% Options concerning the sources (language options)

\subsection{Options concerning the sources (language options)}
for more information on these options, see also \progref
\begin{description}
\item [-Rxxx] \olabel{R} Specifies what assembler you use in your \var{asm} assembler code
blocks. Here \var{xxx} is one of the following:
\begin{description}
\item [att\ ] \var{asm} blocks contain AT\&T assembler.
\item [intel] \var{asm} blocks contain Intel assembler.
\item [direct] \var{asm} blocks should be copied as-is in the assembler
file.   
\end{description}
\item [-S2] \olabel{Stwo} Switch on Delphi 2 extensions.
\item [-Sc] \olabel{Sc} Support C-style operators, i.e. \var{*=, +=, /= and
-=}.
\item [-Sd] tells the compiler to dispose asmlists. This uses less memory,
but is slower.
\item [-Se] \olabel{Se} The compiler stops after the first error. Normally,
the compiler tries to continue compiling after an error, until 50 errors are
reached, or a fatal error is reachd, and then it stops. With this switch,
the compiler will stop after the first error.
\item [-Sg] \olabel{Sg} Support the \var{label} and \var{goto} commands.
\item [-Si] \olabel{Si} Support \var{C++} style INLINE.
\item [-Sm] \olabel{Sm} Support C-style macros.
\item [-So] \olabel{So} Try to be Borland TP 7.0 compatible (no function
overloading etc.).
\item [-Sp] \olabel{Sp} Try to be \file{gpc} (\gnu pascal compiler)
compatible.
\item [-Ss] \olabel{Ss} The name of constructors must be \var{init}, and the
name of destructors should be \var{done}.
\item [-St] \olabel{St} Allow the \var{static} keyword in objects.
\item [-Un] \olabel{Un} Do not check the unit name. Normally, the unit name
is the same as the filename. This option allows both to be different.
\item [-Us] \olabel{Us} Compile a system unit. This option causes the
compiler to define only some very basic types.
\end{description}


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Using the configuration file
\section{Using the configuration file}
\label{se:config_file}
Using the configuration file \file{ppc386.cfg} is an alternative to command
line options. When a configuration file is found, it is read, and the lines
in it are treated like you typed them on the command line. They are treated
before the options that you type on the command line.

You can specify comments in the configuration file with the \var{\#} sign.
Everything from the \var{\#} on will be ignored.

The compiler looks for the \file{ppc386.cfg} file in the following places :
\begin{itemize} 
\item Under \linux
\begin{enumerate}
\item The current directory.
\item In your home directory, it looks for \file{.ppc386.cfg}.
\item The directory specified in the environment variable 
\var{PPC\_CONFIG\_PATH}, and if it's not set under \file{/etc}.
\end{enumerate}
\item Under all other OSes:
\begin{enumerate}
\item The current directory.
\item If it is set, the directory specified in the environment variable.
\var{PPC\_CONFIG\_PATH}.
\item The directory where the compiler is. 
\end{enumerate}
\end{itemize}
When the compiler has finished reading the configuration file, it continues
to treat the command line options.

One of the command-line options allows you to specify a second configuration
file: Specifying \file{@foo} on the command line will open file \file{foo},
and read further options from there. When the compiler has finished reading
this file, it continues to process the command line.

The configuration file allows some kind of preprocessing. It understands the
following directives, which you should place on the first column of a line :
\begin{description}
\item [\#IFDEF]
\item [\#IFNDEF]
\item [\#ELSE]
\item [\#ENDIF]
\item [\#DEFINE]
\item [\#UNDEF]
\item [\#WRITE]
\item [\#INCLUDE]
\item [\#SECTION]
\end{description}
They work the same way as their \{\$...\}  counterparts in Pascal.

What follows is a description of the different directives.

\subsection{\#IFDEF}
Syntax:
\begin{verbatim}
#IFDEF name
\end{verbatim} 
Lines following \var{\#IFDEF} are skipped read if the keyword \var{name}
following it is not defined.

They are read until the keywords \var{\#ELSE} or \var{\#ENDIF} are
encountered, after which normal processing is resumed.

Example :
\begin{verbatim}
#IFDEF VER0_99_5
-Up/usr/lib/fpc/0.99.5/linuxunits
#ENDIF
\end{verbatim}
In the above example, \file{/usr/lib/fpc/0.99.5/linuxunits} will be added to
the path if you're compiling with version 0.99.5 of the compiler.

\subsection{\#IFNDEF}
Syntax:
\begin{verbatim}
#IFNDEF name
\end{verbatim} 
Lines following \var{\#IFDEF} are skipped read if the keyword \var{name}
following it is defined.

They are read until the keywords \var{\#ELSE} or \var{\#ENDIF} are
encountered, after which normal processing is resumed.

Example :
\begin{verbatim}
#IFNDEF VER0_99_5
-Up/usr/lib/fpc/0.99.6/linuxunits
#ENDIF
\end{verbatim}
In the above example, \file{/usr/lib/fpc/0.99.6/linuxunits} will be added to
the path if you're NOT compiling with version 0.99.5 of the compiler.

\subsection{\#ELSE}
Syntax:
\begin{verbatim}
#ELSE
\end{verbatim} 
\var{\#ELSE} can be specified after a \var{\#IFDEF} or \var{\#IFNDEF}
directive as an alternative.
Lines following \var{\#ELSE} are skipped read if the preceding \var{\#IFDEF}
\var{\#IFNDEF} was accepted.

They are skipped until the keyword \var{\#ENDIF} is
encountered, after which normal processing is resumed.

Example :
\begin{verbatim}
#IFDEF VER0_99_5
-Up/usr/lib/fpc/0.99.6/linuxunits
#ELSE
-Up/usr/lib/fpc/0.99.5/linuxunits
#ENDIF
\end{verbatim}
In the above example, \file{/usr/lib/fpc/0.99.5/linuxunits} will be added to
the path if you're compiling with version 0.99.5 of the compiler,
otherwise \file{/usr/lib/fpc/0.99.6/linuxunits} will be added to the path.

\subsection{\#ENDIF}
Syntax:
\begin{verbatim}
#ENDIF
\end{verbatim} 
\var{\#ENDIF} marks the end of a block that started with \var{\#IF(N)DEF},
possibly with an \var{\#ELSE} between it.

\subsection{\#DEFINE}
Syntax:
\begin{verbatim}
#DEFINE name
\end{verbatim}
\var{\#DEFINE} defines a new keyword. This has the same effect as a 
\var{-dname}  command-line option.

\subsection{\#UNDEF}
Syntax:
\begin{verbatim}
#UNDEF name
\end{verbatim}
\var{\#UNDEF} un-defines a keyword if it existed. 
This has the same effect as a \var{-uname}  command-line option.

\subsection{\#WRITE}
Syntax:
\begin{verbatim}
#WRITE Message Text
\end{verbatim}
\var{\#WRITE} writes \var{Message Text} to the screen.
This can be useful to display warnings if certain options are set.

Example:
\begin{verbatim}
#IFDEF DEBUG
#WRITE Setting debugging ON...
-g
#ENDIF
\end{verbatim}
if \var{DEBUG} is defined, this will produce a line
\begin{verbatim}
Setting debugging ON...
\end{verbatim}
and will then switch on debugging information in the compiler.

\subsection{\#INCLUDE}
Syntax:
\begin{verbatim}
#INCLUDE filename
\end{verbatim}
\var{\#INCLUDE} instructs the compiler to read the contents of
\file{filename} before continuing to process the current file.

This can be useful if you want to have a particular configuration file
for a project (or, under \linux, in your home directory), but still want to
have the global options that are set in a global configuration file.

