PERLOS2(1)

💖 PERLOS2(1) 💖 — Perl Programmers Reference Guide, bestie edition

okay so welcome to perlos2, the manual page for running Perl under OS/2, DOS, Win0.3*, Win0.95 and WinNT. Yes, all of those. It's giving retro. It's giving vintage computing realness. Let's get into it. 🫶

✨ NAME ✨

perlos2 — Perl under OS/2, DOS, Win0.3*, Win0.95 and WinNT.

Like, literally that's the whole name section. Short. Iconic. Periodt. 💅

🦋 SYNOPSIS 🦋

Bestie, you can read this document in the following formats:

man perlos2
view perl perlos2
explorer perlos2.html
info perlos2

That's just to list some of them — not all may be available simultaneously, so don't come for me if one of these isn't working on your machine. 🙈

You can also just read it as is: either as README.os2, or pod/perlos2.pod.

Now, to read the .INF version of the documentation (very recommended, fr fr) outside of OS/2, you need one of these:

an IBM's reader — which may or may not be available on IBM ftp sites (?) (URL anyone? 😭), or
one 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

It lives at ?:\JUST_ADD\view.exe. This gives you access to EMX's .INF docs as well — the text form is available in /emx/doc in EMX's distribution. Slay. There's also a different viewer named xview. Options, we love options. 💖

Little note, bestie: if you have lynx.exe or netscape.exe installed, you can follow WWW links from this document in .INF format. And if you have EMX docs installed correctly, you can follow library links too. For that you need to have view emxbook working by setting the EMXBOOK environment variable as it is described in EMX docs. iykyk. 🦋

Okay that's part one, more coming, don't go anywhere. 🌸

✨ DESCRIPTION ✨

🎯 Target 🎯

okay so bestie, here's the dream: make OS/2 one of the best supported platforms out there for using / building / developing Perl and Perl applications, and simultaneously make Perl the best language to use under OS/2. The secondary goal? Try to make all of that work under DOS and Win* too — but like, not too hard, we're not doing backflips. 💅

And fr fr, the current state is pretty close to that target. Here's what's still not perfect:

Some *nix programs use fork() a lot. With the mostly useful flavors of perl for OS/2 (there are several built at the same time) this is supported — slay. But some flavors do not support it (e.g. when Perl is called from inside REXX). And using fork() after using dynamically loading extensions would not work with very old versions of EMX. 🫠
You need a separate perl executable perl__.exe (peep the section "perl__.exe") if you want to use PM code in your application — the way Perl/Tk or OpenGL Perl modules do — without having a text-mode window present.

Using the standard perl.exe from a text-mode window is possible too, but I have seen cases where this causes degradation of system stability 😭. Using perl__.exe avoids that degradation.

There's no simple way to access WPS objects. The only way I know is via the OS2::REXX and SOM extensions (see OS2::REXX, SOM). But we don't have access to the convenience methods of Object-REXX. (Is it possible at all? I know of no Object-REXX API.) The SOM extension (currently in alpha-text) may eventually remove this shortcoming; however, because DII is not supported by the SOM module, using SOM is not as convenient as one would like. 🙈

Please keep this list up-to-date by informing me about other items. 💌

🌍 Other OSes 🌍

Since the 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 the many perl flavors, only one works — see "perl_.exe".

Heads up: 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 run under DOS without any external support by binding emx.exe/rsx.exe to it, see emxbind(1). Note that under DOS, for best results, one should use the 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 the 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 a Perl development environment under DOS. 🔥

One can get RSX from, say:

http://cd.textfiles.com/hobbesos29804/disk1/EMX09C/
ftp://crydee.sai.msu.ru/pub/comp/os/os2/leo/gnu/emx+gcc/contrib/

Contact the author on rainer@mathematik.uni-bielefeld.de.

The latest sh.exe with DOS hooks is available in:

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

as sh_dos.zip or under similar names starting with "sh", "pdksh" etc.

📁 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 the 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 the EMX port, such a shell should be named sh.exe, and located either in the wired-in-during-compile locations (usually F:/bin), or in a 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 an 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", so you're forced to use the -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 the -S switch — see perlrun, and cmdref about "extproc":

view perl perlrun
man perlrun
view cmdref extproc
help extproc

or whatever method you prefer. 🦋

There are also endless possibilities to use executable extensions of 4os2, associations of WPS and so on... However, if you use a *nixish shell (like sh.exe supplied in the binary distribution), you need to follow the syntax specified in "Command Switches" in perlrun.

