perlos2


SYNOPSIS
       One can read this document in the following formats:

               man perlos2
               view perl perlos2
               explorer perlos2.html
               info perlos2

       to list some (not all may be available simultaneously), or it may be
       read as is: either as README.os2, or pod/perlos2.pod.

       To read the .INF version of documentation (very recommended) outside of
       OS/2, one needs an IBM's reader (may be available on IBM ftp sites (?)
       (URL anyone?)) or shipped with PC DOS 7.0 and IBM's Visual Age C++ 3.5.

       A copy of a Win* viewer is contained in the "Just add OS/2 Warp"
       package

         ftp://ftp.software.ibm.com/ps/products/os2/tools/jaow/jaow.zip

       in ?:\JUST_ADD\view.exe. This gives one an access to EMX's .INF docs as
       well (text form is available in /emx/doc in EMX's distribution).  There
       is also a different viewer named xview.

       Note that if you have lynx.exe or netscape.exe installed, you can
       follow WWW links from this document in .INF format. If you have EMX
       docs installed correctly, you can follow library links (you need to
       have "view emxbook" working by setting "EMXBOOK" environment variable
       as it is described in EMX docs).

DESCRIPTION
   Target
       The target is to make OS/2 one of the best supported platform for
       using/building/developing Perl and Perl applications, as well as make
       Perl the best language to use under OS/2. The secondary target is to
       try to make this work under DOS and Win* as well (but not too hard).

       The current state is quite close to this target. Known limitations:

       o    Some *nix programs use fork() a lot; with the mostly useful
            flavors of perl for OS/2 (there are several built simultaneously)
            this is supported; but some flavors do not support this (e.g.,
            when Perl is called from inside REXX).  Using fork() after useing
            dynamically loading extensions would not work with very old
            versions of EMX.

       o    You need a separate perl executable perl__.exe (see perl__.exe) if
            you want to use PM code in your application (as Perl/Tk or OpenGL
            Perl modules do) without having a text-mode window present.

            While using the standard perl.exe from a text-mode window is
            possible too, I have seen cases when this causes degradation of
            the system stability.  Using perl__.exe avoids such a degradation.

   Other OSes
       Since OS/2 port of perl uses a remarkable EMX environment, it can run
       (and build extensions, and - possibly - be built itself) under any
       environment which can run EMX. The current list is DOS,
       DOS-inside-OS/2, Win0.3*, Win0.95 and WinNT. Out of many perl flavors,
       only one works, see "perl_.exe".

       Note that not all features of Perl are available under these
       environments. This depends on the features the extender - most probably
       RSX - decided to implement.

       Cf. Prerequisites.

   Prerequisites
       EMX   EMX runtime is required (may be substituted by RSX). Note that it
             is possible to make perl_.exe to run under DOS without any
             external support by binding emx.exe/rsx.exe to it, see emxbind.
             Note that under DOS for best results one should use RSX runtime,
             which has much more functions working (like "fork", "popen" and
             so on). In fact RSX is required if there is no VCPI present. Note
             the RSX requires DPMI.  Many implementations of DPMI are known to
             be very buggy, beware!

             Only the latest runtime is supported, currently "0.9d fix 03".
             Perl may run under earlier versions of EMX, but this is not
             tested.

             One can get different parts of EMX from, say

               ftp://crydee.sai.msu.ru/pub/comp/os/os2/leo/gnu/emx+gcc/
               http://hobbes.nmsu.edu/h-browse.php?dir=/pub/os2/dev/emx/v0.9d/

             The runtime component should have the name emxrt.zip.

             NOTE. When using emx.exe/rsx.exe, it is enough to have them on
             your path. One does not need to specify them explicitly (though
             this

               emx perl_.exe -de 0

             will work as well.)

       RSX   To run Perl on DPMI platforms one needs RSX runtime. This is
             needed under DOS-inside-OS/2, Win0.3*, Win0.95 and WinNT (see
             "Other OSes"). RSX would not work with VCPI only, as EMX would,
             it requires DMPI.

             Having RSX and the latest sh.exe one gets a fully functional
             *nix-ish environment under DOS, say, "fork", "``" and pipe-"open"
             work. In fact, MakeMaker works (for static build), so one can
             have Perl development environment under DOS.

             One can get RSX from, say

       HPFS  Perl does not care about file systems, but the perl library
             contains many files with long names, so to install it intact one
             needs a file system which supports long file names.

             Note that if you do not plan to build the perl itself, it may be
             possible to fool EMX to truncate file names. This is not
             supported, read EMX docs to see how to do it.

       pdksh To start external programs with complicated command lines (like
             with pipes in between, and/or quoting of arguments), Perl uses an
             external shell. With EMX port such shell should be named sh.exe,
             and located either in the wired-in-during-compile locations
             (usually F:/bin), or in configurable location (see
             "PERL_SH_DIR").

             For best results use EMX pdksh. The standard binary (5.2.14 or
             later) runs under DOS (with RSX) as well, see

               http://www.ilyaz.org/software/os2/

   Starting Perl programs under OS/2 (and DOS and...)
       Start your Perl program foo.pl with arguments "arg1 arg2 arg3" the same
       way as on any other platform, by

               perl foo.pl arg1 arg2 arg3

       If you want to specify perl options "-my_opts" to the perl itself (as
       opposed to your program), use

               perl -my_opts foo.pl arg1 arg2 arg3

       Alternately, if you use OS/2-ish shell, like CMD or 4os2, put the
       following at the start of your perl script:

               extproc perl -S -my_opts

       rename your program to foo.cmd, and start it by typing

               foo arg1 arg2 arg3

       Note that because of stupid OS/2 limitations the full path of the perl
       script is not available when you use "extproc", thus you are forced to
       use "-S" perl switch, and your script should be on the "PATH". As a
       plus side, if you know a full path to your script, you may still start
       it with

               perl ../../blah/foo.cmd arg1 arg2 arg3

       (note that the argument "-my_opts" is taken care of by the "extproc"
       line in your script, see ""extproc" on the first line").

       To understand what the above magic does, read perl docs about "-S"
       switch - see perlrun, and cmdref about "extproc":

       Note that -S switch supports scripts with additional extensions .cmd,
       .btm, .bat, .pl as well.

   Starting OS/2 (and DOS) programs under Perl
       This is what system() (see "system" in perlfunc), "``" (see "I/O
       Operators" in perlop), and open pipe (see "open" in perlfunc) are for.
       (Avoid exec() (see "exec" in perlfunc) unless you know what you do).

       Note however that to use some of these operators you need to have a sh-
       syntax shell installed (see "Pdksh", "Frequently asked questions"), and
       perl should be able to find it (see "PERL_SH_DIR").

       The cases when the shell is used are:

       1.  One-argument system() (see "system" in perlfunc), exec() (see
           "exec" in perlfunc) with redirection or shell meta-characters;

       2.  Pipe-open (see "open" in perlfunc) with the command which contains
           redirection or shell meta-characters;

       3.  Backticks "``" (see "I/O Operators" in perlop) with the command
           which contains redirection or shell meta-characters;

       4.  If the executable called by system()/exec()/pipe-open()/"``" is a
           script with the "magic" "#!" line or "extproc" line which specifies
           shell;

       5.  If the executable called by system()/exec()/pipe-open()/"``" is a
           script without "magic" line, and $ENV{EXECSHELL} is set to shell;

       6.  If the executable called by system()/exec()/pipe-open()/"``" is not
           found (is not this remark obsolete?);

       7.  For globbing (see "glob" in perlfunc, "I/O Operators" in perlop)
           (obsolete? Perl uses builtin globbing nowadays...).

       For the sake of speed for a common case, in the above algorithms
       backslashes in the command name are not considered as shell
       metacharacters.

       Perl starts scripts which begin with cookies "extproc" or "#!"
       directly, without an intervention of shell.  Perl uses the same
       algorithm to find the executable as pdksh: if the path on "#!" line
       does not work, and contains "/", then the directory part of the
       executable is ignored, and the executable is searched in . and on
       "PATH".  To find arguments for these scripts Perl uses a different
       algorithm than pdksh: up to 3 arguments are recognized, and trailing
       whitespace is stripped.

       If a script does not contain such a cooky, then to avoid calling
       sh.exe, Perl uses the same algorithm as pdksh: if $ENV{EXECSHELL} is
       set, the script is given as the first argument to this command, if not
       set, then "$ENV{COMSPEC} /c" is used (or a hardwired guess if
       $ENV{COMSPEC} is not set).

       Note also that executable files on OS/2 can have an arbitrary
       extension, but .exe will be automatically appended if no dot is present
       in the name.  The workaround is as simple as that:  since blah. and
       blah denote the same file (at list on FAT and HPFS file systems), to
       start an executable residing in file n:/bin/blah (no extension) give an
       argument "n:/bin/blah." (dot appended) to system().

