perl/README.vms
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   4
   5=head1 NAME
   6
   7README.vms - Configuring, building, testing, and installing perl on VMS
   8
   9=head1 SYNOPSIS
  10
  11To configure, build, test, and install perl on VMS:
  12
  13    @ Configure
  14    mms
  15    mms test
  16    mms install
  17
  18mmk may be used in place of mms in the last three steps.
  19
  20=head1 DESCRIPTION
  21
  22=head2 Important safety tip
  23
  24For best results, make sure you read the "Configuring the Perl Build",
  25"Building  Perl", and "Installing Perl" sections of this document before
  26you build or install.  Also please note other changes in the current
  27release by having a look at L<perldelta/VMS>.
  28
  29Also note that, as of Perl version 5.005 and later, an ANSI C compliant 
  30compiler is required to build Perl.  VAX C is *not* ANSI compliant, as it 
  31died a natural death some time before the standard was set.  Therefore 
  32VAX C will not compile Perl 5.005 or later.  We are sorry about that.
  33
  34There have been no recent reports of builds using Gnu C, but latent
  35(and most likely outdated) support for it is still present in various
  36parts of the sources.  Currently the HP (formerly Compaq, and even 
  37more formerly DEC) C compiler is the only viable alternative for
  38building Perl.
  39
  40There is minimal support for HP C++ but this support is not complete;
  41if you get it working please write to the vmsperl list (for info see
  42L</"Mailing Lists">).
  43
  44
  45=head2 Introduction to Perl on VMS
  46
  47The VMS port of Perl is as functionally complete as any other Perl port
  48(and as complete as the ports on some Unix systems). The Perl binaries
  49provide all the Perl system calls that are either available under VMS or
  50reasonably emulated. There are some incompatibilities in process handling
  51(e.g. the fork/exec model for creating subprocesses doesn't do what you
  52might expect under Unix), mainly because VMS and Unix handle processes and
  53sub-processes very differently.
  54
  55There are still some unimplemented system functions, and of course we
  56could use modules implementing useful VMS system services, so if you'd like
  57to lend a hand we'd love to have you.  Join the Perl Porting Team Now!
  58
  59There are issues with various versions of DEC C, so if you're not running a
  60relatively modern version, check the "DEC C issues" section later on in this
  61document.
  62
  63=head2 Other required software for Compiling Perl on VMS
  64
  65In addition to VMS and DCL you will need two things:
  66
  67=over 4
  68
  69=item 1  A C compiler. 
  70
  71HP (formerly Compaq, more formerly DEC) C for VMS (VAX, Alpha, or Itanium).
  72
  73=item 2  A make tool. 
  74
  75HP's MMS may work, but MadGoat's free MMS analog MMK (available from
  76http://www.kednos.com/kednos/Resources/MMK) has consistently worked
  77better. Gnu Make might work, but it's been so long since anyone's tested
  78it that we're not sure.  MMK is free though, so go ahead and use that.
  79
  80=back
  81
  82=head2 Additional software that is optional for Perl on VMS
  83
  84You may also want to have on hand:
  85
  86=over 4
  87
  88=item 1  GUNZIP/GZIP.EXE for VMS 
  89
  90A de-compressor for *.gz and *.tgz files available from a number 
  91of web/ftp sites and is distributed on the OpenVMS Freeware CD-ROM 
  92from HP.
  93
  94    http://www.hp.com/go/openvms/freeware/
  95    http://www.crinoid.com/utils/
  96
  97=item 2  VMS TAR 
  98
  99For reading and writing unix tape archives (*.tar files).  Vmstar is also 
 100available from a number of web/ftp sites and is distributed on the OpenVMS
 101Freeware CD-ROM from HP.
 102
 103    http://www.hp.com/go/openvms/freeware/
 104
 105Recent versions of VMS tar on ODS-5 volumes may extract tape archive
 106files with ^. escaped periods in them.  See below for further workarounds.
 107
 108A port of GNU tar is also available as part of the GNV package:
 109
 110    http://h71000.www7.hp.com/opensource/gnv.html
 111
 112=item 3  UNZIP.EXE for VMS
 113
 114A combination decompressor and archive reader/writer for *.zip files.  
 115Unzip is available from a number of web/ftp sites.
