path: root/install/doc/faq.txt

FAQ / Knowledge base

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.

For more comprehensive information on the pascal language, and the runtime
library calls, consult the Free Pascal manuals. Topics covered in this document
:

 1. General information
     1. What is Free Pascal (FPC)?
     2. Which versions exist, and which one should I use?
     3. Free Pascal and GNU Pascal - a comparison
     4. License and copyright information
     5. Getting the compiler
     6. Free Pascal installation hints
     7. Why do i have to supply a user name and password to get Free Pascal ?
     8. Access denied error when connecting to the Free Pascal FTP site
     9. I want a new version NOW
    10. Installing a snapshot
    11. I have to write a program for homework. Can you help?
    12. How do I make a real Windows application with windows and menu bars?
    13. How do I make a game with Free Pascal? Can I make a game like Doom 3?
    14. Getting more information when an application crashes
    15. Increasing the heap size
    16. Compiler seems to skip files in directories -Fu points to
    17. Why are the generated binaries so big?
    18. Configuration file problems (fpc.cfg or ppc386.cfg)
    19. Runtime errors
    20. Standard units
    21. Debugging smartlinked code does not fully work
    22. Debugging shared library (dynamic linked library) code does not fully
        work
    23. PPU files binary compatibility between versions
    24. Can't compile a program using a binary only version of a unit
    25. Will you support ISO Extended Pascal?
    26. What about .NET?
 2. Pascal language related information
     1. Considerations in porting code to other processors
     2. Considerations in porting code to other operating systems
     3. Compiling Delphi code using Free Pascal
     4. Building a unit
     5. Compiling the system unit
     6. How does function overloading work?
     7. Calling C functions
     8. Integrated Assembler syntax
     9. Unit system not found errors
    10. There is a new extension that will be really useful. Will you include
        it?
 3. Runtime library related information
     1. Using the graph unit with Free Pascal
     2. Why do I get wrong colors when using the graph unit?
     3. File sharing and file locks
     4. File denied errors when opening files with reset
 4. DOS related information
     1. Releasing software generated by the DOS compiler
     2. Debugging
     3. Dynamic libraries
     4. Profiling
     5. Running Free Pascal without a math coprocessor
     6. Applications created with Free Pascal crash on 80386 systems
     7. The mouse cursor is not visible in graphics screens
     8. Accessing I/O ports
     9. Accessing DOS memory / Doing graphics programming
    10. Changing the default stack size
    11. Using OS/2 generated applications under DOS
 5. Windows related information
     1. Releasing software generated by the windows compiler
     2. Debugging
     3. Dynamic libraries
     4. Profiling
     5. Graph and problems with keyboard, mouse and "dummy dos windows"
     6. Cygwin binary directory in your path sometimes causes builds to fail
     7. Using the DOS compiler under Windows 95
     8. Using OS/2 generated applications under Windows
     9. Using DOS generated applications under windows
    10. The mouse cursor does not respond in the Windows IDE
 6. UNIX related information
     1. Releasing software generated by the unix compilers
     2. Debugging
     3. Dynamic libraries
     4. Profiling
     5. Libc is missing on platforms other than i386
     6. Why can't the linker find "vga"?
     7. Compiler indicates missing as and ld
     8. An error occurred while linking, or "did you forget -T?"
 7. OS/2 related information
     1. Releasing software generated by the OS/2 compiler
     2. Debugging
     3. Dynamic libraries
     4. Profiling
     5. Using DOS generated applications under OS/2
     6. INSTALL.EXE of version 1.0.6 or below returns an unknown error (-1)
        under OS/2
        or
        INSTALL.EXE of version 1.0.6 or above complains about missing TZ
        variable under OS/2
     7. OS/2 compiler not working after upgrading to 1.9.6 or newer
     8. Compilation under OS/2 fails with error "Can't call the assembler"
 8. BeOS related information
     1. Releasing software generated by the BeOS compiler
     2. Debugging
     3. Dynamic libraries
     4. Profiling
     5. BeOS linking problems
 9. Amiga related information
     1. Releasing software generated by the Amiga compiler
     2. Debugging
     3. Dynamic libraries
     4. Profiling
10. PalmOS related information
     1. Releasing software generated by the PalmOS compiler
     2. Debugging
     3. Dynamic libraries

 1. General information

     1. What is Free Pascal (FPC)?

        Originally named FPK-Pascal, the Free Pascal compiler is a 32 and 64
        bit Turbo Pascal and Delphi compatible Pascal compiler for DOS, Linux,
        Win32, OS/2, FreeBSD, AmigaOS, Mac OS X, Mac OS classic 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).

