Chip Salzenberg > perl5.004 > perlos2


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


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

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).

Note that if you have lynx.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).



The target is to make OS/2 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:

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

Other OSes

Since OS/2 port of perl uses a remarkable EMX environment, it can run (and build extensions, and - possibly - be build 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.



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.

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

One can get different parts of EMX from, say

The runtime component should have the name

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

  emx perl_.exe -de 0

will work as well.)


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

Contact the author on

The latest sh.exe with DOS hooks is available at

Perl does not care about file systems, but to install the whole perl library 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.


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 soon-to-be-available standard binary (5.2.12?) runs under DOS (with RSX) as well, meanwhile use the binary from

Starting Perl programs under OS/2 (and DOS and...)

Start your Perl program with arguments arg1 arg2 arg3 the same way as on any other platform, by

        perl arg1 arg2 arg3

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

        perl -my_opts 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 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:

        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 *nixish shell (like sh.exe supplied in the binary distribution), you need to follow the syntax specified in "Switches" in perlrun.

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 only cases when the shell is not used is the multi-argument system() (see "system" in perlfunc)/exec() (see "exec" in perlfunc), and one-argument version thereof without redirection and shell meta-characters.

Frequently asked questions ^

I cannot run external programs

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

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

If not, 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?

I had reports it does not work. Somebody would need to fix it.

`` 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 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

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. In fact find.exe cannot be started at all using C library API only. Otherwise the following command-lines were equivalent:

  find "pattern" file
  find pattern file


Automatic binary installation

The most convenient way of installing 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


A folder is created on your desktop which contains some useful objects.

Things not taken care of by automatic binary installation:


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



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

  perl -MConfig -le "print $INC{''}"

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.

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:

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

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

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

(have the directory on PATH);

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

(have the directory on PATH);

Main Perl library
  unzip -d f:/perllib/lib

If this directory is preserved, you do not need to change anything. However, for perl to find it if it is changed, you need to set PERLLIB_PREFIX in Config.sys, see "PERLLIB_PREFIX".

Additional Perl modules
  unzip -d f:/perllib/lib/site_perl

If you do not change this directory, do nothing. Otherwise 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.

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

If this directory is preserved, you do not need to change anything. However, for perl to find it if it is changed, you need to set PERLLIB_PREFIX in Config.sys, see "PERLLIB_PREFIX".

Manpages for Perl and utilities
  unzip -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 -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 -d f:/perllib/lib

This is used by by 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.

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

This directory should better be on BOOKSHELF.

  unzip -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 (not tested).

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

  perl -MConfig -le "print $INC{''}"

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


The automatic and manual perl installation leave precompiled paths inside perl executables. While these paths are overwriteable (see "PERLLIB_PREFIX", "PERL_SH_DIR"), one may get better results by 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
  view perl ExtUtils::MakeMaker

(currently the last two may hit a wrong location, but this may improve soon). Under Win* see "SYNOPSIS".

If you want to build the docs yourself, and have OS/2 toolkit, run

        pod2ipf > perl.ipf

in /perllib/lib/pod directory, then

        ipfc /inf perl.ipf

(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.


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


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

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.

GNU info files

Users of Emacs would appreciate it very much, especially with CPerl mode loaded. You need to get latest pod2info from CPAN, or, alternately, prebuilt info pages.

.PDF files

for Acrobat are available on CPAN (for slightly old version of perl).

LaTeX docs

can be constructed using pod2latex.


Here we discuss how to build Perl under OS/2. There is an alternative (but maybe older) view on


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.

Possible locations to get this from are

It is reported that the following archives contain enough utils to build perl:,,,,,, and Note that all these utilities are known to be available from LEO:

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.

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


if you use something like CMD.EXE or latest versions of 4os2.exe.

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


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

Getting perl source

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

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

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.

Change to the directory of extraction.

Application of the patches

You need to apply the patches in ./os2/diff.* and ./os2/POSIX.mkfifo like this:

  gnupatch -p0 < os2\POSIX.mkfifo
  gnupatch -p0 < os2\diff.configure

You may also need to apply the patches supplied with the binary distribution of perl.

