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

- NAME
- SYNOPSIS
- DESCRIPTION

- Target
- Other OSes
- Prerequisites
- Starting Perl programs under OS/2 (and DOS and...)
- Starting OS/2 (and DOS) programs under Perl

- Frequently asked questions

- ``It does not work''
- I cannot run external programs
- I cannot embed perl into my program, or use perl.dll from my
- ```` and pipe-`open` do not work under DOS.
- Cannot start `find.exe "pattern" file`

- INSTALLATION

- Automatic binary installation
- Manual binary installation
- Warning

- Accessing documentation

- OS/2 .INF file
- Plain text
- Manpages
- HTML
- GNU `info` files
- .PDF files
- `LaTeX` docs

- BUILD

- The short story
- Prerequisites
- Getting perl source
- Application of the patches
- Hand-editing
- Making
- Testing
- Installing the built perl
- `a.out`-style build

- Build FAQ

- Some `/` became `\` in pdksh.
- `'errno'` - unresolved external
- Problems with tr or sed
- Some problem (forget which ;-)
- Library ... not found
- Segfault in make
- op/sprintf test failure

- Specific (mis)features of OS/2 port

- `setpriority`, `getpriority`
- `system()`
- `extproc` on the first line
- Additional modules:
- Prebuilt methods:
- Prebuilt variables:
- Misfeatures
- Modifications
- Identifying DLLs
- Centralized management of resources

- Perl flavors

- perl.exe
- perl_.exe
- perl__.exe
- perl___.exe
- Why strange names?
- Why dynamic linking?
- Why chimera build?

- ENVIRONMENT

- `PERLLIB_PREFIX`
- `PERL_BADLANG`
- `PERL_BADFREE`
- `PERL_SH_DIR`
- `USE_PERL_FLOCK`
- `TMP` or `TEMP`

- Evolution

- Priorities
- DLL name mangling
- Threading
- Calls to external programs
- Memory allocation
- Threads

- AUTHOR
- SEE ALSO

# NAME

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

# SYNOPSIS

One can read this document in the following formats:

            man perlos2
            view perl perlos2
            explorer perlos2.html
            info perlos2

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

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

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

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

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

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).

# DESCRIPTION

## Target

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:

- Some *nix programs use `fork()` a lot; with the mostly useful flavors of perl for OS/2 (there are several built simultaneously) this is supported; some flavors do not. Using `fork()` after useing dynamically loading extensions would not work with very old versions of EMX.

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

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

- There is no simple way to access WPS objects. The only way I know is via `OS2::REXX` extension (see the OS2::REXX manpage), and we do not have access to 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.

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 built itself) under any environment which can run EMX. The current list is DOS, DOS-inside-OS/2, Win0.3*, Win0.95 and WinNT. Out of many perl flavors, only one works, see perl_.exe.

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

Cf. Prerequisites.

## Prerequisites

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

  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

        http://www.leo.org/pub/comp/os/os2/leo/gnu/emx+gcc/
        http://powerusersbbs.com/pub/os2/dev/   [EMX+GCC Development]
        http://hobbes.nmsu.edu/pub/os2/dev/emx/v0.9d/

  The runtime component should have the name emxrt.zip.

  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.)

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

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

  One can get RSX from, say

        ftp://ftp.cdrom.com/pub/os2/emx09c/contrib
        ftp://ftp.uni-bielefeld.de/pub/systems/msdos/misc
        ftp://ftp.leo.org/pub/comp/os/os2/leo/devtools/emx+gcc/contrib

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

  The latest sh.exe with DOS hooks is available in

        ftp://ftp.math.ohio-state.edu/pub/users/ilya/os2/

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

HPFS
  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.

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

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

        ftp://ftp.math.ohio-state.edu/pub/users/ilya/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 to your program), use

            perl -my_opts foo.pl arg1 arg2 arg3

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

            extproc perl -S -my_opts

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

            foo arg1 arg2 arg3

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

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

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

To understand what the above magic does, read perl docs about `-S` switch - see the perlrun manpage, 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 the perlrun manpage.

Note that -S switch enables a search with additional extensions .cmd, .btm, .bat, .pl as well.