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:

One-argument system() (see "system" in perlfunc), exec() (see "exec" in perlfunc) with redirection or shell meta-characters;
Pipe-open (see "open" in perlfunc) with the command which contains redirection or shell meta-characters;
Backticks ` ` (see "I/O Operators" in perlop) with the command which contains redirection or shell meta-characters;
If the executable called by system()/exec()/pipe-open()/` ` is a script with the "magic" "#!" line or "extproc" line which specifies shell;
If the executable called by system()/exec()/pipe-open()/` ` is a script without a "magic" line, and $ENV{EXECSHELL} is set to shell;
If the executable called by system()/exec()/pipe-open()/` ` is not found (is not this remark obsolete?);
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 the "#!" 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).

When starting scripts directly, Perl uses exactly the same algorithm as for the search of script given by the -S command-line option: it will look in the current directory, then on components of $ENV{PATH} using the following order of appended extensions: no extension, .cmd, .btm, .bat, .pl.

Note that Perl will start to look for scripts only if OS/2 cannot start the specified application — so "system 'blah'" will not look for a script if there is an executable file blah.exe anywhere on "PATH". In other words, "PATH" is essentially searched twice: once by the OS for an executable, then by Perl for scripts. 😭

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 a 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 the "OS2::Process" module. This is considered to be a feature. ✨

✨ Frequently asked questions ✨

💀 "It does not work"

bestie, breathe. Perl binary distributions ship with a testperl.cmd script that literally tries to sniff out the common problems with a misconfigured installation. There's a pretty large chance it will discover which step of the installation you managed to goof. ;-) 😌

😭 I cannot run external programs

Did you run your programs with -w switch? go look at "Starting OS/2 (and DOS) programs under Perl" 🔍
Are you trying to run internal shell commands, like copy a b (that one's internal for cmd.exe), or glob a*b (internal for ksh)? You need to specify your shell explicitly, like cmd /c copy a b, because Perl literally cannot deduce which commands are internal to your shell. no cap. 🙈

🫠 I cannot embed perl into my program, or use `perl.dll` from my program.

Is your program EMX-compiled with `-Zmt -Zcrtdll`?

Wellll, nowadays the Perl DLL should be usable from a differently compiled program too... If you can run Perl code from REXX scripts (peep OS2::REXX), then there are some other aspects of interaction which are overlooked by the current hackish code that supports 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 the ./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 be 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 command arguments. One of such ports is listed in "Prerequisites" under RSX. Do not forget to set variable "PERL_SH_DIR" as well. 🔧

DPMI is required for RSX.

😵 Cannot start `find.exe "pattern" file`

The whole idea of the "standard C API to start applications" is that the forms "foo" and foo of program arguments are completely interchangeable. find breaks this paradigm;

find "pattern" file
find pattern file

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 a non-conforming program. 💅

🎀 INSTALLATION 🎀

🌸 Automatic binary installation

The most convenient way of installing a binary distribution of perl is via the 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 variable "PERL_SHPATH" into Config.sys. Please remove this variable and put "PERL_SH_DIR" instead. 🚨

🦋 Manual binary installation

As of version 5.00305, OS/2 perl binary distribution comes split into 11 components. Unfortunately, to enable configurable binary installation, the file paths in the zip files are not absolute, but relative to some directory. 🙃

Note that the extraction with the stored paths is still necessary (default with unzip, specify -d to pkunzip). However, you need to know where to extract the files. You need also to manually change 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/5.42.3/

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.

💖 Manpages for Perl and utilities

unzip perl_man.zip -d f:/perllib/man

This directory should better be on "MANPATH". You need to have a working man to access these files.

🌸 Manpages for Perl modules

unzip perl_mam.zip -d f:/perllib/man

This directory should better be on "MANPATH". You need to have a working man to access these files.

✨ 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 overwritable (see "PERLLIB_PREFIX", "PERL_SH_DIR"), some people may prefer binary editing of paths inside the executables/DLLs. 💅

💖 Accessing documentation 💖

okay so depending on how you built/installed perl, you might have the (otherwise identical, fr fr) Perl documentation in a bunch of different formats. pick your fighter 💅

🎀 OS/2 .INF file 🎀

ngl this is most probably the most convenient form. under OS/2 you view it like this:

view perl
view perl perlfunc
view perl less
view perl ExtUtils::MakeMaker

(as of rn the last two may hit a wrong location, but bestie this may improve soon, they're working on it 😭). under Win* see SYNOPSIS.

if you wanna build the docs yourself, and you have the OS/2 toolkit, run

pod2ipf > perl.ipf

in the /perllib/lib/pod directory, and then

ipfc /inf perl.ipf

heads up: expect a lot of errors during the both steps 💀 not a vibe but it is what it is

now move it on your BOOKSHELF path and you're slaying ✨

🌸 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. iykyk 🙈

make sure that the directory above the directory with manpages is on your 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 the 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 👑 (no need to do all that yourself, main character shortcut energy)

🧚 GNU "info" files 🧚

users of Emacs would appreciate it very much, especially with CPerl mode loaded 🥰. you need to get latest pod2texi from CPAN, or, alternately, the prebuilt info pages.