        The Free Pascal compiler is available for several
        architectures: x86, Sparc (v8,v9), ARM, x86_64 (AMD64/Opteron),
        PowerPC and PowerPC64. An older version (the 1.0 series) and
        current development version also support m68k, the current development version also
        supports MIPS (in both big endian and little endian modes).

        The compiler is written in Pascal and is able to compile its own
        sources. The source files are under GPL and included.

        Short history:
          ☆ 06/1993: project start
          ☆ 10/1993: first little programs work
          ☆ 03/1995: the compiler compiles the own sources
          ☆ 03/1996: released to the internet
          ☆ 07/2000: 1.0 version
          ☆ 12/2000: 1.0.4 version
          ☆ 04/2002: 1.0.6 version
          ☆ 07/2003: 1.0.10 version
          ☆ 05/2005: 2.0.0 version
          ☆ 12/2005: 2.0.2 version
          ☆ 08/2006: 2.0.4 version
          ☆ 09/2007: 2.2.0 version
          ☆ 08/2008: 2.2.2 version
          ☆ 04/2009: 2.2.4 version
          ☆ 12/2009: 2.4.0 version
          ☆ 11/2010: 2.4.2 version
          ☆ 05/2011: 2.4.4 version
          ☆ 01/2012: 2.6.0 version
          ☆ 12/2012: 2.6.2 version
          ☆ 02/2014: 2.6.4 version
     2. Which versions exist, and which one should I use?

        The latest official version is 2.6.4, the first fixes release in the 2.6.x
        series. New development is performed in 2.7.x series, which eventually
        gets released as 2.8.0 or 3.0.0, depending on milestones achieved.

        Historic versions

        FPC's version numbering changed a few times over the years. Pre 1.0
        versioning moved to the Wiki 1.0 versioning article.

        Modern versioning

        Together with the release of 1.0 the version numbering was slightly
        changed, and a system in versioning resembling the Linux kernels has
        been introduced.

          ☆ Releases that only fix bugs in version 1.0 are numbered 1.0.x.
          ☆ Post 1.0 development (the so called snapshots) have version number
            1.1.x.
          ☆ 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 on 2.0
            release were numbered 2.0.x, fixes on 2.2 release 2.2.x, fixes on
            the 2.4 release as 2.4.x etc
          ☆ The new development after the 2.4.0 release is numbered 2.5.x and
            so on.
          ☆ 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.
          ☆ The stable branch (fixes_2_4) always has an odd last number (2.4.1,
            2.4.3). Compilers with such versions are snapshots, and e.g. a
            snapshot with 2.4.1 can be anywhere between 2.4.0 and the moment
            2.4.2 branched off (may 2010). Likewise the fixes_2_4 branch will
            hold version 2.4.3 till 2.4.4 is branched off (typically two months
            before its release). After 2.4.4 the stable branch's number is
            updated to 2.4.5 etc.

        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).

        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).

        Development snapshots are often quite useful for certain categories of
        users. Ask in the maillists if it is worth the trouble in your case if
        you're not sure.

        Snapshots of the stable branch (fixes_2_6) 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.

        We advise all users to upgrade to the newest version for their target
        (preferably the new stable 2.6.x series).

        A graphical timeline of the FPC project plus its near future would be:
        [timeline]
     3. Free Pascal and GNU Pascal - a comparison

        Aim:
            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.
        Version:
            Currently, Free Pascal is at version 2.6.4 (February 2014). GNU
            Pascal is at 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).
        Tracking:
            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.
        Operating systems:
            Free Pascal runs on a large amount of platforms of OSes, e.g. DOS,
            Win32 (no Unix porting layer needed), Linux, FreeBSD, NetBSD, OS/2,
            BeOS, Classic Mac OS, Mac OS X, and AmigaOS, on, at the moment the
            following architectures: x86, x86_64 (AMD64), Sparc, PowerPC,
            PowerPC64, ARM, Motorola m68k (m68k only in version 1.0.x and
            the latest development versions) and MIPS (both big endian and
            little endian mode available in the latest development versions).
            GNU Pascal runs basically on any system that can run GNU C, and
            for which the buildprocess was verified.
        Bootstrapping:
            FPC requires a suitable set of binutils (AS,AR,LD) on some
            platforms, gmake and a commandline compiler. New architectures/OSes
            are crosscompiled. GPC bootstraps via a suitable version of GCC,
            and requires a full set of binutils, flex, bison, gmake, a POSIX
            shell and libtool
        Sources:
            Free Pascal is entirely written in Pascal (about 6 MB of source
            code), while GNU Pascal is written in C (it's an adaptation of the
            GNU C compiler: 2.8 MB code + 8 MB of GNU C code)
        Language:
            Free Pascal supports the Borland Pascal dialect, implements the
            Delphi Object Pascal language and has some Mac Pascal extensions.
            GNU Pascal supports ISO 7185, ISO 10206, (most of) Borland Pascal
            7.0
        Extensions:
            Free Pascal implements method, function and operator overloading
            (later Delphi versions add these, so strictly not an extension
            anymore). GNU Pascal implements operator overloading.
        License:
            Both compilers come under the GNU GPL.
        Author:
            Free Pascal was started by Florian Klämpfl, Germany
            (florian@freepascal.org), GNU Pascal was started by Jukka Virtanen,
            Finland (jtv@hut.fi).


