Last revised: 08-Feb-1995 by Charles Bailey  bailey@genetics.upenn.edu

The VMS port of Perl is still under development.  At this time, the Perl
binaries built under VMS handle internal operations properly, for the most
part, as well as most of the system calls which have close equivalents under
VMS. There are still some incompatibilities in process handling (e.g the
fork/exec model for creating subprocesses doesn't do what you might expect
under Unix), and there remain some file handling differences from Unix.  Over
the longer term, we'll try to get many of the useful VMS system services
integrated as well, depending on time and people available.  Of course, if
you'd like to add something yourself, or join the porting team, we'd love to
have you!

The current sources and build procedures have been tested on a VAX using VAXC
and on an AXP using DECC.  If you run into problems with other compilers,
please let us know.

Note to DECC users: Some early versions of the DECCRTL contained a few bugs
which affect Perl performance:
    - Newlines are lost on I/O through pipes, causing lines to run together.
      This shows up as RMS RTB errors when reading from a pipe.  You can
      work around this by having one process write data to a file, and
      then having the other read the file, instead of the pipe.
    - The modf() routine returns a non-integral value for some values above
      INT_MAX; the Perl "int" operator will return a non-integral value in
      these cases.
Both of these bugs have been fixed in later releases of the DECCRTL, but some
systems running AXP/VMS 1.5 still have the old RTLs.  

* Other software required

At the moment, in addition to basic VMS, you'll need two things:
   - a C compiler: VAXC, DECC, or gcc for the VAX; DECC for the AXP
   - a make tool: DEC's MMS or the free analog MMK (available from ftp.spc.edu)
     or a standard make utility (e.g. GNU make, also available from
     ftp.spc.edu).
In addition, you may include socket support if you have a IP stack running
on your system.  See the topic "Socket support" for more information.

* Socket support

Perl includes a number of IP socket routines among its builtin functions,
which are available if you choose to compile Perl with socket support.  Since
IP networking is an optional addition to VMS, there are several different IP
stacks available, it's difficult to automate the process of building Perl with
socket support in a way which will work on all systems.  

By default, Perl is built without IP socket support.  If you define the macro
SOCKET when invoking MMS, however, socket support will be included.  As
distributed, Perl for VMS includes support for the SOCKETSHR socket library,
which is layered on MadGoat software's vendor-independent NETLIB interface. 
This provides support for all socket calls used by Perl except the
[g|s]et*ent() routines, which are replaced for the moment by stubs which
generate a fatal error if a Perl script attempts to call one of these routines. 
If you'd like to link Perl directly to your IP stack to take advantage of these
routines or to eliminate the intermediate NETLIB, then make the following
changes:
  - In Descrip.MMS, locate the section beginning with .ifdef SOCKET, and
    change the SOCKLIB macro so that it translates to  the filespec of your
    IP stack's socket library.  This will be added to the RTL options file.
  - Edit the file SockAdapt.H in the [.VMS] subdirectory so that it
    includes the In.H, NetDb.H, and, if necessary, Errno.H header files
    for your IP stack, or so that it declares the standard TCP/IP data
    structures appropriately (see the distributed copy of SockAdapt.H
    for a collection of the structures needed by Perl.)  You should also
    define any logical names necessary to find these files before invoking
    MMS to build Perl.
  - Edit the file SockAdapt.C in the [.VMS] subdirectory so that it
    contains routines which substitute for any IP library routines
    required by Perl which your IP stack does not provide.  This may
    require a little trial and error; we'll try to compile a complete
    list soon of socket routines required by Perl.