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

This is what `system()` (see system in the perlfunc manpage), ```` (see I/O Operators in the perlop manpage), and open pipe (see open in the perlfunc manpage) are for. (Avoid `exec()` (see exec in the perlfunc manpage) unless you know what you do).

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

The cases when the shell is used are:

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

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

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

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

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

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

7. For globbing (see glob in the perlfunc manpage, I/O Operators in the perlop manpage).

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

Perl starts scripts which begin with cookies `extproc` or `#!` directly, without an intervention of shell. Perl uses the same algorithm to find the executable as pdksh: if the path on `#!` line does not work, and contains `/`, then the 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).

If starting scripts directly, Perl will use exactly the same algorithm as for the search of script given by -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, thus `system 'blah'` will not look for a script if there is an executable file blah.exe anywhere on `PATH`.

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 as as simple as that: since blah. and blah denote the same file, to start an executable residing in file n:/bin/blah (no extension) give an argument `n:/bin/blah.` (dot appended) to system().

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

# Frequently asked questions

## ``It does not work''

Perl binary distributions come with a testperl.cmd script which tries to detect common problems with misconfigured installations. There is a pretty large chance it will discover which step of the installation you managed to goof. `;-)`

## I cannot run external programs

- Did you run your programs with `-w` switch? See Starting OS/2 (and DOS) programs under Perl.

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

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

Is your program EMX-compiled with `-Zmt -Zcrtdll`?
  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 the ExtUtils::Embed manpage?
  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 would be equivalent:

      find "pattern" file
      find pattern file

# INSTALLATION

## Automatic binary installation

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

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

            emxrev

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

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.

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 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/5.8.3/

  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 the perl manpage.

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.

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 (file globbing - if done via shell - may break).

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

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

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

## Warning

The automatic and manual perl installation leave precompiled paths inside perl executables. While these paths are overwriteable (see PERLLIB_PREFIX, PERL_SH_DIR), 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.

## Manpages

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

            man perlfunc
            man 3 less
            man ExtUtils.MakeMaker

to access documentation for different components of Perl. Start with

            man perl

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

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

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

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

## HTML

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

            cd f:/perllib/lib/pod
            pod2html

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

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

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

## 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`.

# BUILD

Here we discuss how to build Perl under OS/2. There is an alternative (but maybe older) view on http://www.shadow.net/~troc/os2perl.html

## The short story

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

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

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

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

What follows is a detailed guide through these steps.

## Prerequisites

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

      find --version
      sort --version

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

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

Possible locations to get this from are

      ftp://hobbes.nmsu.edu/os2/unix/
      ftp://ftp.cdrom.com/pub/os2/unix/
      ftp://ftp.cdrom.com/pub/os2/dev32/
      ftp://ftp.cdrom.com/pub/os2/emx09c/

It is reported that the following archives contain enough utils to build perl: gnufutil.zip, gnusutil.zip, gnututil.zip, gnused.zip, gnupatch.zip, gnuawk.zip, gnumake.zip, bsddev.zip and ksh527rt.zip (or a later version). Note that all these utilities are known to be available from LEO:

      ftp://ftp.leo.org/pub/comp/os/os2/leo/gnu

If you have exactly the same version of Perl installed already, make sure that no copies or perl are currently running. Later steps of the build may fail since an older version of perl.dll loaded into memory may be found.

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

      set BEGINLIBPATH .

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

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

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

      link386

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

## Getting perl source

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

      http://www.perl.com/CPAN/src/5.0
      http://www.perl.com/CPAN/src/5.0/unsupported

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

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

      http://www.perl.com/CPAN/ports/os2/ilyaz/

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.* like this:

      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 (even single-threaded flavor of Perl uses multi-threaded C RTL, for compatibility with XFree86-OS/2). Get a corrected one from

      ftp://ftp.math.ohio-state.edu/pub/users/ilya/os2/db_mt.zip

## Hand-editing

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

## Making

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

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

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

Now

      make

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

## Testing

Now run

      make test

All tests should succeed (with some of them skipped).

