Last updated: Sunday 6-AUG-2000
-Owing to the fear and loathing that procedures like perl's configure.com are +
Owing to the fear and loathing that procedures like Perl's configure.com are subject to I decided to put together a document that describes what configure.com is and why it is written in such a peculiar way.
1. What is
@@ -34,34 +34,34 @@
Configure.com is a DCL procuredure that sets up the build of the perl
+ Configure.com is a DCL procuredure that sets up the build of the Perl
programming language on VMS. Among the many things that it needs to do is set up
-a config.h header file that used used by the build. (Perl is written
-in C and config.h is #included by the perl source code
+a config.h header file that is used by the build. (Perl is written
+in C and config.h is #included by the Perl source code
modules in *.c files). In part because configure.com attempts to be a DCL adaptation of some wily
shell scripting (see also the answer to question 7),
there are also some variations between VMS systems that configure.com needs to
-accomodate to set up a proper perl build. For example, a lot of people are
+accommodate to set up a proper Perl build. For example, a lot of people are
uncomfortable with having to edit Makefiles and many VMS users don't even know
what MMS or MMK are (note that I didn't mean to imply that you dear,
intelligent reader did not know what these utilities do; only that there are
-such folks out there). Configure.com attempts to accomodate everybody and figure
+such folks out there). Configure.com attempts to accommodate everybody and figure
out what it needs to with little human intervention if possible. On top of that
-it also will allow for considerable human intervention of that is dsired (power
+it also will allow for considerable human intervention if that is desired (power
users building with experimental language features, broken kits that can be
fixed with editing descrip.mms files, etc). At one or another time the build of VMS perl needed to accomodate: At one or another time the build of VMS Perl needed to accommodate: It should be born in mind that some of these products have changed
+ It should be borne in mind that some of these products have changed
considerably with the introduction of newer versions. A good example would be
the DEC (now Compaq) C compiler: it may eventualy include flock() and
ioctl() functions. Because it needs to be able to run on any VMS system with minimal
effort (no user required compile e.g. is a good one since configure.com
is supposed to figure out how to invoke the compiler). Basically configure.com
-is written in DCL for the same reason that Configure is written in pidgen Bourne
+is written in DCL for the same reason that Configure is written in pidgin Bourne
shell for unix and unix-like OSes: it provides the power that is needed along
with "portability" (DCL runs on most any recent version of VMS and a shell is
available on most any unix variant.)
1. What is configure.com?
-2. Why is configure.com written in such a peculiar way?
-
Bourne like shells are not very common on VMS. The only ones that I know of +
Bourne-like shells are not very common on VMS. The only ones that I know of include: DEC's POSIX shell which was discontinued a few years ago having suffered from unpopularity since it was considered so slow (no doubt also because government procurement contracts no longer stipulated POSIX conformance), and a few things that were ported to POSIX including bash and -tcsh. Could you imagine the trouble of installing perl from source if the -READM.vms file started out with the following? +tcsh. Could you imagine the trouble of installing Perl from source if the +README.vms file started out with the following?
First install the POSIX environment from an old DEC CD ROM. Next install and configure a GNU tools chain including m4, gcc, ... Then install the VMS port of bash. Then install netlib on - top of your tcp/ip stack. Now run perl's Configure with:That would be a great deal of work. However, since DCL is VMS -native setting up the build of perl works via this simple invocation: -
sh Configure + top of your tcp/ip stack. Now run Perl's Configure with:
sh Configure
@ ConfigureIt is true that perl's Configure script +native, setting up the build of Perl works via this simple invocation: +
@ ConfigureIt is true that Perl's Configure script runs under a shell on several non Unix operating systems including:
DOS: djgpp port of bash OS/390: IBM supplied POSIX shell (folks this is a unix) OS/2: EMX port of GNU public domain k shell (pdksh) Win_NT: Cygwin port of bash or mingwin32 port of bash
but each of those environments requires a considerable extra shell/compiler -set up effort. Note too that on NT most folks who build perl from source do so +set up effort. Note too that on NT most folks who build Perl from source do so with MS Visual C and nmake (or dmake), not with a run of Configure under a non-native shell. Note too that such folks need to edit their -perl Makefiles by hand before starting the build (crude eh? Do note that there +Perl Makefiles by hand before starting the build (crude eh? Do note that there has been some work on a Configure.bat for Windoes NT/2000, as well as a Configure.MPW for Mac OS MPW users).
-In principle there is little stopping anyone from adding to perl's Bourne +
In principle there is little stopping anyone from adding to Perl's Bourne shell Configure script (or perhaps a hints/vms.sh file) in ways that -would accomodate either DEC POSIX or bash (running under POSIX) on VMS. But -retaining a configure.com in DCL will likely still be necessary to accomodate +would accommodate either DEC POSIX or bash (running under POSIX) on VMS. But +retaining a configure.com in DCL will likely still be necessary to accommodate the large number of VMS users or administrators that have only the classic VMS CLI DCL at hand.