     4. License and copyright information

        Applications created by the compiler and using the runtime library come
        under a modified library gnu public license (LGPL), which permit no
        restriction on the type of license the application has. It is therefore
        possible to create closed source or proprietary software using Free
        Pascal.

        This extra exception to the LGPL is added:
        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. Please note that you still have to comply to the LGPL,
        which, for example, requires you to provide the source code of the
        runtime library. If you want to write proprietary closed source
        software, please do this to comply:
          ☆ Most people can satisfy the source code requirement by mentioning
            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.
          ☆ If you made modifications to the runtime library, you cannot keep
            them for yourself, you must make them available if requested.
          ☆ Distribute the LGPL license with your product.

        The compiler source code, on the other hand, comes under the GNU Public
        license, which means that any usage of the compiler source can only be
        used in software projects which have the same license.
     5. Getting the compiler

        The latest official stable Free Pascal release is available for
        download from all official mirrors
     6. Free Pascal installation hints

          ☆ Do not install the compiler in a directory which contains spaces in
            its name, since some of the compiler tools do not like these
     7. Why do i have to supply a user name and password to get Free Pascal ?

        You are trying to login in to an ftp site. You must use the login name:
        anonymous and as your password, you should put your e-mail address.
     8. Access denied error when connecting to the Free Pascal FTP site

        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.
     9. I want a new version NOW

        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 under progress, so in addition to old bugs
        fixed and new features added, this may also contain new bugs.

        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 doesn't work, try again one
        or two days later.

        The latest snapshot can always be downloaded from the development web
        page.
    10. Installing a snapshot

        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.

        Make sure that you extract the ZIP archive such that the included
        directory structure remains intact. For example if you use PKUNZIP, use
        "pkunzip -d" instead of just "pkunzip" (InfoZIP unzip doesn't require
        any special parameters). Note that snapshots also contain a new RTL
        which most likely can't be used with the previous release version, so
        backup your old RTL as well.
    11. I have to write a program for homework. Can you help?

        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.
    12. How do I make a real Windows application with windows and menu bars?

        The easiest way is to download Lazarus. It won't be just a Windows
        application, it will also work under Linux, FreeBSD and Mac OS X.
    13. How do I make a game with Free Pascal? Can I make a game like Doom 3?

        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
        www.pascalgamedevelopment.com is a community of people who program
        games in Free Pascal and Delphi.

        If you want a start, please start to study JEDI-SDL or PTCPas. Also you
        can try to study an existing game, for example The Sheep Killer is a
        very simple game and it should not be very hard to understand its code.
    14. Getting more information when an application crashes

         1. 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.
         2. For more comprehensive checking, compile the program with debugging
            information (use the -g command line option)
         3. Load the program in the debugger

            gdb(pas)(w) --directory=<src dirs> myprog.exe

            Notes:
              ○ Under UNIX systems (Linux, the BSD's), don't add the ".exe"
                after myprog
              ○ "src dirs" is a list of directories containing the source code
                files of myprog and the units it uses seperated by semi-colons
                (";"). The current directory is automatically included.
         4. Once inside the debugger, you can (optionally) set the command line
            options that will be passed to your program using the command "set
            args <option1 option2 ...>"
         5. To start the program, type "run" and press enter
         6. 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.
         7. If you then type "bt" (BackTrace), the addreses in 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

            info line *<address>

            For example:

            info line *0x05bd8

    15. Increasing the heap size

        By default Free Pascal allocates a small part of RAM for your
        application as heap memory. If it just allocated all it could get,
        people running Windows would have problems as Windows would increase
        the swap file size to give the program more memory on and on, until the
        swap file drive would be full.

        You can specify the size of the heap with -Chxxxx.

        However, the heap size doesn't really matter, since the Heap is able to
        grow: if you've used all the available heap space, the program will try
        to get more memory from the Operating system (OS), so the heap is
        limited to the maximum amount of free memory provided by the OS.

        It is only handy if you know you will need at least a certain amount of
        memory. You can then specify this value using the -Ch parameter, so
        your program will allocate it at once on startup. This is slightly
        faster than growing the heap a number of times.
    16. Compiler seems to skip files in directories that -Fu points to

        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 touch
        will solve it.