Example:
\begin{verbatim}
#IFDEF LINUX
  #INCLUDE /etc/ppc386.cfg
#ELSE
  #IFDEF GO32V2
    #INCLUDE c:\pp\bin\ppc386.cfg
  #ENDIF
#ENDIF
\end{verbatim}
This will include \file{/etc/ppc386.cfg} if you're on a linux machine,
and will include \verb+c:\pp\bin\ppc386.cfg+
on a dos machine.

\subsection{\#SECTION}
Syntax:
\begin{verbatim}
#SECTION name
\end{verbatim}
The \var{\#SECTION} directive acts as a \var{\#IFDEF} directive, only
it doesn't require an \var{\#ENDIF} directive. the special name \var{COMMON}
always exists, i.e. lines following \var{\#SECTION COMMON} are always read.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Porting.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\chapter{Porting Turbo Pascal Code}

\fpc was designed to resemble Turbo Pascal as closely as possible. There
are, of course, restrictions. Some of these are due to the fact that \fpc is
a 32-bit compiler. Other restrictions result from the fact that \fpc works
on more than one operating system.

In general we can say that if you keep your program code close to ANSI
Pascal, you will have no problems porting from Turbo Pascal, or even Delphi, to
\fpc. To a large extent, the constructs defined by Turbo Pascal are
supported. This is even more so if you use the \var{-So} or \var{-S2}
switches.

In the following sections we will list the Turbo Pascal constructs which are
not supported in \fpc, and we will list in what ways \fpc extends the Turbo
Pascal language.


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Things that will not work
\section{Things that will not work}
Here we give a list of things which are defined/allowed in Turbo Pascal, but
which are not supported by \fpc. Where possible, we indicate the reason. 
\begin{enumerate}
\item Parameter lists of previously defined functions and procedures must
match exactly. The reason for this is the function overloading mechanism of
\fpc. (however, the \var{-So} switch solves this. \seeo{So})
\item \var {(* ... *)} as comment delimiters are not allowed in versions
older than 0.9.1. This can easily be remedied with a grown-up editor. 
\item The \var{MEM, MEMW, MEML} and \var{PORT} variables for memory and port
access are not available. This is due to the operating system. Under
\dos, the extender unit (\file {GO32.PPU}) implements the mem constuct.
under \linux, the \file{ports} unit implements such a construct.
\item \var{PROTECTED, PUBLIC, PUBLISHED, TRY, FINALLY, EXCEPT, RAISE} 
are reserved words. This means you cannot create procedures or variables 
with the same name. While they are not reserved words in Turbo Pascal, 
they are in Delphi. Using the \var{-So} switch will solve this problem if
you want to compile Turbo Pascal code that uses these words.
\item The reserved words \var{FAR, NEAR} are ignored. This is
because \fpc is a 32 bit compiler, so they're obsolete.
\item \var{INTERRUPT} only will work on a DOS machine.
\item Boolean expressions are only evaluated until their result is completely
determined. The rest of the expression will be ignored.
\item By default the compiler uses  \var{AT\&T} assembler syntax. 
This is mainly because \fpc uses \gnu \var{as}. However other assembler
forms are available, \progref.
\item Turbo Vision is not available.
\item The 'overlay' unit is not available. It also isn't necessary, since
\fpc is a 32 bit compiler, so program size shouldn't be a point.
\item There are more reserved words. (see appendix \ref{ch:reserved} for a
list of all reserved words.)
\item The command-line parameters of the compiler are different.
\item Compiler switches and directives are mostly the same, but some extra
exist.
\item Units are not binary compatible.
\end{enumerate}



%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Things which are extra
\section{Things which are extra}
Here we give a list of things which are possible in \fpc, but which
didn't exist in Turbo Pascal or Delphi.
\begin{enumerate}
\item There are more reserved words. (see appendix \ref{ch:reserved} for a
list of all reserved words.)
\item Functions can also return complex types, such as records and arrays.
\item You can handle function results in the function itself, as a variable. 
Example
\begin{verbatim}
function a : longint;

begin
   a:=12;
   while a>4 do
     begin
        {...}
     end;
end;
\end{verbatim}
The example above would work with TP, but the compiler would assume
that the \var{a>4} is a recursive call. To do a recursive call in
this you must append \var{()} behind the function name: 
\begin{verbatim}
function a : longint;

begin
   a:=12;
   { this is the recursive call }
   if a()>4 then
     begin
        {...}
     end;
end;
\end{verbatim}
\item There is partial support of Delphi constructs. (see the \progref for
more information on this).
\item The \var{exit} call accepts a return value for functions.
\begin{verbatim}
function a : longint;

begin
   a:=12;
   if a>4 then
     begin
        exit(a*67); {function result upon exit is a*67 }
     end;
end;
\end{verbatim}
\item \fpc supports function overloading. That is, you can define many
functions with the same name, but with different arguments. For example:
\begin{verbatim}
procedure DoSomething (a : longint);
begin
{...}
end;

procedure DoSomething (a : real);
begin
{...}
end;
\end{verbatim} 
You can then call procedure \var{DoSomething} with an argument of type
\var{Longint} or \var{Real}.\\
This feature has the consequence that a previously declared function must
always be defined with the header completely the same:
\begin{verbatim}
procedure x (v : longint); forward;

{...} 

procedure x;{ This will overload the previously declared x}
begin
{...}
end;
\end{verbatim}
This construction will generate a compiler error, because the compiler
didn't find a definition of \var{procedure x (v : longint);}. Instead you
should define your procedure x as:
\begin{verbatim}
procedure x (v : longint);
{ This correctly defines the previously declared x}
begin
{...}
end;
\end{verbatim}
(The \seeo{So} switch disables overloading. When you use it, the above will
compile, as in Turbo Pascal.
\item Operator overloading. \fpc allows to overload operators, i.e. you can
define e.g. the '+' operator for matrices.
\item On FAT16 and FAT32 systems, long file names are supported.
\end{enumerate}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Turbo Pascal compatibility mode
\section{Turbo Pascal compatibility mode}
When you compile a program with the \var{-So} switch, the compiler will
attempt to mimic the Turbo Pascal compiler in the following ways:
\begin{itemize}
\item Assigning a procedural variable doesn't require a @ operator. One of
the differences between Turbo Pascal and \fpc is that the latter requires
you to specify an address operator when assigning a value to a procedural
variable. In Turbo Pascal compatibility mode, this is not required.
\item Procedure overloading is disabled. This means that function header and
implementation can be different (i.e. the function iplementation doesn't
need to repeat the function header).
\item Forward defined procedures don't need the full parameter list when
they are defined. Due to the procedure overloading feature of \fpc, you must
always specify the parameter list of a function when you define it, even
when it was declared earlier with \var{Forward}. In Turbo Pascal
compatibility mode, there is no function overloading, hence you can omit the
parameter list:
\begin{verbatim}
Procedure a (L : Longint); Forward;

...

Procedure a ; { No need to repeat the (L : Longint) }

begin
 ...
end;

\end{verbatim}
\item recursive function calls are handled dfferently. Consider the
following example :
\begin{verbatim}
Function expr : Longint;

begin
  ...
  Expr:=L:
  Writeln (Expr); 
  ...
end;
\end{verbatim}
In Turbo Pascal compatibility mode, the function will be called recursively 
when the \var{writeln} statement is processed. In \fpc, the function result
will be printed. In order to call the function recusively under \fpc, you
need to implement it as follows :
\begin{verbatim}
Function expr : Longint;

begin
  ...
  Expr:=L:
  Writeln (Expr()); 
  ...
end;
\end{verbatim}
\item Any text after the final \var{End.} statement is ignored. Normally,
this text is processed too.
\item You cannot assign procedural variables to void pointers.
\item The @ operator is typed when applied on procedures.
\item You cannot nest comments. 
\end{itemize}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Utilities.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\chapter{Utilities and units that come with Free Pascal}
\label{ch:Utilities}
Besides the compiler and the Run-Time Library, \fpc comes with some utility
programs and units. Here we list these programs and units. 