🍓 PDF files 🍓

for Acrobat are available on CPAN (may be for slightly older version of perl, so like… check the version bestie 💀).

🌈 "LaTeX" docs 🌈

can be constructed using pod2latex. periodt ✨

🛠️ BUILD ✨

okay bestie so this is the part where we actually build Perl under OS/2 💖 buckle up, it's a whole journey but we're doing it together 🫶

📖 The short story 🌸

so assuming you're a seasoned porter (main character energy, honestly 👑), you already know all the tools are on your system, and you know how to get the Perl source distribution. Untar it, cd into the extract directory, and then:

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

that drops the executables into f:/perllib/bin 💅. Now manually move them to the PATH, and manually move the built perl*.dll to LIBPATH — and bestie, that * in Perl DLL is literally a not-very-meaningful hex checksum, it's giving chaos ngl 😭 — and then run:

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

assuming the man-files landed somewhere sensible, that's the whole installation of a minimal Perl system, done and dusted ✨ (the binary distribution also has a LOT of extra modules, plus the docs in INF format, so there's more if you want it 👀)

what follows is the detailed guide through all of these steps, so like, the long version. no cap.

🧰 Prerequisites 💅

you need 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 deal with sort.exe — to check, run):

find --version
sort --version

you also 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 grab 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's been reported that these 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 ksh527rt.zip (or a later version). and note that all of these utilities are known to be available from LEO:

ftp://crydee.sai.msu.ru/pub/comp/os/os2/leo/gnu/

also also — the db.lib and db.a from the EMX distribution are NOT suitable for multi-threaded compile (even the single-threaded flavor of Perl uses multi-threaded C RTL, for compatibility with XFree86-OS/2, so yeah it matters fr). grab a corrected one from:

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

if you already have exactly the same version of Perl installed, make sure no copies of perl are running right now 🚨 later build steps may fail because an older version of perl.dll loaded into memory might get found. and running make test becomes meaningless, since the tests would be checking a previous build of perl (this situation gets detected and reported by the os2/os2_base.t test, so at least there's a heads-up 💀). do NOT forget to unset PERL_EMXLOAD_SEC in the environment, bestie, I'm serious.

also make sure you have a /tmp directory on the current drive, and . in your LIBPATH. you can try to fix that last one with:

set BEGINLIBPATH .\.

if you're using something like CMD.EXE or the latest versions of 4os2.exe. (just a heads-up: setting BEGINLIBPATH to just . gets ignored by the OS/2 kernel 🙈 so that trailing \. is doing real work.)

make sure your gcc is good for -Zomf linking: run the omflibs script in the /emx/lib directory 🧚

check that you have link386 installed. it comes standard with OS/2, but might not be installed depending on customization. if typing:

link386

shows you don't have it, do a Selective install, and choose "Link object modules" in Optional system utilities/More 🎀 and if you end up in link386 prompts, hit Ctrl-C to bail 💅

📦 Getting perl source 🌈

you need to fetch the latest perl source (including developers releases). with some probability it lives at:

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

if not, you might need to dig through the indices to find it in the directory of the current maintainer 🔍

quick cycles of developers release can break the OS/2 build from time to time, so looking into:

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

may tell you the latest release that 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 might see a message about errors while extracting Configure. that's because there's a conflict with a similarly-named file configure 🙃 (classic). then change to the directory of extraction.