 116
 117    http://www.info-zip.org/UnZip.html
 118    http://www.hp.com/go/openvms/freeware/
 119    ftp://ftp.hp.com/pub/openvms
 120    ftp://ftp.process.com/vms-freeware/fileserv
 121
 122=item 4  MOST
 123
 124Most is an optional pager that is convenient to use with perldoc (unlike 
 125TYPE/PAGE, MOST can go forward and backwards in a document and supports 
 126regular expression searching).  Most builds with the slang 
 127library on VMS.  Most and slang are available from:
 128
 129    ftp://space.mit.edu/pub/davis/
 130    ftp://ftp.process.com/vms-freeware/narnia/
 131
 132=item 5 GNU PATCH and DIFFUTILS for VMS
 133
 134Patches to Perl are usually distributed as GNU unified or contextual diffs. 
 135Such patches are created by the GNU diff program (part of the diffutils
 136distribution) and applied with GNU patch.  VMS ports of these utilities are
 137available here:
 138
 139    http://www.antinode.info/dec/sw/diffutils.html
 140    http://www.hp.com/go/openvms/freeware/
 141
 142=back
 143
 144Please note that UNZIP and GUNZIP are not the same thing (they work with
 145different formats).  Many of the useful files from CPAN (the Comprehensive
 146Perl Archive Network) are in *.tar.gz or *.tgz format (this includes copies 
 147of the source code for perl as well as modules and scripts that you may 
 148wish to add later) hence you probably want to have GUNZIP.EXE and 
 149VMSTAR.EXE on your VMS machine.
 150
 151If you want to include socket support, you'll need a TCP/IP stack and either
 152DEC C, or socket libraries.  See the "Socket Support (optional)" topic 
 153for more details.
 154
 155=head1 Unpacking the Perl source code
 156
 157You may need to set up a foreign symbol for the unpacking utility of choice.
 158
 159As of version 5.10.0, Perl will still build and run on ODS-2 volumes,
 160including on VAX, but there are a number of modules whose temporary
 161files and tests are much happier residing on ODS-5 volumes.  For
 162example, CPANPLUS will fail most of its tests on an ODS-2 volume because
 163it includes files with multiple dots that will have been converted to
 164underscores and the tests will have difficulty finding them.  So your
 165best bet is to unpack the Perl source kit on an ODS-5 volume using
 166recent versions of vmstar (e.g. V3.4 or later).  Contrary to advice
 167provided with previous versions of Perl, do I<not> use the ODS-2
 168compatability qualifier.  Instead, use a command like the following:
 169
 170    vmstar /extract/verbose perl-V^.VIII^.III.tar
 171
 172or:
 173
 174    vmstar -xvf perl-5^.10^.1.tar
 175
 176Then rename the top-level source directory like so:
 177
 178    set security/protection=(o:rwed) perl-5^.10^.1.dir
 179    rename perl-5^.10^.1.dir perl-5_10_1.dir
 180
 181The reason for this last step is that while filenames with multiple dots
 182are generally supported by Perl on VMS, I<directory> names with multiple
 183dots are a special case with special problems because the dot is the
 184traditional directory delimiter on VMS.  Rudimentary support for
 185multi-dot directory names is available, but some of the oldest and most
 186essential parts of Perl (such as searching for and loading library
 187modules) do not yet fully support the ODS-5 caret-escape syntax.
 188
 189=head1 Configuring the Perl build
 190
 191To configure perl (a necessary first step), issue the command
 192
 193   @ Configure
 194
 195from the top of an unpacked perl source directory.  You will be asked a 
 196series of questions, and the answers to them (along with the capabilities 
 197of your C compiler and network stack) will determine how perl is custom 
 198built for your machine.
 199
 200If you have multiple C compilers installed, you'll have your choice of
 201which one to use.  Various older versions of DEC C had some caveats, so if
 202you're using a version older than 5.2, check the "DEC C Issues" section.