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Supplied programs
\section{Supplied programs}

\subsection{ppudump program}

\file{ppudump} is a program which shows the contents of a \fpc unit. It
is distributed with the compiler you can just issue the following command
\begin{verbatim}
  ppudump [options] foo.ppu
\end{verbatim}
to display the contents of the \file{foo.ppu} unit. You can specify multiple
files on the command line.

The options can be used to change the verbosity of the display. By default,
all available information is displayed. 
You can set the verbosity level using the \var{-Vxxx} option. 
Here, \var{xxx} is a combination of the following
letters:
\begin{description}
\item [h:\ ] show header info.
\item [i:\ ] show interface information.
\item [m:\ ] show implementation information.
\item [d:\ ] show only (interface) definitions.
\item [s:\ ] show only (interface) symbols.
\item [b:\ ] show browser info.
\item [a:\ ] show everything (default if no -V option is present).
\end{description}

\subsection{Demo programs}
Also distributed with \fpc comes a series of demonstration programs.
These programs have no other purpose than demonstrating the capabilities of
\fpc. They are located in the \file{demo} directory of the sources.

\subsection{Documentation Example programs}

All example programs of the documentation are available. Check out the
directories that end on \file{ex} in the documentation sources. There you
will find all example sources.
\subsection{ppumove program}

\file{ppumove} is a program to make shared or static libraries from
multiple units. It can be compared with the \file{tpumove} program that 
comes with
Turbo Pascal.

It should be distributed in binary form along with the compiler.

It's usage is very simple:
\begin{verbatim}
ppumove [options] unit1.ppu unit2.ppu ... unitn.ppu
\end{verbatim}
Where \var{options} is a combination of
\begin{description}
\item[-b:\ ] If specified, ppumve will generate a batch file that will
contain the external linking and archiving commands that must be 
executed. The name of this batch file is \file{pmove.sh} on \linux, and 
\file{pmove.bat} otherwise. 
\item[-d xxx:\ ] If specified, the output files will put in the directory
\file{xxx}
\item[-e xxx:\ ] Sets the extension of the moved unit files to \file{xxx}.
By default, this is \file{.ppl}. You don't have to specify the dot.
\item[-o xxx:\ ] sets the name of the output file, i.e. the name of the file
containing all the units. This parameter is mandatory when you use multiple
files. On \linux, \file{ppumove} will prepend this name with \file{lib} if it isn't
already there, and will add an extension appropriate to the type of library.
\item [-q:\ ] Causes \file{ppumove} to operate silently.
\item [-s:\ ] Tells \file{ppumove} to make a static library instead of a 
dynamic one; By default a dynamic library is made on \linux.
\item [-w:\ ] Tells ppumove that it is working under \windowsnt. This will
change the names of te linker and archiving program to \file{ldw} and
\file{arw}, respectively.
\item[-h or -?:\ ] will display a short help.
\end{description}

The action of the ppumve program is as follows:
It takes each of the unit files, and modifies it so that the compile will
know that it should look for the unit code in the library. The new unit 
files will have an extension \file{.ppu}, this can be changed with the
\var{-e} option. It will then put together all the object files of the units
into one library, static or dynamic, depending on the presence of the
\var{-s} option. 

The name of this library must be set with the \var{-o} option. 
If needed, the prefix \file{lib} will be prepended under \linux.. 
The extension will be set to \file{.a} for static libraries, 
for shared libraries the extensions are \var{.so} on linux, and \var{.dll} 
under \windowsnt and \ostwo.

As an example, the following command
\begin{verbatim}
./ppumove -o both -e ppl ppu.ppu timer.ppu
\end{verbatim}
under linux, will generate the following output:
\begin{verbatim}
PPU-Mover Version 0.99.7
Copyright (c) 1998 by the Free Pascal Development Team

Processing ppu.ppu... Done.
Processing timer.ppu... Done.
Linking timer.o ppu.o
Done.
\end{verbatim}
And it will produce the following files:
\begin{enumerate}
\item \file{libboth.so} : The shared library containing the code from 
\file{ppu.o} and \file{timer.o}. Under \windowsnt, this file would be called
\file{both.dll}.
\item \file{timer.ppl} : The unit file that tells the \fpc compiler to look
for the timer code in the library.
\item \file{ppu.ppl} : The unit file that tells the \fpc compiler to look
for the timer code in the library.
\end{enumerate}
You could then use or distribute the files \file{libboth.so}, \file{timer.ppl}
and \file{ppu.ppl}.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Supplied units
\section{Supplied units}
Here we list the units that come with the \fpc distribution. Since there is
a difference in the supplied units per operating system, we list them
separately per system. They are documented in the \unitsref.

%
% Under DOS
%
\subsection{Under DOS}
\begin{itemize}
\item [strings] This unit provides basic
string handling routines for the \var{pchar} type, comparable to similar
routines in standard \var{C} libraries.
\item [objects]  This unit provides basic
routines for handling objects.
\item [dos] This unit provides basic routines for
accessing the operating system \dos. It provides almost the same
functionality as the Turbo Pascal unit. 
\item [printer]  This unit provides all you
need for rudimentary access to the printer.
\item [getopts] This unit gives you the
\gnu \var{getopts} command-line arguments  handling mechanism. 
It also supports long options.
\item [crt] This unit provides basic screen
handling routines. It provides the same functionality  as the Turbo Pascal \var{CRT}
unit.
\item [graph] This unit provides basic graphics
handling, with routines to draw lines on the screen, display texts etc. It
provides the same functions as the Turbo Pascal unit.
\item [go32] This unit provides access to possibilities of the \var{GO32}
\dos extender.
\item [emu387] This unit provides support for the coprocessor emulator.
\item [mmx] This unit provides support for \var{mmx} extensions in your
code.
\end{itemize}

%
% Under Linux
%
\subsection{Under Linux}
\begin{itemize}
\item [strings] This unit provides basic
string handling routines for the \var{PChar} type, comparable to similar
routines in standard \var{C} libraries.
\item [objects] This unit provides basic
routines for handling objects.
\item [crt] This unit provides basic screen
handling routines. It provides the same functionality Turbo Pascal \var{CRT}
unit. It works on any terminal which supports the \var{vt100} escape
sequences.
\item [dos] This unit provides an emulation of the
same unit under \dos. It is intended primarily for easy porting of Pascal
programs from \dos to \linux. For good performance, however, it is
recommended to use the \var{linux} unit.
\item [linux] This unit provides access to the
\linux operating system. It provides most file and I/O handling routines
that you may need. It implements most of the standard \var{C} library constructs
that you will find on a Unix system. If you do a lot of disk/file
operations, the use of this unit is recommended over the one you use under
Dos.
\item [printer] This unit provides an
interface to the standard Unix printing mechanism.
\item [getopts] This unit gives you the
\gnu \var{getopts} command-line arguments  handling mechanism. 
It also supports long options.
\item [mmx] This unit provides support for \var{mmx} extensions in your
code.
\item [sockets] This unit gives you access to sockets and TCP/IP
programming.
\item [graph] Is an implementation of Borlands \file{graph} unit, which
works on the Linux console. It's implementation is fairly complete, the only
non-functional things are the fillpatterns and line styles. It uses the
libvga and libvgagl graphics libraries, so you need these installed for this
unit to work. Also, programs using this library need to be run as root, or
setuid  root, and hence are a potential security risk.
\item [ports] This implements the various \var{port[]} constructs. These are 
provided for compatibility only, and it is not recommended to use them
extensively. Programs using this construct must be run as ruit or setuid
root, and are a serious security risk on your system.
\end{itemize}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Debugging
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\chapter{Debugging your Programs}

\fpc supports debug information for the \gnu debugger \var{gdb}. 
This chapter describes shortly how to use this feature. It doesn't attempt
to describe completely the \gnu debugger, however.
For more information on the workings of the \gnu debugger, see the \var{gdb}
users' guide.