        Also note that FPC, contrary to Turbo Pascal keeps track of
        includefiles. Modified includefiles or duplicate names might trigger an
        attempt at recompiling
    17. Why are the generated binaries so big?

        There are several reasons and remedies for this:
         1. 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 (-XS in 0.99.12 and
            earlier) command line option when compiling a program.
         2. 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 won't do
            anything when compiling units)
         3. You can use UPX to pack the .EXEs (just like e.g. pklite) for Dos
            (GO32v2) and Windows targets. Look here for more info.
         4. You can use LXLITE for packing EMX binaries, but you won't be able
            to run them under DOS (with extender) any more then. This issue is
            not relevant for native OS/2 binaries compiled for target OS2 with
            version 1.9.x and above, because these don't run under DOS anyway.
            In addition, it might not be possible to use compressed binaries on
            lower OS/2 versions (like 2.x) depending on chosen type of
            compression. LXLITE can be found e.g. on Hobbes, search for LXLITE.
         5. Turn on optimalisations, both for supplied packages (RTL, FV, FCL)
            and for your own code, this will also decrease the code size.
         6. Keep in mind that under Windows NT/2k/XP/Vista, compressed binaries
            startup relatively slow. Test under various conditions (OS, CPU
            speed, memory) if the behaviour is acceptable before compressing
        Generally Free Pascal generates smaller binaries than modern competing
        compilers, however, it doesn't 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
        Size Matters wiki entry.
    18. Configuration file problems (fpc.cfg or ppc386.cfg)

        Starting from version 1.0.6 of Free Pascal, the configuration file is
        called fpc.cfg instead of ppc386.cfg. For backward compatibility ,
        ppc386.cfg is still searched first and, if found, is used instead of
        fpc.cfg.

        Since 1.0.6 is now over 5 years old, the ppc386.cfg support will be
        phased out. 2.2.2 will warn, and 2.4.0+ will no longer search
        ppc386.cfg

        Versions prior to Free Pascal 1.0.6 do not recognize fpc.cfg, so if you
        wish to use an earlier version of the compiler using the same
        configuration file used with FPC version 1.0.6 (or later), the
        configuration file should be renamed to ppc386.cfg.
    19. Runtime errors

        When there is abnormal termination of an application generated by Free
        Pascal, it is very probable that a runtime error will be generated.
        These errors have the form :

                    Runtime error 201 at $00010F86
                      $00010F86  main,  line 7 of testr.pas
                      $0000206D


        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 call
        stack when the error occured.
    20. Standard units

        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.
    21. Debugging smartlinked code does not fully work

        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.

        While debugging, it is not recommended to use the smartlinking option.
    22. Debugging shared library (dynamic linked library) code does not fully
        work

        Debugging shared libraries (or dynamic linked libraries) produced by
        the Free Pascal compiler is not officially supported.
    23. PPU files binary compatibility between versions

        Can't compile a program using a binary only version of a unit

        Sometimes, even though there is a binary version of a module (unit file
        and object file) available, the compiler still gives compilation
        errors. This can be caused either by an incompatibility in the PPU file
        format (which should change only between major versions of the
        compiler), or by a change in one of the units of the RTL which has
        changed in between releases.

        To get more information, compile the code using the -va (show all
        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.

        So 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.

        In other words, the unit (PPU) file format does not change
        significantly in between minor releases of the compiler (for exemple :
        from 1.0.4 and 1.0.6) which means they are binary compatible, but
        because the interface of the units of the RTL certainly changes between
        versions, recompilation will be required for each version anyways.
    24. Will you support ISO Extended Pascal?

        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. All
        of these are incompatible to some extent with the ISO Standard and
        Extended Pascal languages. While in theory it would be possible to add
        a separate ISO Standard or Extended Pascal mode, until now no people
        interested in such functionality have stepped up to work on such
        features.

        GNU-Pascal 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.
    25. What about .NET?

        Occasionally, users ask about a FPC that supports .NET, or our plans in
        that direction.

        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 won't be possible in the future.

        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:
         1. 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.
         2. FPC's libraries don't base on .NET classes and datamodels (and
            can't be changed to do so without effectively rewriting them),
            moreover the libraries could only be unmanaged too, or they would
            be incompatible
         3. There is nothing practical 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
         4. The fact that on Windows 80% of the .NET code seems to be ASP.NET
            doesn't 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
         5. Operating System dependant code wouldn't work anymore, since the
            win32 interface is unmanaged.

        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. This is not
        adding support for .NET in FPC, but reimplementing FPC on .NET from
        near scratch without backwards compatibility. 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.

        While unmanaged code has some uses (allows to integrate with managed
        code inside windows easier), this still needs a codegenerator backend
        to be written, interfaces and libraries defined, for little practical
        use. This means a lot of work and since .NET take up is not really
        high, this might not be worth it, since an unmanaged FPC/.NET would
        only be minimally used.