 203
 204If you have any symbols or logical names in your environment that may 
 205interfere with the build or regression testing of perl then configure.com 
 206will try to warn you about them.  If a logical name is causing
 207you trouble but is in an LNM table that you do not have write access to
 208then try defining your own to a harmless equivalence string in a table 
 209such that it is resolved before the other (e.g. if TMP is defined in the
 210SYSTEM table then try DEFINE TMP "NL:" or somesuch in your process table) 
 211otherwise simply deassign the dangerous logical names.  The potentially 
 212troublesome logicals and symbols are:
 213
 214    COMP    "LOGICAL"
 215    EXT     "LOGICAL"
 216    FOO     "LOGICAL"
 217    LIB     "LOGICAL"
 218    LIST    "LOGICAL"
 219    MIME    "LOGICAL"
 220    POSIX   "LOGICAL"
 221    SYS     "LOGICAL"
 222    T       "LOGICAL"
 223    THREAD  "LOGICAL"
 224    THREADS "LOGICAL"
 225    TIME    "LOGICAL"
 226    TMP     "LOGICAL"
 227    UNICODE "LOGICAL"
 228    UTIL    "LOGICAL"
 229    TEST    "SYMBOL"
 230
 231As a handy shortcut, the command:
 232
 233    @ Configure "-des"
 234
 235(note the quotation marks and case) will choose reasonable defaults 
 236automatically (it takes DEC C over Gnu C, DEC C sockets over SOCKETSHR 
 237sockets, and either over no sockets).  Some options can be given
 238explicitly on the command line; the following example specifies a 
 239non-default location for where Perl will be installed:
 240
 241    @ Configure "-d" "-Dprefix=dka100:[utils.perl5.]"
 242
 243Note that the installation location would be by default where you unpacked 
 244the source with a "_ROOT." appended.  For example if you unpacked the perl 
 245source into:
 246
 247   DKA200:[PERL-5_10_2...]
 248
 249Then the PERL_SETUP.COM that gets written out by CONFIGURE.COM will
 250try to DEFINE your installation PERL_ROOT to be:
 251
 252   DKA200:[PERL-5_10_2_ROOT.]
 253
 254More help with configure.com is available from:
 255
 256    @ Configure "-h"
 257
 258See the "Changing compile-time options (optional)" section below to learn
 259even more details about how to influence the outcome of the important 
 260configuration step.  If you find yourself reconfiguring and rebuilding 
 261then be sure to also follow the advice in the "Cleaning up and starting 
 262fresh (optional)" and the checklist of items in the "CAVEATS" sections 
 263below.
 264
 265=head2 Changing compile-time options (optional) for Perl on VMS
 266
 267Most of the user definable features of Perl are enabled or disabled in
 268configure.com, which processes the hints file config_h.SH.  There is
 269code in there to Do The Right Thing, but that  may end up being the
 270wrong thing for you.  Make sure you understand what you are doing since
 271inappropriate changes to configure.com or config_h.SH can render perl 
 272unbuildable; odds are that there's nothing in there you'll need to
 273change.
 274
 275=head2 Socket Support (optional) for Perl on VMS
 276
 277Perl includes a number of functions for IP sockets, which are available if
 278you choose to compile Perl with socket support.  Since IP networking is an 
 279optional addition to VMS, there are several different IP stacks available.  
 280How well integrated they are into the system depends on the stack, your 
 281version of VMS, and the version of your C compiler.
 282
 283The default solution available is to use the socket routines built into DEC
 284C. Which routines are available depend on the version of VMS you're
 285running, and require proper UCX emulation by your TCP/IP vendor.
 286Relatively current versions of Multinet, TCPWare, Pathway, and UCX all
 287provide the required libraries--check your manuals or release notes to see
 288if your version is new enough.
 289
 290The other solution uses the SOCKETSHR library. Before VAX/VMS 5.5-2 it was
 291the most portable solution.  The SOCKETSHR library has not been maintained
 292since VAX/VMS 5.5-2, and it is not known if will even compile with the ANSI
 293C that Perl currently requires.  It remains an option for historical reasons,
 294just in case someone might find it useful.
 295
 296In combination with either UCX or NetLib, this supported all the major TCP
 297stacks (Multinet, Pathways, TCPWare, UCX, and CMU) on all versions of VMS
 298Perl ran on up to VAX/VMS 6.2 and Alpha VMS 1.5 with all the compilers on
 299both VAX and Alpha. The portion of the socket interface was also consistent
 300across versions of VMS and C compilers.
 301
 302It has a problem with UDP sockets when used with Multinet, though, so you
 303should be aware of that.
 304
 305As of VAX/VMS 5.5-2 and later, CMU is the only TCP/IP program that requires
 306socketshr, and the sources have been lost to the most recent CMU bug fixes,
 307so CMU is limited to OpenVMS/VAX 6.2 or earlier, which is the last release
 308that binaries for the last released patches are known to exist.
 309
 310There is currently no official web site for downloading either CMU or
 311SOCKETSHR; however, copies may be found in the DECUS archives.