       Perl will start PM programs from VIO (=text-mode) Perl process in a
       separate PM session; the opposite is not true: when you start a non-PM
       program from a PM Perl process, Perl would not run it in a separate
       session.  If a separate session is desired, either ensure that shell
       will be used, as in "system 'cmd /c myprog'", or start it using
       optional arguments to system() documented in "OS2::Process" module.
       This is considered to be a feature.

Frequently asked questions
   "It does not work"
       Perl binary distributions come with a testperl.cmd script which tries
       to detect common problems with misconfigured installations.  There is a
       pretty large chance it will discover which step of the installation you
       managed to goof.  ";-)"

   I cannot run external programs
       o   Did you run your programs with "-w" switch? See "2 (and DOS)
           programs under Perl" in Starting OS.

       o   Do you try to run internal shell commands, like "`copy a b`"
           (internal for cmd.exe), or "`glob a*b`" (internal for ksh)? You
           need to specify your shell explicitly, like "`cmd /c copy a b`",
           since Perl cannot deduce which commands are internal to your shell.

   I cannot embed perl into my program, or use perl.dll from my program.
       Is your program EMX-compiled with "-Zmt -Zcrtdll"?
           Well, nowadays Perl DLL should be usable from a differently
           compiled program too...  If you can run Perl code from REXX scripts
           (see OS2::REXX), then there are some other aspect of interaction
           which are overlooked by the current hackish code to support
           differently-compiled principal programs.

           If everything else fails, you need to build a stand-alone DLL for
           perl. Contact me, I did it once. Sockets would not work, as a lot
           of other stuff.

       Did you use ExtUtils::Embed?
           Some time ago I had reports it does not work.  Nowadays it is
           checked in the Perl test suite, so grep ./t subdirectory of the
           build tree (as well as *.t files in the ./lib subdirectory) to find
           how it should be done "correctly".

   "``" and pipe-"open" do not work under DOS.
       This may a variant of just "I cannot run external programs", or a
       deeper problem. Basically: you need RSX (see "Prerequisites") for these
       commands to work, and you may need a port of sh.exe which understands

       are not equivalent; find cannot be started directly using the above
       API.  One needs a way to surround the doublequotes in some other
       quoting construction, necessarily having an extra non-Unixish shell in
       between.

       Use one of

         system 'cmd', '/c', 'find "pattern" file';
         `cmd /c 'find "pattern" file'`

       This would start find.exe via cmd.exe via "sh.exe" via "perl.exe", but
       this is a price to pay if you want to use non-conforming program.

INSTALLATION
   Automatic binary installation
       The most convenient way of installing a binary distribution of perl is
       via perl installer install.exe. Just follow the instructions, and 99%
       of the installation blues would go away.

       Note however, that you need to have unzip.exe on your path, and EMX
       environment running. The latter means that if you just installed EMX,
       and made all the needed changes to Config.sys, you may need to reboot
       in between. Check EMX runtime by running

               emxrev

       Binary installer also creates a folder on your desktop with some useful
       objects.  If you need to change some aspects of the work of the binary
       installer, feel free to edit the file Perl.pkg.  This may be useful
       e.g., if you need to run the installer many times and do not want to
       make many interactive changes in the GUI.

       Things not taken care of by automatic binary installation:

       "PERL_BADLANG" may be needed if you change your codepage after perl
                      installation, and the new value is not supported by EMX.
                      See "PERL_BADLANG".

       "PERL_BADFREE" see "PERL_BADFREE".

       Config.pm      This file resides somewhere deep in the location you
                      installed your perl library, find it out by

                        perl -MConfig -le "print $INC{'Config.pm'}"

                      While most important values in this file are updated by
                      the binary installer, some of them may need to be hand-
                      edited. I know no such data, please keep me informed if
                      you find one.  Moreover, manual changes to the installed
                      version may need to be accompanied by an edit of this
                      file.

       NOTE. Because of a typo the binary installer of 5.00305 would install a
       entries in Config.sys to reflect where did you put the files. Note that
       if you have some primitive unzipper (like "pkunzip"), you may get a lot
       of warnings/errors during unzipping. Upgrade to "(w)unzip".

       Below is the sample of what to do to reproduce the configuration on my
       machine.  In VIEW.EXE you can press "Ctrl-Insert" now, and cut-and-
       paste from the resulting file - created in the directory you started
       VIEW.EXE from.

       For each component, we mention environment variables related to each
       installation directory.  Either choose directories to match your values
       of the variables, or create/append-to variables to take into account
       the directories.

       Perl VIO and PM executables (dynamically linked)
            unzip perl_exc.zip *.exe *.ico -d f:/emx.add/bin
            unzip perl_exc.zip *.dll -d f:/emx.add/dll

          (have the directories with "*.exe" on PATH, and "*.dll" on LIBPATH);

       Perl_ VIO executable (statically linked)
            unzip perl_aou.zip -d f:/emx.add/bin

          (have the directory on PATH);

       Executables for Perl utilities
            unzip perl_utl.zip -d f:/emx.add/bin

          (have the directory on PATH);

       Main Perl library
            unzip perl_mlb.zip -d f:/perllib/lib

          If this directory is exactly the same as the prefix which was
          compiled into perl.exe, you do not need to change anything. However,
          for perl to find the library if you use a different path, you need
          to "set PERLLIB_PREFIX" in Config.sys, see "PERLLIB_PREFIX".

       Additional Perl modules
            unzip perl_ste.zip -d f:/perllib/lib/site_perl/5.14.2/

          Same remark as above applies.  Additionally, if this directory is
          not one of directories on @INC (and @INC is influenced by
          "PERLLIB_PREFIX"), you need to put this directory and subdirectory
          ./os2 in "PERLLIB" or "PERL5LIB" variable. Do not use "PERL5LIB"
          unless you have it set already. See "ENVIRONMENT" in perl.

          [Check whether this extraction directory is still applicable with
          the new directory structure layout!]

       Tools to compile Perl modules
            unzip perl_blb.zip -d f:/perllib/lib

          Same remark as for perl_ste.zip.

       Source for Perl documentation
            unzip perl_pod.zip -d f:/perllib/lib

          This is used by the "perldoc" program (see perldoc), and may be used
          to generate HTML documentation usable by WWW browsers, and
          documentation in zillions of other formats: "info", "LaTeX",
          "Acrobat", "FrameMaker" and so on.  [Use programs such as pod2latex
          etc.]

       Perl manual in .INF format
            unzip perl_inf.zip -d d:/os2/book

          This directory should better be on "BOOKSHELF".

       Pdksh
            unzip perl_sh.zip -d f:/bin

          This is used by perl to run external commands which explicitly
          require shell, like the commands using redirection and shell
          metacharacters. It is also used instead of explicit /bin/sh.

          Set "PERL_SH_DIR" (see "PERL_SH_DIR") if you move sh.exe from the
          above location.

          Note. It may be possible to use some other sh-compatible shell
          (untested).

       After you installed the components you needed and updated the
       Config.sys correspondingly, you need to hand-edit Config.pm. This file
       resides somewhere deep in the location you installed your perl library,
       find it out by

         perl -MConfig -le "print $INC{'Config.pm'}"

       You need to correct all the entries which look like file paths (they
       currently start with "f:/").

   Warning
       The automatic and manual perl installation leave precompiled paths
       inside perl executables. While these paths are overwriteable (see
       "PERLLIB_PREFIX", "PERL_SH_DIR"), some people may prefer binary editing
       of paths inside the executables/DLLs.

Accessing documentation
       Depending on how you built/installed perl you may have (otherwise
       identical) Perl documentation in the following formats:

   OS/2 .INF file
       Most probably the most convenient form. Under OS/2 view it as

         view perl
         view perl perlfunc
         view perl less

       (Expect a lot of errors during the both steps.) Now move it on your
       BOOKSHELF path.

   Plain text
       If you have perl documentation in the source form, perl utilities
       installed, and GNU groff installed, you may use

               perldoc perlfunc
               perldoc less
               perldoc ExtUtils::MakeMaker

       to access the perl documentation in the text form (note that you may
       get better results using perl manpages).

       Alternately, try running pod2text on .pod files.

   Manpages
       If you have man installed on your system, and you installed perl
       manpages, use something like this:

               man perlfunc
               man 3 less
               man ExtUtils.MakeMaker

       to access documentation for different components of Perl. Start with

               man perl

       Note that dot (.) is used as a package separator for documentation for
       packages, and as usual, sometimes you need to give the section - 3
       above - to avoid shadowing by the less(1) manpage.

       Make sure that the directory above the directory with manpages is on
       our "MANPATH", like this

         set MANPATH=c:/man;f:/perllib/man

       for Perl manpages in "f:/perllib/man/man1/" etc.

