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# pumpkin

- NAME
- SYNOPSIS
- DESCRIPTION
- Where Do I Get Perl Sources and Related Material?
  - Perl5-porters mailing list
- How are Perl Releases Numbered?
  - Maintenance and Development Subversions
  - Why is it called the patch pumpkin?
- Philosophical Issues in Patching and Porting Perl
  - Solve problems as generally as possible
  - Seek consensus on major changes
  - Keep the documentation up-to-date
  - Avoid machine-specific #ifdef's
  - Machine-specific files
  - Allow for lots of testing
  - Test popular applications and modules.
  - Automated generation of derivative files
- How to Make a Distribution
  - Announce your intentions
  - refresh pod/perltoc.pod
  - run installhtml to check the validity of the pod files
  - update patchlevel.h
  - run metaconfig
  - MANIFEST
  - Check permissions
  - Run Configure
  - Update Porting/config.sh and Porting/config_H
  - make run_byacc
  - make regen_all
  - make regen_headers
  - make regen_pods
  - global.sym, interp.sym and perlio.sym
  - Binary compatibility
  - Changes
  - Todo
  - OS/2-specific updates
  - VMS-specific updates
  - Making the new distribution
  - Making a new patch
  - Testing your patch
  - More testing
  - Other tests
- Running Purify
- Common Gotcha's
- Miscellaneous Topics
  - Autoconf
  - Why isn't there a directory to override Perl's library?
  - APPLLIB
  - Shared libperl.so location
- Upload Your Work to CPAN
- Help Save the World
- Todo
  - Good ideas waiting for round tuits
  - Probably good ideas waiting for round tuits
  - Vague possibilities
- AUTHORS
- LAST MODIFIED

## NAME

Pumpkin - Notes on handling the Perl Patch Pumpkin

## SYNOPSIS

There is no simple synopsis, yet.

## DESCRIPTION

This document attempts to begin to describe some of the considerations involved in patching, porting, and maintaining perl.

This document is still under construction, and still subject to significant changes. Still, I hope parts of it will be useful, so I'm releasing it even though it's not done.

For the most part, it's a collection of anecdotal information that already assumes some familiarity with the Perl sources. I really need an introductory section that describes the organization of the sources and all the various auxiliary files that are part of the distribution.

## Where Do I Get Perl Sources and Related Material?

The Comprehensive Perl Archive Network (or CPAN) is the place to go. There are many mirrors, but the easiest thing to use is probably http://www.perl.com/CPAN/README.html , which automatically points you to a mirror site "close" to you.

### Perl5-porters mailing list

The mailing list perl5-porters@perl.org is the main group working with the development of perl. If you're interested in all the latest developments, you should definitely subscribe. The list is high volume, but generally has a fairly low noise level.

    Subscribe by sending the message (in the body of your letter)

    	subscribe perl5-porters

to perl5-porters-request@perl.org .

    Archives of the list are held at:

        http://www.rosat.mpe-garching.mpg.de/mailing-lists/perl-porters/

## How are Perl Releases Numbered?

Beginning with v5.6.0, even versions will stand for maintenance releases and odd versions for development releases, i.e., v5.6.x for maintenance releases, and v5.7.x for development releases. Before v5.6.0, subversions _01 through _49 were reserved for bug-fix maintenance releases, and subversions _50 through _99 for unstable development versions.

For example, in v5.6.1, the revision number is 5, the version is 6, and 1 is the subversion.

    For compatibility with the older numbering scheme the composite floating
    point version number continues to be available as the magic variable $],
    and amounts to $revision + $version/1000 + $subversion/100000.  This
    can still be used in comparisons.

    	print "You've got an old perl\n" if $] < 5.005_03;

    In addition, the version is also available as a string in $^V.

    	print "You've got a new perl\n" if $^V and $^V ge v5.6.0;

    You can also require particular version (or later) with:

            use 5.006;

    or using the new syntax available only from v5.6 onward:

    	use v5.6.0;

At some point in the future, we may need to decide what to call the next big revision. In the .package file used by metaconfig to generate Configure, there are two variables that might be relevant: $baserev=5 and $package=perl5.

Perl releases produced by the members of perl5-porters are usually available on CPAN in the `src/5.0/maint` and `src/5.0/devel` directories.

### Maintenance and Development Subversions

The first rule of maintenance work is "First, do no harm."

Trial releases of bug-fix maintenance releases are announced on perl5-porters. Trial releases use the new subversion number (to avoid testers installing it over the previous release) and include a 'local patch' entry in patchlevel.h. The distribution file contains the string `MAINT_TRIAL` to make clear that the file is not meant for public consumption.

    In general, the names of official distribution files for the public
    always match the regular expression:

        ^perl\d+\.(\d+)\.\d+(-MAINT_TRIAL_\d+)\.tar\.gz$

`$1` in the pattern is always an even number for maintenance versions, and odd for developer releases.