🩹 Application of the patches 🫶

you need to apply the patches in ./os2/diff.* like this:

gnupatch -p0 < os2\diff.configure

you may also need to apply the patches supplied with the binary distribution of perl. it also makes sense to look on the perl5-porters mailing list for the latest OS/2-related patches (see <http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/>). those patches usually contain the strings "/os2/" and "patch", so it makes sense to search for those strings 🔎

✍️ Hand-editing 🌸

you may look into the file ./hints/os2.sh and correct anything wrong you find in there. I don't expect it's needed anywhere, but like, it's there if you want it 💖

🔨 Making 🔥

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

prefix means: where to install the resulting perl library 📍 giving a correct prefix means you can skip having to specify PERLLIB_PREFIX, see ""PERLLIB_PREFIX"".

ignore the message about missing ln, and about the -c option to tr. the latter is most probably already fixed, and if you see it and can trace where that spurious warning comes from, please let me know 🙏

now:

make

at some point the build may die, reporting a version mismatch or unable to run perl 💀 that means you don't have . in your LIBPATH, so perl.exe can't find the perl67B2.dll it needs (treat those hex digits as line noise, honestly). once that's 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 be testing 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 these 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's considered to be a feature. one can easily disable this by appropriate sighandlers. however the test engine bleeds these messages to screen in unexpected moments 🙃 two messages of this kind should be present during testing.

to get finer test reports, call:

perl t/harness

the report with io/pipe.t failing may look like this:

 Failed Test  Status Wstat Total Fail  Failed  List of failed
 ------------------------------------------------------------
 io/pipe.t                    12    1   8.33%  9
 7 tests skipped, plus 56 subtests skipped.
 Failed 1/195 test scripts, 99.49% okay. 1/6542 subtests failed,
    99.98% okay.

the reasons for the 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

that puts the generated files into the needed locations 📍 manually put perl.exe, perl__.exe and perl___.exe to a location on your PATH, and 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 the .EXE-utilities on path manually. they're installed in $prefix/bin, where $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 the configuring and making steps — hindsight is 20/20 bestie 😌)

🌀 "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 💖

Note. the build process for perl_ does not know about all the dependencies, so you should make sure that everything is up-to-date, say, by doing:

make perl_dll

first 🫶

Building a binary distribution

okay so this section is like, a short overview only — that's literally what the original says, bestie, don't come for me 💅

So the way you build this thing depends on whether the perl version you're installing is already on your system and being used, or if it's a brand new version nobody's touched yet. The steps below assume it's new, so installing its DLLs and .pm files won't mess up your system even if some middle steps are still kinda half-baked. No cap. 🦋

The other cases? They need a lil more convoluted procedure, ngl. Below we're pretending the current Perl version is 5.8.2, so the executables are named accordingly. iykyk.

Fully build and test the whole Perl distribution. Make sure no tests are failing with the test and aout_test targets — fix the bugs in Perl and the Perl test suite that these tests catch. Make sure the all_test make target runs as clean as humanly possible. And check that os2/perlrexx.cmd runs fine. ✨
Fully install Perl, installcmd target included. Copy the generated DLLs to LIBPATH; copy the numbered Perl executables (like perl5.8.2.exe) to PATH; copy perl_.exe to PATH as perl_5.8.2.exe. Now think about whether you need backward-compatibility DLLs. Most of the time you don't need to install them yet, but sometimes it makes the next steps simpler.
Make sure CPAN.pm can actually download files from CPAN. If it can't, you might need to manually install Net::FTP.
Install the bundle Bundle::OS2_default

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

This can take a couple of hours on a 1GHz processor (when you run it the first time). And it should not necessarily be a smooth procedure, fr fr. Some modules might not list their required dependencies, so you may need to repeat this whole thing 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 still fail. 😭

Fix as many discovered bugs as you can. Document all the bugs you don't fix, 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 installing some modules may fail too — like, the DLLs to update might already be loaded by CPAN.pm. Inspect the install logs (in the example above, 00cpan_i_1 etc) for errors, and install things manually, like so:

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

Some distributions may fail some tests, but you might wanna install them anyway (as above, or via the force install command of CPAN.pm shell-mode).

Since this procedure can take a very long time to complete, it makes sense to "freeze" your CPAN config by disabling periodic updates of the local copy of the CPAN index: set index_expire to some big value (the original author uses 365), then save the settings.

CPAN> o conf index_expire 365
CPAN> o conf commit

Reset it back to the default value 1 when you're finished. 🎀

When you're 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're ready to be used. 💅
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 it on the BOOKSHELF path.

Now's the time to build the statically linked executable perl_.exe which includes the modules newly installed via Bundle::OS2_default. Testing via CPAN.pm is gonna be painfully slow, since it statically links a new executable per XS extension. 🙈

Here's 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 wouldn't 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're 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

whichever is appropriate.) Also, make sure that the DLLs for external libraries are usable with executables compiled without -Zmtd options.

When you're sure that only a few subdirectories lead to failures, you may wanna add the -j4 option to make to speed up skipping subdirectories with already finished build.