Some tests may generate extra messages similar to

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

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

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

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 most important skipped tests are:

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

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

## Installing the built perl

If you haven't yet moved perl.dll onto LIBPATH, do it now.

Run

      make install

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

Run

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

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

## `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 anything is up-to-date, say, by doing

      make perl_dll

first.

# 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.

## 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 can lock the system before Warp3 fixpak22.

## `system()`

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

When finding a program to run, Perl first asks the OS to look for executables on `PATH`. 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 is not found, and appending of executable extensions to /bin/bash does not help either, then Perl looks for an executable bash 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 different type than the current session, it will start the new process in a separate session of necessary type. Call via `OS2::Process` to disable this magic.

## `extproc` on the first line

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

## Additional modules:

the OS2::Process manpage, the OS2::DLL manpage, the OS2::REXX manpage, the OS2::PrfDB manpage, the OS2::ExtAttr manpage. 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.

## Prebuilt methods:

`File::Copy::syscopy`
  used by `File::Copy::copy`, see the File::Copy manpage.

`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)`
  chanes 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 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`.

`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 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.

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

## Prebuilt variables:

$OS2::emx_rev
  same as _emx_rev of EMX, a string 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`.

## 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.

- Since sh.exe is used for globing (see glob in the perlfunc manpage), the bugs of sh.exe plague perl as well.

  In particular, uppercase letters do not work in `[...]`-patterns with the current pdksh.

- 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 unpredictablity 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 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` special-cases /dev/tty and /dev/con.

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

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

## Identifying DLLs

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

## Centralized management of resources

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

Perl provides a centralized management of these resources:

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

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

        extern int Perl_hab_GET(void);

  instead.

`HMQ`
  There are two cases:
  - the extension needs an `HMQ` only because some API will not work otherwise. Use `serve = 0` below.

  - the extension needs an `HMQ` since 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)`. Perl process will automatically morph/unmorph itself into/from a PM process if HMQ is needed/not-needed. Perl will automatically enable/disable `WM_QUIT` message during shutdown if the message queue is served/not-served.

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

# Perl flavors

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

## perl.exe

The main workhorse. This is a chimera executable: it is compiled as an `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().

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

## perl_.exe

This is a statically linked `a.out`-style executable. It cannot load dynamic Perl extensions. The executable supplied in binary distributions has a lot of extensions prebuilt, thus the above restriction is important only if you use custom-built extensions. This executable is a VIO application.

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

## perl__.exe

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

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

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

      pm_prog args 2>&1 | cat -

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

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

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

## perl___.exe

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

It is a VIO application.

## Why strange names?

Since Perl processes the `#!`-line (cf. DESCRIPTION in the perlrun manpage, Switches in the perlrun manpage, Not a perl script in the perldiag manpage, No Perl script found in input in the perldiag manpage), 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 the complicated-to-developers but very quick and convenient-to-users ``hard'' dynamic linking used by OS/2.

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

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

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

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

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

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

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

## 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 `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,

- `open FH, "|-"`

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

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

# ENVIRONMENT

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

## `PERLLIB_PREFIX`

Specific for EMX port. Should have the form

      path1;path2

or

      path1 path2

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

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

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

This will cause Perl with the prebuilt @INC of

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

to use the following @INC:

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

## `PERL_BADLANG`

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

## `PERL_BADFREE`

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

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

## `PERL_SH_DIR`

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

## `USE_PERL_FLOCK`

Specific for EMX port. 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`.

## `TMP` or `TEMP`

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

# Evolution

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

## Priorities

`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 when a different version of Perl is compiled. In particular, DLLs (including perl.dll) are now created with the names which contain a checksum, thus allowing workaround for OS/2 scheme of caching DLLs.

It may be possible to code a simple workaround which would

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

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

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

- edit the internal `IMPORT` tables and change the name of the ``old'' perl????.dll to the ``new'' perl????.dll.

## 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. 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.

# AUTHOR

Ilya Zakharevich, ilya@math.ohio-state.edu

# SEE ALSO

perl(1).

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