Note also that the db.lib and db.a from the EMX distribution are not suitable for multi-threaded compile (note that currently perl is not multithread-safe, but is compiled as multithreaded for compatibility with XFree86-OS/2). Get a corrected one from


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


  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. In fact if you can trace where the latter spurious warning comes from, please inform me.



At some moment the built may die, reporting a version mismatch or unable to run perl. This means that most of the build has been finished, and it is the time to move the constructed perl.dll to some absolute location in LIBPATH. After this is done the build should finish without a lot of fuss. One can avoid the interruption if one has the correct prebuilt version of perl.dll on LIBPATH, but probably this is not needed anymore, since miniperl.exe is linked statically now.

Warnings which are safe to ignore: mkfifo() redefined inside POSIX.c.


Now run

  make test

Some tests (4..6) should fail. Some perl invocations should end in a segfault (system error SYS3175). To get finer error reports,

  cd t
  perl harness

The report you get may look like

  Failed Test  Status Wstat Total Fail  Failed  List of failed
  io/fs.t                      26   11  42.31%  2-5, 7-11, 18, 25
  lib/io_pipe.t     3   768     6   ??       %  ??
  lib/io_sock.t     3   768     5   ??       %  ??
  op/stat.t                    56    5   8.93%  3-4, 20, 35, 39
  Failed 4/140 test scripts, 97.14% okay. 27/2937 subtests failed, 99.08% okay.

Note that using `make test' target two more tests may fail: op/exec:1 because of (mis)feature of pdksh, and lib/posix:15, which checks that the buffers are not flushed on _exit (this is a bug in the test which assumes that tty output is buffered).

I submitted a patch to EMX which makes it possible to fork() with EMX dynamic libraries loaded, which makes lib/io* tests pass. This means that soon the number of failing tests may decrease yet more.

However, the test lib/io_udp.t is disabled, since it never terminates, I do not know why. Comments/fixes welcome.

The reasons for failed tests are:


Checks file system operations. Tests:

2-5, 7-11

Check link() and inode count - nonesuch under OS/2.


Checks atime and mtime of stat() - I could not understand this test.


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


Checks IO::Pipe module. Some feature of EMX - test fork()s with dynamic extension loaded - unsupported now.


Checks IO::Socket module. Some feature of EMX - test fork()s with dynamic extension loaded - unsupported now.


Checks stat(). Tests:


Checks inode count - nonesuch under OS/2.


Checks mtime and ctime of stat() - I could not understand this test.


Checks -x - determined by the file extension only under OS/2.


Needs /usr/bin.


Checks -t of /dev/null. Should not fail!

In addition to errors, you should get a lot of warnings.

A lot of `bad free'

in databases related to Berkeley DB. This is a confirmed bug of DB. 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 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.

*/sh.exe: ln: not found
ls: /dev: No such file or directory

The last two should be self-explanatory. The test suite discovers that the system it runs on is not that much *nixish.

A lot of `bad free'... in databases, bug in DB confirmed on other platforms. You may disable it by setting PERL_BADFREE environment variable to 1.

Installing the built perl


  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.


  make cmdscripts 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.

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.

Since perl_ has the extensions prebuilt, it does not suffer from the dynamic extensions + fork() syndrome, thus the failing tests look like

  Failed Test  Status Wstat Total Fail  Failed  List of failed
  io/fs.t                      26   11  42.31%  2-5, 7-11, 18, 25
  op/stat.t                    56    5   8.93%  3-4, 20, 35, 39
  Failed 2/118 test scripts, 98.31% okay. 16/2445 subtests failed, 99.35% okay.

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

  make perl.dll


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

reported with very old version of tr.

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.

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.


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

extproc on the first line

If the first chars of a 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).

Additional modules:

OS2::Process, OS2::REXX, OS2::PrfDB, OS2::ExtAttr. This modules provide access to additional numeric argument for system, to DLLs having functions with REXX signature and to 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 my ftp directory, mirrored on CPAN.

Prebuilt methods:


used by File::Copy::copy, see File::Copy.


used by DynaLoader for DLL name mangling.


Self explanatory.


leaves drive as it is.


means has drive letter and is_rooted.


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


means changes with current dir.


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.