 312
 313=head1 Building Perl
 314
 315The configuration script will print out, at the very end, the MMS or MMK
 316command you need to compile perl.  Issue it (exactly as printed) to start
 317the build.  
 318
 319Once you issue your MMS or MMK command, sit back and wait.  Perl should 
 320compile and link without a problem.  If a problem does occur check the 
 321"CAVEATS" section of this document.  If that does not help send some 
 322mail to the VMSPERL mailing list.  Instructions are in the "Mailing Lists" 
 323section of this document.
 324
 325=head1 Testing Perl
 326
 327Once Perl has built cleanly you need to test it to make sure things work.
 328This step is very important since there are always things that can go wrong
 329somehow and yield a dysfunctional Perl for you.
 330
 331Testing is very easy, though, as there's a full test suite in the perl
 332distribution.  To run the tests, enter the *exact* MMS line you used to
 333compile Perl and add the word "test" to the end, like this:
 334
 335If the compile command was:
 336
 337    MMS
 338
 339then the test command ought to be:
 340
 341    MMS test
 342
 343MMS (or MMK) will run all the tests.  This may take some time, as there are 
 344a lot of tests.  If any tests fail, there will be a note made on-screen. 
 345At the end of all the tests, a summary of the tests, the number passed and 
 346failed, and the time taken will be displayed.
 347
 348The test driver invoked via MMS TEST has a DCL wrapper ([.VMS]TEST.COM) that
 349downgrades privileges to NETMBX, TMPMBX for the duration of the test run,
 350and then restores them to their prior state upon completion of testing. 
 351This is done to ensure that the tests run in a private sandbox and can do no
 352harm to your system even in the unlikely event something goes badly wrong in
 353one of the test scripts while running the tests from a privileged account. 
 354A side effect of this safety precaution is that the account used to run the
 355test suite must be the owner of the directory tree in which Perl has been
 356built; otherwise the manipulations of temporary files and directories
 357attempted by some of the tests will fail.
 358
 359If any tests fail, it means something is wrong with Perl, or at least
 360with the particular module or feature that reported failure. If the test suite
 361hangs (some tests can take upwards of two or three minutes, or more if
 362you're on an especially slow machine, depending on your machine speed, so
 363don't be hasty), then the test *after* the last one displayed failed. Don't
 364install Perl unless you're confident that you're OK. Regardless of how
 365confident you are, make a bug report to the VMSPerl mailing list.
 366
 367If one or more tests fail, you can get more information on the failure by 
 368issuing this command sequence:
 369
 370    @ [.VMS]TEST .typ "" "-v" [.subdir]test.T
 371
 372where ".typ" is the file type of the Perl images you just built (if you
 373didn't do anything special, use .EXE), and "[.subdir]test.T" is the test
 374that failed. For example, with a normal Perl build, if the test indicated
 375that t/op/time failed, then you'd do this:
 376
 377    @ [.VMS]TEST .EXE "" "-v" [.OP]TIME.T
 378
 379Note that test names are reported in UNIX syntax and relative to the
 380top-level build directory.  When supplying them individually to the test
 381driver, you can use either UNIX or VMS syntax, but you must give the path
 382relative to the [.T] directory and you must also add the .T extension to the
 383filename.  So, for example if the test lib/Math/Trig fails, you would run:
 384
 385    @ [.VMS]TEST .EXE "" -"v" [-.lib.math]trig.t
 386
 387When you send in a bug report for failed tests, please include the output
 388from this command, which is run from the main source directory:
 389
 390    MCR []MINIPERL "-V"
 391
 392Note that -"V" really is a capital V in double quotes. This will dump out a
 393couple of screens worth of configuration information, and can help us 
 394diagnose the problem.  If (and only if) that did not work then try enclosing 
 395the output of:
 396
 397    MMS printconfig
 398
 399If (and only if) that did not work then try enclosing the output of:
 400
 401    @ [.vms]myconfig
 402
 403You may also be asked to provide your C compiler version ("CC/VERSION NL:" 
 404with DEC C, "gcc --version" with GNU CC).  To obtain the version of MMS or 
 405MMK you are running try "MMS/ident" or "MMK /ident".  The GNU make version 
 406can be identified with "make --version".