   HTML
       If you have some WWW browser available, installed the Perl
       documentation in the source form, and Perl utilities, you can build
       HTML docs. Cd to directory with .pod files, and do like this

               cd f:/perllib/lib/pod
               pod2html

       After this you can direct your browser the file perl.html in this
       directory, and go ahead with reading docs, like this:

               explore file:///f:/perllib/lib/pod/perl.html

       Alternatively you may be able to get these docs prebuilt from CPAN.

BUILD
       Here we discuss how to build Perl under OS/2.

   The short story
       Assume that you are a seasoned porter, so are sure that all the
       necessary tools are already present on your system, and you know how to
       get the Perl source distribution.  Untar it, change to the extract
       directory, and

         gnupatch -p0 < os2\diff.configure
         sh Configure -des -D prefix=f:/perllib
         make
         make test
         make install
         make aout_test
         make aout_install

       This puts the executables in f:/perllib/bin.  Manually move them to the
       "PATH", manually move the built perl*.dll to "LIBPATH" (here for Perl
       DLL * is a not-very-meaningful hex checksum), and run

         make installcmd INSTALLCMDDIR=d:/ir/on/path

       Assuming that the "man"-files were put on an appropriate location, this
       completes the installation of minimal Perl system.  (The binary
       distribution contains also a lot of additional modules, and the
       documentation in INF format.)

       What follows is a detailed guide through these steps.

   Prerequisites
       You need to have the latest EMX development environment, the full GNU
       tool suite (gawk renamed to awk, and GNU find.exe earlier on path than
       the OS/2 find.exe, same with sort.exe, to check use

         find --version
         sort --version

       ). You need the latest version of pdksh installed as sh.exe.

       Check that you have BSD libraries and headers installed, and -
       optionally - Berkeley DB headers and libraries, and crypt.

       Possible locations to get the files:

         ftp://ftp.uni-heidelberg.de/pub/os2/unix/
         http://hobbes.nmsu.edu/h-browse.php?dir=/pub/os2
         http://cd.textfiles.com/hobbesos29804/disk1/DEV32/
         http://cd.textfiles.com/hobbesos29804/disk1/EMX09C/

       It is reported that the following archives contain enough utils to
       build perl: gnufutil.zip, gnusutil.zip, gnututil.zip, gnused.zip,
       gnupatch.zip, gnuawk.zip, gnumake.zip, gnugrep.zip, bsddev.zip and
       If you have exactly the same version of Perl installed already, make
       sure that no copies or perl are currently running.  Later steps of the
       build may fail since an older version of perl.dll loaded into memory
       may be found.  Running "make test" becomes meaningless, since the test
       are checking a previous build of perl (this situation is detected and
       reported by lib/os2_base.t test).  Do not forget to unset
       "PERL_EMXLOAD_SEC" in environment.

       Also make sure that you have /tmp directory on the current drive, and .
       directory in your "LIBPATH". One may try to correct the latter
       condition by

         set BEGINLIBPATH .\.

       if you use something like CMD.EXE or latest versions of 4os2.exe.
       (Setting BEGINLIBPATH to just "." is ignored by the OS/2 kernel.)

       Make sure your gcc is good for "-Zomf" linking: run "omflibs" script in
       /emx/lib directory.

       Check that you have link386 installed. It comes standard with OS/2, but
       may be not installed due to customization. If typing

         link386

       shows you do not have it, do Selective install, and choose "Link object
       modules" in Optional system utilities/More. If you get into link386
       prompts, press "Ctrl-C" to exit.

   Getting perl source
       You need to fetch the latest perl source (including developers
       releases). With some probability it is located in

         http://www.cpan.org/src/
         http://www.cpan.org/src/unsupported

       If not, you may need to dig in the indices to find it in the directory
       of the current maintainer.

       Quick cycle of developers release may break the OS/2 build time to
       time, looking into

         http://www.cpan.org/ports/os2/

       may indicate the latest release which was publicly released by the
       maintainer. Note that the release may include some additional patches
       to apply to the current source of perl.

       Extract it like this

         tar vzxf perl5.00409.tar.gz

       You may see a message about errors while extracting Configure. This is
       because there is a conflict with a similarly-named file configure.
       <http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/>).  Such
       patches usually contain strings "/os2/" and "patch", so it makes sense
       looking for these strings.

   Hand-editing
       You may look into the file ./hints/os2.sh and correct anything wrong
       you find there. I do not expect it is needed anywhere.

   Making
         sh Configure -des -D prefix=f:/perllib

       "prefix" means: where to install the resulting perl library. Giving
       correct prefix you may avoid the need to specify "PERLLIB_PREFIX", see
       "PERLLIB_PREFIX".

       Ignore the message about missing "ln", and about "-c" option to tr. The
       latter is most probably already fixed, if you see it and can trace
       where the latter spurious warning comes from, please inform me.

       Now

         make

       At some moment the built may die, reporting a version mismatch or
       unable to run perl.  This means that you do not have . in your LIBPATH,
       so perl.exe cannot find the needed perl67B2.dll (treat these hex digits
       as line noise).  After this is fixed the build should finish without a
       lot of fuss.

   Testing
       Now run

         make test

       All tests should succeed (with some of them skipped).  If you have the
       same version of Perl installed, it is crucial that you have "." early
       in your LIBPATH (or in BEGINLIBPATH), otherwise your tests will most
       probably test the wrong version of Perl.

       Some tests may generate extra messages similar to

       A lot of "bad free"
           in database tests related to Berkeley DB. This should be fixed
           already.  If it persists, you may disable this warnings, see
           "PERL_BADFREE".

       Process terminated by SIGTERM/SIGINT
           This is a standard message issued by OS/2 applications. *nix
           applications die in silence. It is considered to be a feature. One
           can easily disable this by appropriate sighandlers.

           However the test engine bleeds these message to screen in
           unexpected moments. Two messages of this kind should be present
           during testing.

       The reasons for most important skipped tests are:

       op/fs.t
               18  Checks "atime" and "mtime" of "stat()" - unfortunately,
                   HPFS provides only 2sec time granularity (for compatibility
                   with FAT?).

               25  Checks "truncate()" on a filehandle just opened for write -
                   I do not know why this should or should not work.

       op/stat.t
               Checks "stat()". Tests:

               4   Checks "atime" and "mtime" of "stat()" - unfortunately,
                   HPFS provides only 2sec time granularity (for compatibility
                   with FAT?).

   Installing the built perl
       If you haven't yet moved "perl*.dll" onto LIBPATH, do it now.

       Run

         make install

       It would put the generated files into needed locations. Manually put
       perl.exe, perl__.exe and perl___.exe to a location on your PATH,
       perl.dll to a location on your LIBPATH.

       Run

         make installcmd INSTALLCMDDIR=d:/ir/on/path

       to convert perl utilities to .cmd files and put them on PATH. You need
       to put .EXE-utilities on path manually. They are installed in
       "$prefix/bin", here $prefix is what you gave to Configure, see Making.

       If you use "man", either move the installed */man/ directories to your
       "MANPATH", or modify "MANPATH" to match the location.  (One could have
       avoided this by providing a correct "manpath" option to ./Configure, or
       editing ./config.sh between configuring and making steps.)

   "a.out"-style build
       Proceed as above, but make perl_.exe (see "perl_.exe") by

         make perl_

       test and install by

         make aout_test
         make aout_install

       Manually put perl_.exe to a location on your PATH.

       perl you install is already present and used on your system, or is a
       new version not yet used.  The description below assumes that the
       version is new, so installing its DLLs and .pm files will not disrupt
       the operation of your system even if some intermediate steps are not
       yet fully working.

       The other cases require a little bit more convoluted procedures.  Below
       I suppose that the current version of Perl is 5.8.2, so the executables
       are named accordingly.

       1.  Fully build and test the Perl distribution.  Make sure that no
           tests are failing with "test" and "aout_test" targets; fix the bugs
           in Perl and the Perl test suite detected by these tests.  Make sure
           that "all_test" make target runs as clean as possible.  Check that
           "os2/perlrexx.cmd" runs fine.

       2.  Fully install Perl, including "installcmd" target.  Copy the
           generated DLLs to "LIBPATH"; copy the numbered Perl executables (as
           in perl5.8.2.exe) to "PATH"; copy "perl_.exe" to "PATH" as
           "perl_5.8.2.exe".  Think whether you need backward-compatibility
           DLLs.  In most cases you do not need to install them yet; but
           sometime this may simplify the following steps.

       3.  Make sure that "CPAN.pm" can download files from CPAN.  If not, you
           may need to manually install "Net::FTP".