        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.

        Since support for generating JVM bytecode 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.

 2. Pascal language related information

     1. Considerations in porting to other processors

        Because the compiler now supports processors other than the Intel, it
        is important to take a few precautions so that your code will execute
        correctly on all processors.
          ☆ Limit your use of asm statements unless it is time critical code
          ☆ Try not to rely on the endian of the specific machines when doing
            arithmetic operations. Furthermore, reading and writing of binary
            data to/from files will probably require byte swaps across
            different endian machines (swap is your friend in this case). This
            is even more important if you write binary data to files.
            Freepascal defines ENDIAN_LITTLE or ENDIAN_BIG to indicate the
            target endian.
          ☆ Try limiting your local variables in subroutines to 32K, as this is
            the limit of some processors, use dynamic allocation instead.
          ☆ Try limiting the size of parameters passed to subroutines to 32K,
            as this is the limit of some processors, use const or var
            parameters instead.
          ☆ The CPU32 or CPU64 (defined by FPC starting from version 1.9.3) are
            defined indicating if the target is a 32-bit or 64-bit cpu; This
            can help you separate 32-bit and 64-bit specific code.
          ☆ Use the ptruint type (defined by FPC starting from version 1.9.3)
            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.

     2. Considerations in porting code to other operating systems

        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.
          ☆ 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
            furnished in sysutils.
          ☆ 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
            don't like it when some things are left allocated or opened.
          ☆ Some operating systems limit the local stack space which can be
            allocated, therefore it is important to limit subroutine nesting,
            and the amount of local variables. Limiting total stack space usage
            at a given moment to at most 256 KBytes while make porting easier.
          ☆ Do not hard code paths to files, try to use relative paths instead
          ☆ Use the following constants (defined in the system unit) to get
            information on files, line endings, and to build paths:
              ○ LineEnding : Indicates the characters which end a text line
              ○ LFNSupport : Indicates if long filenames are supported (more
                then 8.3 characters)
              ○ DirectorySeparator : The character or characters which separate
                path components
              ○ DriveSeparator : The character which separate the drive
                specification from the rest of the path
              ○ PathSeparator : The character which separates directories in
                the search path environment
              ○ FileNameCaseSensitive : Boolean indicating if the filenames for
                this system are case-sensitive or not
              ○ AllFilesMask : String containing a wildcard expression for all
                files
            It is also possible to use the PathDelim, PathSep and DriveDelim
            constants defined in sysutils.

     3. Compiling Delphi code using Free Pascal

        The compiler supports the Delphi classes. Make sure you use the -S2 or
        -Sd switches (see the manuals for the meaning of these switches). For a
        list of Delphi incompatibilities also check the manual.
     4. Building a unit

        It works like in Turbo Pascal. The first keyword in the file must be
        UNIT (not case sensitive). The compiler will generate two files:
        XXX.PPU and XXX.O. 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.
     5. Compiling the system unit

        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/go32v2) and do a 'make'
        there.

        It is possible to do all this manually, but you need more detailed
        knowledge of the RTL tree structure for that.
     6. How does procedure overloading work?

        Here is a procedure overloading example:

                            procedure a(i : integer);
                            begin
                            end;

                            procedure a(s : string);
                            begin
                            end;

                            begin
                                a('asdfdasf');
                                a(1234);
                            end.


        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's not enough if their
        return types are different.
     7. Calling C functions

        It is possible to call functions coded in C, which were compiled with
        the GNU C compiler (GCC). For calling the C function strcmp declare the
        following:

        function strcmp(s1 : pchar;s2 : pchar) : integer;cdecl;external;

     8. Integrated Assembler syntax

        The default assembler syntax (AT&T style) is different from the one in
        Borland Pascal (Intel style).

        However, as of version 0.99.0, the compiler supports Intel style
        assembly syntax. See the documentation for more info on how to use
        different assembler styles.

        Since version 1.9.2, the compiler also uses the register calling
        convention, which means the compiler can assemble assembler routines in
        Delphi source code without modification.

        Since version 1.9.8, the register calling convention is default for
        Delphi mode.

        A description of the AT&T syntax can be found in the GNU Assembler
        documentation.
     9. Unit system not found errors

        System (syslinux - not the bootloader, sysos2 or syswin32, depending on
        platform) is Pascal's base unit which is implicitely used in all
        programs. This unit defines several standard procedures and structures,
        and must be found to be able to compile any pascal program by FPC.

        The location of the system.ppu and syslinux.o files are determined by
        the -Fu switch which can be specified commandline, but is usually in
        the ppc386.cfg or fpc.cfg configuration file.

