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<h1>FAQ / Knowledge base</h1>
<p>This document gives last minute information regarding the compiler. Furthermore,
it answers frequently asked questions and gives solutions to common problems
found with Free Pascal. The information presented herein always supersedes those
found in the Free Pascal documentation.
<p> For more comprehensive information on the pascal language, and the runtime library
calls, consult the Free Pascal manuals. Topics covered in this document :
<OL>
<li>General information
<OL>
<li><a href="#WhatIsFP">What is Free Pascal (FPC)?</a>
<li><a href="#versions">Which versions exist, and which one should I use?</a>
<li><a href="#FPandGNUPascal">Free Pascal and GNU Pascal - a comparison</a>
<li><a href="#general-license">License and copyright information</a>
<li><a href="#WhereToGetFP">Getting the compiler</a>
<li><a href="#general-install">Free Pascal installation hints</a>
<li><a href="#ftpproblems">Why do i have to supply a user name and password to get Free Pascal ?</a>
<li><a href="#general-connectftp">Access denied error when connecting to the Free Pascal FTP site</a>
<li><a href="#snapshot">I want a new version NOW</a>
<li><a href="#installsnap">Installing a snapshot</a>
<li><a href="#HOMEWORK">I have to write a program for homework. Can you help?</a>
<li><a href="#windowsapp">How do I make a real Windows application with windows and menu bars?</a>
<li><a href="#game">How do I make a game with Free Pascal? Can I make a game like Doom 3?</a>
<li><a href="#ErrorPos">Getting more information when an application crashes</a>
<li><a href="#general-doesntfindfiles">Compiler seems to skip files in directories -Fu points to</a>
<li><a href="#binariesbig">Why are the generated binaries so big?</a>
<li><a href="#runerror">Runtime errors</a>
<li><a href="#stdunits">Standard units</a>
<li><a href="#debugsmart">Debugging smartlinked code does not fully work</a>
<!--
<li><a href="#debugshared">Debugging shared library (dynamic linked library) code does not fully work</a>
-->
<li><a href="#cantfindunit">Cannot compile a program using a binary-only version of a unit</a>
<li><a href='#isoxpascal'>Will you support ISO Extended Pascal?</a>
<li><a href="#dotnet">What about .NET?</a>
</OL>
<li>Pascal language related information
<OL>
<li><a href="#PortingCPU">Considerations in porting code to other processors</a>
<li><a href="#PortingOS">Considerations in porting code to other operating systems</a>
<li><a href="#OOP">Compiling Delphi code using Free Pascal</a>
<li><a href="#HowcanIbuildaunit">Building a unit</a>
<li><a href="#CompileSystemUnit">Compiling the system unit</a>
<li><a href="#Howdoesprocedureoverloadingwork">How does function overloading work?</a>
<li><a href="#HowToCallCFuncuntions">Calling C functions</a>
<li><a href="#IntegratedAssemblerSyntax">Integrated Assembler syntax</a>
<li><a href="#systemnotfound">Unit system not found errors</a>
<li><a href="#extensionselect">There is a new language extension that would be really useful. Will you include it?</a>
</OL>
<li>Runtime library related information
<OL>
<!--
<li><a href="#HowToUseGraph">Using the graph unit with Free Pascal</a>
-->
<li><a href="#WrongColors">Why do I get wrong colors when using the graph unit?</a>
<li><a href="#fileshare">File sharing and file locks</a>
<li><a href="#filemode">File denied errors when opening files with reset</a>
</OL>
<li>Windows-related information
<OL>
<li><a href="#win-release">Releasing software generated by the windows compiler</a>
<li><a href="#win-debugging">Debugging</a>
<li><a href="#win-dll">Dynamic libraries</a>
<li><a href="#win-profile">Profiling</a>
<li><a href="#win-graph">Graph and problems with keyboard, mouse and "dummy dos windows"</a>
<li><a href="#win-cygwin">Cygwin binary directory in your path sometimes causes builds to fail</a>
<li><a href="#win95-fpc">Using the DOS compiler under Windows 95</a>
<!--
<li><a href="#win-os2">Using OS/2 generated applications under Windows</a>
-->
<li><a href="#win-dos">Using DOS generated applications under windows</a>
<li><a href="#win-ide-mouse">The mouse cursor does not respond in the Windows IDE</a>
</OL>
<li>UNIX-related information
<OL>
<li><a href="#unix-release">Releasing software generated by the UNIX compilers</a>
<li><a href="#unix-debugging">Debugging</a>
<li><a href="#unix-dll">Dynamic libraries</a>
<li><a href="#unix-profile">Profiling</a>
<li><a href="#libci386">Libc is missing on platforms other than i386</a>
<li><a href="#vgamissing">Why can't the linker find "vga"?</a>
<li><a href="#unix-asldmissing">Compiler indicates missing as and ld</a>
<li><a href="#unix-ld219">An error occurred while linking, or "did you forget -T?"</a>
</OL>
<li>OS/2-related information
<OL>
<li><a href="#os2-release">Releasing software generated by the OS/2 compiler</a>
<li><a href="#os2-debugging">Debugging</a>
<li><a href="#os2-dll">Dynamic libraries</a>
<li><a href="#os2-profile">Profiling</a>
<li><a href="#os2-dos">Using DOS generated applications under OS/2</a>
<li><a href="#instal106os2">INSTALL.EXE complains about a missing TZ variable under OS/2</a>
<li><a href="#os2-fp">OS/2 compiler not working after upgrading to 1.9.6 or newer</a>
<li><a href="#os2-as-failing">Compilation under OS/2 fails with error "Can't call the assembler"</a>
</OL>
<li>DOS-related information
<OL>
<li><a href="#dos-release">Releasing software generated by the DOS compiler</a>
<li><a href="#dos-debugging">Debugging</a>
<li><a href="#dos-dll">Dynamic libraries</a>
<li><a href="#dos-profile">Profiling</a>
<li><a href="#FPwithoutfpu">Running Free Pascal without a math coprocessor</a>
<li><a href="#fp386">Applications created with Free Pascal crash on 80386 systems</a>
<li><a href="#nomousegraph">The mouse cursor is not visible in graphics screens</a>
<li><a href="#accessioports">Accessing I/O ports</a>
<li><a href="#HowToAccessDosMemory">Accessing DOS memory / Doing graphics programming</a>
<li><a href="#dos-stack">Changing the default stack size</a>
<!--
<li><a href="#dos-os2">Using OS/2 generated applications under DOS</a>
-->
</OL>
<!--
<li>BeOS-related information
<OL>
<li><a href="#beos-release">Releasing software generated by the BeOS compiler</a>
<li><a href="#beos-debugging">Debugging</a>
<li><a href="#beos-dll">Dynamic libraries</a>
<li><a href="#beos-profile">Profiling</a>
<li><a href="#beos-linking">BeOS linking problems</a>
</OL>
-->
<!--
<li>Amiga-related information
<OL>
<li><a href="#amiga-release">Releasing software generated by the Amiga compiler</a>
<li><a href="#amiga-debugging">Debugging</a>
<li><a href="#amiga-dll">Dynamic libraries</a>
<li><a href="#amiga-profile">Profiling</a>
</OL>
<li>PalmOS-related information
<OL>
<li><a href="#palmos-release">Releasing software generated by the PalmOS compiler</a>
<li><a href="#palmos-debugging">Debugging</a>
<li><a href="#palmos-dll">Dynamic libraries</a>
</OL>
-->
</OL>
<OL>
<li><h2>General information</h2>
<OL>
<li><a name='WhatIsFP'></a>
<h3>What is Free Pascal (FPC)?</h3>
<p>Originally named FPK-Pascal, the Free Pascal compiler is a 16,32
and 64 bit Turbo Pascal and Delphi compatible Pascal compiler for
Linux, Windows, OS/2, FreeBSD, Mac OS X, DOS and
several other platforms (the number of supported targets grows
all the time, although not all of them are on the same level as
the main ones).