       4.  Install the bundle "Bundle::OS2_default"

             perl5.8.2 -MCPAN -e "install Bundle::OS2_default" < nul |& tee 00cpan_i_1

           This may take a couple of hours on 1GHz processor (when run the
           first time).  And this should not be necessarily a smooth
           procedure.  Some modules may not specify required dependencies, so
           one may need to repeat this procedure several times until the
           results stabilize.

             perl5.8.2 -MCPAN -e "install Bundle::OS2_default" < nul |& tee 00cpan_i_2
             perl5.8.2 -MCPAN -e "install Bundle::OS2_default" < nul |& tee 00cpan_i_3

           Even after they stabilize, some tests may fail.

           Fix as many discovered bugs as possible.  Document all the bugs
           which are not fixed, and all the failures with unknown reasons.
           Inspect the produced logs 00cpan_i_1 to find suspiciously skipped
           tests, and other fishy events.

           Keep in mind that installation of some modules may fail too: for
           example, the DLLs to update may be already loaded by CPAN.pm.
           Inspect the "install" logs (in the example above 00cpan_i_1 etc)
           for errors, and install things manually, as in

             cd $CPANHOME/.cpan/build/Digest-MD5-2.31
             make install


           Reset back to the default value 1 when you are finished.

       5.  When satisfied with the results, rerun the "installcmd" target.
           Now you can copy "perl5.8.2.exe" to "perl.exe", and install the
           other OMF-build executables: "perl__.exe" etc.  They are ready to
           be used.

       6.  Change to the "./pod" directory of the build tree, download the
           Perl logo CamelGrayBig.BMP, and run

             ( perl2ipf > perl.ipf ) |& tee 00ipf
             ipfc /INF perl.ipf |& tee 00inf

           This produces the Perl docs online book "perl.INF".  Install in on
           "BOOKSHELF" path.

       7.  Now is the time to build statically linked executable perl_.exe
           which includes newly-installed via "Bundle::OS2_default" modules.
           Doing testing via "CPAN.pm" is going to be painfully slow, since it
           statically links a new executable per XS extension.

           Here is a possible workaround: create a toplevel Makefile.PL in
           $CPANHOME/.cpan/build/ with contents being (compare with "Making
           executables with a custom collection of statically loaded
           extensions")

             use ExtUtils::MakeMaker;
             WriteMakefile NAME => 'dummy';

           execute this as

             perl_5.8.2.exe Makefile.PL <nul |& tee 00aout_c1
             make -k all test <nul |& 00aout_t1

           Again, this procedure should not be absolutely smooth.  Some
           "Makefile.PL"'s in subdirectories may be buggy, and would not run
           as "child" scripts.  The interdependency of modules can strike you;
           however, since non-XS modules are already installed, the
           prerequisites of most modules have a very good chance to be
           present.

           If you discover some glitches, move directories of problematic
           modules to a different location; if these modules are non-XS
           modules, you may just ignore them - they are already installed; the
           remaining, XS, modules you need to install manually one by one.

           After each such removal you need to rerun the "Makefile.PL"/"make"
           process; usually this procedure converges soon.  (But be sure to
           convert all the necessary external C libraries from .lib format to
           .a format: run one of

             emxaout foo.lib
             emximp -o foo.a foo.lib
             make install |& tee 00aout_i

           Now you can rename the file ./perl.exe generated during the last
           phase to perl_5.8.2.exe; place it on "PATH"; if there is an inter-
           dependency between some XS modules, you may need to repeat the
           "test"/"install" loop with this new executable and some excluded
           modules - until the procedure converges.

           Now you have all the necessary .a libraries for these Perl modules
           in the places where Perl builder can find it.  Use the perl
           builder: change to an empty directory, create a "dummy" Makefile.PL
           again, and run

             perl_5.8.2.exe Makefile.PL |& tee 00c
             make perl                  |& tee 00p

           This should create an executable ./perl.exe with all the statically
           loaded extensions built in.  Compare the generated perlmain.c files
           to make sure that during the iterations the number of loaded
           extensions only increases.  Rename ./perl.exe to perl_5.8.2.exe on
           "PATH".

           When it converges, you got a functional variant of perl_5.8.2.exe;
           copy it to "perl_.exe".  You are done with generation of the local
           Perl installation.

       8.  Make sure that the installed modules are actually installed in the
           location of the new Perl, and are not inherited from entries of
           @INC given for inheritance from the older versions of Perl: set
           "PERLLIB_582_PREFIX" to redirect the new version of Perl to a new
           location, and copy the installed files to this new location.  Redo
           the tests to make sure that the versions of modules inherited from
           older versions of Perl are not needed.

           Actually, the log output of pod2ipf during the step 6 gives a very
           detailed info about which modules are loaded from which place; so
           you may use it as an additional verification tool.

           Check that some temporary files did not make into the perl install
           tree.  Run something like this

             pfind . -f "!(/\.(pm|pl|ix|al|h|a|lib|txt|pod|imp|bs|dll|ld|bs|inc|xbm|yml|cgi|uu|e2x|skip|packlist|eg|cfg|html|pub|enc|all|ini|po|pot)$/i or /^\w+$/") | less

           in the install tree (both top one and sitelib one).

           Compress all the DLLs with lxlite.  The tiny .exe can be compressed
           with "/c:max" (the bug only appears when there is a fixup in the
           last 6 bytes of a page (?); since the tiny executables are much
           smaller than a page, the bug will not hit).  Do not compress
           "perl_.exe" - it would not work under DOS.

       9.  Now you can generate the binary distribution.  This is done by
           running the test of the CPAN distribution "OS2::SoftInstaller".
           Tune up the file test.pl to suit the layout of current version of
           your work.

       11. Brace yourself for thanks, bug reports, hate mail and spam coming
           as result of the previous step.  No good deed should remain
           unpunished!

Building custom .EXE files
       The Perl executables can be easily rebuilt at any moment.  Moreover,
       one can use the embedding interface (see perlembed) to make very
       customized executables.

   Making executables with a custom collection of statically loaded extensions
       It is a little bit easier to do so while decreasing the list of
       statically loaded extensions.  We discuss this case only here.

       1.  Change to an empty directory, and create a placeholder
           <Makefile.PL>:

             use ExtUtils::MakeMaker;
             WriteMakefile NAME => 'dummy';

       2.  Run it with the flavor of Perl (perl.exe or perl_.exe) you want to
           rebuild.

             perl_ Makefile.PL

       3.  Ask it to create new Perl executable:

             make perl

           (you may need to manually add "PERLTYPE=-DPERL_CORE" to this
           commandline on some versions of Perl; the symptom is that the
           command-line globbing does not work from OS/2 shells with the
           newly-compiled executable; check with

             .\perl.exe -wle "print for @ARGV" *

           ).

       4.  The previous step created perlmain.c which contains a list of
           newXS() calls near the end.  Removing unnecessary calls, and
           rerunning

             make perl

           will produce a customized executable.

   Making executables with a custom search-paths
       The default perl executable is flexible enough to support most usages.
       However, one may want something yet more flexible; for example, one may
       want to find Perl DLL relatively to the location of the EXE file; or
       one may want to ignore the environment when setting the Perl-library
       search patch, etc.

       1.  Looks for Perl DLL in the directory "$exedir/../dll";

       2.  Prepends the above directory to "BEGINLIBPATH";

       3.  Fails if the Perl DLL found via "BEGINLIBPATH" is different from
           what was loaded on step 1; e.g., another process could have loaded
           it from "LIBPATH" or from a different value of "BEGINLIBPATH".  In
           these cases one needs to modify the setting of the system so that
           this other process either does not run, or loads the DLL from
           "BEGINLIBPATH" with "LIBPATHSTRICT=T" (available with kernels after
           September 2000).

