[xml] building libxml 2.4.6 under OpenVMS

I've managed to get libxml2 2.4.6 built under OpenVMS after a number
of changes and much help from Bjorn Reese and Daniel Veillard.  It seems
okay (programs built and run), though I haven't put the package through
its paces yet.

Below are my notes on the issues I had to deal with.  Hopefully this
will be included as a readme file in future distros.  Attached is the
Unix doffs file for the code changes I had to make and the following
notes as readme file.  Anyone wanting a VMS doffs file can email me :-)

I also had to re-write the VMS build command file.  Daniel tells me
this will be included in 2.4.7 onwards.

Cheers, Jaf

------- 8< --------- cut here ----------- 8< -----------------------

Issues in porting libxml to VMS

Here's a summary of the issues I encountered when building LIBXML
under VMS.  There was some VMS support in the version I got, but
it was a little out of date with the result that some newer files
had problems.

I present this list "as is" to hopefully act as a guide to anyone
having problems in the future.

That's it.  Good luck!

John A Fotheringham (jaf jafsoft com)
October 2001

Installation kit

- File attributes.  Having downloaded essentially a Unix distribution,
  some of the file attributes weren't correct... especially those in
  the [.VMS] subdirectory.  In EDT you could see line feeds and
  carriage returns as <LF><CR> etc.  To correct this use the command

        $ set file <filespec> /attr=rfm=stm

  This sets the record format to be "stream".  Other variants may be
  used instead depending on how you got the files onto your system.
  Files will look okay in an EDT editor once the attributes are set.
  Without this the command file may not run correctly, since it may
  be interpreted as a single line.

- VMS-specific files are in a [.VMS] directory.  If you've found this
  file then you already know this :-)  This directory contains

      BUILD_LIBXML.COM  - a build command file, which I've
                                  radically re-worked
      CONFIG.VMS                - a configuration file to replace config.h

- Don't execute BUILD_LIBXML.COM until you've done all the following

  - read these notes
  - copied CONFIG.VMS to CONFIG.H
  - reviewed the configuration section of BUILD_LIBXML.COM, and in
    particular updated the module lists in line with MAKEFILE
  - edited XMLVERSION.H so that WITH_TRIO is defined
  - identified the location of the include files, so that you can
    manually set the LIBXML logical if need be.
  - re-read these notes :-p

  instructions for all these steps are below.

- the file [.vms]config.vms should be used to replace config.h.
  This file contains a number of define statements that identify the
  software options required under VMS

- The include files are in a [.INCLUDE.LIBXML] subdirectory.  You
  need a logical "libxml" to point to this so that include statements
  of the form

        #include <libxml/parser.h>

  will work correctly.  The source files are mostly two levels
  above this directory, although there are some .h files there
  as well.

- The command file BUILD_LIBXML.COM will do the following

  - setup some logicals
  - set def to the source directory
  - compile modules and place them into a LIBXML.OLB library
  - compile and link a number of self-test programs
  - compile and link a number of utilities and test programs
  - set def back to the original directory (i.e. if it fails you
    might not be where you started :-)

  before running this command file review the configuration segment
  at the top.  In particular compare the lists of modules with those
  in the most recent version of the Unix MAKEFILE.  Instructions are
  contained in the command file itself.

  The command file will attempt to set two logicals

  - xml_srcdir.  The directory containing the source files
  - libxml.  The include file directory.

  It attempts this by looking for modules globals.c and globals.h
  in nearby directories.  If this logic fails, you'll need to
  manually define these logicals.

The TRIO package
- A sub-package TRIO is used to provide some functions not
  naturally available under VMS.  These include support for infinite
  and undefined numbers, and specialised print functions like

  I had to make several changes to trionan.c in discussion with
  the author (hopefully these are now included in the distro, so I
  won't list them here)

  To build this software we need to add


  to the compile command for xpath.c and trio.c, and to any main
  program that uses this functionality.  BUILD_LIBXML.COM should
  do this for you.

- to build in trio support you need the define WITH_TRIO to be
  set.  This is done by editing xmlversion.h

Compiler and linker errors
- the DEC C compiler will produce a number of warnings when
  compiling the C code.  These include

    - Implicit function warnings.  These indicate functions whose
      type is not defined in a .h file.  This will probably only
      happen if your configuration is not correct (e.g. for
      "snprintf" if you haven't edited xmlversion.h to set WITH_TRIO

      These messages also occur for "read" and "write" when
      compiling trio.c

    - uninitialised variables.  Not usually a problem.  You can
      solve this by editing the code to initialise the variables

  and with respect to the trionan code

    - no main module for UNDERFLOW_TO_ZERO
    - float overflow when compiling trionan.c STANDALONE

  You can suppress these "expected" messages by using the compile


  This can be achieved by specifying "NOWARN" as the first command
  parameter to BUILD_LIBXML as follows


- the Linker will report the following error

      %LINK-W-MULDEF, symbol DECC$STRERROR multiply defined
        in module DECC$SHR file SYS$COMMON:[SYSLIB]DECC$SHR.EXE;5

  This is complaining that DECC$STRERROR is multiply defined, which
  in turn is because this system symbol is getting added to
  LIBXML.OLB when strio.c is compiled.

  I'm not sure what the solution for this is, but this is a fairly
  benign error.

Changes made to the codebase
- I changed all dummy declarations in trio.c to be

    va_list dummy = NULL;

  to prevent compiler whinge in TRIO.C about uninitialised variables

- I had to add the following to nanoftp.c

    #if defined(VMS) || defined(__VMS)
      #define SOCKLEN_T unsigned int

  This matches similar lines already added to nanohttp.c

- Several variables and function names exceed the 31 character limit
  used in VMS.  This leads to compiler warnings.  The solution adopted
  has been

  a) where variables or functions are defined, set up an ifdef on VMS
     to define a variable/function of a shorter name.  This may need to
     be done in the .h file, and in the implementation .c file

  b) use define statements to map the long name onto a shorter name.
     That way all future code can refer to the function/variable by the
     long name, reducing the need to add VMS-specific code everywhere.

  In the current distro, I had to do this for the following names

  in globals.c, parserinternals.c, globals.h, parser.h

  in globals.c, globals.h

  in xmlio.c, xmlio.h

  in xpath.c and xpathinternals.h

John A Fotheringham (Jaf)                        http://www.jafsoft.com/
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