 407
 408=head2 Cleaning up and starting fresh (optional) installing Perl on VMS
 409
 410If you need to recompile from scratch, you have to make sure you clean up
 411first.  There is a procedure to do it--enter the *exact* MMS line you used 
 412to compile and add "realclean" at the end, like this:
 413
 414if the compile command was:
 415
 416    MMS
 417
 418then the cleanup command ought to be:
 419
 420    MMS realclean
 421
 422If you do not do this things may behave erratically during the subsequent 
 423rebuild attempt.  They might not, too, so it is best to be sure and do it.
 424
 425=head1 Installing Perl
 426
 427There are several steps you need to take to get Perl installed and
 428running.
 429
 430=over 4
 431
 432=item 1
 433
 434Check your default file protections with
 435
 436     SHOW PROTECTION /DEFAULT
 437
 438and adjust if necessary with SET PROTECTION=(code)/DEFAULT.
 439
 440=item 2
 441
 442Decide where you want Perl to be installed (unless you have already done so
 443by using the "prefix" configuration parameter -- see the example in the
 444"Configuring the Perl build" section).
 445
 446The DCL script PERL_SETUP.COM that is written by CONFIGURE.COM will help you
 447with the definition of the PERL_ROOT and PERLSHR logical names and the PERL
 448foreign command  symbol.  Take a look at PERL_SETUP.COM and modify it if you
 449want to.  The installation process will execute PERL_SETUP.COM and copy
 450files to the directory tree pointed to by the PERL_ROOT logical name defined
 451there, so make sure that you have write access to the parent directory of
 452what will become the root of your Perl installation.
 453
 454=item 3
 455
 456Run the install script via:
 457
 458    MMS install
 459
 460or
 461
 462    MMK install
 463
 464If for some reason it complains about target INSTALL being up to date,
 465throw a /FORCE switch on the MMS or MMK command.
 466
 467=back
 468
 469Copy PERL_SETUP.COM to a place accessible to your perl users.  
 470
 471For example:
 472
 473    COPY PERL_SETUP.COM SYS$LIBRARY: 
 474
 475If you want to have everyone on the system have access to perl
 476then add a line that reads
 477
 478    $ @sys$library:perl_setup
 479
 480to SYS$MANAGER:SYLOGIN.COM.
 481
 482Two alternatives to the foreign symbol would be to install PERL into 
 483DCLTABLES.EXE (Check out the section "Installing Perl into DCLTABLES 
 484(optional)" for more information), or put the image in a 
 485directory that's in your DCL$PATH (if you're using VMS V6.2 or higher).
 486
 487An alternative to having PERL_SETUP.COM define the PERLSHR logical name
 488is to simply copy it into the system shareable library directory with:
 489
 490    copy perl_root:[000000]perlshr.exe sys$share:
 491
 492See also the "INSTALLing images (optional)" section.
 493
 494=head2 Installing Perl into DCLTABLES (optional) on VMS
 495
 496Execute the following command file to define PERL as a DCL command.
 497You'll need CMKRNL privilege to install the new dcltables.exe.
 498
 499    $ create perl.cld
 500    !
 501    ! modify to reflect location of your perl.exe
 502    !
 503    define verb perl
 504      image perl_root:[000000]perl.exe
 505      cliflags (foreign)
 506    $!
 507    $ set command perl /table=sys$common:[syslib]dcltables.exe -
 508     /output=sys$common:[syslib]dcltables.exe
 509    $ install replace sys$common:[syslib]dcltables.exe
 510    $ exit
 511
 512=head2 INSTALLing Perl images (optional) on VMS
 513
 514On systems that are using perl quite a bit, and particularly those with 
 515minimal RAM, you can boost the performance of perl by INSTALLing it as
 516a known image.  PERLSHR.EXE is typically larger than 3000 blocks
 517and that is a reasonably large amount of IO to load each time perl is 
 518invoked. 
 519
 520   INSTALL ADD PERLSHR/SHARE
 521   INSTALL ADD PERL/HEADER
 522
 523should be enough for PERLSHR.EXE (/share implies /header and /open), 
 524while /HEADER should do for PERL.EXE (perl.exe is not a shared image).
 525
 526If your code 'use's modules, check to see if there is a shareable image for
 527them, too.  In the base perl build, POSIX, IO, Fcntl, Opcode, SDBM_File,
 528DCLsym, and Stdio, and other extensions all have shared images that can be
 529installed /SHARE.
 530
 531How much of a win depends on your memory situation, but if you are firing
 532off perl with any regularity (like more than once every 20 seconds or so)
 533it is probably beneficial to INSTALL at least portions of perl.