\fpc also suports \var{gprof}, the \gnu profiler, see section \ref{se:gprof}
for more information on profiling.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Compiling your program with debugger support
\section{Compiling your program with debugger support}
First of all, you must be sure that the compiler is compiled with debugging
support. Unfortunately, there is no way to check this at run time, except by
trying to compile a program with debugging support.

To compile a program with debugging support, just specify the \var{-g}
option on the command-line, as follows:
\begin{verbatim}
ppc386 -g hello.pp
\end{verbatim}
This will generate debugging information in the executable from your
program. You will notice that the size of the executable increases
substantially because of this\footnote{A good reason not to include debug
information in an executable you plan to distribute.}. 

Note that the above will only generate debug information {\var for the code
that has been generated} when compiling \file{hello.pp}. This means that if
you used some units (the system unit, for instance) which were not compiled
with debugging support, no debugging support will be available for the code
in these units. 

There are 2 solutions for this problem. 
\begin{enumerate}
\item Recompile all units manually with the \var{-g} option. 
\item Specify the 'build' option (\var{-B}) when compiling with debugging
support. This will recompile all units, and insert debugging information in
each of the units.
\end{enumerate}
The second option may have undesirable side effects. It may be that some
units aren't found, or compile incorrectly due to missing conditionals,
etc..

If all went well, the executable now contains the necessary information with 
which you can debug it using \gnu \var{gdb}.


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Using gdb
\section{Using \var{gdb} to debug your program}

To use gdb to debug your program, you can start the debugger, and give it as
an option the {\em full} name of your program:
\begin{verbatim}
gdb hello
\end{verbatim}
Or, under \dos :
\begin{verbatim}
gdb hello.exe
\end{verbatim}

This starts the debugger, and the debugger immediately loads your program
into memory, but it does not run the program yet. Instead, you are presented
with the following (more or less) message, followed by the \var{gdb} prompt
\var{'(gdb)'}:
\begin{verbatim}
GDB is free software and you are welcome to distribute copies of it
 under certain conditions; type "show copying" to see the conditions.
There is absolutely no warranty for GDB; type "show warranty" for details.
GDB 4.15.1 (i486-slackware-linux),
Copyright 1995 Free Software Foundation, Inc...
(gdb)
\end{verbatim}
To start the program you can use the \var{run} command. You can optionally 
specify command-line parameters, which will then be fed to your program, for
example:
\begin{verbatim}
(gdb) run -option -anotheroption needed_argument
\end{verbatim}
If your program runs without problems, \var{gdb} will inform you of this,
and return the exit code of your program. If the exit code was zero, then
the message \var{'Program exited normally'}.

If something went wrong (a segmentation fault or so), \var{gdb} will stop
the execution of your program, and inform you of this with an appropriate
message. You can then use the other \var{gdb} commands to see what happened.  
Alternatively, you can instruct \var{gdb} to stop at a certain point in your
program, with the \var{break} command.

Here is a short list of \var{gdb} commands, which you are likely to need when
debugging your program:
\begin{description}
\item [quit\ ] Exits the debugger.
\item [kill\ ] Stops a running program.
\item [help\ ] Gives help on all \var{gdb} commands.
\item [file\ ] Loads a new program into the debugger.
\item [directory\ ] Add a new directory to the search path for source
files.\\
{\em Remark:} My copy of gdb needs '.' to be added explicitly to the search
path, otherwise it doesn't find the sources.
\item [list\ ] Lists the program sources per 10 lines. As an option you can
specify a line number or function name.
\item [break\ ] Sets a breakpoint at a specified line or function
\item [awatch\ ] Sets a watch-point for an expression. A watch-point stops
execution of your program whenever the value of an expression is either 
read or written. 
\end{description}

for more information, see the \var{gdb} users' guide, or use the \var{'help'}
function in \var{gdb}.

The appendix {\ref{ch:GdbIniFile}} contains a sample init file for
\var{gdb}, which produces good results when debugging \fpc programs.

It is also possible to use \file{RHIDE}, a text-based IDE that uses gdb.
There is a version of RHIDE available that can work together with FPC.

\section{Caveats when debugging with \var{gdb}}

There are some peculiarities of \fpc which you should be aware of when using
\var{gdb}. We list the main ones here:
\begin{enumerate}
\item \fpc generates information for GDB in uppercare letters. This is a
consequence of the fact that pascal is a case insensitive language. So, when
referring to a variable or function, you need to make it's name all
uppercase.

As an example, of you want to watch the value of a loop variable
\var{count}, you should type
\begin{verbatim}
watch COUNT
\end{verbatim}
Or if you want stop when a certain function (e.g \var{MyFunction}) is called, 
type
\begin{verbatim}
break MYFUNCTION
\end{verbatim}

\item Line numbers may be off by a little. This is a bug in \fpc and will be
fixed as soon as possible.

\item \var{gdb} does not know sets.

\item \var{gdb} doesn't know strings. Strings are represented in \var{gdb} 
as records with a length field and an array of char contaning the string.

You can also use the following user function to print strings:
\begin{verbatim}
define pst
set $pos=&$arg0
set $strlen = {byte}$pos
print {char}&$arg0.st@($strlen+1)
end

document pst
  Print out a Pascal string
end 
\end{verbatim}
If you insert it in your \file{gdb.ini} file, you can look at a string with this
function. There is a sample \file{gdb.ini} in appendix \ref{ch:GdbIniFile}.

\item Objects are difficult to handle, mainly because \var{gdb} is oriented
towards C and C++. The workaround implemented in \fpc is that object methods
are represented as functions, with an extra parameter \var{this} (all
lowercase !) The name of this function is a concatenation of the object type
and the function name, separated by two underscore characters.

For example, the method \var{TPoint.Draw} would be converted to
\var{TPOINT\_\_DRAW}, and could be stopped at with
\begin{verbatim}
break TPOINT__DRAW
\end{verbatim}

\item Global overloaded functions confuse \var{gdb} because they have the same
name. Thus you cannot set a breakpoint at an overloaded function, unless you
know it's line number, in which case you can set a breakpoint at the
starting linenumber of the function.
\end{enumerate}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Using gprof
\section{Support for \var{gprof}, the \gnu profiler}
\label{se:gprof}

You can compile your programs with profiling support. for this, you just
have to use the compiler switch \var{-pg}. The compiler wil insert the
necessary stuff for profiling. 

When you have done this, you can run your program uder the gnu profiler,
\var{gprof}, as follows :
\begin{verbatim}
gprog yourexe
\end{verbatim}
Where \file{yourexe} is the name of your executable.

You may want to capture the outpus of the profiler in a file, since it can
be quite a lot, as follows:
\begin{verbatim}
gprog yourexe >gprof.out
\end{verbatim}

For more information on the \gnu profiler \var{gprof}, see its manual.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% CGI.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\chapter{CGI programming in Free Pascal}
\label{ch:CGIProgramming}

In these days of heavy WWW traffic on the Internet, CGI scripts have become
an important topic in computer programming. While CGI programming can be
done with almost any tool you wish, most languages aren't designed for it.
Perl may be a notable exception, but perl is an interpreted language, the
executable is quite big, and hence puts a big load on the server machine.

Because of its simple, almost intuitive, string handling and its easy syntax, 
Pascal is very well suited for CGI programming. Pascal allows you to quickly
produce some results, while giving you all the tools you need for more
complex programming. The basic RTL routines in principle are enough to get
the job done, but you can create, with relatively little effort, some units
which can be used as a base for more complex CGI programming.