When you're satisfied with the results of tests, install the build C libraries for extensions:

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's 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 the 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're done with generation of the local Perl installation. 🔥

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(1) during step 6 gives super detailed info about which modules are loaded from which place; so you can use it as an additional verification tool. ⭐

Check that some temporary files did not make it 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 the top one and the sitelib one).

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

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 the current version of Perl first. Don't forget to pack the necessary external DLLs accordingly. Include the description of the bugs and test suite failures you couldn't fix. Include the small-stack versions of Perl executables from the Perl build directory.

Include perl5.def so that people can relink the perl DLL preserving binary compatibility, or can create compatibility DLLs. Include the diff files (diff -pu old new) of fixes you did so that people can rebuild your version. Include perl5.map so that one can use remote debugging.

Share what you did with other people. Relax. Enjoy the fruits of your work. 🍓
Brace yourself for thanks, bug reports, hate mail and spam coming as a result of the previous step. No good deed should remain unpunished! 🌈

💅 Building custom .EXE files

okay so bestie, the Perl executables? you can rebuild them literally whenever you want. no big deal. and if you're feeling extra, you can use the embedding interface (go peek at perlembed) to make very customized executables. main character executables, if you will. ✨

Making executables with a custom collection of statically loaded extensions

ngl this is a lil bit easier when you're shrinking the list of statically loaded extensions. so that's the only case we're talking about here, periodt.

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

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

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

perl_ Makefile.PL

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" *

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. slay 💅

Making executables with a custom search-paths

The default perl executable is flexible enough to support most usages. like, she's doing her best and her best is honestly pretty good. 🫶

BUT. 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.

If you fill comfortable with embedding interface (see perlembed), such things are easy to do repeating the steps outlined in "Making executables with a custom collection of statically loaded extensions", and doing more comprehensive edits to main() of perlmain.c. The people with little desire to understand Perl can just rename main(), and do necessary modification in a custom main() which calls the renamed function in appropriate time. (iconic workaround honestly)

However, there is a third way: perl DLL exports the main() function and several callbacks to customize the search path. Below is a complete example of a "Perl loader" which

Looks for Perl DLL in the directory "$exedir/../dll";
Prepends the above directory to "BEGINLIBPATH";
Fails if the Perl DLL found via "BEGINLIBPATH" is different from what was loaded on step 1; e.g., another process could have loaded it from "LIBPATH" or from a different value of "BEGINLIBPATH". In these cases one needs to modify the setting of the system so that this other process either does not run, or loads the DLL from "BEGINLIBPATH" with "LIBPATHSTRICT=T" (available with kernels after September 2000).
Loads Perl library from "$exedir/../dll/lib/".
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);
typedef int (*main_t)(int type, char *argv[], char *env[]);
typedef int (*handler_t)(void* data, int which);

#ifndef PERL_DLL_BASENAME
#  define PERL_DLL_BASENAME "perl"
#endif

static HMODULE
load_perl_dll(char *basename)
{
    char buf[300], fail[260];
    STRLEN l, dirl;
    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) )
        die_with(PERL_DLL_BASENAME,
                 ": Can't install @INC manglers",
                 "",
                 "");
    if (DosQueryProcAddr(handle, 0, "dll_perlmain", (PFN*)&f))
        die_with(PERL_DLL_BASENAME,
                 ": DLL exports no symbol ",
                 "dll_perlmain",
                 "");
    return f(argc, argv, env);
}

🌈 Build FAQ

Some "/" became "" in pdksh

You have a very old pdksh. See "Prerequisites". 💀

'errno' - unresolved external

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. (not her sabotaging the build, it's the old dll, i promise 😭)

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. 💀 fr fr be careful.

`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

system qw(C:/emx.add/bin/bash.exe -x -c C:/emx/bin/foo.cmd bar baz)

One additional translation is performed: instead of /bin/sh Perl uses the hardwired-or-customized shell (see ""PERL_SH_DIR"").

The above search for "interpreter" is recursive: if bash executable is not found, but bash.btm is found, Perl will investigate its first line etc. The only hardwired limit on the recursion depth is implicit: there is a limit 4 on the number of additional arguments inserted before the actual arguments given to system(). In particular, if no additional arguments are specified on the "magic" first lines, then the 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 the .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 a "#!"-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) — Interface to cwd from EMX. Used by "Cwd::cwd".
"Cwd::sys_abspath(name, dir)" — Really really odious function to implement. Returns absolute name of file which would have "name" if CWD were "dir". "Dir" defaults to the current dir.
Cwd::extLibpath([type]) — Get 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".
"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.