 534
 535While there is code in perl to remove privileges as it runs you are advised
 536to NOT INSTALL PERL.EXE with PRIVs!
 537
 538=head2 Running h2ph to create perl header files (optional) on VMS
 539
 540If using HP C, ensure that you have extracted loose versions of your 
 541compiler's header or *.H files.  Be sure to check the contents of:
 542
 543    SYS$LIBRARY:DECC$RTLDEF.TLB
 544    SYS$LIBRARY:SYS$LIB_C.TLB
 545    SYS$LIBRARY:SYS$STARLET_C.TLB
 546
 547etcetera.
 548
 549If using GNU cc then also check your GNU_CC:[000000...] tree for the locations
 550of the GNU cc headers.
 551
 552=head1 Reporting Bugs
 553
 554If you come across what you think might be a bug in Perl, please report
 555it. There's a script in PERL_ROOT:[UTILS], perlbug, that walks you through
 556the process of creating a bug report. This script includes details of your
 557installation, and is very handy. Completed bug reports should go to
 558perlbug@perl.com.
 559
 560=head1 CAVEATS
 561
 562Probably the single biggest gotcha in compiling Perl is giving the wrong
 563switches to MMS/MMK when you build. Use *exactly* what the configure.com 
 564script prints!
 565
 566The next big gotcha is directory depth.  Perl can create directories four,
 567five, or even six levels deep during the build, so you don't have to be 
 568too deep to start to hit the RMS 8 level limit (for ODS 2 volumes which were
 569common on versions of VMS prior to V7.2 and even with V7.3 on the VAX).  
 570It is best to do:
 571
 572    DEFINE/TRANS=(CONC,TERM) PERLSRC "disk:[dir.dir.dir.perldir.]"
 573    SET DEFAULT PERLSRC:[000000]
 574
 575before building in cases where you have to unpack the distribution so deep
 576(note the trailing period in the definition of PERLSRC).  Perl modules 
 577from CPAN can be just as bad (or worse), so watch out for them, too. Perl's
 578configuration script will warn if it thinks you are too deep (at least on 
 579a VAX or on Alpha versions of VMS prior to 7.2).  But MakeMaker will not 
 580warn you if you start out building a module too deep in a directory.
 581
 582As noted above ODS-5 escape sequences such as ^. can break the perl
 583build.  Solutions include renaming files and directories as needed or
 584being careful to use the -o switch or /ODS2 qualifier with latter
 585versions of the vmstar utility when unpacking perl or CPAN modules
 586on ODS-5 volumes.
 587
 588Be sure that the process that you use to build perl has a PGFLQ greater
 589than 100000.  Be sure to have a correct local time zone to UTC offset
 590defined (in seconds) in the logical name SYS$TIMEZONE_DIFFERENTIAL before
 591running the regression test suite.  The SYS$MANAGER:UTC$CONFIGURE_TDF.COM 
 592procedure will help you set that logical for your system but may require 
 593system privileges.  For example, a location 5 hours west of UTC (such as 
 594the US East coast while not on daylight savings time) would have:
 595
 596    DEFINE SYS$TIMEZONE_DIFFERENTIAL "-18000"
 597
 598A final thing that causes trouble is leftover pieces from a failed
 599build.  If things go wrong make sure you do a "(MMK|MMS|make) realclean"
 600before you rebuild.
 601
 602=head2 DEC C issues with Perl on VMS
 603
 604Note to DEC C users: Some early versions (pre-5.2, some pre-4. If you're DEC
 605C 5.x or higher, with current patches if any, you're fine) of the DECCRTL
 606contained a few bugs which affect Perl performance:
 607
 608=over 4
 609
 610=item - pipes
 611
 612Newlines are lost on I/O through pipes, causing lines to run together.
 613This shows up as RMS RTB errors when reading from a pipe.  You can
 614work around this by having one process write data to a file, and
 615then having the other read the file, instead of the pipe.  This is
 616fixed in version 4 of DEC C.
 617
 618=item - modf()
 619
 620The modf() routine returns a non-integral value for some values above
 621INT_MAX; the Perl "int" operator will return a non-integral value in
 622these cases.  This is fixed in version 4 of DEC C.
 623
 624=item - ALPACRT ECO
 625
 626On the AXP, if SYSNAM privilege is enabled, the CRTL chdir() routine
 627changes the process default device and directory permanently, even
 628though the call specified that the change should not persist after
 629Perl exited.  This is fixed by DEC CSC patch ALPACRT04_061 or later.