That's why, in this chapter, we will discuss the basics of CGI in \fpc.
In the subsequent, we will assume that the server for which the programs are 
created, are based upon the NCSA \var{httpd} WWW server, as the examples
will be based upon the NCSA method of CGI programming\footnote{... and it's 
the only WWW-server I have to my disposition at the moment.}.
They have been tested with the \file{apache} server on \linux, and 
the \file{xitami} server on \windowsnt.

The two example programs in this chapter have been tested on the command line 
and worked, under the condition that no spaces were present in the name and 
value pairs provided to them.

There is however, a faster and generally better \file{uncgi} unit available,
you can find it on the contributed units page of the \fpc web site. It uses
techniques discussed here, but in a generally more efficient way, and it
also provides some extra functionality, not discussed here.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Getting your data
\section{Getting your data}
Your CGI program must react on data the user has filled in on the form which
your web-server gave him. The Web server takes the response on the form, and
feeds it to the CGI script.

There are essentially two ways of feeding the data to the CGI script. We will
discuss both.

%
%

% Data coming through standard input.
\subsection{Data coming through standard input.}
The first method of getting your data is through standard input. This method
is invoked when the form uses a form submission method of \var{POST}.
The web browser sets three environment variables \var{REQUEST\_METHOD},
\var{CONTENT\_TYPE} and \var{CONTENT\_LENGTH}. It feeds then the results of
the different fields through standard input to the CGI script.
All the Pascal program has to do is :
\begin{itemize}
\item Check the value of the \var{REQUEST\_METHOD} environment variable. The
\var{getenv} function will retrieve this value this for you.
\item Check the value of the \var{CONTENT\_TYPE} environment variable.
\item Read \var{CONTENT\_LENGTH} characters from standard input. \var{read
(c)} with \var{c} of type \var{char} will take care of that.
\end{itemize}
if you know that the request method will always be \var{POST}, and the
\var{CONTENT\_TYPE} will be correct, then you can skip the first two steps.
The third step can be done easier: read characters until you reach the
end-of-file marker of standard input.

The following example shows how this can be achieved:
\begin{verbatim}
program cgi_post;

uses dos; 

const max_data = 1000;

type datarec = record
  name,value : string;
  end;

var data : array[1..max_data] of datarec;
    i,nrdata : longint;
    c  : char;
    literal,aname : boolean;

begin
writeln ('Content-type: text/html');
writeln;
if getenv('REQUEST_METHOD')<>'POST' then
   begin
   writeln ('This script should be referenced with a METHOD of POST');
   write ('If you don''t understand this, see this ');
   write ('< A HREF="http://www.ncsa.uiuc.edu/SDG/Softare/Mosaic');
   writeln ('/Docs/fill-out-forms/overview.html">forms overview</A>.');
   halt(1);
   end;
if getenv('CONTENT_TYPE')<>'application/x-www-form-urlencoded' then
   begin
   writeln ('This script can only be used to decode form results');
   halt(1)
   end;
nrdata:=1;
aname:=true;
while not eof(input) do
  begin
  literal:=false;
  read(c);
  if c='\' then
     begin 
     literal:=true;
     read(c);
     end;
  if literal or ((c<>'=') and (c<>'&')) then
     with data[nrdata] do
        if aname then name:=name+c else value:=value+c
  else
     begin
     if c='&' then 
         begin
         inc (nrdata);
         aname:=true;
         end 
      else 
         aname:=false;
      end
  end;
writeln ('<H1>Form Results :</H1>');
writeln ('You submitted the following name/value pairs :');
writeln ('<UL>');
for i:=1 to nrdata do writeln ('<LI> ',data[i].name,' = ',data[i].value);
writeln ('</UL>');
end.
\end{verbatim}
While this program isn't shorter than the C program provided as an example
at NCSA, it doesn't need any other units. everythig is done using standard
Pascal procedures\footnote{actually, this program will give faulty results,
since spaces in the input are converted to plus signs by the web browser. 
The program doesn't check for this, but that is easy to change. 
The main concern here is to give the working principle.}.

Note that this program has a limitation: the length of names and values is
limited to 255 characters. This is due to the fact that strings in Pascal
have a maximal length of 255. It is of course easy to redefine the
\var{datarec} record in such a way that longer values are allowed.
In case you have to read the contents of a \var{TEXTAREA} form element,
this may be needed.


% Data passed through an environment variable
\subsection{Data passed through an environment variable}
If your form uses the \var{GET} method of passing it's data, the CGI script
needs to read the \var{QUERY\_STRING} environment variable to get it's data. 
Since this variable can, and probably will, be more than 255 characters long, 
you will not be able to use normal string methods, present in pascal. \fpc
implements the \var{pchar} type, which is a pointer to a null-terminated
array of characters.
And, fortunately, \fpc has a
\seestrings\  unit, which eases the use of the
\var{pchar} type.


The following example illustrates what to do in case of a method of \var{GET}
\begin{verbatim}
program cgi_get;

uses strings,linux; 

const max_data = 1000;

type datarec = record
  name,value : string;
  end;

var data : array[1..max_data] of datarec;
    i,nrdata : longint;
    p  : PChar;
    literal,aname : boolean;

begin
Writeln ('Content-type: text/html');
Writeln;
if StrComp(GetEnv('REQUEST_METHOD'),'POST')<>0 then
   begin
   Writeln ('This script should be referenced with a METHOD of GET');
   write ('If you don''t understand this, see this ');
   write ('< A HREF="http://www.ncsa.uiuc.edu/SDG/Softare/Mosaic');
   Writeln ('/Docs/fill-out-forms/overview.html">forms overview</A>.');
   halt(1);
   end;
p:=GetEnv('QUERY_STRING');
nrdata:=1;
aname:=true;
while p^<>#0  do
  begin
  literal:=false;
  if p^='\' then
     begin 
     literal:=true;
     inc(longint(p));
     end;
  if ((p^<>'=') and (p^<>'&')) or literal then
     with data[nrdata] do
        if aname then name:=name+p^ else value:=value+p^
  else
     begin
     if p^='&' then 
         begin
         inc (nrdata);
         aname:=true;
         end 
      else 
         aname:=false;
      end;
  inc(longint(p));
  end;
Writeln ('<H1>Form Results :</H1>');
Writeln ('You submitted the following name/value pairs :');
Writeln ('<UL>');
for i:=1 to nrdata do writeln ('<LI> ',data[i].name,' = ',data[i].value);
Writeln ('</UL>');
end.
\end{verbatim}
Although it may not be written in the most elegant way, this program does
the same thing as the previous one. It also suffers from the same drawback,
namely the limited length of the \var{value} field of the \var{datarec}.

This drawback can be remedied by redefining \var{datarec} as follows:
\begin{verbatim}
type datarec = record;
      name,value : pchar;
     end;
\end{verbatim}
and assigning at run time enough space to keep the contents of the value
field. This can be done with a
\begin{verbatim}
 getmem (data[nrdata].value,needed_number_of_bytes);
\end{verbatim}
call. After that you can do a 
\begin{verbatim}
strlcopy (data[nrdata].value,p,needed_number_of_bytes);
\end{verbatim}
to copy the data into place.

You may have noticed the following unorthodox call : 
\begin{verbatim}
inc(longint(p));
\end{verbatim}
\fpc doesn't give you pointer arithmetic as in C. However, \var{longints} and
\var{pointers} have the same length (namely 4 bytes). Doing a type-cast to a
\var{longint} allows you to do arithmetic on the \var{pointer}.

Note however, that this is a non-portable call. This may work on the I386
processor, but not on a ALPHA processor (where a pointer is 8 bytes long). 
This will be remedied in future releases of \fpc.