OS2::Serve_Messages(force) — Fake on-demand retrieval of outstanding PM messages. If "force" is false, will not dispatch messages if a real message loop is known to be present. Returns number of messages retrieved.

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

"OS2::Process_Messages(force [, cnt])" — Retrieval of PM messages until window creation/destruction. If "force" is false, will not dispatch messages if a real message loop is known to be present.

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 file. (Some messages in this file have an "SYS0003"-like id prepended, some not.)

💀 Misfeatures 💀

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".
Here is the list of things which may be "broken" on EMX (from EMX docs):
- The functions recvmsg(3), sendmsg(3), and socketpair(3) are not implemented.
- sock_init(3) is not required and not implemented.
- flock(3) is not yet implemented (dummy function). (Perl has a workaround.)
- kill(3): Special treatment of PID=0, PID=1 and PID=-1 is not implemented.
- 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.

See "Text-mode filehandles".
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.

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 would die a horrible death.

To circumvent this, Perl uses two hacks. They help against one type of damage only: FP flags changed when loading a DLL.

One of the hacks is to disable floating point exceptions on Perl startup (as is the default with EMX). This helps only with compile-time-linked DLLs changing the flags before main() had a chance to be called.

The other hack is to restore FP flags after a call to dlopen(). This helps against similar damage done by DLLs _DLLInitTerm() at 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 — these special-case /dev/tty and /dev/con for you. bestie behaviour fr 💅
mkdir, rmdir — okay so these EMX functions are lowkey broken if the path has a trailing /. Not us though — Perl has a workaround coded in, so we're fine ✨
flock — flock(3) exists in EMX but it's giving decorative, it doesn't actually function 😭 so perl emulates it instead. Wanna turn the emulation off? Set the environment variable USE_PERL_FLOCK=0. periodt.

Identifying DLLs 🎀

Every DLL built with the current versions of Perl carries ID strings that spill the tea on the name of the extension, its version, and the version of Perl this DLL needs. Run bldlevel DLL-name to find this info. iykyk 🦋

Centralized management of resources 🫶

So here's the vibe: to call certain OS/2 API you need a correctly initialized Win subsystem, which means OS/2-specific extensions might need to grab HABs and HMQs. And if every extension just went and did that on its own? Chaos. Another extension could fail to initialize entirely 💀 So Perl does the whole thing centrally instead:

`HAB` ✨

To get the HAB, the extension should call hab = perl_hab_GET() in C. Once that call has happened, hab may be accessed as Perl_hab. And no, you do not need to release the HAB after it's used — no cleanup era, we love that for us 💖

If for some reason perl.h can't be included, use this instead:

extern int Perl_hab_GET(void);

`HMQ` 🌸

Two cases, and you gotta know which one you're in:

the extension needs an HMQ only because some API will not work otherwise. Use serve = 0 below.
the extension needs an HMQ because it wants to engage in a PM event loop. Use serve = 1 below.

To get an HMQ, the extension should call hmq = perl_hmq_GET(serve) in C. After this call is performed, hmq may be accessed as Perl_hmq.

To signal to Perl that HMQ is not needed any more, call perl_hmq_UNSET(serve). The 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. main character energy, honestly 👑

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. like, seriously, don't 🙈

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. yeah. the 0 is doing double duty. it's giving unhinged 💀

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.
CheckWinError(expr) — Returns true on error, sets $^E. Expects expr() be a call of Win*-style API.
SaveWinError(expr) — Returns expr, sets $^E from WinGetLastError() if expr is false.
SaveCroakWinError(expr,die,name1,name2) — Returns expr, sets $^E from WinGetLastError() if expr is false, and die()s if die and $^E are true. The message to die is the concatenated strings name1 and name2, separated 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. And 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. not the ✨flexible✨ vibe we're going for, bestie 😭

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.

So 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. two vibes, one function, we love to see it 💅

🌸 Perl flavors 🌸

ok so bestie, here's the tea: OS/2 is built different (derogatory) and you literally cannot have all your eggs in one basket. The EMX environment is out here trying SO hard to overcome these limitations, so maybe someday the situation improves a lil bit. Anyway, the distribution hands you 4 executables for Perl:

💖 perl.exe

The main workhorse, the moment, the icon. This one is a chimera executable: it's compiled as an a.out-style executable, but it's linked against the omf-style dynamic library perl.dll, and against a dynamic CRT DLL. It's a VIO application.