<p>The Free Pascal compiler is available for several
architectures: x86 (16,32 and 64 bit), ARM, PowerPC (32 and 64 bit),
SPARC (v8, v9), Java Virtual Machine (under development) and MIPS (little and big endian, under development).
An older version (the 1.0 series) and current development versions also supported m68k.
<p>The compiler is written in Pascal and is able to compile its
own sources. The source files are distributed under the GPLv2+ and included.
<p>Short history:
<ul>
<li>06/1993: project start
<li>10/1993: first small programs work
<li>03/1995: the compiler compiles its own sources
<li>03/1996: released on the Internet
<li>07/2000: 1.0 released
<li>12/2000: 1.0.4 released
<li>04/2002: 1.0.6 released
<li>07/2003: 1.0.10 released
<li>05/2005: 2.0.0 released
<li>12/2005: 2.0.2 released
<li>08/2006: 2.0.4 released
<li>09/2007: 2.2.0 released
<li>08/2008: 2.2.2 released
<li>04/2009: 2.2.4 released
<li>12/2009: 2.4.0 released
<li>11/2010: 2.4.2 released
<li>05/2011: 2.4.4 released
<li>01/2012: 2.6.0 released
<li>02/2013: 2.6.2 released
<li>03/2014: 2.6.4 released
<li>01/2015: 3.0.0 released
<li>02/2017: 3.0.2 released
<li>xx/2017: 3.0.4 released
</ul>
<li><a name='versions'></a>
<h3>Which versions exist, and which one should I use?</h3>
<p>The latest official version is 3.0.4, the third release in the 3.0.x series.
New development is performed in the 3.1.x series, which will eventually
be released as 3.2.0 or 4.0.0, depending on milestones achieved.
<h4>Historic versions</h4>
<p>FPC's version numbering changed a few times over the years. Pre-1.0 versioning information has been
moved to the <a href="http://wiki.freepascal.org/1.0_versioning">Wiki 1.0 versioning article.</a>
<h4>Modern versioning</h4>
<p>With the release of 1.0, the version numbering was
slightly changed to a system resembling one used for the Linux
kernels.
<p>
<ul>
<li>Releases that only fix bugs in version 1.0 are numbered 1.0.x.
<li>Post-1.0 development (the so called snapshots) have version number
1.1.x.
<li>Eventually the 1.1.x versions, when stabilized, were released
as the 2.0.x series, preceded by betas marked as 1.9.x. Fixes to the
2.0 release were numbered 2.0.x, fixes to the 2.2 release 2.2.x, fixes to the 2.4 release as 2.4.x etc</li>
<li>The new development version after the 2.4.0 release was numbered 2.5.x
and so on.
<li>Repackagings that affect sources are indicated with a single letter as
suffix (e.g. 2.0.4a). This is usually the case for platforms that weren't part of the original release round.
<li>The stable branch (currently, fixes_3_0, previously fixes_2_6) always has an odd last number (2.6.1, 2.6.3 and 3.0.1).
Compilers with such versions are snapshots, and e.g. a snapshot with 2.6.1 can
be anywhere between 2.6.0 and the moment 2.6.2 branched off (Jan 2013). Likewise,
after the release of 2.6.2 the fixes_2_6 branch identified itself as version 2.6.3 till 2.6.4 branched off (typically
two months before its release). After 2.6.4, the stable branch's number was updated to 2.6.5,
after 3.0.0 to 3.0.1 etc.
</ul>
<p>
<p>Normally, you would want to use a release. Releases are considered
stable, and easier to support (the bugs, quirks and unintended
"features" are well known after a period of time, and workarounds
exist).
<p>Development snapshots (which are generated daily) reflect the current
status of the compiler. Development versions probably have new features
and larger bugs fixed since the last release, but might have some
temporary stability drawbacks (which are usually fixed by the next day).
<p>Development snapshots are often quite useful for certain categories of
users. Ask on the mailing lists if it is worth the trouble in your case if
you are not sure.
<p>Snapshots of the stable branch (fixes_3_0) are meant to test release engineering. They are
mainly interesting in the months before a release to extensively
test the branch from which the release is created.
<p>We advise all users to upgrade to the newest version for their
target (preferably the new stable 3.0.x series).
<p> A graphical timeline of the FPC project plus its near future would
be:
<img src="pic/timeline.png">
<li><a name='FPandGNUPascal'></a>
<h3>Free Pascal and GNU Pascal - a comparison</h3>
<DL>
<DT><b>Aim:</b>
<DD>Free Pascal tries to implement a Borland compatible pascal
compiler on as many platforms as possible. GNU Pascal tries to
implement a portable pascal compiler based on POSIX.
<DT><b>Version:</b>
<DD>Currently, Free Pascal is at version 3.0.0 (November 2015). GNU Pascal is stopped
version 2.1 (from 2002, which can be built with several different GCC's as backend;
their Mac OS X version is an exception though, as it follows the GCC version number).</DD>
<DT><b>Tracking:</b>
<DD>Between releases, development versions of FPC are available through daily snapshots
and the source via SVN. GPC issues a set of patches to the last version a few times
a year, and there are regular snapshot for OS X and Windows, made by users.
<DT><b>Operating systems:</b>
<DD>Free Pascal runs on a large number of platforms,
inlcuding DOS (16/32-bit), Win32 (no UNIX porting layer needed), Linux, FreeBSD,
NetBSD, OS/2, BeOS, Mac OS X, on the following architectures:
x86 (32 and 64 bit),
SPARC, PowerPC (32 and 64 bit), ARM, Java Virtual Machine (under development), and
MIPS (under development).
GNU Pascal runs basically on any system that supported by GCC, and for which the build process was verified.
<DT><b>Bootstrapping:</b>
<DD>FPC requires a suitable set of binutils (AS, AR, LD) on some platforms, GNU make and a command line bootstrap compiler. New architectures/OSes are cross-compiled.
GPC bootstraps via a suitable version of GCC, and requires a full set of binutils, flex, bison, gmake, a POSIX shell and libtool
<DT><b>Sources:</b>
<DD>Free Pascal is entirely written in Pascal, while GNU Pascal is written in C (it's an adaptation of the GNU
C compiler)
<DT><b>Language:</b>
<DD>Free Pascal supports the Borland Pascal dialect,
implements the Delphi Object Pascal language, Objective-Pascal and has some support for ISO 7185 Pascal and Mac Pascal extensions.
GNU Pascal supports ISO 7185, ISO 10206 and (most of) Borland Pascal 7.0
<DT><b>Extensions:</b>
<DD>Free Pascal implements method, function and operator overloading (later Delphi versions have also added these, so strictly they are not extensions anymore)
GNU Pascal implements operator overloading.
<DT><b>License:</b>
<DD>Both compilers come under the GNU GPL.
<DT><b>Author:</b>
<DD>Free Pascal was started by Florian Klämpfl, Germany
(florian@freepascal.org), GNU Pascal was started by Jukka Virtanen,
Finland (jtv@hut.fi). </DD></DL><br>
<li><a name='general-license'></a>
<h3>License and copyright information</h3>
<p> Applications created by the compiler and using the runtime
library (RTL) come under a modified Library GNU Public License (LGPL).
This license does not impose any kind of license on the created applications. It is therefore possible to create closed source
or proprietary software using the Free Pascal Compiler.
<p>The following exception has been added to the LGPL variant
that applies to the FPC RTL:<p><I> As a special
exception, the copyright holders of this library give you
permission to link this library with independent modules to
produce an executable, regardless of the license terms of
these independent modules, and to copy and distribute the
resulting executable under terms of your choice, provided
that you also meet, for each linked independent module, the
terms and conditions of the license of that module. An
independent module is a module which is not derived from or
based on this library. If you modify this library, you may
extend this exception to your version of the library, but
you not obligated to do so. If you do not wish to do so,
delete this exception statement from your version.</I>
<p>Please note that you still have to comply to the LGPL as far as sources of the runtime library itself are concerned. This, for example,
requires you to provide the source code of the runtime library if a recipient of your application asks for it. If you want
to write proprietary closed source software, please comply with the following terms:
<ul>
<li>Most people can satisfy the source code requirement by mentioning
that the RTL source code can be downloaded at the Free Pascal
web site: if you did not modify the rtl this is considered adequate to
satisfy the LGPL requirement of providing source code.