       4.  Loads Perl library from "$exedir/../dll/lib/".

       5.  Uses Bourne shell from "$exedir/../dll/sh/ksh.exe".

       For best results compile the C file below with the same options as the
       Perl DLL.  However, a lot of functionality will work even if the
       executable is not an EMX applications, e.g., if compiled with

         gcc -Wall -DDOSISH -DOS2=1 -O2 -s -Zomf -Zsys perl-starter.c -DPERL_DLL_BASENAME=\"perl312F\" -Zstack 8192 -Zlinker /PM:VIO

       Here is the sample C file:

         #define INCL_DOS
         #define INCL_NOPM
         /* These are needed for compile if os2.h includes os2tk.h, not os2emx.h */
         #define INCL_DOSPROCESS
         #include <os2.h>

         #include "EXTERN.h"
         #define PERL_IN_MINIPERLMAIN_C
         #include "perl.h"

         static char *me;
         HMODULE handle;

         static void
         die_with(char *msg1, char *msg2, char *msg3, char *msg4)
         {
            ULONG c;
            char *s = " error: ";

            DosWrite(2, me, strlen(me), &c);
            DosWrite(2, s, strlen(s), &c);
            DosWrite(2, msg1, strlen(msg1), &c);
            DosWrite(2, msg2, strlen(msg2), &c);
            DosWrite(2, msg3, strlen(msg3), &c);
            DosWrite(2, msg4, strlen(msg4), &c);
            DosWrite(2, "\r\n", 2, &c);
            exit(255);
         }

         typedef ULONG (*fill_extLibpath_t)(int type, char *pre, char *post, int replace, char *msg);
             fill_extLibpath_t f;
             ULONG rc_fullname;
             HMODULE handle, handle1;

             if (_execname(buf, sizeof(buf) - 13) != 0)
                 die_with("Can't find full path: ", strerror(errno), "", "");
             /* XXXX Fill `me' with new value */
             l = strlen(buf);
             while (l && buf[l-1] != '/' && buf[l-1] != '\\')
                 l--;
             dirl = l - 1;
             strcpy(buf + l, basename);
             l += strlen(basename);
             strcpy(buf + l, ".dll");
             if ( (rc_fullname = DosLoadModule(fail, sizeof fail, buf, &handle)) != 0
                  && DosLoadModule(fail, sizeof fail, basename, &handle) != 0 )
                 die_with("Can't load DLL ", buf, "", "");
             if (rc_fullname)
                 return handle;                /* was loaded with short name; all is fine */
             if (DosQueryProcAddr(handle, 0, "fill_extLibpath", (PFN*)&f))
                 die_with(buf, ": DLL exports no symbol ", "fill_extLibpath", "");
             buf[dirl] = 0;
             if (f(0 /*BEGINLIBPATH*/, buf /* prepend */, NULL /* append */,
                   0 /* keep old value */, me))
                 die_with(me, ": prepending BEGINLIBPATH", "", "");
             if (DosLoadModule(fail, sizeof fail, basename, &handle1) != 0)
                 die_with(me, ": finding perl DLL again via BEGINLIBPATH", "", "");
             buf[dirl] = '\\';
             if (handle1 != handle) {
                 if (DosQueryModuleName(handle1, sizeof(fail), fail))
                     strcpy(fail, "???");
                 die_with(buf, ":\n\tperl DLL via BEGINLIBPATH is different: \n\t",
                          fail,
                          "\n\tYou may need to manipulate global BEGINLIBPATH and LIBPATHSTRICT"
                          "\n\tso that the other copy is loaded via BEGINLIBPATH.");
             }
             return handle;
         }

         int
         main(int argc, char **argv, char **env)
         {
             main_t f;
             handler_t h;

             me = argv[0];
             /**/
             handle = load_perl_dll(PERL_DLL_BASENAME);

             if (DosQueryProcAddr(handle, 0, "Perl_OS2_handler_install", (PFN*)&h))
                 die_with(PERL_DLL_BASENAME, ": DLL exports no symbol ", "Perl_OS2_handler_install", "");
             if ( !h((void *)"~installprefix", Perlos2_handler_perllib_from)
                  || !h((void *)"~dll", Perlos2_handler_perllib_to)
                  || !h((void *)"~dll/sh/ksh.exe", Perlos2_handler_perl_sh) )

       You do not have MT-safe db.lib. See Prerequisites.

   Problems with tr or sed
       reported with very old version of tr and sed.

   Some problem (forget which ;-)
       You have an older version of perl.dll on your LIBPATH, which broke the
       build of extensions.

   Library ... not found
       You did not run "omflibs". See Prerequisites.

   Segfault in make
       You use an old version of GNU make. See Prerequisites.

   op/sprintf test failure
       This can result from a bug in emx sprintf which was fixed in 0.9d fix
       03.

Specific (mis)features of OS/2 port
   "setpriority", "getpriority"
       Note that these functions are compatible with *nix, not with the older
       ports of '94 - 95. The priorities are absolute, go from 32 to -95,
       lower is quicker. 0 is the default priority.

       WARNING.  Calling "getpriority" on a non-existing process could lock
       the system before Warp3 fixpak22.  Starting with Warp3, Perl will use a
       workaround: it aborts getpriority() if the process is not present.
       This is not possible on older versions "2.*", and has a race condition
       anyway.

   "system()"
       Multi-argument form of "system()" allows an additional numeric
       argument. The meaning of this argument is described in OS2::Process.

       When finding a program to run, Perl first asks the OS to look for
       executables on "PATH" (OS/2 adds extension .exe if no extension is
       present).  If not found, it looks for a script with possible extensions
       added in this order: no extension, .cmd, .btm, .bat, .pl.  If found,
       Perl checks the start of the file for magic strings "#!" and "extproc
       ".  If found, Perl uses the rest of the first line as the beginning of
       the command line to run this script.  The only mangling done to the
       first line is extraction of arguments (currently up to 3), and ignoring
       of the path-part of the "interpreter" name if it can't be found using
       the full path.

       E.g., "system 'foo', 'bar', 'baz'" may lead Perl to finding
       C:/emx/bin/foo.cmd with the first line being

        extproc /bin/bash    -x   -c

       If /bin/bash.exe is not found, then Perl looks for an executable
       bash.exe on "PATH".  If found in C:/emx.add/bin/bash.exe, then the
       above system() is translated to
       limit on the depth is 4.

       If Perl finds that the found executable is of PM type when the current
       session is not, it will start the new process in a separate session of
       necessary type.  Call via "OS2::Process" to disable this magic.

       WARNING.  Due to the described logic, you need to explicitly specify
       .com extension if needed.  Moreover, if the executable perl5.6.1 is
       requested, Perl will not look for perl5.6.1.exe.  [This may change in
       the future.]

   "extproc" on the first line
       If the first chars of a Perl script are "extproc ", this line is
       treated as "#!"-line, thus all the switches on this line are processed
       (twice if script was started via cmd.exe).  See "DESCRIPTION" in
       perlrun.

   Additional modules:
       OS2::Process, OS2::DLL, OS2::REXX, OS2::PrfDB, OS2::ExtAttr. These
       modules provide access to additional numeric argument for "system" and
       to the information about the running process, to DLLs having functions
       with REXX signature and to the REXX runtime, to OS/2 databases in the
       .INI format, and to Extended Attributes.

       Two additional extensions by Andreas Kaiser, "OS2::UPM", and
       "OS2::FTP", are included into "ILYAZ" directory, mirrored on CPAN.
       Other OS/2-related extensions are available too.

   Prebuilt methods:
       "File::Copy::syscopy"
           used by "File::Copy::copy", see File::Copy.

       "DynaLoader::mod2fname"
           used by "DynaLoader" for DLL name mangling.

       "Cwd::current_drive()"
           Self explanatory.

       "Cwd::sys_chdir(name)"
           leaves drive as it is.

       "Cwd::change_drive(name)"
           changes the "current" drive.

       "Cwd::sys_is_absolute(name)"
           means has drive letter and is_rooted.

       "Cwd::sys_is_rooted(name)"
           means has leading "[/\\]" (maybe after a drive-letter:).

       "Cwd::sys_is_relative(name)"
           means changes with current dir.

       "Cwd::sys_cwd(name)"
       "Cwd::extLibpath_set( path [, type ] )"
           Set current value of extended library search path. If "type" is
           present and positive, works with <END_LIBPATH>, if negative, works
           with "LIBPATHSTRICT", otherwise with "BEGIN_LIBPATH".

       "OS2::Error(do_harderror,do_exception)"
           Returns   "undef" if it was not called yet, otherwise bit 1 is set
           if on the previous call do_harderror was enabled, bit 2 is set if
           on previous call do_exception was enabled.

           This function enables/disables error popups associated with
           hardware errors (Disk not ready etc.) and software exceptions.

           I know of no way to find out the state of popups before the first
           call to this function.

       "OS2::Errors2Drive(drive)"
           Returns "undef" if it was not called yet, otherwise return false if
           errors were not requested to be written to a hard drive, or the
           drive letter if this was requested.

           This function may redirect error popups associated with hardware
           errors (Disk not ready etc.) and software exceptions to the file
           POPUPLOG.OS2 at the root directory of the specified drive.
           Overrides OS2::Error() specified by individual programs.  Given
           argument undef will disable redirection.

           Has global effect, persists after the application exits.

           I know of no way to find out the state of redirection of popups to
           the disk before the first call to this function.

       OS2::SysInfo()
           Returns a hash with system information. The keys of the hash are

                   MAX_PATH_LENGTH, MAX_TEXT_SESSIONS, MAX_PM_SESSIONS,
                   MAX_VDM_SESSIONS, BOOT_DRIVE, DYN_PRI_VARIATION,
                   MAX_WAIT, MIN_SLICE, MAX_SLICE, PAGE_SIZE,
                   VERSION_MAJOR, VERSION_MINOR, VERSION_REVISION,
                   MS_COUNT, TIME_LOW, TIME_HIGH, TOTPHYSMEM, TOTRESMEM,
                   TOTAVAILMEM, MAXPRMEM, MAXSHMEM, TIMER_INTERVAL,
                   MAX_COMP_LENGTH, FOREGROUND_FS_SESSION,
                   FOREGROUND_PROCESS

       OS2::BootDrive()
           Returns a letter without colon.