It can load perl dynamic extensions, and it can fork().

Note: pls keep in mind that fork() is what you need to open a pipe to yourself. yeah. that.

💖 perl_.exe

This one is a statically linked a.out-style executable. It cannot load dynamic Perl extensions. The executable you get in binary distributions has a lot of extensions prebuilt already, so that restriction only actually bites if you're using custom-built extensions. It's a VIO application.

This is the only executable that doesn't require OS/2. Your friends locked into the "M$" world would lowkey appreciate the fact that this executable runs under DOS, Win0.3*, Win0.95 and WinNT — with an appropriate extender, of course. See "Other OSes".

💖 perl__.exe

Same executable as perl___.exe, but it's a PM application.

Note: usually (unless it's explicitly redirected during startup) STDIN, STDERR, and STDOUT of a PM application are redirected to nul. BUT — you can see them if you start perl__.exe from a PM program that emulates a console window, like Shell mode of Emacs or EPM. So it's genuinely possible to use the Perl debugger (see perldebug) to debug your PM application. ⚠️ But beware of message loop lockups — this will NOT work if you've got 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 that isn't cmd.exe, so it doesn't create a link between a VIO session and the session of pm_porg. (Yeah, that kind of link closes the VIO window, rip.) 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 what you need if you wanna start your program without a VIO window present, but not "detach"ed (run help detach for more info). Super useful for extensions that use PM, like "Perl/Tk" or "OpenGL". 💅

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

💖 perl___.exe

This is an omf-style executable, dynamically linked to perl.dll and CRT DLL. ngl I know of no advantages of this executable over perl.exe... except it cannot fork() at all. 💀 Well, one advantage: the build process isn't as convoluted as it is with perl.exe.

It is a VIO application.

🦋 Why strange names? 🦋

Since Perl processes the #!-line (cf. "DESCRIPTION" in perlrun, "Command Switches" in perlrun, "No Perl script found in input" in perldiag), it should know when a program is a Perl. There's a naming convention that lets Perl tell the correct lines from the wrong ones. The names above are almost the only names allowed by this convention that don't contain digits (which have absolutely different semantics, ok?).

🦋 Why dynamic linking? 🦋

So like, having several executables dynamically linked to the same huge library does have its advantages, but honestly that alone would not justify the extra work to make it compile. The real reason is the complicated-to-developers but very quick and convenient-to-users "hard" dynamic linking that OS/2 uses.

There are two distinctive features of the dyna-linking model of OS/2:

all the references to external functions are resolved at compile time;
there is no runtime fixup of the DLLs after they're 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 those cases, "other" models of dyna-linking just choose between the two entry points using some random criterion — with predictable disasters as the result. 😭 But it's the second feature that requires building perl.dll.

The address tables of DLLs are patched only once, when they're 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 a DLL is loaded, its code is read-only. ✨

While this allows some (significant?) performance advantages, it makes life much harder for developers, because the above scheme makes it impossible for a DLL to be "linked" to a symbol in the .EXE file. fr fr — that would need a DLL to have different relocations tables for the (different) executables that use that 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 — because the arguments live on the perl internal evaluation stack. The solution? Put the main code of the interpreter into a DLL, and make the .EXE file just load this DLL into memory and supply command-arguments. The extension DLL can't link to symbols in .EXE, but it has zero problems linking to symbols in the .DLL. 👑

This greatly increases the load time for the application (as well as the complexity of the compilation). And since the interpreter is in a DLL, the C RTL is basically forced to reside in a DLL as well (otherwise extensions wouldn't be able to use CRT). There are some advantages if you use different flavors of perl, like running perl.exe and perl__.exe at the same time — they share the memory of perl.dll. 🫶

NOTE. There's one additional effect which makes DLLs more wasteful: DLLs are loaded in the shared memory region, which is a scarse (yes, that's the manpage spelling bestie, we don't fix it) resource given the 512M barrier of the "standard" OS/2 virtual memory. The code of .EXE files is also shared by all the processes that use that particular .EXE, but they're "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, so all the processes have these sections loaded at the 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 you'd need the address range of any of the loaded DLLs in the system to be available in all the processes which didn't load a particular DLL yet. This is why the DLLs are mapped to the shared memory region.

🦋 Why chimera build? 🦋

Current EMX environment does not allow DLLs compiled using Unixish a.out format to export symbols for data (or at least some types of data). This forces an omf-style compile of perl.dll.