        If the compiler can't find this unit there are three possible causes:
         1. The ppc386.cfg or fpc.cfg isn't in the same path as the compiler
            executable (go32v2, win32 and OS/2) or can't be found as "/etc/
            fpc.cfg" or ".fpc.cfg" in your homedirectory (Linux).
         2. The fpc.cfg or ppc386.cfg doesn't contain the -Fu line, or a wrong
            one. See the build faq (PDF), especially the chapters about the
            fpc.cfg and the directory structure.
         3. The files ARE found but the wrong version or platform. Correct
            ppc386.cfg or fpc.cfg to point to the right versions or reinstall
            the right versions (this can happen if you try to use a snapshot
            compiler while the -Fu statement in the used fpc.cfg still points
            to the RTL that came with the official release compiler).

        A handy trick can be executing "ppc386 programname -vt", this shows
        where the compiler is currently looking for the system unit's files.
        You might want to pipe this through more (Dos, OS/2, Windows) or less
        (Linux), since it can generate more than one screen information:

                            Dos, OS/2, Windows: ppc386 programname -vt |more

                            unix, linux: ppc386 programname -vt |less



    10. There is a new extension that will be really useful. Will you include
        it?

        Occasionally somebody asks for a new 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:
         1. 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.
         2. 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 can't be done otherwise or be a
            compatibility item
         3. The change must fit in with the scope of the project, implementing
            a Pascal compiler which can have a RAD and generic DB system. This
            excludes features like inline SQL, and large garbage collected
            objectframeworks.
        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 aren't easily recognizable unless
        one has tried to make extensions before. Best is to make a thoroughly
        written proposal that the devels can review with
          ☆ Explanation of the feature
          ☆ Why it is needed, what does it make possible?
          ☆ How you would implement it?
          ☆ Lots of examples of typical use, and tests for possible problem
            cases
        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.

        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 devels are volunteers with to-do lists that are booked till the
        next decade. You can't simply expect they'll 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, and submit
        patches, 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.
 3. Runtime library related information

     1. Using the graph unit with Free Pascal

        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.
     2. Why do I get wrong colours when using the graph unit?

        If you use detect 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 all
        graphics cards made in at least the last 5 years, you will most likely
        get a 16 bit mode.

        The main problem is that in 16 (and 15, 24, 32, ...) bit modes, the
        colors aren't 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't change this
        color. The color is encoded as follows (for most graphics cards on PC's
        at least):
          ☆ 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.
          ☆ 16 bit color: lower 5 bits are blue intensite, next come *6* bits
            of green and then 5 bits of red.

        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
        D8BIT as graphdriver and DetectMode 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 GrNotDetected
        after you called InitGraph and you can retry with graphdriver D4BIT.
        Make sure you use the constant names (D8BIT, D4BIT, ...) and not their
        actual numeric values, because those values can change with the next
        release! That is the very reason why such symbolic constants exist.
     3. File sharing and file locks

        The standard runtime library file I/O routines open files in the
        default sharing mode of the operating system (system, objects units).
        Because of this, you might get problems if the file is opened more than
        once either by another process or the same process.

        Generally the behaviors for the different operating systems are as
        follows :
          ☆ UNIX systems : There is no verification at all.
          ☆ Windows : An access denied error will be reported.
          ☆ Amiga : An access denied error will be reported.
          ☆ 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.

        There are two ways to solve this problem:
          ☆ Use specific operating system calls (such as file locking on UNIX
            and Amiga systems) to get the correct behavior.
          ☆ Use the sysutils unit or the Free Component Library TFileStream
            File I/O routines, which try to simulate, as much as possible, file
            sharing mechanisms.
     4. File denied errors when opening files with reset

        Trying to open files using reset on non-text files might cause a
        Runtime Error 5 (Access denied).

        All files opened using the above system unit routine use the current
        filemode value to determine how the file is opened. By default,
        filemode is set to 2 (Read/Write access).

        So, a call to reset on non-text files does not indicate that the file
        will be opened read-only. So, trying to open a file using reset with
        the defaults will fail on read-only files. filemode should be set to 0
        (Real-only access) before calling reset to solve this problem. A sample
        solution is shown below.

                      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.


        For more information, consult the Free Pascal reference manual
 4. DOS related information

     1. Releasing software generated by the DOS compiler

          ☆ If your program uses floating point code (which is very probable),
            make sure to read "Applications created with Free Pascal crash on
            80386 systems" regarding special issues which might occur. Math
            coprocessor emulation software is then required (wmemu387.dxe
            should be redistributed with your software)
          ☆ The target system must have a DPMI server. To avoid problems, the
            file cwsdpmi.exe should always be redistributed with your
            application
          ☆ The target system must have DOS 3.3 or later
          ☆ The default heap size is 2 Megabytes. Automatic growing of the heap
            is supported
          ☆ The default stack size is 256 Kbytes. See also "Changing the
            default stack size"
          ☆ The stack checking option is available on this platform.