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Producing output
\section{Producing output}
The previous section concentrated mostly on getting input from the web
server. To send the reply to the server, you don't need to do anything
special.You just print your data on standard output, and the Web-server will
intercept this, and send your output to the WWW-client waiting for it.

You can print anything you want, the only thing you must take care of is
that you supply a \var{Contents-type} line, followed by an empty line, as
follows:
\begin{verbatim}
Writeln ('Content-type: text/html');
Writeln;
{ ...start output of the form... }

\end{verbatim}

And that's all there is to it !


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% I'm under Windows, what now ?
\section{I'm under Windows, what now ?}
Under Windows the system of writing CGI scripts can be totally different. 
If you use \fpc under Windows then you also should be able to do CGI 
programming, but the above instructions may not work. They are known to work
for the \file{xitami} server, however.

If some kind soul is willing to write a section on CGI programming under
Windows for other servers, I'd be willing to include it here.
\appendix


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% APPENDIX A.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\chapter{Alphabetical listing of command-line options}
The following is alphabetical listing of all command-line options, as
generated by the compiler:
\begin{verbatim}
ppc386 [options] <inputfile> [options]
put + after a boolean switch option to enable it, - to disable it
  -a     the compiler doesn't delete the generated assembler file
           -al        list sourcecode lines in assembler file
  -B     build all modules
  -C     code generation options
           -CD        create dynamic library
           -Ch<n>     <n> bytes heap (between 1023 and 67107840)
           -Ci        IO-checking
           -Cn        omit linking stage
           -Co        check overflow of integer operations
           -Cr        range checking
           -Cs<n>     set stack size to <n>
           -Ct        stack checking
           -CS        create static library
           -Cx        use smartlinking
  -d<x>  defines the symbol <x>
  -e<x>  set path to executable
  -E     same as -Cn
  -F     set file names and paths
           -FD<x>     sets the directory where to search for compiler utilities
           -Fe<x>     redirect error output to <x>
           -FE<x>     set exe/unit output path to <x>
           -Fg<x>     same as -Fl
           -Fi<x>     adds <x> to include path
           -Fl<x>     adds <x> to library path
           -FL<x>     uses <x> as dynamic linker
           -Fo<x>     adds <x> to object path
           -Fr<x>     load error message file <x>
           -Fu<x>     adds <x> to unit path
           -FU<x>     set unit output path to <x>, overrides -FE
  -g     generate debugger information
           -gg        use gsym
           -gd        use dbx
           -gh        use heap trace unit
  -i     information
           -iD        return compiler date
           -iV        return compiler version
           -iSO       return source OS
           -iSP       return source processor
           -iTO       return target OS
           -iTP       return target processor
  -I<x>  adds <x> to include path
  -k<x>  Pass <x> to the linker
  -l     write logo
  -n     don't read the default config file
  -o<x>  change the name of the executable produced to <x>
  -pg    generate profile code for gprof
  -P     use pipes instead of creating temporary assembler files
  -S     syntax options
           -S2        switch some Delphi 2 extensions on
           -Sc        supports operators like C (*=,+=,/= and -=)
           -Sd        tries to be Delphi compatible
           -Se        compiler stops after the first error
           -Sg        allow LABEL and GOTO
           -Si        support C++ stlyed INLINE
           -Sm        support macros like C (global)
           -So        tries to be TP/BP 7.0 compatible
           -Sp        tries to be gpc compatible
           -Ss        constructor name must be init (destructor must be done)
           -St        allow static keyword in objects
  -s     don't call assembler and linker (only with -a)
  -u<x>  undefines the symbol <x>
  -U     unit options
           -Un        don't check the unit name
           -Up<x>     same as -Fu<x>
           -Us        compile a system unit
  -v<x>  Be verbose. <x> is a combination of the following letters :
           e : Show errors (default)       d : Show debug info
           w : Show warnings               u : Show unit info
           n : Show notes                  t : Show tried/used files
           h : Show hints                  m : Show defined macros
           i : Show general info           p : Show compiled procedures
           l : Show linenumbers            c : Show conditionals
           a : Show everything             0 : Show nothing (except errors)
           b : Show all procedure          r : Rhide/GCC compatibility mode
               declarations if an error    x : Executable info (Win32 only)
               occurs
  -X     executable options
           -Xc        link with the c library
           -XD        link with dynamic libraries (defines FPC_LINK_DYNAMIC)
           -Xs        strip all symbols from executable
           -XS        link with static libraries (defines FPC_LINK_STATIC)

Processor specific options:
  -A<x>  output format
           -Ao        coff file using GNU AS
           -Anasmcoff coff file using Nasm
           -Anasmelf  elf32 (linux) file using Nasm
           -Anasmobj  obj file using Nasm
           -Amasm     obj using Masm (Mircosoft)
           -Atasm     obj using Tasm (Borland)
  -R<x>  assembler reading style
           -Ratt      read AT&T style assembler
           -Rintel    read Intel style assembler
           -Rdirect   copy assembler text directly to assembler file
  -O<x>  optimizations
           -Og        generate smaller code
           -OG        generate faster code (default)
           -Or        keep certain variables in registers (still BUGGY!!!)
           -Ou        enable uncertain optimizations (see docs)
           -O1        level 1 optimizations (quick optimizations)
           -O2        level 2 optimizations (-O1 + slower optimizations)
           -O3        level 3 optimizations (same as -O2u)
           -Op        target processor
                     -Op1  set target processor to 386/486
                     -Op2  set target processor to Pentium/PentiumMMX (tm)
                     -Op3  set target processor to PPro/PII/c6x86/K6 (tm)
  -T<x>  Target operating system
           -TGO32V1   version 1 of DJ Delorie DOS extender
           -TGO32V2   version 2 of DJ Delorie DOS extender
           -TLINUX    Linux
           -TOS2      OS/2 2.x
           -TWin32    Windows 32 Bit
  
  -?     shows this help
  -h     shows this help without waiting
\end{verbatim}


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% APPENDIX B.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\chapter{Alphabetical list of reserved words}
\label{ch:reserved}
\begin{latexonly}
\begin{multicols}{3}
\input{reserved.tex}
\end{multicols}
\end{latexonly}
\begin{htmlonly}
\input{reserved.tex}
\end{htmlonly}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% APPENDIX C.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\chapter{Compiler messages}
\label{ch:ErrorMessages}
This appendix is meant to list all the compiler messages. The list of 
messages is generated from he compiler source itself, and should be faitly
complete. At this point, only assembler errors are not in the list.

% Message file is generated with msg2inc.
\input {messages.tex}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Assembler reader errors
\section{Assembler reader errors.}

This section lists the errors that are generated by the inline assembler reader.
They are {\em not} the messages of the assembler itself.

% General assembler errors.
\subsection{General assembler errors}
\begin{description}
\item [Divide by zero in asm evaluator]
This fatal error is reported when a constant assembler expressions
does a division by zero.

\item [Evaluator stack overflow, Evaluator stack underflow]
These fatal errors are reported when a constant assembler expression
is too big to evaluate by the constant parser. Try reducing the
number of terms.

\item [Invalid numeric format in asm evaluator]
This fatal error is reported when a non-numeric value is detected
by the constant parser. Normally this error should never occur.

\item [Invalid Operator in asm evaluator]
This fatal error is reported when a mathematical operator is detected
by the constant parser. Normally this error should never occur.

\item [Unknown error in asm evaluator]
This fatal error is reported when an internal error is detected
by the constant parser. Normally this error should never occur.

\item [Invalid numeric value]
This warning is emitted when a conversion from octal,binary or hexadecimal
to decimal is outside of the supported range.

\item [Escape sequence ignored]
This error is emitted when a non ANSI C escape sequence is detected in
a C string.