 630See also:
 631
 632    http://ftp.support.compaq.com/patches/.new/openvms.shtml
 633
 634=back
 635
 636Please note that in later versions "DEC C" may also be known as 
 637"Compaq C".
 638
 639=head2 GNU issues with Perl on VMS
 640
 641It has been a while since the GNU utilities such as GCC or GNU make
 642were used to build perl on VMS.  Hence they may require a great deal
 643of source code modification to work again.
 644
 645    http://slacvx.slac.stanford.edu/HELP/GCC
 646    http://www.progis.de/
 647    http://www.lp.se/products/gnu.html
 648
 649=head2 Floating Point Considerations
 650
 651Prior to 5.8.0, Perl simply accepted the default floating point options of the
 652C compiler, namely representing doubles with D_FLOAT on VAX and G_FLOAT on
 653Alpha.  Single precision floating point values are represented in F_FLOAT
 654format when either D_FLOAT or G_FLOAT is in use for doubles.  Beginning with
 6555.8.0, Alpha builds now use IEEE floating point formats by default, which in
 656VMS parlance are S_FLOAT for singles and T_FLOAT for doubles.  IEEE is not
 657available on VAX, so F_FLOAT and D_FLOAT remain the defaults for singles and
 658doubles respectively.  The available non-default options are G_FLOAT on VAX
 659and D_FLOAT or G_FLOAT on Alpha.
 660
 661The use of IEEE on Alpha introduces NaN, infinity, and denormalization
 662capabilities not available with D_FLOAT and G_FLOAT.  When using one of those
 663non-IEEE formats, silent underflow and overflow are emulated in the conversion
 664of strings to numbers, but it is preferable to get the real thing by using
 665IEEE where possible.
 666
 667Regardless of what floating point format you consider preferable, be aware
 668that the choice may have an impact on compatibility with external libraries,
 669such as database interfaces, and with existing data, such as data created with
 670the C<pack> function and written to disk, or data stored via the Storable
 671extension.  For example, a C<pack("d", $foo)")> will create a D_FLOAT,
 672G_FLOAT, or T_FLOAT depending on what your Perl was configured with.  When
 673written to disk, the value can only be retrieved later by a Perl configured
 674with the same floating point option that was in effect when it was created.
 675
 676To obtain a non-IEEE build on Alpha, simply answer no to the "Use IEEE math?"
 677question during the configuration.  To obtain an option different from the C
 678compiler default on either VAX or Alpha, put in the option that you want in
 679answer to the "Any additional cc flags?" question.  For example, to obtain a
 680G_FLOAT build on VAX, put in C</FLOAT=G_FLOAT>.
 681
 682=head2 Multinet issues with Perl on VMS
 683
 684Prior to the release of Perl 5.8.0 it was noted that the regression
 685test for lib/Net/hostent (in file [.lib.Net]hostent.t) will fail owing
 686to problems with the hostent structure returned by C calls to either
 687gethostbyname() or gethostbyaddr() using DEC or Compaq C with a
 688Multinet TCP/IP stack.  The problem was noted in Multinet 4.3A
 689using either Compaq C 6.5 or DEC C 6.0, and with Multinet 4.2A
 690using DEC C 5.2, but could easily affect other versions of Multinet.
 691Process Software Inc. has acknowledged a bug in the Multinet version 
 692of UCX$IPC_SHR and has provided an ECO for it. The ECO is called
 693UCX_LIBRARY_EMULATION-010_A044 and is available from:
 694
 695    http://www.multinet.process.com/eco.html
 696
 697As of this writing, the ECO is only available for Multinet versions 
 6984.3A and later.  You may determine the version of Multinet that you 
 699are running using the command:
 700
 701    multinet show /version
 702
 703from the DCL command prompt.
 704
 705If the ECO is unavailable for your version of Multinet and you are 
 706unable to upgrade, you might try using Perl programming constructs 
 707such as:
 708
 709    $address = substr($gethostbyname_addr,0,4);
 710
 711to temporarily work around the problem, or if you are brave
 712and do not mind the possibility of breaking IPv6 addresses,
 713you might modify the pp_sys.c file to add an ad-hoc correction
 714like so:
 715
 716
 717    --- pp_sys.c;1        Thu May 30 14:42:17 2002
 718    +++ pp_sys.c        Thu May 30 12:54:02 2002
 719    @@ -4684,6 +4684,10 @@
 720             }
 721     #endif
 722
 723    +    if (hent) {
 724    +        hent->h_length = 4;
 725    +    }
 726    +
 727         if (GIMME != G_ARRAY) {
 728             PUSHs(sv = sv_newmortal());
 729             if (hent) {
 730
 731then re-compile and re-test your perl.  After the installation
 732of the Multinet ECO you ought to back out any such changes though.