<li>If you made modifications to the runtime library, you cannot keep them
for yourself, you must make them available if requested by recipients of your application.
<li>Distribute the modified LGPL license with your product, indicating to which parts of your application it applies (the FPC RTL).
</ul>
<p> The compiler source code, on the other hand, comes under
the GNU General Public License, which means that the compiler
source can only be used in software projects that are distributed
under a compatible license (or that are not distributed at all).
<li><a name='WhereToGetFP'></a>
<h3>Getting the compiler</h3>
<p>The latest official stable Free Pascal release is available for download
from all <a href="http://www.freepascal.org/download.var">official mirrors</a>
<li><a name='general-install'></a>
<h3>Free Pascal installation hints</h3>
<ul>
<li> Do not install the compiler in a directory that has spaces
in its name, since some of the compiler tools do not like these
</ul>
<li><a name='ftpproblems'></a>
<h3>Why do i have to supply a user name and password to get Free Pascal ?</h3>
<p> You are trying to login to an ftp site. You have to use the login name
"anonymous" and your e-mail address as your password.
<li><a name='general-connectftp'></a>
<h3>Access denied error when connecting to the Free Pascal FTP site</h3>
<p>The Free Pascal main ftp site can only accept a maximum number of
simultaneous connections. If this error occurs, it is because
this limit has been reached. The solution is either to wait and
retry later, or better still use one of the Free Pascal mirror sites.
<li><a name='snapshot'></a>
<h3>I want a new version NOW</h3>
<p>In the time between the release of new official versions, you can
have a look at and test developer versions (so-called "snapshots"). Be
warned though: this is work in progress, so in addition to old bugs
fixed and new features added, this may also contain new bugs.
<p>Snapshots are generated automatically each night from the current
source at that moment. Sometimes this may fail due to bigger changes not
yet fully implemented. If your version does not work, try again one or
two days later.
<p>The latest snapshot can always be downloaded from the <A
href="http://www.freepascal.org/develop.var#snapshot">development</a>
web page.
</trn>
<li><a name='installsnap'></a>
<h3>Installing a snapshot</h3>
<p>To install a snapshot, extract the zip archive into the existing
program directory of the last official version of Free Pascal (after
making a backup of the original, of course). You can also extract it into
an empty directory and then move the files to the program directory,
overwriting existing files.
<li><a name='HOMEWORK'></a>
<h3>I have to write a program for homework. Can you help?</h3>
<p>No. Please, don't send us mail about homework, we are no teachers.
The Free Pascal development team tries to give good support for the Free
Pascal compiler and are trying to always reply to emails. If we get
emails like this, this becomes harder and harder.
<li><a name="windowsapp"></a>
<h3>How do I make a real Windows application with windows and menu bars?</h3>
The easiest way is to <a href='http://www.lazarus.freepascal.org'>download Lazarus</a>.
It won't be just a Windows application, it will also work under Linux, FreeBSD and
Mac OS X.
<li><a name="game"></a>
<h3>How do I make a game with Free Pascal? Can I make a game like Doom 3?</h3>
Yes, you can make games with Free Pascal and if you are really good you can make
a game like Doom 3. Making games is difficult, you need to be an experienced
programmer to make them. The web site <a href='http://www.pascalgamedevelopment.com'>
www.pascalgamedevelopment.com</a> is a community of people who program games in Free
Pascal and Delphi.
<p>
If you want a start, please start to study <a href='http://sourceforge.net/projects/jedi-sdl/'>JEDI-SDL</a>
or <a href='http://ptcpas.sourceforge.net'>PTCPas</a>. Also you can try to study an existing game, for example
<a href='http://www.lugato.net/thesheepkiller/'>The Sheep Killer</a> is a very simple game and it should not be
very hard to understand its code.
<li><a name='ErrorPos'></a>
<h3>Getting more information when an application crashes</h3>
<OL>
<li>The easiest possibility is to recompile your program with -gl
debugging option. This way unit LineInfo is automatically linked in,
and the printout after a program crash then contains source line
numbers in addition to addresses of the crash. To see runtime library (RTL)
functions in the backtrace with their real name, you have to recompile
the RTL with -gl too.
<li>For more comprehensive checking, compile the
program with debugging information (use the -g command line option)
<li>Load the program in the debugger <PRE>gdb --directory=<src dirs> myprog.exe</PRE>Notes:
<ul>
<li>Under UNIX systems (Linux, the BSD's), don't add the ".exe" after myprog
<li>"<TT>src dirs</TT>" is a list of directories containing the
source code files of myprog and the units it uses seperated by
semi-colons (";") on Windows, or colons (":") on UNIX platforms. The current directory is automatically included.
</ul>
<li>Once inside the debugger, you can (optionally) set the command
line options that will be passed to your program using the command
"<TT>set args <option1 option2 ...></TT>"
<li>To start the program, type "<TT>run</TT>" and press enter
<li>After the program has crashed, the address of the instruction
where the crash occurred will be shown. The debugger will try to
display the source code line corresponding with this address. Note
that this can be inside a procedure of the RTL, so the source may not
always be available and most likely the RTL wasn't compiled with
debugging information.
<li>If you then type "<TT>bt</TT>" (BackTrace), the addreses on the
call stack will be shown (the addresses of the procedures which were
called before the program got to the current address). You can see
which source code lines these present using the command
<PRE>info line *<address></PRE>For example:<PRE>info line *0x05bd8</PRE>
</OL>
<li><a name='general-doesntfindfiles'></a>
<h3>Compiler seems to skip files in directories that -Fu points to</h3>
<p>This sometimes happens with installation/compilation scripts if the
copying command doesn't preserve dates. The object files get older than
the PPU file, and the compiler tries to recompile them. A simple <TT>touch</TT>
will solve it.
<p>
Also note that FPC, contrary to Turbo Pascal keeps track of include files. Modified
include files or duplicate names can trigger an attempt to recompile.
<li><a name='binariesbig'></a>
<h3>Why are the generated binaries so big?</h3>
There are several reasons and remedies for this:
<OL>
<li>
You can create smartlinked applications. To turn on
the generation of smartlinkable units, use the -CX command
line option when compiling your units. To turn on
the linking of previously generated smarlinkable units, use the -XX
command line option when compiling a program.
<li>Normally, all symbol information is included in the resulting
program (for easier debugging). You can remove this by using the -Xs
command line option when compiling your program (it will not do
anything when compiling units)
<li>Turn on optimisations, both for supplied packages (RTL, FV, FCL)
and for your own code, this will also decrease the code size.
</OL>
Generally Free Pascal generates smaller binaries than modern competing compilers,
however, it does not hide code in large dynamic libraries. Free Pascal generates
larger binaries than compilers from long ago do. Large framework libraries result
in larger executables.
See also the <a href="http://wiki.freepascal.org/Size_Matters">Size Matters wiki entry</a>.
<li><a name='runerror'></a>
<h3>Runtime errors</h3>
<p> When an application generated by FPC terminates in an abnormal way,
it is very likely that a runtime error will be
generated. These errors have the form :
<PRE>
Runtime error 201 at $00010F86
$00010F86 main, line 7 of testr.pas
$0000206D
</PRE>
<p> The 201 in this case indicates the runtime error
number. The definition of the different runtime error numbers is
described in the Free Pascal user's manual, Appendix D. The
hexadecimal numbers represent the addresses on the call stack when the error occured.
<li><a name='stdunits'></a>
<h3>Standard units</h3>
<p> To see the list of base units supplied with Free Pascal, and
on which platform they are supported, consult the Free Pascal user's manual.
There is also a short description of what each unit does in the same section
of the manual.