     2. Debugging

        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.

     3. Dynamic Libraries

        Creation or use of shared libraries (also called dynamic link
        libraries) is not supported under this platform.
     4. Profiling

        Profiling with gprof is supported for this platform.
     5. Running Free Pascal without a math coprocessor?

        On the Intel version the emulator is automatically loaded by the
        compiler if you add the following commands to your autoexec.bat:

                            SET 387=N
                            SET EMU387=C:\PP\BIN\GO32V2\WEMU387.DXE


        (don't forget to replace the C:\PP with the directory where you
        installed FPC)
     6. Applications created with Free Pascal crash on 80386 systems

          ☆ Trying to run an application which does floating point operations
            on a 386 system without a math co-processor will crash unless the
            emu387 unit is used, as this unit loads the math co-processor
            emulator (called wmemu387.dxe). You can add the unit as follows:

                                    program myprog;
                                    uses emu387, ...


            When the application is released, the software package should also
            include the wmemu387.dxe redistributable file to avoid problems. .
          ☆ Some 80386 systems have a hardware bug which corrupt the
            accumulator register EAX if it is used in a MOV instruction just
            after a POPAL 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

     7. The mouse cursor is not visible in graphics screens

        A lot of DOS mouse drivers don't support mouse cursors in VESA modes
        properly. Logitech is said to have a decent mouse driver, which can be
        found here
     8. Accessing I/O ports

        With versions before 0.99.10: if you're under DOS you can use the
        outport* and inport* procedures of the go32 unit.

        Since version 0.99.8, the Port array is supported like in TP, as long
        as you use the ports unit in your program (not available under Win32).

        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)
     9. Accessing DOS memory / Doing graphics programming

        You can do like in Turbo Pascal, via absolute or mem[]. For larger
        memory blocks use the dosmemput/dosmemget routines in the Go32 unit.
    10. Changing the default stack size

        Under the DOS (GO32V2) target, the default stack size to 256 bKbytes.
        This can be modified with a special DJGPP utility called stubedit. 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.

    11. Using OS/2 generated applications under DOS

        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 (emx.exe) to execute
        properly. It may be necessary to distribute these files with the
        generated application.

        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.
 5. Windows related information

     1. Releasing software generated by the windows compiler

        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:
          ☆ The default heap size is 256 Kbytes. Automatic growing of the heap
            is supported. It is to note that Windows 95, Windows 98 and Windows
            Me limit the heap to 256 Mbytes (this is a limitation of those
            Operating systems, not of Free Pascal, consult MSDN article Q198959
            for more information).
          ☆ Stack size is unlimited
          ☆ The stack checking option is not available on this platform.

     2. Debugging

        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 windows
        targets.

     3. Dynamic libraries

        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.
     4. Profiling

        Profiling is supported using gprof, starting with version 1.0.7. It
        requires mingw to be installed, and that fpc.cfg point to the correct
        library paths.
     5. Graph and problems with keyboard, mouse and "dummy dos windows"

        Problem:
          ☆ If you use the Graph unit under Win32, you can't 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 window popped up is a GUI
            window, and not a console one.
        Solution:
          ☆ Use units WinMouse and WinCrt instead.

        Problem:
          ☆ 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.
        Solution:
          ☆ Set the application type to GUI:

            {$apptype GUI}

            and put this line before your programs InitGraph statement:

            ShowWindow(GetActiveWindow,0);


            This will hide the dos window window.

        Some of the demos (like fpctris) use these techniques
     6. Cygwin binary directory in your path sometimes causes strange problems

        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.

        Solution: don't put cygwin in your global path for now, only add it
        when needed. Efforts are made to work around this.

        Possible untested workaround: add mingw sh.exe to a directory before
        the cygwin binary directory in the path
     7. Using the DOS compiler under Windows 95

        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).
     8. Using OS/2 generated applications under Windows

        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 note about running OS/2 applications under DOS 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.
     9. Using DOS generated applications under windows

        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.
    10. The mouse cursor does not respond in the Windows IDE

        In windowed mode, the mouse cursor 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.
 6. UNIX related information

    This section also applies to most unix variants, such as linux, freebsd and
    netbsd.
     1. Releasing software generated by the unix compilers

          ☆ The default heap size is 256 Kbytes for the intel version, and 128
            Kb for the m68k versions. Automatic growing of the heap is
            supported.
          ☆ There is no stack space usage limit.
          ☆ Under Solaris and QNX, stack checking is simulated.
          ☆ Minimal operating system versions :
              ○ Linux : Kernel v2.4.x or later.
              ○ FreeBSD : version 5.x or later. (4.x can be made to work with
                minor work)
              ○ NetBSD : version 1.5 or later.
              ○ Solaris : version 5.7 of SunOS or later (should work with
                earlier versions, but untested).
              ○ Qnx : version 6.1.0 or later (should work with earlier
                versions, but untested).
              ○ Mac OS X : version 10.3.9 or later

     2. Debugging

        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. For FreeBSD a recent GDB
        (v5) SVN snapshot is recommended for Pascal support and ease of
        building

     3. Dynamic libraries

        These operating systems do support shared libraries (also called
        dynamic link libraries), Free Pascal currently does not emit position
        independant code (PIC), as required for the creation of shared
        libraries.