* Building Perl under VMS

Since you're reading this, presumably you've unpacked the Perl distribution
into its directory tree, in which you will find a [.vms] subdirectory below
the directory in which this file is found.  If this isn't the case, then you'll
need to unpack the distribution properly, or manually edit Descrip.MMS or
the VMS Makefile to alter directory paths as necessary.  (I'd advise using the 
`normal' directory tree, at least for the first time through.)  This
subdirectory contains several files, among which are the following:
  Config.VMS     - A template C header file set up for VMS.
  Descrip.MMS    - The MMS/MMK dependency file for building Perl
  GenConfig.Pl   - A Perl script to generate Config.SH retrospectively
                   from Config.VMS, since the Configure shell script which
                   normally generates Config.SH doesn't run under VMS.
  GenOpt.Com     - A little DCL procedure used to write some linker options
                   files, since not all make utilities can do this easily.
  Gen_ShrFls.Pl  - A Perl script which generates linker options files and
                   MACRO declarations for PerlShr.Exe.
  Makefile      - The make dependency file for building Perl  
  MMS2Make.Pl    - A Perl script used to generate Makefile from Descrip.MMS
  VMSish.H       - C header file containing VMS-specific definitions
  VMS.C          - C source code for VMS-specific routines
  WriteMain.Pl   - A Perl script used to generate perlmain.c during the build.
There may also be other files pertaining to features under development; for the
most part, you can ignore them.

Config.VMS and Decrip.MMS/Makefile are set up to build a version of Perl which
includes all features known to work when this release was assembled.  If you
have code at your site which would support additional features (e.g. emulation
of Unix system calls), feel free to make the appropriate changes to these
files.  (Note: Do not use or edit config.h in the main Perl source directory;
it is superseded by the current Config.VMS during the build.)  You may also
wish to make site-specific changes to Descrip.MMS or Makefile to reflect local
conventions for naming of files, etc.

At the moment, system-specific information which becomes part of the Perl
Config extension is hard-coded into the file genconfig.pl in the vms
subdirectory.  Before you build Perl, you should make any changes to the list
at the end of this file necessary to reflect your system (e.g your hostname and
VMS version).

Examine the information at the beginning of Descrip.MMS for information about
specifying alternate C compilers or building a version of Perl with debugging
support.  For instance, if you want to use DECC, you'll need to include the
/macro="decc=1" qualifier to MMS  (If you're using make, these options are not
supported.)  If you're on an AXP system, define the macro __AXP__ (MMK does
this for you), and DECC will automatically be selected.

To start the build, set default to the main source directory.  Since
Descrip.MMS assumes that VMS commands have their usual meaning, and makes use
of command-line macros, you may want to be certain that you haven't defined DCL
symbols which would interfere with the build.  Then, if you are using MMS or
MMK, say
$ MMS/Descrip=[.VMS] ! or MMK
If you are using make, say
$ Make -f [.VMS]Makefile
Note that the Makefile doesn't support conditional compilation, is
set up to use VAXC on a VAX, and does not include socket support.  You can
either edit the Makefile by hand, using Descrip.MMS as a guide, or use the
Makefile to build Miniperl.Exe, and then run the Perl script MMS2Make.pl,
found in the [.VMS] subdirectory, to generate a new Makefile with the options
appropriate to your site.

Note for sites using early versions of DECC:  A bug in some versions of the
DECC RTL causes newlines to be lost when writing to a pipe.  This causes
Gen_ShrFls.pl to fail, since it can't read the preprocessor output to identify
global variables and routines.  You can work around this problem by defining
the macro DECC_PIPES_BROKEN when you invoke MMS or MMK.

This will build the following files:
  Miniperl.Exe        - a stand-alone version of without any extensions.
                        Miniperl has all the intrinsic capabilities of Perl,
                        but cannot make use of the DynaLoader or any
                        extensions which use XS code.
  PerlShr.Exe         - a shareable image containing most of Perl's internal
                        routines and global variables.  Perl.Exe is linked to
                        this image, as are all dynamic extensions, so everyone's
                        using the same set of global variables and routines.
  Perl.Exe            - the main Perl executable image.  It's contains the
                        main() routine, plus code for any statically linked
                        extensions.
  PerlShr_Attr.Opt    - A linker options file which specifies psect attributes
                        matching those in PerlShr.Exe.  It should be used when
                        linking images against PerlShr.Exe
  PerlShr_Bld.Opt     - A linker options file which specifies various things
                        used to build PerlShr.Exe.  It should be used when
                        rebuilding PerlShr.Exe via MakeMaker-produced
                        Descrip.MMS files for static extensions.
  [.Lib]Config.pm     - the Perl extension which saves configuration information
                        about Perl and your system.
  [.lib]DynaLoader.pm - The Perl extension which performs dynamic linking of
                        shareable images for extensions.
There are, of course, a number of other files created for use during the build. 
Once you've got the binaries built, you may wish to `build' the `tidy' or
`clean' targets to remove extra files.