<!--
<li><a name=internaldocs></a>
<h3>How does the compiler work internally?</h3>
<p>A draft document describing the internals of the Free Pascal compiler is
available <a href="ftp://ftp.freepascal.org/pub/fpc/docs/fpc-int10.zip">here</a>.
-->
<li><a name=debugsmart></a>
<h3>Debugging smartlinked code does not fully work</h3>
<p>Debugging smart linked code might not work correctly. This is
due to the fact that no type information is emitted for
smartlinked code. If this would not be done, the files
would become enormous.
<p> While debugging, it is not recommended to use the
smartlinking option.
<!--
<li><a name=debugshared></a>
<h3>Debugging shared library (dynamic linked library) code does not fully work</h3>
<p>Debugging shared libraries (or dynamic linked libraries) produced
by the Free Pascal compiler is not officially supported.
-->
<li><a name='cantfindunit'></a>
<h3>Cannot compile a program using a binary-only version of a unit</h3>
<p>
Sometimes, even though there is a binary version of a module (unit file and object file)
available, the compiler claims it cannot find the unit This can be caused either by an
incompatibility in the PPU file format (which can change across
compiler versions), or by a change in one of the units of the RTL
that has changed in between releases.
<p>
To get more information, compile the code using the -vtu (show tried and used unit information)
compiler switch, and the unit loading phase will be displayed. You might
discover that the unit being loaded requires to be recompiled because one
of the unit it uses has changed.
<p>If you plan on distributing a module without the source code, the binaries
should be compiled and made available for all versions of the compiler you
wish to support, otherwise compilation errors are bound to occur.
<li><a name='isoxpascal'></a>
<h3>Will you support ISO Extended Pascal?</h3>
FPC's primary goal is to be a Turbo Pascal and Delphi-compatible compiler, and it also
supports a subset of the Mac-Pascal dialect and of Standard ISO Pascal. While in theory it would be possible
to add a complete ISO Standard or Extended Pascal modes, until now no people interested in
such functionality have stepped up to work on such features.
<p>
<a href="http://www.gnu-pascal.de/">GNU-Pascal</a> is however a modern compiler that can
compile ISO Extended Pascal. If you have any need for the ISO Extended Pascal dialect, we
recommend you to take a look at this compiler.
<li><a name='dotnet'></a>
<h3>What about .NET?</h3>
Occasionally, users ask about a FPC that supports .NET, or our
plans in that direction. <p>
Mainly the users are either interested because of .NET's
portability aspects (Mono is quoted over and over again), or
because it is supposed to be the next big thing in Windows
programming, and they think Windows programming will not be possible
in the future.<p>
While the FPC core developpers are somewhat interested out of
academic curiousity (mainly because it could be a pilot for a
generalized backend creating bytecode) there are however several
problems with .NET in combination with FPC:
<OL>
<li>
Pascal is a language that uses pointers, and existing codebases
can only be unmanaged. Unmanaged code is not portable under .NET,
so that already kills most possible benefits. This also means that
existing FPC and Delphi code won't run on .NET. There are more
such little language problems.</li>
<li>FPC's libraries are not based on .NET classes and data models (and
cannot be changed to do so without effectively rewriting them),
moreover the libraries could only be unmanaged too, or they
would be incompatible</li>
<li>There is nothing <em>practical</em> known yet about how portable
an average .NET program will be. Little experiments with hello
world level code mean nothing, that kind of code works with
nearly any language. A good test would be to see existing non trivial
codebases run unmodified under mono, that were not designed with mono
in mind. Just like we try to do for
Delphi</li>
<li> The fact that on Windows 80% of the .NET code seems to be
ASP.NET does not help either. This makes porting existing code
less useful (since ASP.NET is tied to IIS), and new codebases of
portable code can be set in nearly every language </li>
<li>Operating System dependant code would not work anymore, since
the Win32/64 interface is unmanaged.
</OL> <p>
So effectively this means that for FPC to benefit from .NET you
would have to significantly adapt the language (thus compiler) and
libraries, and be incompatible with the existing native sourcecode.
Moreover
that also means that existing apps would have to be rewritten for
.NET, since it would take more than a simple recompile with a
FPC/.NET compiler.<p>
While unmanaged code has some uses (easier integration with managed
code inside Windows), this still requires writing a code generator and
defining interfaces and libraries. This means a <b>lot of work</b> and
since .NET take-up is not really high, this might not be worth it. <p>
However if a FPC user does the bulk of the work (e.g. a bytecode
codegenerator, and maybe some base libraries) and if the work is
suitable for inclusion in FPC (a very big if), we will of course
include it.<p>
Since support for <a href="http://wiki.freepascal.org/FPC_JVM">generating JVM bytecode</a> has been added to the
compiler, such a project may be more realistic now than it has been
in the past. Many of the caveats mentioned above still hold though:
language compatibility is not 100% and most standard units will have
to be reimplemented.<p>
</OL>
<li><h2>Pascal language related information</h2>
<OL>
<li><a name='PortingCPU'></a>
<h3>Considerations in porting to other processors</h3>
<p>Because the compiler supports multiple processor architectures, it
is important to take a few precautions so that your code will execute
correctly on all processors.
<ul>
<li>Limit your use of asm statements unless it is time critical code
<li>Try not to rely on the endianness of the specific machines when performing operations depending on data layout. In particular, reading and writing binary data
to/from files will probably require byte swaps across different endianness
machines (swapendian is your friend in this case). Freepascal defines
<CODE>FPC_LITTLE_ENDIAN</CODE> or <CODE>FPC_BIG_ENDIAN</CODE> to indicate the
target endianness.
<li>Try limiting your local variables in subroutines to 32K, as this
is the limit of some processors. Use dynamic allocation instead.
<li>Try limiting the size of parameters passed to subroutines to 32K,
as this is the limit of some processors. Use const or var parameters
where appropriate.
<li><TT>CPU16</TT>,<TT>CPU32</TT> or <TT>CPU64</TT> is defined indicating
whether the target is a 16,32-bit or 64-bit cpu. This can help with
incorporating 16,32-bit and 64-bit specific code.
<li>Use the <TT>ptruint</TT> type when declaring an ordinal that will store
a pointer, since pointers can be either 32-bit or 64-bit depending on
the processor and operating system. For 16-bit it is memory model dependent.
</ul>
<p>
<li><a name='PortingOS'></a>
<h3>Considerations in porting code to other operating systems</h3>
<p>Because the compiler supports several different operating systems,
is important to take a few precautions so that your code will execute
correctly on all systems.
<ul>
<li>File sharing is implemented differently on different operating
systems, so opening already opened files may fail on some operating
systems (such as Windows). The only correct way to make sure to
have the same file sharing behavior is to use the I/O routines
provided by the <TT>sysutils</TT> unit.
<li>Clean up at the end of your program, i.e. close all files on exit, and
release all allocated heap memory, as some operating systems do not like it
when some things are left allocated or opened.
<li> Some operating systems limit the stack space that can be allocated,
therefore it is important to limit subroutine nesting, and the number of
local variables. Limiting total stack space usage at a given moment to
at most 256 KBytes will make porting easier.
<li> Do not hardcode paths to files, try to use relative paths
instead
<li> Use the following constants (defined in the system unit)
to get information on files, line endings, and to build paths:
<ul>
<li> <TT>LineEnding</TT> : Indicates the characters which end a text line
<li> <TT>LFNSupport</TT> : Indicates if long filenames are supported (more than 8.3 characters)
<li> <TT>DirectorySeparator</TT> : The character or characters that separate path components
<li> <TT>DriveSeparator</TT> : The character that separates the drive specification from the rest
of the path
<li> <TT>PathSeparator</TT> : The character that separates directories in the path lists (such as the search path)
<li> <TT>FileNameCaseSensitive</TT> : Boolean indicating if the filenames for this system may be case-sensitive or not
<li> <TT>AllFilesMask</TT> : String containing a wildcard expression for all files
</ul>
It is also possible to use the <TT>PathDelim</TT>, <TT>PathSep</TT> and <TT>DriveDelim</TT> constants
defined in the <TT>sysutils</TT> unit.