        Therefore, even though the linux compiler target permits creating
        shared libraries, the usage of that shared library may result in
        undefined behavior, especially if accessing global variables in the
        library. Creation of shared libraries is not recommended with the
        current version of the compiler.

        Importing code from shared libraries does work as expected though,
        since it does not require usage of position independant code.
     4. Profiling

        Profiling is supported using gprof 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.
     5. Libc is missing on platforms other than Linux/i386

        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.

        To access Unix functionality, please use units like baseunix and unix.
     6. Why can't the linker find "vga"?

        This error typically looks like this:

                         Free Pascal Compiler version 2.2.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


        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
     7. Compiler indicates missing as and ld

        Normally unix systems have the assembler (as) and linker (ld)
        pre-installed and already in the search path. That is the reason why
        these tools are not supplied with the compiler.

        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.

        It is to note that the Solaris version of FPC contains these tools.
     8. An error occurred while linking, or "did you forget -T?"

        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.

        At the same time, LD has been modified to emit a warning of the form

                       /usr/bin/ld: warning: link.res contains output sections; did you forget -T?


        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.

 7. OS/2 related information

     1. Releasing software generated by the OS/2 compiler

        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:
          ☆ 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 emxrt.zip
          ☆ Under OS/2, LIBPATH should be modified to add the EMX DLL paths.
            Otherwise, programs will not run and will abort with an error
            'Cannot find EMX.dll'.
          ☆ The default heap size is 256 Kbytes. Automatic growing of the heap
            is supported.
          ☆ Stack can grow up to 256 Kbytes by default. This can be changed by
            the user or developper using the emxstack or emxbind utilities.

     2. Debugging

        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.

     3. Dynamic libraries

        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).
     4. Profiling

        Profiling is currently not supported for this platform.
     5. Using DOS generated applications under OS/2

        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.

        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.
     6. INSTALL.EXE of version 1.0.6 or below fails with an unknown error (-1)
        under OS/2

        or

        INSTALL.EXE of version 1.0.6 or above complains about missing TZ
        variable under OS/2

        You are most probably using an older version of OS/2 (like OS/2 Warp
        3.0) and don't 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 TIME868
        package.
     7. OS/2 compiler not working after upgrading to 1.9.6 or newer

        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. WarpUpdates site 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.
     8. Compilation under OS/2 fails with error "Can't call the assembler"

        Apart from the point mentioned above, 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.
 8. BeOS related information

    The BeOS port is current no longer maintained
     1. Releasing software generated by the BeOS compiler

        Software generated for the BeOS target will only work on the intel
        based version of BeOS.
          ☆ The target system must have at least BeOS v4.0 or later (BeOS 5.1d
            'Dano' is not supported)
          ☆ The default heap size is 256 Kbytes. Automatic growing of the heap
            is supported
          ☆ Stack size is set to 256 Kbytes. This cannot be changed

     2. Debugging

        This operating system uses DWARF debugging information, and Free Pascal
        does not support emitting DWARF debugging information. It is currently
        impossible to debug applications under BeOS

     3. Dynamic libraries

        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).
     4. Profiling

        Profiling is currently not supported for this platform.
     5. BeOS Linking problems

        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
        site.

 9. Amiga related information

     1. Releasing software generated by the Amiga compiler

          ☆ The target system must have AmigaOS v2.04 or higher
          ☆ The default heap size is 128 Kbytes. Automatic growing of the heap
            is supported.
          ☆ Stack size is not set by the compiler, but by the stack 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.
          ☆ By default, the compiler generates code for the 68020+ processor.
            The code generated will not work on 68000 and 68010 systems unless
            the -O0 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.
          ☆ All floating point operations are simulated, and use the single
            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.

     2. Debugging

        Source level debugging is not supported for the Amiga target. Assembler
        target debugging is possible though, using the excellent Barfly
        debugger.

     3. Dynamic libraries

        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.
     4. Profiling

        Profiling is currently not supported for this platform.
10. PalmOS related information

     1. Releasing software generated by the PalmOS compiler

     2. Debugging

     3. Dynamic libraries