Get current value of extended library search path. If type is present and true, works with END_LIBPATH, otherwise with BEGIN_LIBPATH.

Cwd::extLibpath_set( path [, type ] )

Set current value of extended library search path. If type is present and true, works with END_LIBPATH, otherwise with BEGIN_LIBPATH.

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



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


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


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


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


a dummy implementation.


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

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:


The main workhorse. This is a chimera executable: it is compiled as an a.out-style executable, but is linked with omf-style dynamic library perl.dll, and with dynamic CRT DLL. This executable is a VIO application.

It can load perl dynamic extensions, and it can fork(). Unfortunately, with the current version of EMX it cannot fork() with dynamic extensions loaded (may be fixed by patches to EMX).

Note. Keep in mind that fork() is needed to open a pipe to yourself.


This is a statically linked a.out-style executable. It can fork(), but cannot load dynamic Perl extensions. The supplied executable has a lot of extensions prebuilt, thus there are situations when it can perform tasks not possible using perl.exe, like fork()ing when having some standard extension loaded. This executable is a VIO application.

Note. A better behaviour could be obtained from perl.exe if it were statically linked with standard Perl extensions, but dynamically linked with the Perl DLL and CRT DLL. Then it would be able to fork() with standard extensions, and would be able to dynamically load arbitrary extensions. Some changes to Makefiles and hint files should be necessary to achieve this.

This is also 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".


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

Note. Usually 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.

This flavor is required if you load extensions which use PM, like the forthcoming Perl/Tk.


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 found in input" in perldiag), it should know when a program is a Perl. There is some naming convention which allows Perl to distinguish correct lines from wrong ones. The above names are almost the only names allowed by this convention which do not contain digits (which have absolutely different semantics).

Why dynamic linking?

Well, having several executables dynamically linked to the same huge library has its advantages, but this would not substantiate the additional work to make it compile. The reason is stupid-but-quick "hard" dynamic linking used by OS/2.

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

While this allows some performance advantages, this makes life terrible for developers, since the above scheme makes it impossible for a DLL to be resolved to a symbol in the .EXE file, since this would need a DLL to have different relocations tables for the executables which use it.

However, a Perl extension is forced to use some symbols from the perl executable, say to know how to find the arguments provided on the perl internal evaluation stack. The solution is that the main code of interpreter should be contained in a DLL, and the .EXE file just loads this DLL into memory and supplies command-arguments.

This greatly increases the load time for the application (as well as the number of problems during compilation). Since interpreter is in a DLL, the CRT is basically forced to reside in a DLL as well (otherwise extensions would not be able to use CRT).

Why chimera build?

Current EMX environment does not allow DLLs compiled using Unixish a.out format to export symbols for data. This forces omf-style compile of perl.dll.

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

explicit fork()

in the script, and

open FH, "|-"
open FH, "-|"

opening pipes to itself.

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


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.


Specific for EMX port. Should have the form



  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. Say, 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


If 1, perl ignores setlocale() failing. May be useful with some strange locales.


If 1, perl would not warn of in case of unwarranted free(). May be useful in conjunction with the module DB_File, since Berkeley DB memory handling code is buggy.


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


Specific for EMX port. Used as storage place for temporary files, most notably -e scripts.

Evolution ^

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


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

DLL name mangling

With the release 5.003_01 the dynamically loadable libraries should be rebuilt. In particular, DLLs are now created with the names which contain a checksum, thus allowing workaround for OS/2 scheme of caching DLLs.


As of release 5.003_01 perl is linked to multithreaded CRT DLL. Perl itself is not multithread-safe, as is not perl malloc(). However, extensions may use multiple thread on their own risk.

Needed to compile Perl/Tk for XFree86-OS/2 out-of-the-box.

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 drive F: 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. Thus 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 asyncroneous 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.

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. Unfortunately, it is also quite frivolous with memory usage as well.

Since kitchen-top machines are usually low on memory, perl is compiled with all the possible memory-saving options. This probably makes perl's malloc() as greedy with memory as the neighbor's malloc(), but still much quickier. Note that this is true only for a "typical" usage, it is possible that the perl malloc will be worse for some very special usage.

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.)


Ilya Zakharevich,



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