</ul>
<p>
<li><a name='OOP'></a>
<h3>Compiling Delphi code using Free Pascal</h3>
<p>The compiler supports Delphi-style classes. Make sure you use the -S2 or
-Sd command line switches (see the manuals for the meaning of these switches), or add <tt>{$mode objfpc}</tt> or <tt>{$mode delphi}</tt> to your source code. For a
list of Delphi incompatibilities also check the manual.
<li><a name='HowcanIbuildaunit'></a>
<h3>Building a unit</h3>
<p>It works like in Turbo Pascal. The first keyword in the file must be
UNIT (not case sensitive). The compiler will generate two files:
<TT>XXX.PPU</TT> and <TT>XXX.O</TT>. The PPU file contains the interface
information for the compiler and the O-file the machine code (an object
file, whose precise structure depends on the assembler you used). To use
this unit in another unit or program, you must include its name in the
USES clause of your program.
<li><a name='CompileSystemUnit'></a>
<h3>Compiling the system unit</h3>
<p>To recompile the system unit, it is recommended to have GNU make
installed. typing 'make' in the rtl source directory will then recompile
all RTL units including the system unit. You may choose to descend into
the directory of your OS (e.g. rtl/linux) and do a 'make' there.
<p>It is possible to do all this manually, but you need more detailed
knowledge of the RTL tree structure for that.
<li><a name='Howdoesprocedureoverloadingwork'></a>
<h3>How does procedure overloading work?</h3>
<p>Here is a procedure overloading example in FPC or ObjFPC mode:
<PRE>
procedure a(i : integer);
begin
end;
procedure a(s : string);
begin
end;
begin
a('asdfdasf');
a(1234);
end.
</PRE>
<p>You must be careful. If one of your overloaded functions is in the
interface part of your unit, then all overloaded functions must be in
the interface part. If you leave one out, the compiler will complain
with a 'This overloaded function can't be local' message. Overloaded
functions must differ in their parameters; it is not enough if only their
return types are different.
<li><a name='HowToCallCFuncuntions'></a>
<h3>Calling C functions</h3>
<p>
It is possible to call functions written in C and compiled
by the GNU C compiler (<TT>GCC</TT>). E.g., for calling the
C function strcmp, declare the following (the <tt>cint</tt> type is
declared in the <tt>ctypes</tt> unit):
<PRE>function strcmp(s1 : pchar;s2 : pchar) : cint;cdecl;external;</PRE>
<li><a name='IntegratedAssemblerSyntax'></a>
<h3>Integrated Assembler syntax</h3>
<p>The default assembler syntax (AT&T style) is different from the
one in Borland Pascal (Intel style). FPC however supports both styles.
See the documentation for more info on how to use
different assembler styles.
<p>A description of the AT&T syntax can be found in the GNU
Assembler documentation.
<li><a name='systemnotfound'></a>
<h3>Unit system not found errors</h3>
<p>System is Pascal's base unit and is implicitly used by all programs.
This unit defines several standard procedures and structures, and must be found to
be able to compile any Pascal program by FPC.
<p>The location of the system and other unit files is passed on to the
compiler by the -Fu switch. This switch can be specified on the command line, but is usually located in the fpc.cfg configuration file.
<p>If the compiler cannot find this unit, there are three possible causes:
<OL>
<li>The fpc.cfg file is not in the same directory as the compiler
executable (msdos,go32v2, win32 and OS/2) or cannot be found as
"/etc/fpc.cfg" or ".fpc.cfg" in your homedirectory (UNIX platforms).
<li>The fpc.cfg file does not contain the -Fu parameter, or a wrong one.
See the <a href="http://www.stack.nl/~marcov/buildfaq.pdf">build faq (PDF)</a>, especially the chapters
about the fpc.cfg and the directory structure.
<li>The unit files ARE found, but are the wrong version or for a different platform. Correct
fpc.cfg to point to the right versions or reinstall the right
versions (this can e.g. happen if you try to use a <A
href="#snapshot">snapshot</a>
compiler while the -Fu statement in the used fpc.cfg still points to
the RTL that came with the official release compiler).
</OL>
<p>A handy trick can be executing "fpc programname -vtu". This will show
where the compiler is currently looking for the unit files. You
might want to pipe this through more (Dos, OS/2, Windows) or less
(UNIX), since it can generate more than one screen information:
<p>
<PRE>
Dos, OS/2, Windows: fpc programname -vt |more<br>
UNIX, Linux: fpc programname -vt |less<br>
</PRE>
<p>
<li><a name='extensionselect'></a>
<h3>There is a new language extension that would be really useful. Will you include it?</h3>
Occasionally somebody asks for a new language extension on the maillist,
and the discussions that follow have a recurring pattern. An
extension is quite a big deal for the FPC team, and there are
some criteria that are used to select if an extension is
"worth" the trouble. The most important pre-selection criteria are:
<OL>
<li>Compatibility must not be compromised in any way. Existing
codebases on at least the Pascal level must keep
running. This is often more difficult than most people
think.
<li>The extension must have real value. Anything that is only
a shorter notation does not apply, unless it is
out of compatibility with an existing Pascal/Delphi
codebase. Practically it means it must make something
possible that cannot be done otherwise or be a compatibility
item
<li>The change must fit in with the scope of the project:
implementing a Pascal compiler with support for RAD
and a generic DB system. This excludes features like
inline SQL, and large garbage collected object frameworks.
</OL>
Exceptions to the second rule are sometimes made for
platform-specific reasons (e.g. interfacing to some other language or
OS). The first rule is often a problem, because issues are not
easily recognizable unless one has tried to make extensions
before. Best is to make a thoroughly written proposal that the
developers can review, including
<ul><li>an explanation of the feature
<li> why it is needed, what does it make possible?
<li> how you would implement it?
<li> many examples of typical use, and tests for possible problem
cases
</ul>
Try to be verbose and really try to view this from the viewpoint
of somebody who has to implement it, and try to make examples
that span multiple units and procedures, and review what happens.
Be critical, try to punch holes in your
own reasoning and find possible problematic cases, and document
them.
<p>
Besides these pre-selection rules and documentation, the other
important question is who is going to do the work. Keep in mind
that the FPC developers are volunteers with todo-lists that are
booked till the next decade. You cannot expect they will
drop everything from their hands and implement the feature
because you need it urgently, or think it is nice. If you are
not willing to implement it yourself, submit patches and maintain
it in the future,
chances are slim. Remarks as "this will attract a lot of
users because..." are considered with a lot of scepsis, since
that applies to any new development.
</OL>
<li><h2>Runtime library related information</h2>
<OL>
<!--
<li><a name='HowToUseGraph'></a>
<h3>Using the graph unit with Free Pascal</h3>
<p>Since version 1.0, we have a completely platform independent way
of selecting resolutions and bitdepths. You are strongly encouraged to
use it, because other ways will probably fail on one or other platform.
See the documentation of the graph unit for more information.
-->
<li><a name=WrongColors></a>
<h3>Why do I get wrong colours when using the graph unit?</h3>
<p>If you use <TT>detect</TT> as graphdriver, you will end up with the
highest supported bitdepth. Since the graph unit currently only supports
up to 16 bits per pixel modes and since this bitdepth is supported by
virtually all graphics cards, you will most likely get a 16 bit mode.
<p>The main problem is that in 16 (and 15, 24, 32, ...) bit modes, the
colors are not set anymore using an index in a palette (the palettized
way is called "indexed color"). In these modes, the color number itself
determines what color you get on screen and you can not change this color.
The color is encoded as follows (for most graphics cards on PC's at
least):
<ul>
<li>15 bit color: lower 5 bits are blue intensity, next come 5 bits of
green and then 5 bits of red. The highest bit of the word is ignored.