       "OS2::MorphPM(serve)", "OS2::UnMorphPM(serve)"
           Transforms the current application into a PM application and back.
           The argument true means that a real message loop is going to be
           served.  OS2::MorphPM() returns the PM message queue handle as an
           integer.

           See "Centralized management of resources" for additional details.

           Returns change in number of windows.  If "cnt" is given, it is
           incremented by the number of messages retrieved.

           Dies with "QUITing..." if WM_QUIT message is obtained.

       "OS2::_control87(new,mask)"
           the same as _control87(3) of EMX.  Takes integers as arguments,
           returns the previous coprocessor control word as an integer.  Only
           bits in "new" which are present in "mask" are changed in the
           control word.

       OS2::get_control87()
           gets the coprocessor control word as an integer.

       "OS2::set_control87_em(new=MCW_EM,mask=MCW_EM)"
           The variant of OS2::_control87() with default values good for
           handling exception mask: if no "mask", uses exception mask part of
           "new" only.  If no "new", disables all the floating point
           exceptions.

           See "Misfeatures" for details.

       "OS2::DLLname([how [, \&xsub]])"
           Gives the information about the Perl DLL or the DLL containing the
           C function bound to by &xsub.  The meaning of "how" is: default
           (2): full name; 0: handle; 1: module name.

       (Note that some of these may be moved to different libraries -
       eventually).

   Prebuilt variables:
       $OS2::emx_rev
           numeric value is the same as _emx_rev of EMX, a string value the
           same as _emx_vprt (similar to "0.9c").

       $OS2::emx_env
           same as _emx_env of EMX, a number similar to 0x8001.

       $OS2::os_ver
           a number "OS_MAJOR + 0.001 * OS_MINOR".

       $OS2::is_aout
           true if the Perl library was compiled in AOUT format.

       $OS2::can_fork
           true if the current executable is an AOUT EMX executable, so Perl
           can fork.  Do not use this, use the portable check for
           $Config::Config{dfork}.

       $OS2::nsyserror
           This variable (default is 1) controls whether to enforce the
           contents of $^E to start with "SYS0003"-like id.  If set to 0, then
           the string value of $^E is what is available from the OS/2 message
               implemented.

           o   sock_init(3) is not required and not implemented.

           o   flock(3) is not yet implemented (dummy function).  (Perl has a
               workaround.)

           o   kill(3):  Special treatment of PID=0, PID=1 and PID=-1 is not
               implemented.

           o   waitpid(3):

                     WUNTRACED
                             Not implemented.
                     waitpid() is not implemented for negative values of PID.

           Note that "kill -9" does not work with the current version of EMX.

       o   See "Text-mode filehandles".

       o   Unix-domain sockets on OS/2 live in a pseudo-file-system
           "/sockets/...".  To avoid a failure to create a socket with a name
           of a different form, "/socket/" is prepended to the socket name
           (unless it starts with this already).

           This may lead to problems later in case the socket is accessed via
           the "usual" file-system calls using the "initial" name.

       o   Apparently, IBM used a compiler (for some period of time around
           '95?) which changes FP mask right and left.  This is not that bad
           for IBM's programs, but the same compiler was used for DLLs which
           are used with general-purpose applications.  When these DLLs are
           used, the state of floating-point flags in the application is not
           predictable.

           What is much worse, some DLLs change the floating point flags when
           in _DLLInitTerm() (e.g., TCP32IP).  This means that even if you do
           not call any function in the DLL, just the act of loading this DLL
           will reset your flags.  What is worse, the same compiler was used
           to compile some HOOK DLLs.  Given that HOOK dlls are executed in
           the context of all the applications in the system, this means a
           complete unpredictability of floating point flags on systems using
           such HOOK DLLs.  E.g., GAMESRVR.DLL of DIVE origin changes the
           floating point flags on each write to the TTY of a VIO (windowed
           text-mode) applications.

           Some other (not completely debugged) situations when FP flags
           change include some video drivers (?), and some operations related
           to creation of the windows.  People who code OpenGL may have more
           experience on this.

           Perl is generally used in the situation when all the floating-point
           exceptions are ignored, as is the default under EMX.  If they are
           not ignored, some benign Perl programs would get a "SIGFPE" and
           runtime.  Currently no way to switch these hacks off is provided.

   Modifications
       Perl modifies some standard C library calls in the following ways:

       "popen"  "my_popen" uses sh.exe if shell is required, cf.
                "PERL_SH_DIR".

       "tmpnam" is created using "TMP" or "TEMP" environment variable, via
                "tempnam".

       "tmpfile"
                If the current directory is not writable, file is created
                using modified "tmpnam", so there may be a race condition.

       "ctermid"
                a dummy implementation.

       "stat"   "os2_stat" special-cases /dev/tty and /dev/con.

       "mkdir", "rmdir"
                these EMX functions do not work if the path contains a
                trailing "/".  Perl contains a workaround for this.

       "flock"  Since flock(3) is present in EMX, but is not functional, it is
                emulated by perl.  To disable the emulations, set environment
                variable "USE_PERL_FLOCK=0".

   Identifying DLLs
       All the DLLs built with the current versions of Perl have ID strings
       identifying the name of the extension, its version, and the version of
       Perl required for this DLL.  Run "bldlevel DLL-name" to find this info.

   Centralized management of resources
       Since to call certain OS/2 API one needs to have a correctly
       initialized "Win" subsystem, OS/2-specific extensions may require
       getting "HAB"s and "HMQ"s.  If an extension would do it on its own,
       another extension could fail to initialize.

       Perl provides a centralized management of these resources:

       "HAB"
           To get the HAB, the extension should call "hab = perl_hab_GET()" in
           C.  After this call is performed, "hab" may be accessed as
           "Perl_hab".  There is no need to release the HAB after it is used.

           If by some reasons perl.h cannot be included, use

             extern int Perl_hab_GET(void);

           instead.

       "HMQ"
           There are two cases:
           "perl_hmq_UNSET(serve)".  Perl process will automatically
           morph/unmorph itself into/from a PM process if HMQ is
           needed/not-needed.  Perl will automatically enable/disable
           "WM_QUIT" message during shutdown if the message queue is
           served/not-served.

           NOTE.  If during a shutdown there is a message queue which did not
           disable WM_QUIT, and which did not process the received WM_QUIT
           message, the shutdown will be automatically cancelled.  Do not call
           perl_hmq_GET(1) unless you are going to process messages on an
           orderly basis.

       Treating errors reported by OS/2 API
           There are two principal conventions (it is useful to call them
           "Dos*" and "Win*" - though this part of the function signature is
           not always determined by the name of the API) of reporting the
           error conditions of OS/2 API.  Most of "Dos*" APIs report the error
           code as the result of the call (so 0 means success, and there are
           many types of errors).  Most of "Win*" API report success/fail via
           the result being "TRUE"/"FALSE"; to find the reason for the failure
           one should call WinGetLastError() API.

           Some "Win*" entry points also overload a "meaningful" return value
           with the error indicator; having a 0 return value indicates an
           error.  Yet some other "Win*" entry points overload things even
           more, and 0 return value may mean a successful call returning a
           valid value 0, as well as an error condition; in the case of a 0
           return value one should call WinGetLastError() API to distinguish a
           successful call from a failing one.

           By convention, all the calls to OS/2 API should indicate their
           failures by resetting $^E.  All the Perl-accessible functions which
           call OS/2 API may be broken into two classes: some die()s when an
           API error is encountered, the other report the error via a false
           return value (of course, this does not concern Perl-accessible
           functions which expect a failure of the OS/2 API call, having some
           workarounds coded).

           Obviously, in the situation of the last type of the signature of an
           OS/2 API, it is must more convenient for the users if the failure
           is indicated by die()ing: one does not need to check $^E to know
           that something went wrong.  If, however, this solution is not
           desirable by some reason, the code in question should reset $^E to
           0 before making this OS/2 API call, so that the caller of this
           Perl-accessible function has a chance to distinguish a
           success-but-0-return value from a failure.  (One may return undef
           as an alternative way of reporting an error.)

           The macros to simplify this type of error propagation are

           "CheckOSError(expr)"
               Returns true on error, sets $^E.  Expects expr() be a call of
               "Dos*"-style API.

               by ": " from the contents of $^E.

           "WinError_2_Perl_rc"
               Sets "Perl_rc" to the return value of WinGetLastError().

           "FillWinError"
               Sets "Perl_rc" to the return value of WinGetLastError(), and
               sets $^E to the corresponding value.