 733
 734=head1 Mailing Lists
 735
 736There are several mailing lists available to the Perl porter.  For VMS
 737specific issues (including both Perl questions and installation problems)
 738there is the VMSPERL mailing list.  It is usually a low-volume (10-12
 739messages a week) mailing list.
 740
 741To subscribe, send a mail message to VMSPERL-SUBSCRIBE@PERL.ORG. The VMSPERL
 742mailing list address is VMSPERL@PERL.ORG.  Any mail sent there gets echoed
 743to all subscribers of the list.  There is a searchable archive of the list
 744on the web at:
 745
 746    http://www.xray.mpe.mpg.de/mailing-lists/vmsperl/
 747
 748To unsubscribe from VMSPERL send a message to VMSPERL-UNSUBSCRIBE@PERL.ORG.
 749Be sure to do so from the subscribed account that you are canceling.
 750
 751=head2 Web sites for Perl on VMS
 752
 753Vmsperl pages on the web include:
 754
 755    http://www.sidhe.org/vmsperl/index.html
 756    http://www.cpan.org/modules/by-module/VMS/
 757    http://www.xray.mpe.mpg.de/mailing-lists/vmsperl/
 758    http://www-ang.kfunigraz.ac.at/~binder/perl.html
 759    http://lists.perl.org/showlist.cgi?name=vmsperl
 760    http://archive.develooper.com/vmsperl@perl.org/
 761    http://h71000.www7.hp.com/openvms/products/ips/apache/csws_modperl.html
 762
 763=head1 SEE ALSO
 764
 765Perl information for users and programmers about the port of perl to VMS is
 766available from the [.POD]PERLVMS.POD file that gets installed as L<perlvms>.
 767For administrators the perlvms document also includes a detailed discussion 
 768of extending vmsperl with CPAN modules after Perl has been installed.
 769
 770=head1 AUTHORS
 771
 772Originally by Charles Bailey bailey@newman.upenn.edu.  See the git repository
 773for history.
 774
 775=head1 ACKNOWLEDGEMENTS
 776
 777A real big thanks needs to go to Charles Bailey
 778bailey@newman.upenn.edu, who is ultimately responsible for Perl 5.004
 779running on VMS. Without him, nothing the rest of us have done would be at
 780all important.
 781
 782There are, of course, far too many people involved in the porting and testing
 783of Perl to mention everyone who deserves it, so please forgive us if we've
 784missed someone.  That said, special thanks are due to the following:
 785
 786  Tim Adye T.J.Adye@rl.ac.uk
 787     for the VMS emulations of getpw*()
 788  David Denholm denholm@conmat.phys.soton.ac.uk
 789     for extensive testing and provision of pipe and SocketShr code,
 790  Mark Pizzolato mark@infocomm.com
 791     for the getredirection() code
 792  Rich Salz rsalz@bbn.com
 793     for readdir() and related routines
 794  Peter Prymmer pvhp@best.com 
 795     for extensive testing, as well as development work on
 796     configuration and documentation for VMS Perl,
 797  Dan Sugalski dan@sidhe.org
 798     for extensive contributions to recent version support,
 799     development of VMS-specific extensions, and dissemination
 800     of information about VMS Perl,
 801  the Stanford Synchrotron Radiation Laboratory and the
 802     Laboratory of Nuclear Studies at Cornell University for
 803     the opportunity to test and develop for the AXP,
 804  John Hasstedt John.Hasstedt@sunysb.edu
 805     for VAX VMS V7.2 support
 806  John Malmberg wb8tyw@qsl.net
 807     for ODS-5 filename handling and other modernizations
 808
 809and to the entire VMSperl group for useful advice and suggestions.  In
 810addition the perl5-porters deserve credit for their creativity and
 811willingness to work with the VMS newcomers.  Finally, the greatest debt of
 812gratitude is due to Larry Wall larry@wall.org, for having the ideas which
 813have made our sleepless nights possible.
 814
 815Thanks,
 816The VMSperl group
 817
 818=cut
 819
 820
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