* Installing Perl once it's built

Once the build is complete, you'll need to do the following:
  - Put PerlShr.Exe in a common directory, and make it world-readable.
    If you place it in a location other than Sys$Share, you'll need to
    define the logical name PerlShr to point to the image.
  - Put Perl.Exe in a common directory, and make it world executable
  - Define a foreign command to invoke Perl, using a statement like
    $ Perl == "$dev:[dir]Perl.Exe"
  - Create a world-readable directory tree for Perl library modules,
    scripts, and what-have-you, and define PERL_ROOT as a rooted logical
    name pointing to the top of this tree (i.e. if your Perl files were
    going to live in DKA1:[Util.Perl5...], then you should
      $ Define/Translation=Concealed Perl_Root DKA1:[Util.Perl5.]
    (Be careful to follow the rules for rooted logical names; in particular,
    remember that a rooted logical name cannot have as its device portion
    another rooted logical name - you've got to supply the actual device name
    and directory path to the root directory.)
  - Define the logical name PERLSHR as the full file specification of
    PERLSHR.EXE, so executable images linked to it can find it.  Alternatively,
    you can justput PERLSHR.EXE int SYS$SHARE.
  - Place the files from the [.lib] subdirectory in the distribution package
    into a [.lib] subdirectory off the root directory described above.
  - Most of the Perl documentation lives in the [.pod] subdirectory, and
    is written in a simple markup format which can be easily read.  In this
    directory as well are pod2man and pod2html translators to reformat the
    docs for common display engines; a pod2hlp translator is under development.
    Information on Perl can also be gleaned from the files in the [.doc]
    subdirectory (internals documents and summaries of changes), and from
    the test scripts in the [.t...] subdirectories.
For now, that's it.


* For more information

If you're interested in more information on Perl in general, consult the Usenet
newsgroup comp.lang.perl.  The FAQ for that group provides pointers to other
online sources of information, as well as books describing Perl in depth.

If you're interested in up-to-date information on Perl development and
internals, you might want to subscribe to the perl5-porters mailing list.  You
can do this by sending a message to perl5-porters-request@nicoh.com, containing
the single line
subscribe perl5-porters
This is a moderately high-volume list at the moment (25-50 messages/day).

Finally, if you're interested in ongoing information about the VMS port, you
can subscribe to the VMSperl mailing list by sending a request to
bailey@genetics.upenn.edu (it's to a human, not a list server - this is a small
operation at the moment).  And, as always, we welcome any help or code you'd
like to offer - you can send mail to bailey@genetics.upenn.edu or directly to
the VMSperl list at vmsperl@genetics.upenn.edu.

Good luck using Perl.  Please let us know how it works for you - we can't
guarantee that we'll be able to fix bugs quickly, but we'll try, and we'd
certainly like to know they're out there.


* Acknowledgements

There are, of course, far too many people involved in the porting and testing
of Perl to mention everyone who deserves it, so please forgive us if we've
missed someone.  That said, special thanks are due to the following:
  Tim Adye <T.J.Adye@rl.ac.uk>
     for the VMS emulations of getpw*()
  David Denholm <denholm@conmat.phys.soton.ac.uk>
     for extensive testing and provision of pipe and SocketShr code,
  Mark Pizzolato <mark@infocomm.com>
     for the getredirection() code
  Rich Salz <rsalz@bbn.com>
     for readdir() and related routines
  Denis Haskin <DWH@epub.ziff.com>
     for work on a pod-to-hlp translator for the Perl documentation
  Richard Dyson <dyson@blaze.physics.uiowa.edu> and
  Kent Covert <kacovert@miavx1.acs.muohio.edu>
     for additional testing on the AXP.
and to the entire VMSperl group for useful advice and suggestions.  In addition
the perl5-porters, especially Andy Dougherty <doughera@lafcol.lafayette.edu>
and Tim Bunce <Tim.Bunce@ig.co.uk>,  deserve credit for their creativity and
willingness to work with the VMS newcomers.  Finally, the greatest debt of
gratitude is due to Larry Wall <lwall@netlabs.com>, for having the ideas which
have made our sleepless nights possible.

Thanks,
The VMSperl group