<li>16 bit color: lower 5 bits are blue intensity, next come *6* bits
of green and then 5 bits of red.
</ul>
<p>This means that either you have to rewrite your program so it can
work with this so-called "direct color" scheme, or that you have to use
<TT>D8BIT</TT> as graphdriver and <TT>DetectMode</TT> as graphmode. This
will ensure that you end up with a 256 (indexed) color mode. If there
are no 256 color modes supported, then graphresult will contain the
value <TT>GrNotDetected</TT> after you called InitGraph and you can
retry with graphdriver <TT>D4BIT</TT>.
<li><a name='fileshare'></a>
<h3>File sharing and file locks</h3>
<p> The standard runtime library file I/O routines open
files in the default sharing mode of the operating system
(<TT>system, objects</TT> units). Because of this, you
might get problems if the file is opened more than once either
by another process or the same process.
<p> Generally the behaviors for the different operating
systems are as follows :
<ul>
<li> UNIX systems : There is no verification at all.
<li> Windows : An access denied error will be reported.
<!-- <li> Amiga : An access denied error will be reported. -->
<li> DOS / OS/2 : If the file is opened more than once by
the same process, no errors will occur, otherwise an
access denied error will be reported.
</ul>
<p>There are two ways to solve this problem:
<ul>
<li> Use specific operating system calls (such as file locking
on UNIX systems) to get the correct behavior.
<li> Use the <TT>sysutils</TT> unit or the Free Component Library
<TT>TFileStream</TT> File I/O routines, which try
to simulate, as much as possible, file sharing mechanisms.
</ul>
<li><a name='filemode'></a>
<h3>File denied errors when opening files with reset</h3>
<p> Trying to open files using <CODE>reset</CODE> on non-text files
might cause a Runtime Error 5 (Access denied).
<p> All files opened using the above system unit routine use the current
<CODE>filemode</CODE> value to determine how the file is opened. By
default, <CODE>filemode</CODE> is set to 2 (Read/Write access).
<p>So, a call to <CODE>reset</CODE> on non-text files does <EM>not</EM>
indicate that the file will be opened read-only. So, trying to open a file
using <CODE>reset</CODE> with the defaults will fail on read-only files.
<CODE>filemode</CODE> should be set to 0 (Real-only access) before
calling <CODE>reset</CODE> to solve this problem. A sample solution
is shown below.
<PRE>
const
{ possible values for filemode }
READ_ONLY = 0;
WRITE_ONLY = 1;
READ_WRITE = 2;
var
oldfilemode : byte;
f: file;
begin
assign(f,'myfile.txt');
oldfilemode := filemode;
{ reset will open read-only }
filemode := READ_ONLY;
reset(f,1);
{ restore file mode value }
filemode := oldfilemode;
// ...
close(f);
end.
</PRE>
<p> For more information, consult the Free Pascal reference manual
</OL>
<LI><h2>Windows-related information</h2>
<OL>
<li><a name=win-release></a>
<h3>Releasing software generated by the windows compiler</h3>
<p> There is no special requirements for releasing software
for the Windows platform, it will work directly out of the box. The following
are default for the Windows platform:
<ul>
<li> Stack size is unlimited
<li> The stack checking option is not available on this platform.
</ul>
<p>
<li><a name=win-debugging></a>
<h3>Debugging</h3>
<p>The GNU debugger v6.4 and later have been tested, and generally work as
they should. Because the GNU debugger is C oriented, some pascal types might not be
represented as they should. It is suggested to use the text mode IDE instead of GDB,
which is available for windows targets.
<p>
<li><a name=win-dll></a>
<h3>Dynamic libraries</h3>
<p>Creation and use of shared libraries (also called dynamic link libraries) is
fully supported by the compiler. Refer to the Programmer's Reference Manual for
more information on shared library creation and use.
<li><a name=win-profile></a>
<h3>Profiling</h3>
<p>Profiling is supported using <TT>gprof</TT>.
It requires mingw to be installed, and that <TT>fpc.cfg</TT> points to the
correct library paths.
<li><a name=win-graph></a>
<h3>Graph and problems with keyboard, mouse and "dummy dos windows"</h3>
<p>Problem:
<ul>
<li>If you use the Graph unit under Win32, you cannot use the API mouse
unit for mouse support or use the win32 Crt unit to get keyboard data.
The reason for this is that the created window is a GUI window, and
not a console one.
</ul>
Solution:
<ul>
<li>Use units WinMouse and WinCrt instead.
</ul>
<p>
<p>Problem:
<ul>
<li>When you follow the above advice, and you run your purely Graph
based win32 program from the RUN menu in windows, a dummy dos window
is opened.
</ul>
Solution:
<ul>
<li>Set the application type to GUI: <PRE>{$apptype GUI}</PRE>
and put this line before your programs InitGraph statement:
<PRE>ShowWindow(GetActiveWindow,0);
</PRE>This will hide the dos window window.
</ul>
<p>
<p>Some of the demos (like fpctris) use these techniques
<li><a name=win-cygwin></a>
<h3>Cygwin binary directory in your path sometimes causes strange problems</h3>
<p>The mingw make tool seems to look for a "sh.exe", which it
finds when the cygwin binary directory is in the path. The
way directories are searched changes, and the build process dies.
<p>Solution: do not put cygwin in your global path for now, only
add it when needed. Efforts are made to work around this.
<p>Possible untested workaround: add mingw sh.exe to a directory before
the cygwin binary directory in the path
<li><a name=win95-fpc></a>
<h3>Using the DOS compiler under Windows 95</h3>
<p>There is a problem with the DOS (GO32V2) compiler and Windows 95 on
computers with less than 16 Megabytes of RAM. First set in the
properties of the DOS box the DPMI memory size to max value. Now try
to start a demo program in the DOS box, e.g. HELLO (starting may take
some time). If this works you will be able to get the compiler to work
by recompiling it with a smaller heap size, perhaps 2 or 4 MB
(option -Chxxxx).
<!--
<li><a name=win-os2></a>
<h3>Using OS/2 generated applications under Windows</h3>
<p>Normally OS/2 applications (including the compiler) created with version 1.0.x
and before should work under Windows, since they are based on EMX - see
<a href="#dos-os2">note about running OS/2 applications under DOS</a> for
more detailed information. You need the RSX extender (rsx.exe) to do this.
There have been problems reported while trying to run EMX applications under
NT / 2000 / XP systems though. This seems to be a problem with EMX (RSX) itself.
It is not recommended to use Free Pascal OS/2 compiled programs under NT / 2000
and XP, as it might produce unexpected results.
-->
<li><a name=win-dos></a>
<h3>Using DOS generated applications under windows</h3>
<p>Several problems have been found running DOS software
under certain versions of Windows (NT / 2000 / XP). These
seem to be problems with the DOS emulation layers (emulated
DPMI services or the Go32 extender). These problems may not occur with all software
generated by FPC. Either applications should be tested on these systems
before being released, or Windows versions should be generated instead.
<li><a name=win-ide-mouse></a>
<h3>The mouse cursor does not respond in the Windows IDE</h3>
<p>In windowed mode, the IDE might not respond to
mouse moves and clicks. Just change the properties of the console,
and remove the quick edit mode option. This should solve the mouse
response problems.
</OL>
<LI><h2>UNIX-related information </h2>
<p>This section also applies to most UNIX variants, such as
Linux, FreeBSD and Mac OS X.
<OL>
<li><a name=unix-release></a>
<h3>Releasing software generated by the UNIX compilers</h3>
<ul>
<li> There is no stack space usage limit.
<li> Stack checking is simulated.
<li> Minimal operating system versions :
<ul>
<li> Linux : Kernel v2.4.x or later.
<li> FreeBSD : version 5.x or later. (4.x can be made to work with minor work)
<li> NetBSD : version 1.5 or later.
<li> Solaris : version 5.7 of SunOS or later
(should work with earlier versions, but untested).