           "FillOSError(rc)"
               Sets "Perl_rc" to "rc", and sets $^E to the corresponding
               value.

       Loading DLLs and ordinals in DLLs
           Some DLLs are only present in some versions of OS/2, or in some
           configurations of OS/2.  Some exported entry points are present
           only in DLLs shipped with some versions of OS/2.  If these DLLs and
           entry points were linked directly for a Perl executable/DLL or from
           a Perl extensions, this binary would work only with the specified
           versions/setups.  Even if these entry points were not needed, the
           load of the executable (or DLL) would fail.

           For example, many newer useful APIs are not present in OS/2 v2;
           many PM-related APIs require DLLs not available on floppy-boot
           setup.

           To make these calls fail only when the calls are executed, one
           should call these API via a dynamic linking API.  There is a
           subsystem in Perl to simplify such type of calls.  A large number
           of entry points available for such linking is provided (see
           "entries_ordinals" - and also "PMWIN_entries" - in os2ish.h).
           These ordinals can be accessed via the APIs:

             CallORD(), DeclFuncByORD(), DeclVoidFuncByORD(),
             DeclOSFuncByORD(), DeclWinFuncByORD(), AssignFuncPByORD(),
             DeclWinFuncByORD_CACHE(), DeclWinFuncByORD_CACHE_survive(),
             DeclWinFuncByORD_CACHE_resetError_survive(),
             DeclWinFunc_CACHE(), DeclWinFunc_CACHE_resetError(),
             DeclWinFunc_CACHE_survive(), DeclWinFunc_CACHE_resetError_survive()

           See the header files and the C code in the supplied OS/2-related
           modules for the details on usage of these functions.

           Some of these functions also combine dynaloading semantic with the
           error-propagation semantic discussed above.

Perl flavors
       Because of idiosyncrasies of OS/2 one cannot have all the eggs in the
       same basket (though EMX environment tries hard to overcome this
       limitations, so the situation may somehow improve). There are 4
       executables for Perl provided by the distribution:

   perl.exe
       The main workhorse. This is a chimera executable: it is compiled as an
       restriction is important only if you use custom-built extensions. This
       executable is a VIO application.

       This is the only executable with does not require OS/2. The friends
       locked into "M$" world would appreciate the fact that this executable
       runs under DOS, Win0.3*, Win0.95 and WinNT with an appropriate
       extender. See "Other OSes".

   perl__.exe
       This is the same executable as perl___.exe, but it is a PM application.

       Note. Usually (unless explicitly redirected during the startup) STDIN,
       STDERR, and STDOUT of a PM application are redirected to nul. However,
       it is possible to see them if you start "perl__.exe" from a PM program
       which emulates a console window, like Shell mode of Emacs or EPM. Thus
       it is possible to use Perl debugger (see perldebug) to debug your PM
       application (but beware of the message loop lockups - this will not
       work if you have a message queue to serve, unless you hook the serving
       into the getc() function of the debugger).

       Another way to see the output of a PM program is to run it as

         pm_prog args 2>&1 | cat -

       with a shell different from cmd.exe, so that it does not create a link
       between a VIO session and the session of "pm_porg".  (Such a link
       closes the VIO window.)  E.g., this works with sh.exe - or with Perl!

         open P, 'pm_prog args 2>&1 |' or die;
         print while <P>;

       The flavor perl__.exe is required if you want to start your program
       without a VIO window present, but not "detach"ed (run "help detach" for
       more info).  Very useful for extensions which use PM, like "Perl/Tk" or
       "OpenGL".

       Note also that the differences between PM and VIO executables are only
       in the default behaviour.  One can start any executable in any kind of
       session by using the arguments "/fs", "/pm" or "/win" switches of the
       command "start" (of CMD.EXE or a similar shell).  Alternatively, one
       can use the numeric first argument of the "system" Perl function (see
       OS2::Process).

   perl___.exe
       This is an "omf"-style executable which is dynamically linked to
       perl.dll and CRT DLL. I know no advantages of this executable over
       "perl.exe", but it cannot fork() at all. Well, one advantage is that
       the build process is not so convoluted as with "perl.exe".

       It is a VIO application.

   Why strange names?
       Since Perl processes the "#!"-line (cf.  "DESCRIPTION" in perlrun,
       "Switches" in perlrun, "Not a perl script" in perldiag, "No Perl script

       There are two distinctive features of the dyna-linking model of OS/2:
       first, all the references to external functions are resolved at the
       compile time; second, there is no runtime fixup of the DLLs after they
       are loaded into memory.  The first feature is an enormous advantage
       over other models: it avoids conflicts when several DLLs used by an
       application export entries with the same name.  In such cases "other"
       models of dyna-linking just choose between these two entry points using
       some random criterion - with predictable disasters as results.  But it
       is the second feature which requires the build of perl.dll.

       The address tables of DLLs are patched only once, when they are loaded.
       The addresses of the entry points into DLLs are guaranteed to be the
       same for all the programs which use the same DLL.  This removes the
       runtime fixup - once DLL is loaded, its code is read-only.

       While this allows some (significant?) performance advantages, this
       makes life much harder for developers, since the above scheme makes it
       impossible for a DLL to be "linked" to a symbol in the .EXE file.
       Indeed, this would need a DLL to have different relocations tables for
       the (different) executables which use this DLL.

       However, a dynamically loaded Perl extension is forced to use some
       symbols from the perl executable, e.g., to know how to find the
       arguments to the functions: the arguments live on the perl internal
       evaluation stack. The solution is to put the main code of the
       interpreter into a DLL, and make the .EXE file which just loads this
       DLL into memory and supplies command-arguments.  The extension DLL
       cannot link to symbols in .EXE, but it has no problem linking to
       symbols in the .DLL.

       This greatly increases the load time for the application (as well as
       complexity of the compilation). Since interpreter is in a DLL, the C
       RTL is basically forced to reside in a DLL as well (otherwise
       extensions would not be able to use CRT).  There are some advantages if
       you use different flavors of perl, such as running perl.exe and
       perl__.exe simultaneously: they share the memory of perl.dll.

       NOTE.  There is one additional effect which makes DLLs more wasteful:
       DLLs are loaded in the shared memory region, which is a scarse resource
       given the 512M barrier of the "standard" OS/2 virtual memory.  The code
       of .EXE files is also shared by all the processes which use the
       particular .EXE, but they are "shared in the private address space of
       the process"; this is possible because the address at which different
       sections of the .EXE file are loaded is decided at compile-time, thus
       all the processes have these sections loaded at same addresses, and no
       fixup of internal links inside the .EXE is needed.

       Since DLLs may be loaded at run time, to have the same mechanism for
       DLLs one needs to have the address range of any of the loaded DLLs in
       the system to be available in all the processes which did not load a
       particular DLL yet.  This is why the DLLs are mapped to the shared
       memory region.

       o   "open FH, "-|"", in other words, opening pipes to itself.

       While these operations are not questions of life and death, they are
       needed for a lot of useful scripts. This forces "a.out"-style compile
       of perl.exe.

ENVIRONMENT
       Here we list environment variables with are either OS/2- and DOS- and
       Win*-specific, or are more important under OS/2 than under other OSes.

   "PERLLIB_PREFIX"
       Specific for EMX port. Should have the form

         path1;path2

       or

         path1 path2

       If the beginning of some prebuilt path matches path1, it is substituted
       with path2.

       Should be used if the perl library is moved from the default location
       in preference to "PERL(5)LIB", since this would not leave wrong entries
       in @INC.  For example, if the compiled version of perl looks for @INC
       in f:/perllib/lib, and you want to install the library in h:/opt/gnu,
       do

         set PERLLIB_PREFIX=f:/perllib/lib;h:/opt/gnu

       This will cause Perl with the prebuilt @INC of

         f:/perllib/lib/5.00553/os2
         f:/perllib/lib/5.00553
         f:/perllib/lib/site_perl/5.00553/os2
         f:/perllib/lib/site_perl/5.00553
         .

       to use the following @INC:

         h:/opt/gnu/5.00553/os2
         h:/opt/gnu/5.00553
         h:/opt/gnu/site_perl/5.00553/os2
         h:/opt/gnu/site_perl/5.00553
         .

   "PERL_BADLANG"
       If 0, perl ignores setlocale() failing. May be useful with some strange
       locales.

   "PERL_BADFREE"
       If 0, perl would not warn of in case of unwarranted free(). With older
       perls this might be useful in conjunction with the module DB_File,
       which was buggy when dynamically linked and OMF-built.

   "TMP" or "TEMP"
       Specific for EMX port. Used as storage place for temporary files.

Evolution
       Here we list major changes which could make you by surprise.

   Text-mode filehandles
       Starting from version 5.8, Perl uses a builtin translation layer for
       text-mode files.  This replaces the efficient well-tested EMX layer by
       some code which should be best characterized as a "quick hack".