\item [Asm syntax error - Prefix not found]
This occurs when trying to use a non-valid prefix instruction

\item [Asm syntax error - Trying to add more than one prefix]
This occurs when you try to add more than one prefix instruction

\item [Asm syntax error - Opcode not found]
You have tried to use an unsupported or unknown opcode

\item [Constant value out of bounds]
This error is reported when the constant parser determines that the
value you are using is out of bounds, either with the opcode or with
the constant declaration used.

\item [Non-label pattern contains @]
This only applied to the m68k and Intel styled assembler, this is reported
when you try to use a non-label identifier with a '@' prefix.
\item [Internal error in Findtype()]
\item [Internal Error in ConcatOpcode()]
\item [Internal Errror converting binary]
\item [Internal Errror converting hexadecimal]
\item [Internal Errror converting octal]
\item [Internal Error in BuildScaling()]
\item [Internal Error in BuildConstant()]
\item [internal error in BuildReference()]
\item [internal error in HandleExtend()]
\item [Internal error in ConcatLabeledInstr()]
\label{InternalError}
These errors should never occur, if they do then you have found
a new bug in the assembler parsers. Please contact one of the
developers.
\item [Opcode not in table, operands not checked]
This warning only occurs when compiling the system unit, or related
files. No checking is performed on the operands of the opcodes.

\item [@CODE and @DATA not supported]
This Turbo Pascal construct is not supported.
\item [SEG and OFFSET not supported]
This Turbo Pascal construct is not supported.
\item [Modulo not supported]
Modulo constant operation is not supported.
\item [Floating point binary representation ignored]
\item [Floating point hexadecimal representation ignored]
\item [Floating point octal representation ignored]
These warnings occur when a floating point constant are declared in
a base other then decimal. No conversion can be done on these formats.
You should use a decimal representation instead.
\item [Identifier supposed external]
This warning occurs when a symbol is not found in the symolb table, it
is therefore considered external.
\item [Functions with void return value can't return any value in asm code]
Only routines with a return value can have a return value set.

\item [Error in binary constant]
\item [Error in octal constant]
\item [Error in hexadecimal constant]
\item [Error in integer constant]
\label{ErrorConst}
These errors are reported when you tried using an invalid constant expression,
or that the value is out of range.

\item [Invalid labeled opcode]
\item [Asm syntax error - error in reference]
\item [Invalid Opcode]
\item [Invalid combination of opcode and operands]
\item [Invalid size in reference]
\item [Invalid middle sized operand]
\item [Invalid three operand opcode]
\item [Assembler syntax error]
\item [Invalid operand type]
You tried using an invalid combination of opcode and operands, check the syntax
and if you are sure it is correct, please contact one of the developers.

\item [Unknown identifier]
The identifier you are trying to access does not exist, or is not within the
current scope.

\item [Trying to define an index register more than once]
\item [Trying to define a segment register twice]
\item [Trying to define a base register twice]
You are trying to define an index/segment register more then once.

\item [Invalid field specifier]
The record or object field you are trying to access does not exist, or
is incorrect.

\item [Invalid scaling factor]
\item [Invalid scaling value]
\item [Scaling value only allowed with index]
Allowed scaling values are 1,2,4 or 8.


\item [Cannot use SELF outside a method]
You are trying to access the SELF identifier for objects outside a method.


\item [Invalid combination of prefix and opcode]
This opcode cannot be prefixed by this instruction

\item [Invalid combination of override and opcode]
This opcode cannot be overriden by this combination

\item [Too many operands on line]
At most three operand instructions exist on the m68k, and i386, you
are probably trying to use an invalid syntax for this opcode.

\item [Duplicate local symbol]
You are trying to redefine a local symbol, such as a local label.

\item [Unknown label identifer]
\item [Undefined local symbol]
\item [local symbol not found inside asm statement]
This label does not seem to have been defined in the current scope


\item [Assemble node syntax error]
\item [Not a directive or local symbol]
The assembler statement is invalid, or you are not using a recognized
directive.

\end{description}

% I386 specific errors
\subsection{I386 specific errors}

\begin{description}
\item [repeat prefix and a segment override on \var{<=} i386 ...]
A problem with interrupts and a prefix instruction may occur and may cause
false results on 386 and earlier computers.

\item [Fwait can cause emulation problems with emu387]
This warning is reported when using the FWAIT instruction, it can
cause emulation problems on systems which use the em387.dxe emulator.

\item [You need GNU as version >= 2.81 to compile this MMX code]
MMX assembler code can only be compiled using GAS v2.8.1 or later.

\item [NEAR ignored]
\item [FAR ignored]
\label{FarIgnored}
\var{NEAR} and \var{FAR} are ignored in the intel assemblers, but are still accepted
for compatiblity with the 16-bit code model.

\item [Invalid size for MOVSX/MOVZX]

\item [16-bit base in 32-bit segment]
\item [16-bit index in 32-bit segment]
16-bit addressing is not supported, you must use 32-bit addressing.


\item [Constant reference not allowed]
It is not allowed to try to address a constant memory address in protected
mode.

\item [Segment overrides not supported]
Intel style (eg: rep ds stosb) segment overrides are not support by
the assembler parser.

\item [Expressions of the form [sreg:reg...] are currently not supported]
To access a memory operand in a different segment, you should use the
sreg:[reg...] snytax instead of [sreg:reg...]

\item [Size suffix and destination register do not match]
In intel AT\&T syntax, you are using a register size which does
not concord with the operand size specified.

\item [Invalid assembler syntax. No ref with brackets]
\item [ Trying to use a negative index register ]
\item [ Local symbols not allowed as references ]
\item [ Invalid operand in bracket expression ]
\item [ Invalid symbol name:  ]
\item [ Invalid Reference syntax ]
\item [ Invalid string as opcode operand: ]
\item [ Null label references are not allowed ]
\item [ Using a defined name as a local label ]
\item [ Invalid constant symbol  ]
\item [ Invalid constant expression ]
\item [ / at beginning of line not allowed ]
\item [ NOR not supported ]
\item [ Invalid floating point register name ]
\item [ Invalid floating point constant:  ]
\item [ Asm syntax error - Should start with bracket ]
\item [ Asm syntax error - register:  ]
\item [ Asm syntax error - in opcode operand ]
\item [ Invalid String expression ]
\item [ Constant expression out of bounds ]
\item [ Invalid or missing opcode ]
\item [ Invalid real constant expression ]
\item [ Parenthesis are not allowed ]
\item [ Invalid Reference ]
\item [ Cannot use \_\_SELF outside a method ]
\item [ Cannot use \_\_OLDEBP outside a nested procedure ]
\item [ Invalid segment override expression ]
\item [ Strings not allowed as constants ]
\item [ Switching sections is not allowed in an assembler block ]
\item [ Invalid global definition ]
\item [ Line separator expected ]
\item [ Invalid local common definition ]
\item [ Invalid global common definition ]
\item [ assembler code not returned to text ]
\item [ invalid opcode size ]
\item [ Invalid character: < ]
\item [ Invalid character: > ]
\item [ Unsupported opcode ]
\item [ Invalid suffix for intel assembler ]
\item [ Extended not supported in this mode ]
\item [ Comp not supported in this mode ]
\item [ Invalid Operand: ]
\item [ Override operator not supported ]
\end{description}

% m68k specific errors
\subsection{m68k specific errors.}
\begin{description}
\item [Increment and Decrement mode not allowed together]
You are trying to use dec/inc mode together.