<li> Mac OS X : version 10.4 or later (Intel), or 10.3.9 or later (PowerPC)
</ul>
</ul>
<p>
<li><a name=unix-debugging></a>
<h3>Debugging</h3>
<p>The GNU debugger v6.5 and later have been tested, and generally work as
they should. Because the GNU debugger is C oriented, some pascal types might not be represented as they should.
<p>
<li><a name=unix-dll></a>
<h3> Dynamic libraries </h3>
<p>Creating dynamic libraries under UNIX-like operating systems is supported.
<p>
Importing code from shared libraries does work as expected though, since
it does not require usage of position independant code.
<li><a name=unix-profile></a>
<h3>Profiling</h3>
<p>Profiling is supported using <TT>gprof</TT> under linux,
FreeBSD and NetBSD, the latter two only since 1.0.8. On other
other UNIX-like operating systems, profiling is currently not
supported.
<li><a name=libci386></a>
<h3>Libc is missing on platforms other than Linux/i386</h3>
<P>Libc is a Kylix compatibility unit. Because it contains many
i386 specific code and features structures from legacy kernels,
it has not been made available on other platforms.
<P>To access UNIX functionality, please use units like baseunix
and unix.
<li><a name=vgamissing></a>
<h3>Why can't the linker find "vga"?</h3>
<p>This error typically looks like this:<PRE>
Free Pascal Compiler version 3.0.x [xxxx/yy/zz] for i386
Copyright (c) 1993-2008 by Florian Klaempfl
Target OS: Linux for i386
Compiling test.pp
Assembling test
Linking test
/usr/bin/ld: cannot find -lvga
test.pp(6,4) Warning: Error while linking Closing script ppas.sh 5 Lines
compiled, 0.2 sec
</PRE>
<p>
<p>This error is not an error in the installation of FPC or FPC itself,
but a missing Svgalib library in your UNIX install. Please install the
required library using your favourite package manager tool
<li><a name=unix-asldmissing></a>
<h3>Compiler indicates missing as and ld</h3>
<p> Normally UNIX systems have the assembler (<TT>as</TT>) and linker
(<TT>ld</TT>) pre-installed and already in the search path. That is
the reason why these tools are not supplied with the compiler.
<p>If the compiler cannot find these tools, either they are not in
your search path, or they are not installed. You should either add the
path where the tools are located to your search path, and / or you
should install these tools.
<li><a name=unix-ld219></a>
<h3>An error occurred while linking, or "did you forget -T?"</h3>
<p>There is a bug in GNU LD 2.19 and 2.19.1 that causes it to crash
when processing FPC-generated linker scripts. This bug has been fixed
in the mean time.</p>
<p>At the same time, LD has been modified to emit a warning of the form
<pre>
/usr/bin/ld: warning: link.res contains output sections; did you forget -T?
</pre></p>
<p>This warning is benign, and FPC intentionally does not pass -T to LD. The reason
is that if -T is used, LD's internal linker script is ignored and only
FPC's linker script is used. Such linker scripts also contain paths to
libraries however, and if we would ignore the internal linker script then
LD would no longer find libraries in distribution-specific directories.</p>
</OL>
<LI><h2>OS/2-related information </h2>
<OL>
<li><a name=os2-release></a>
<h3>Releasing software generated by the OS/2 compiler</h3>
<p> The OS/2 compiler version 1.0.x and before is based on EMX, therefore
it should work both on OS/2 and on vanilla DOS systems. In version 1.9.x and
above this functionality is preserved in newly added target EMX, whereas binaries
for target OS2 can only run under real OS/2. The following notes apply to OS2
target in 1.0.x and EMX in 1.9.x and above:
<ul>
<li> All applications generated for the OS/2 (EMX) target require
the EMX 0.9d (or later) runtime files to run. These files
should be redistributed with your software. All the files
which should be redistributed are included in <TT>emxrt.zip</TT>
<li> Under OS/2, <TT>LIBPATH</TT> should be modified to add the EMX
DLL paths. Otherwise, programs will not run and will abort
with an error 'Cannot find EMX.dll'.
<li> Stack can grow up to 256 Kbytes by default. This can be changed by
the user or developper using the <TT>emxstack</TT> or <TT>emxbind</TT>
utilities.
</ul>
<p>
<li><a name=os2-debugging></a>
<h3>Debugging</h3>
<p>The GNU debugger v4.16 (EMX port) has been tested (including
its PM add-on, pmgdb.exe) and generally works as it should.
Because the GNU debugger is C oriented, some pascal types
might not be represented correctly.
<p>
<li><a name=os2-dll></a>
<h3> Dynamic libraries </h3>
<p>
Even though this operating system permits the creation and usage of
shared libraries (also called dynamic link libraries), the compiler
currently only permits importing routines from dynamic libraries (creation of
dynamic libraries is unsupported).
<li><a name=os2-profile></a>
<h3>Profiling</h3>
<p>Profiling is currently not supported for this platform.
<li><a name=os2-dos></a>
<h3>Using DOS generated applications under OS/2</h3>
<p>It has been reported that some DOS (GO32V2) applications
(including the DOS compiler itself) generated by the compiler fail on
some OS/2 installations. This is due to problems in the OS/2 DPMI server.
<p>You should use native OS/2 applications under OS/2 (including the native OS/2
compiler) or try installing a new OS/2 fixpack to see if it solves the
problem.
<li><a name="instal106os2"></a><h3>INSTALL.EXE complains about a missing TZ variable under OS/2</h3>
<p>
You are most probably using an older version of OS/2 (like OS/2 Warp 3.0)
and do not have TZ variable in your environment. The easiest solution is to add
"SET TZ=..." (e.g. "SET TZ=CET-1CEST,3,-1,0,7200,10,-1,0,10800,3600" for most
of western and central Europe) line to your CONFIG.SYS, and restart OS/2.
The proper setting for you can be found e.g. using the TZCALC tool from
<a href="http://hobbes.nmsu.edu/pub/os2/apps/internet/time/time868f.zip">TIME868</a>
package.
<li><a name="os2-fp"></a><h3>OS/2 compiler not working after upgrading to 1.9.6 or newer</h3>
<p>An updated version of GNU assembler (as.exe) is packaged with release 1.9.6 (newer version
was necessary to get support for features of modern CPUs). This version of the GNU tool
was created with Innotek port of GNU C and relies on its libc. This results in higher
limitations regarding supported configurations, because this libc needs recent version
of OS/2 Unicode support libraries (LIBUNI.DLL and UCONV.DLL) not available in base OS/2 Warp 3.0
and OS/2 Warp 4.0. The updated versions were distributed by IBM in corrective packages (fixpaks)
- see e.g. <a href="http://www.warpupdates.mynetcologne.de/english/basesystem.html">WarpUpdates site</a>
for information about OS/2 fixpaks and links for downloading them.
This issue isn't valid for WarpServer for e-Business, MCP and eComStation - these already have
the correct version.
<li><a name="os2-as-failing"></a><h3>Compilation under OS/2 fails with error "Can't call the assembler"</h3>
<p>Apart from the point mentioned <a href="#os2-fp">above</a>,
there is at least one more potential reason for issues with
executing the assembler and resulting in error message "Can't call
the assembler, error 2 switching to external assembling". This
error may be result of the OS/2 system not being able to find DLLs
required for the assembler. Make sure that you installed FPC
completely (these DLLs are part of file asldos2.zip) and that you
have set LIBPATH according to instructions in README.TXT (and
restarted afterwards). If in doubts, running the assembler directly
from the command line (e.g. "as --version" to show the installed
as.exe version) may be helpful to see name of the missing dynamic
library or other details about the problem.
</OL>
<LI><h2>BeOS-related information </h2>
<OL>
<li><a name=beos-release></a>
<h3>Releasing software generated by the BeOS compiler</h3>
<p> Software generated for the BeOS target will only work
on the Intel based version of BeOS.