A binary configure.exe would be possible but it would not be -readily modifiable by folks deploying perl. It would also be necessary to have a +readily modifiable by folks deploying Perl. It would also be necessary to have a separate binary for VAX and for Alpha.
In the case of perl, configure.com produces a config.sh +
In the case of Perl, configure.com produces a config.sh file that is used to produce the config.h C header file with the help -of munchconfig and later on, after most of perl gets built -config.sh is used to help create the Config.pm perl module. +of munchconfig and later on, after most of Perl gets built +config.sh is used to help create the Config.pm Perl module.
Configure.com also uses the information stored in config.sh to extract the descrip.mms file from the [.vms]descrip_mms.template file.
Perhaps it is now clear that the config.sh file, although it employs Bourne shell syntax, is an important storehouse of information about -your system that perl needs both during its build and also later on for +your system that Perl needs both during its build and also later on for reference for any script or module that contains:
use Config;and the use of the %Config hash (like most Makefile.PLs do). @@ -138,9 +138,9 @@ perl_setup.com DCL file that you can use to set up the PERL_ROOT logical name and either the PERL foreign symbol or the PERL DCL command verb (the latter done with the PERL.CLD file that configure.com will write out if you are not -using a command verb to invoke perl). If you opted to install PERL into your DCL -tables configure.com will also write out a PERL_INSTALL.COM that will replce -your DCLTABLE.EXE with one that has a system wide PERL verb in it. +using a command verb to invoke Perl). If you opted to install PERL into your DCL +tables configure.com will also write out a PERL_INSTALL.COM that will replace +your DCLTABLES.EXE with one that has a system wide PERL verb in it.
A post on comp.os.vms a long time ago mentioned the optimization that can come from writing DCL IN CAPS (like $ @@ -148,12 +148,12 @@ write in CAPS there is less work for the CLI to do since it wouldn't have to convert strings to UPCASE. This nano-optimization is probably negligible in performance, but any such optimizer can't hurt and the CAPS also have the effect -of helping non VMS savvy maintainers of Configure.com that they are treading on +of helping non VMS savvy maintainers of Configure.com know that they are treading on non Bourne shell ground. That said, there has been considerable effort to use variables with names exactly as they appear in the Unix Configure and config.sh scripts (e.g. prefix rather than PREFIX or -Prefix) so as to help the Unix hackers that maintains the shell -script also maintain the DCL script (they may not be familiar with DCLs case +Prefix) so as to help the Unix hackers that maintain the shell +script also maintain the DCL script (they may not be familiar with DCL's case insensitivity).
DCL procedures of any non-trivial size tend to use some symbol for replacing the tedium of writing $ WRITE SYS$OUTPUT ... all over the place. Some -(perl or ksh like) procedures use the symbol print, while some that +(Perl or ksh like) procedures use the symbol print, while some that are more Rexx inspired use say. Since configure.com is a DCL port of -a Bourns shell script it is completely natural to use echo. In places +a Bourne shell script, it is completely natural to use echo. In places where Configure may say something important such as:
The analogous message in Configure.com is:
Ah for the days of such simplicity! Nevertheless, the configure.com process -allows vmsperl to track changes in the Unix version of perl more closely since +allows vmsperl to track changes in the Unix version of Perl more closely since it can adapt the config.h and descrip.mms files to new features. Also the old way of doing things was exploiting the conditional make facility that the VMS port of GNU make did not have (IIRC).
@@ -256,10 +256,10 @@along with:
The perl source was converted to ANSI prototype standard and no provision was +
The Perl source was converted to ANSI prototype standard and no provision was made for classic K & R style function declarations. VAX C only handled K & R style and was retired about 1993. In principle it is merely a matter of going through the source and writing:
You'd be a big hero among HP-UX folks for doing that as well (there the ANSI -compiler costs extra and is now required to build perl if you have not installed +compiler costs extra and is now required to build Perl if you have not installed gcc on your HP-UX box, hence some HP-UX folks would appreciate a K & R -compilation alternative for perl).
+compilation alternative for Perl).I don't know. We'd like to have them back if they are not currently supported.
@@ -300,8 +300,8 @@MMK is free for use on OpenVMS, but a universal make replacment is possible. -More than one has been written in perl (see ppt or cons on CPAN). You could not -use one written in perl to build perl unless it could make use of a mini or +More than one has been written in Perl (see ppt or cons on CPAN). You could not +use one written in Perl to build Perl unless it could make use of a mini or micro perl. I thought imake had been ported to VMS at one time (?) At any rate build tools are a separate software development category from configuration tools and this was a FAQ about configure.com after all.