\item [Invalid Register list in movem/fmovem]
The register list is invalid, normally a range of registers should
be separated by - and individual registers should be separated by
a slash.
\item [Invalid Register list for opcode]
\item [68020+ mode required to assemble]
\end{description}

\chapter{Run time errors}
The \fpc Run-tim library generates the following errors at run-time
\footnote{The \linux port will generate only a subset of these.}:

\begin{description}
\item [1  Invalid function number]
You tried to call a \dos function which doesn't exist.
\item [2  File not found]
You can get this error when you tried to do an operation on a file which
doesn't exist.
\item [3  Path not found]
You can get this error when you tried to do an operation on a file which
doesn't exist, or when you try to change to, or remove a directory that doesn't exist,
or try to make a subdirectory  of a subdirectory that doesn't exist.
\item [4  Too many open files]
When attempting to open a file for reading or writing, you can get this
error when your program has too many open files.
\item [5  File access denied]
You don't have access to the specified file.
\item [6  Invalid file handle]
If this happens, the file variable you are using is trashed; it
indicates that your memory is corrupted.
\item [12  Invalid file access code]
This will happen if you do a reset or rewrite of a file when \var{FileMode}
is invalid. 
\item [15  Invalid drive number]
The number given to the Getdir function specifies a non-existent disk.
\item [16  Cannot remove current directory]
You get this if you try to remove the current diirectory.
\item [17  Cannot rename across drives]
You cannot rename a file such that it would end up on another disk or
partition.
\item [100  Disk read error]
\dos only. An error occurred when reading from disk. Typically when you try
to read past the end of a file.
\item [101  Disk write error]
\dos only. Reported when the disk is full, and you're trying to write to it.
\item [102  File not assigned]
This is reported by Reset, Rewrite, Append, Rename and Erase, if you call
them with an unassigne function as a parameter.
\item [103  File not open]
Reported by the following functions : Close , Read, Write, Seek,
EOf, FilePos, FileSize, Flush, BlockRead, and BlockWrite if the file isn't
open.
\item [104  File not open for input]
Reported by Read, BlockRead, Eof, Eoln, SeekEof or SeekEoln if the file
isn't opened with Reset.
\item [105  File not open for output]
Reported by write if a text file isn't opened with Rewrite.
\item [106  Invalid numeric format]
Reported when a non-numerice value is read from a text file, when a numeric
value was expected.
\item [150  Disk is write-protected]
(Critical error, \dos only.) 
\item [151  Bad drive request struct length]
(Critical error, \dos only.) 
\item [152  Drive not ready]
(Critical error, \dos only.) 
\item [154  CRC error in data]
(Critical error, \dos only.) 
\item [156  Disk seek error]
(Critical error, \dos only.) 
\item [157  Unknown media type]
(Critical error, \dos only.) 
\item [158  Sector Not Found]
(Critical error, \dos only.) 
\item [159  Printer out of paper]
(Critical error, \dos only.) 
\item [160  Device write fault]
(Critical error, \dos only.) 
\item [161  Device read fault]
(Critical error, \dos only.) 
\item [162  Hardware failure]
(Critical error, \dos only.) 
\item [200  Division by zero]
You are dividing a number by zero.
\item [201  Range check error]
If you compiled your program with range checking on, then you can get this
error in the following cases:
\begin{enumerate}
\item An array was accessed with an index outside its declared range.
\item You're trying to assign a value to a variable outside its range (for
instance a enumerated type).
\end{enumerate} 
\item [202  Stack overflow error]
The stack has grown beyond itss maximum size. This error can easily occur if
you have recursive functions. 
\item [203  Heap overflow error]
The heap has grown beyond its boundaries, ad you are rying to get more
memory. Please note that \fpc provides a growing heap, i.e. the heap will
try to allocate more memory if needed. However, if the heap has reached the
maximum size allowed by the operating system or hardware, then you will get
this error.
\item [204  Invalid pointer operation]
This you will get if you call dispose or Freemem with an invalid pointer
(notably, \var{Nil})
\item [205  Floating point overflow]
You are trying to use or produce too large real numbers. 
\item [206  Floating point underflow]
You are trying to use or produce too small real numbers. 
\item [207  Invalid floating point operation]
Can occur if you try to calculate the square root or logarithm of a negative
number.
\item [210  Object not initialized]
When compiled with range checking on, a program will report this error if
you call a virtal method without having initialized the VMT.
\item [211  Call to abstract method]
Your program tried to execute an abstract virtual method. Abstract methods
should be overridden, and the overriding method should be called.
\item [212  Stream registration error]
This occurs when an invalid type is registered in the objects unit.
\item [213  Collection index out of range]
You are trying to access a collection item with an invalid index.
(objects unit) 
\item [214  Collection overflow error]
The collection has reached its maximal size, and you are trying to add
another element. (objects unit)
\item [216  General Protection fault]
You are trying to access memory outside your appointed memory.
\item [217 Unhandled expetion occurred]
An exception occurred, and there was no exception handler present.
The \file{sysutils} unit installs a default exception handler which catches
all excpetions and exits gracefully.
\end{description}


\chapter{The Floating Point Coprocessor emulator}

In this appendix we note some caveats when using the floating point 
emulator on GO32V2 systems. Under GO32V1 systems, all is as described in
the installation section.

{\em Q: I don't have an 80387. How do I compile and run floating point
   programs under GO32V2?

     Q: What shall I install on a target machine which lacks hardware
   floating-point support?
}

{\em A :}
 Programs which use floating point computations and could be run on
   machines without an 80387 should be allowed to dynamically load the
\file{emu387.dxe}
   file at run-time if needed. To do this you must link the \var{emu387} unit to your
   exectuable program, for example:

\begin{verbatim}
      Program MyFloat;

      Uses emu387;

      var
       r: real;
      Begin
       r:=1.0;
       WriteLn(r);
      end.
\end{verbatim}

   \var{Emu387} takes care of loading the dynamic emulation point library.

   You should always add emulation when you distribute floating-point
   programs.

   A few users reported that the emulation won't work for them unless
   they explicitly tell \var{DJGPP} there is no \var{x87} hardware, like this:

\begin{verbatim}
       set 387=N
       set emu387=c:/djgpp/bin/emu387.dxe
\end{verbatim}

   There is an alternative FP emulator called WMEMU. It mimics a real
   coprocessor more closely.

   {\em WARNING:} We strongly suggest that you use WMEMU as FPU emulator, since
   \file{emu387.dxe} does not emulate all the instructions which are used by the
   Run-Time Libary such as \var{FWAIT}.


{\em   Q: I have an 80387 emulator installed in my AUTOEXEC.BAT, but
   DJGPP-compiled floating point programs still doesn't work. Why?
}


{\em   A :} DJGPP switches the CPU to protected mode, and the information
   needed to emulate the 80387 is different. Not to mention that the
   exceptions never get to the real-mode handler. You must use emulators
   which are designed for DJGPP. Apart of emu387 and WMEMU, the only
   other emulator known to work with DJGPP is Q87 from QuickWare. Q87 is
   shareware and is available from the QuickWare Web site.


{\em   Q: I run DJGPP in an \ostwo DOS box, and I'm told that \ostwo will install
   its own emulator library if the CPU has no FPU, and will transparently
   execute FPU instructions. So why won't DJGPP run floating-point code
   under \ostwo on my machine?
}

{\em   A} : \ostwo installs an emulator for native \ostwo images, but does not
   provide FPU emulation for DOS sessions.


\chapter{A sample \file{gdb.ini} file}
\label{ch:GdbIniFile}

Here you have a sample \file{gdb.ini} file listing, which gives better
results when using \var{gdb}. Under \linux you should put this in a
\file{.gdbinit} file in your home directory or the current directory..  
 
\begin{verbatim}
set print demangle off
set gnutarget auto
set verbose on
set complaints 1000
dir ./rtl/dosv2
set language c++
set print vtbl on
set print object on
set print sym on
set print pretty on
disp /i $eip

define pst
set $pos=&$arg0
set $strlen = {byte}$pos
print {char}&$arg0.st@($strlen+1)
end

document pst
  Print out a pascal string
end    
\end{verbatim}

\end{document}