<ul>
<li> The target system must have at least BeOS v4.0 or later
(BeOS 5.1d 'Dano' is <em>not</em> supported)
<li> Stack size is set to 256 Kbytes. This cannot be changed
</ul>
<p>
<li><a name=beos-debugging></a>
<h3>Debugging</h3>
<p>
Debugging works with the system-supplied gdb version.
<p>
<li><a name=beos-dll></a>
<h3> Dynamic libraries </h3>
<p>
Even though this operating system permits the creation and usage of
shared libraries (also called dynamic link libraries), the compiler
currently only permits importing routines from dynamic libraries (creation of
dynamic libraries is unsupported).
<li><a name=beos-profile></a>
<h3>Profiling</h3>
<p>Profiling is currently not supported for this platform.
<li><a name=beos-linking></a>
<h3>BeOS Linking problems</h3>
<p>It has been reported that certain versions of the linker
that shipped with some versions of BeOS are broken. If you get
an error when linking fpc applications, try updating your version
of ld from the following
<a href="http://open-beos.sourceforge.net/dev.php">site.</a>
<p>
</OL>
<!--
<LI><h2>Amiga-related information </h2>
<OL>
<li><a name=amiga-release></a>
<h3>Releasing software generated by the Amiga compiler</h3>
<ul>
<li> The target system must have AmigaOS v2.04 or higher
<li> Stack size is not set by the compiler, but by the <TT>stack</TT>
command on the CLI. Because of this, and because default
stack sizes for this target are small, it is recommended
to always compile software with stack checking enabled.
<li> By default, the compiler generates code for the 68020+
processor. The code generated will not work on 68000
and 68010 systems unless the <TT>-O0</TT> compiler switch
is used, and there is no runtime checking. It is up
to you to implement CPU verification at program startup. The
standard runtime libraries have been compiled for the
68000 target, and should not cause any problems.
<li> All floating point operations are simulated,
and use the <TT>single</TT> floating point type.
You will need to recompile all standard runtime
libraries and your application, with the software floating point
option off, if you wish to use hardware floating point.
</ul>
<p>
<li><a name=amiga-debugging></a>
<h3>Debugging</h3>
<p> Source level debugging is not supported for the Amiga target. Assembler
target debugging is possible though, using the excellent <TT>Barfly</TT>
debugger.
<p>
<li><a name=amiga-dll></a>
<h3> Dynamic libraries </h3>
<p>
Even though this operating system permits the creation and usage of
shared libraries (also called dynamic link libraries), the compiler
does not support either the importing or creation of shared libraries.
Importing must be done manually in assembler.
<li><a name=amiga-profile></a>
<h3>Profiling</h3>
<p>Profiling is currently not supported for this platform.
</OL>
<LI><h2>PalmOS-related information </h2>
<OL>
<li><a name=palmos-release></a>
<h3>Releasing software generated by the PalmOS compiler</h3>
<ul>
</ul>
<p>
<li><a name=palmos-debugging></a>
<h3>Debugging</h3>
<li><a name=palmos-dll></a>
<h3> Dynamic libraries </h3>
<p>
<p>
</OL>
-->
<LI><h2>DOS-related information</h2>
<OL>
<li><a name=dos-release></a>
<h3>Releasing software generated by the DOS compiler</h3>
<ul>
<li> If your program uses floating point code (which is
very probable), make sure to read "<a href="#fp386">Applications created
with Free Pascal crash on 80386 systems</a>" regarding special issues
which might occur. Math coprocessor emulation software is then
required (<TT>wmemu387.dxe</TT> should be redistributed with your software)
<li> The target system must have a DPMI server. To avoid problems,
the file <TT>cwsdpmi.exe</TT> should always be redistributed with your
application
<li> The target system must have DOS 3.3 or later
<li> The default stack size is 256 Kbytes. See also "<a href="#dos-stack">Changing
the default stack size</a>"
<li> The stack checking option is available on this platform.
</ul>
<p>
<li><a name=dos-debugging></a>
<h3>Debugging</h3>
<p>The GNU debugger v4.16 and later have been tested, and generally work as
they should. Because the GNU debugger is C oriented, some pascal types might not be
represented as they should. It is suggested to use the text mode IDE instead of GDB,
which is available for the DOS target.
<p>
<li><a name=dos-dll></a>
<h3>Dynamic Libraries</h3>
<p>Creation or use of shared libraries (also called dynamic link libraries) is not
supported under this platform.
<li><a name=dos-profile></a>
<h3>Profiling</h3>
<p>Profiling with <TT>gprof</TT> is supported for this platform.
<li><a name=FPwithoutfpu></a>
<h3>Running Free Pascal without a math coprocessor?</h3>
<p>On the Intel version the emulator is automatically loaded by the
compiler if you add the following commands to your autoexec.bat:
<p><PRE>
SET 387=N
SET EMU387=C:\PP\BIN\GO32V2\WEMU387.DXE
</PRE>(do not forget to replace the <TT>C:\PP</TT> with the directory
where you installed FPC)
<li><a name=fp386></a>
<h3>Applications created with Free Pascal crash on 80386 systems</h3>
<ul>
<li>
<p>Trying to run an application which performs floating point operations
on a 386 system without a math co-processor will crash unless
the <TT>emu387</TT> unit is used, as this unit loads the math co-processor
emulator (called <TT>wmemu387.dxe</TT>). You can add the unit as follows:
<p><PRE>
program myprog;
uses emu387, ...
</PRE>
<p>When the application is released, the software package should also
include the wmemu387.dxe redistributable file to avoid problems. .
<li>
<p>Some 80386 systems have a hardware bug which corrupt the accumulator
register <TT>EAX</TT> if it is used in a <TT>MOV</TT> instruction just
after a <TT>POPAL</TT> instruction. Prior to version 1.0.5, the compiler
and runtime library could generate such code sequences. This is now
fixed and should no longer cause problems
</ul>
<p>
<li><a name=nomousegraph></a>
<h3>The mouse cursor is not visible in graphics screens</h3>
<p>Many DOS mouse drivers do not properly support mouse cursors in VESA modes. Logitech is said to have a decent mouse driver, which can be
found <A
href="ftp://ftp.logitech.com/pub/techsupport/mouse/m643 w31.exe">here</a>
<li><a name=accessioports></a>
<h3>Accessing I/O ports</h3>
<p>The Port array is supported like in TP, as long
as you use the ports unit in your program (not available under Win32).
<p>I/O port access is possible under Linux, but that requires root
privileges. Check the manuals for the IOPerm, ReadPort and WritePort
procedures. (Unit Linux)
<li><a name=HowToAccessDosMemory></a>
<h3>Accessing DOS memory / Doing graphics programming</h3>
<p>You can do like in Turbo Pascal, via absolute or mem[]. For larger memory
blocks use the dosmemput/dosmemget routines in the <TT>Go32</TT> unit.
<li><a name=dos-stack></a>
<h3>Changing the default stack size</h3>
<p>Under the DOS (GO32V2) target, the default stack size to 256 bKbytes. This can
be modified with a special DJGPP utility called <TT>stubedit</TT>. It is to note
that the stack may also be changed with some compiler switches, this stack size,
if greater then the default stack size will be used instead, otherwise the default
stack size is used.
<p>
<!--
<li><a name=dos-os2></a>
<h3>Using OS/2 generated applications under DOS</h3>
<p>OS/2 applications (including the compiler) created with version 1.0.x
and before should work correctly under vanilla DOS, since they are based
on EMX (versions prior to 1.0.5 had big problems with EMX under DOS, this
is now fixed). It is important to note that the compiled applications
require the EMX runtime files (<TT>emx.exe</TT>) to execute properly. It may be
necessary to distribute these files with the generated application.
<p>Binaries created for target OS2 with version 1.9.x and above cannot
run under DOS any more, because they directly use OS/2 API functions not
available when running under extender - you need to compile for a newly added
EMX target which provides this capability of running on both platforms.
-->
</OL>
</OL>
</body></html>
distrib
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7
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armv7hl
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media
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245a4d71f49aa1a61e797fff1cb4e99f
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files
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