Current EMX environment does not allow .EXE files compiled in omf format to fork(). And fork() is needed for exactly three Perl operations:

explicit fork() in the script,
open FH, "|-"
open FH, "-|", in other words, opening pipes to itself.

While these operations aren't exactly questions of life and death, they are needed for a lot of useful scripts. This forces an a.out-style compile of perl.exe. slay. 🎀

✨ ENVIRONMENT ✨

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

💜 `PERLLIB_PREFIX`

Specific for the EMX port. It should have the form

path1;path2

path1 path2

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

You should use this if the perl library is moved from the default location, in preference to "PERL(5)LIB", since that would 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 it's 0, perl ignores setlocale() failing. May be useful with some strange locales. 🌈

💜 `PERL_BADFREE`

If it's 0, perl would not warn in case of an 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.

Should not be set with newer Perls, since this may hide some real problems. ⚠️

💜 `PERL_SH_DIR`

Specific for the EMX port. Gives the directory part of the location for sh.exe.

💜 `USE_PERL_FLOCK`

Specific for the EMX port. Since flock(3) is present in EMX but is not functional, it's emulated by perl. To disable the emulation, set the environment variable USE_PERL_FLOCK=0.

💜 `TMP` or `TEMP`

Specific for the EMX port. Used as the storage place for temporary files. 🍓

🌈 Evolution 🌈

Here we list the major changes which could make you go "wait what 😭" 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 with some code which should best be characterized as a "quick hack".

On top of 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 names that contain a checksum, thus allowing a workaround for the OS/2 scheme of caching DLLs.

It may be possible to code a simple workaround which would:

find the old DLLs by looking through the old @INC;
mangle the names according to the scheme of the new perl and copy the DLLs to these names;
edit the internal "LX" tables of the DLL to reflect the change of the name (probably not needed for Perl extension DLLs, since the internally coded names aren't used for "specific" DLLs — they're used only for "global" DLLs).

🦋💅✨

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 💅

okay so real talk — the mangling of extension DLLs happened because someone misunderstood the OS/2 dynaloading model. no cap. OS/2 (effectively) keeps two totally separate 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.

When resolving a request for a global DLL, the table of already-loaded specific DLLs is (effectively) ignored; moreover, specific DLLs are always loaded from the prescribed path.

There is/was a minor twist which makes this scheme fragile: what to do with DLLs loaded from

BEGINLIBPATH and ENDLIBPATH — (which depend on the process)
. from LIBPATH — which effectively depends on the process (although LIBPATH is the 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 — and this is the plot twist — 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. slay, honestly.

This may break in two ways:

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. 😭
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 beginning of 2002, . is not allowed, but .\. is — and it has the same effect.)

REMARK. LIBPATHSTRICT, BEGINLIBPATH and ENDLIBPATH are not environment variables, although cmd.exe emulates them on SET ... lines. From Perl they may be accessed by Cwd::extLibpath and Cwd::extLibpath_set.

🧚 DLL forwarder generation 🧚

Assume that the old DLL is named perlE0AC.dll (as is one for 5.005_53), and the new version is 5.6.1. Create a file perl5shim.def-leader with

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).

Note that this a lesser issue now when we do not spawn sh.exe unless needed (metachars found).

One can always start cmd.exe explicitly via

system 'cmd', '/c', 'mycmd', 'arg1', 'arg2', ...

If you need to use cmd.exe, and do not want to hand-edit thousands of your scripts, the long-term solution proposed on p5-p is to have a directive

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 "Starting OS/2 (and DOS) programs under Perl". Set us mention a couple of features:

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

Note that these problems should not discourage experimenting, since they have a low probability of affecting small programs. 🫶

💀 BUGS 💀

This description is not updated often (since 5.6.1?), see ./os2/Changes for more info.

👑 AUTHOR 👑

Ilya Zakharevich, cpan@ilyaz.org

🌈 SEE ALSO 🌈

perl(1).

okay bestie that's the whole thing, we ate and left zero crumbs 💅 this was perl v5.42.3, dated 2026-08-03 — iconic of her honestly, periodt. 🎀✨

📦 where this page comes from

fedora 43: perl-doc 5.42.3-524.fc43 · (GPL-1.0-or-later OR Artistic-1.0-Perl) AND Unicode-3.0 AND LicenseRef-Fedora-UltraPermissive
fedora 44: perl-doc 5.42.3-525.fc44 · (GPL-1.0-or-later OR Artistic-1.0-Perl) AND Unicode-3.0 AND LicenseRef-Fedora-UltraPermissive
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash on 2026-10-13: a language model's rewrite of the original, under its terms