       In addition to possible bugs and an inability to follow changes to the
       translation policy with off/on switches of TERMIO translation, this
       introduces a serious incompatible change: before sysread() on text-mode
       filehandles would go through the translation layer, now it would not.

   Priorities
       "setpriority" and "getpriority" are not compatible with earlier ports
       by Andreas Kaiser. See "setpriority, getpriority".

   DLL name mangling: pre 5.6.2
       With the release 5.003_01 the dynamically loadable libraries should be
       rebuilt when a different version of Perl is compiled. In particular,
       DLLs (including perl.dll) are now created with the names which contain
       a checksum, thus allowing workaround for OS/2 scheme of caching DLLs.

       It may be possible to code a simple workaround which would

       o   find the old DLLs looking through the old @INC;

       o   mangle the names according to the scheme of new perl and copy the
           DLLs to these names;

       o   edit the internal "LX" tables of DLL to reflect the change of the
           name (probably not needed for Perl extension DLLs, since the
           internally coded names are not used for "specific" DLLs, they used
           only for "global" DLLs).

       o   edit the internal "IMPORT" tables and change the name of the "old"
           perl????.dll to the "new" perl????.dll.

   DLL name mangling: 5.6.2 and beyond
       In fact mangling of extension DLLs was done due to misunderstanding of
       the OS/2 dynaloading model.  OS/2 (effectively) maintains two different
       tables of loaded DLL:

       Global DLLs
           those loaded by the base name from "LIBPATH"; including those
           associated at link time;

       specific DLLs
           loaded by the full name.

           same for all the processes).

       Unless "LIBPATHSTRICT" is set to "T" (and the kernel is after
       2000/09/01), such DLLs are considered to be global.  When loading a
       global DLL it is first looked in the table of already-loaded global
       DLLs.  Because of this the fact that one executable loaded a DLL from
       "BEGINLIBPATH" and "ENDLIBPATH", or . from "LIBPATH" may affect which
       DLL is loaded when another executable requests a DLL with the same
       name.  This is the reason for version-specific mangling of the DLL name
       for perl DLL.

       Since the Perl extension DLLs are always loaded with the full path,
       there is no need to mangle their names in a version-specific ways:
       their directory already reflects the corresponding version of perl, and
       @INC takes into account binary compatibility with older version.
       Starting from 5.6.2 the name mangling scheme is fixed to be the same as
       for Perl 5.005_53 (same as in a popular binary release).  Thus new
       Perls will be able to resolve the names of old extension DLLs if @INC
       allows finding their directories.

       However, this still does not guarantee that these DLL may be loaded.
       The reason is the mangling of the name of the Perl DLL.  And since the
       extension DLLs link with the Perl DLL, extension DLLs for older
       versions would load an older Perl DLL, and would most probably segfault
       (since the data in this DLL is not properly initialized).

       There is a partial workaround (which can be made complete with newer
       OS/2 kernels): create a forwarder DLL with the same name as the DLL of
       the older version of Perl, which forwards the entry points to the newer
       Perl's DLL.  Make this DLL accessible on (say) the "BEGINLIBPATH" of
       the new Perl executable.  When the new executable accesses old Perl's
       extension DLLs, they would request the old Perl's DLL by name, get the
       forwarder instead, so effectively will link with the currently running
       (new) Perl DLL.

       This may break in two ways:

       o   Old perl executable is started when a new executable is running has
           loaded an extension compiled for the old executable (ouph!).  In
           this case the old executable will get a forwarder DLL instead of
           the old perl DLL, so would link with the new perl DLL.  While not
           directly fatal, it will behave the same as new executable.  This
           beats the whole purpose of explicitly starting an old executable.

       o   A new executable loads an extension compiled for the old executable
           when an old perl executable is running.  In this case the extension
           will not pick up the forwarder - with fatal results.

       With support for "LIBPATHSTRICT" this may be circumvented - unless one
       of DLLs is started from . from "LIBPATH" (I do not know whether
       "LIBPATHSTRICT" affects this case).

       REMARK.  Unless newer kernels allow . in "BEGINLIBPATH" (older do not),
       this mess cannot be completely cleaned.  (It turns out that as of the
         LIBRARY 'perlE0AC' INITINSTANCE TERMINSTANCE
         DESCRIPTION '@#perl5-porters@perl.org:5.006001#@ Perl module for 5.00553 -> Perl 5.6.1 forwarder'
         CODE LOADONCALL
         DATA LOADONCALL NONSHARED MULTIPLE
         EXPORTS

       modifying the versions/names as needed.  Run

        perl -wnle "next if 0../EXPORTS/; print qq(  \"$1\") if /\"(\w+)\"/" perl5.def >lst

       in the Perl build directory (to make the DLL smaller replace perl5.def
       with the definition file for the older version of Perl if present).

        cat perl5shim.def-leader lst >perl5shim.def
        gcc -Zomf -Zdll -o perlE0AC.dll perl5shim.def -s -llibperl

       (ignore multiple "warning L4085").

   Threading
       As of release 5.003_01 perl is linked to multithreaded C RTL DLL.  If
       perl itself is not compiled multithread-enabled, so will not be perl's
       malloc(). However, extensions may use multiple thread on their own
       risk.

       This was needed to compile "Perl/Tk" for XFree86-OS/2 out-of-the-box,
       and link with DLLs for other useful libraries, which typically are
       compiled with "-Zmt -Zcrtdll".

   Calls to external programs
       Due to a popular demand the perl external program calling has been
       changed wrt Andreas Kaiser's port.  If perl needs to call an external
       program via shell, the f:/bin/sh.exe will be called, or whatever is the
       override, see "PERL_SH_DIR".

       Thus means that you need to get some copy of a sh.exe as well (I use
       one from pdksh). The path F:/bin above is set up automatically during
       the build to a correct value on the builder machine, but is overridable
       at runtime,

       Reasons: a consensus on "perl5-porters" was that perl should use one
       non-overridable shell per platform. The obvious choices for OS/2 are
       cmd.exe and sh.exe. Having perl build itself would be impossible with
       cmd.exe as a shell, thus I picked up "sh.exe". This assures almost 100%
       compatibility with the scripts coming from *nix. As an added benefit
       this works as well under DOS if you use DOS-enabled port of pdksh (see
       "Prerequisites").

       Disadvantages: currently sh.exe of pdksh calls external programs via
       fork()/exec(), and there is no functioning exec() on OS/2. exec() is
       emulated by EMX by an asynchronous call while the caller waits for
       child completion (to pretend that the "pid" did not change). This means
       that 1 extra copy of sh.exe is made active via fork()/exec(), which may
       lead to some resources taken from the system (even if we do not count
       extra work needed for fork()ing).
         use OS2::Cmd;

       which will override system(), exec(), "``", and "open(,'...|')". With
       current perl you may override only system(), readpipe() - the explicit
       version of "``", and maybe exec(). The code will substitute the one-
       argument call to system() by "CORE::system('cmd.exe', '/c', shift)".

       If you have some working code for "OS2::Cmd", please send it to me, I
       will include it into distribution. I have no need for such a module, so
       cannot test it.

       For the details of the current situation with calling external
       programs, see "2 (and DOS) programs under Perl" in Starting OS.  Set us
       mention a couple of features:

       o   External scripts may be called by their basename.  Perl will try
           the same extensions as when processing -S command-line switch.

       o   External scripts starting with "#!" or "extproc " will be executed
           directly, without calling the shell, by calling the program
           specified on the rest of the first line.

   Memory allocation
       Perl uses its own malloc() under OS/2 - interpreters are usually
       malloc-bound for speed, but perl is not, since its malloc is lightning-
       fast.  Perl-memory-usage-tuned benchmarks show that Perl's malloc is 5
       times quicker than EMX one.  I do not have convincing data about memory
       footprint, but a (pretty random) benchmark showed that Perl's one is 5%
       better.

       Combination of perl's malloc() and rigid DLL name resolution creates a
       special problem with library functions which expect their return value
       to be free()d by system's free(). To facilitate extensions which need
       to call such functions, system memory-allocation functions are still
       available with the prefix "emx_" added. (Currently only DLL perl has
       this, it should propagate to perl_.exe shortly.)

   Threads
       One can build perl with thread support enabled by providing "-D
       usethreads" option to Configure.  Currently OS/2 support of threads is
       very preliminary.

       Most notable problems:

       "COND_WAIT"
           may have a race condition (but probably does not due to edge-
           triggered nature of OS/2 Event semaphores).  (Needs a
           reimplementation (in terms of chaining waiting threads, with the
           linked list stored in per-thread structure?)?)

       os2.c
           has a couple of static variables used in OS/2-specific functions.
           (Need to be moved to per-thread structure, or serialized?)




perl v5.14.2                      2011-09-26                        PERLOS2(1)
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