In the past it has been observed that pumkings tend to invent new naming conventions on the fly. If you are a pumpking, before you invent a new name for any of the three types of perl distributions, please inform the guys from the CPAN who are doing indexing and provide the trees of symlinks and the like. They will have to know in advance what you decide.

### Why is it called the patch pumpkin?

Chip Salzenberg gets credit for that, with a nod to his cow orker, David Croy. We had passed around various names (baton, token, hot potato) but none caught on. Then, Chip asked:

    [begin quote]

       Who has the patch pumpkin?

To explain: David Croy once told me once that at a previous job, there was one tape drive and multiple systems that used it for backups. But instead of some high-tech exclusion software, they used a low-tech method to prevent multiple simultaneous backups: a stuffed pumpkin. No one was allowed to make backups unless they had the "backup pumpkin".

[end quote]

The name has stuck.

## Philosophical Issues in Patching and Porting Perl

There are no absolute rules, but there are some general guidelines I have tried to follow as I apply patches to the perl sources. (This section is still under construction.)

### Solve problems as generally as possible

Never implement a specific restricted solution to a problem when you can solve the same problem in a more general, flexible way.

For example, for dynamic loading to work on some SVR4 systems, we had to build a shared libperl.so library. In order to build "FAT" binaries on NeXT 4.0 systems, we had to build a special libperl library. Rather than continuing to build a contorted nest of special cases, I generalized the process of building libperl so that NeXT and SVR4 users could still get their work done, but others could build a shared libperl if they wanted to as well.

Contain your changes carefully. Assume nothing about other operating systems, not even closely related ones. Your changes must not affect other platforms.

Spy shamelessly on how similar patching or porting issues have been settled elsewhere.

If feasible, try to keep filenames 8.3-compliant to humor those poor souls that get joy from running Perl under such dire limitations.

### Seek consensus on major changes

If you are making big changes, don't do it in secret. Discuss the ideas in advance on perl5-porters.

### Keep the documentation up-to-date

If your changes may affect how users use perl, then check to be sure that the documentation is in sync with your changes. Be sure to check all the files `pod/*.pod` and also the `INSTALL` document.

Consider writing the appropriate documentation first and then implementing your change to correspond to the documentation.

### Avoid machine-specific #ifdef's

To the extent reasonable, try to avoid machine-specific #ifdef's in the sources. Instead, use feature-specific #ifdef's. The reason is that the machine-specific #ifdef's may not be valid across major releases of the operating system. Further, the feature-specific tests may help out folks on another platform who have the same problem.

### Machine-specific files

source code
  If you have many machine-specific #defines or #includes, consider creating an "osish.h" (os2ish.h, vmsish.h, and so on) and including that in perl.h. If you have several machine-specific files (function emulations, function stubs, build utility wrappers) you may create a separate subdirectory (djgpp, win32) and put the files in there. Remember to update `MANIFEST` when you add files.

  If your system supports dynamic loading but none of the existing methods at `ext/DynaLoader/dl_*.xs` work for you, you must write a new one. Study the existing ones to see what kind of interface you must supply.

build hints
  There are two kinds of hints: hints for building Perl and hints for extensions. The former live in the `hints` subdirectory, the latter in `ext/*/hints` subdirectories.

  The top level hints are Bourne-shell scripts that set, modify and unset appropriate Configure variables, based on the Configure command line options and possibly existing config.sh and Policy.sh files from previous Configure runs.

  The extension hints are written in Perl (by the time they are used miniperl has been built) and control the building of their respective extensions. They can be used to for example manipulate compilation and linking flags.

build and installation Makefiles, scripts, and so forth
  Sometimes you will also need to tweak the Perl build and installation procedure itself, like for example `Makefile.SH` and `installperl`. Tread very carefully, even more than usual. Contain your changes with utmost care.
test suite
  Many of the tests in `t` subdirectory assume machine-specific things like existence of certain functions, something about filesystem semantics, certain external utilities and their error messages. Use the `$^O` and the `Config` module (which contains the results of the Configure run, in effect the `config.sh` converted to Perl) to either skip (preferably not) or customize (preferable) the tests for your platform.
modules
  Certain standard modules may need updating if your operating system sports for example a native filesystem naming. You may want to update some or all of the modules File::Basename, File::Spec, File::Path, and File::Copy to become aware of your native filesystem syntax and peculiarities.
documentation
  If your operating system comes from outside UNIX you almost certainly will have differences in the available operating system functionality (missing system calls, different semantics, whatever). Please document these at `pod/perlport.pod`. If your operating system is the first not to have a system call also update the list of "portability-bewares" at the beginning of `pod/perlfunc.pod`.

  A file called `README.youros` at the top level that explains things like how to install perl at this platform, where to get any possibly required additional software, and for example what test suite errors to expect, is nice too. Such files are in the process of being written in pod format and will eventually be renamed `INSTALL.youros`.

  You may also want to write a separate `.pod` file for your operating system to tell about existing mailing lists, os-specific modules, documentation, whatever. Please name these along the lines of `perl`youros.pod. [unfinished: where to put this file (the pod/ subdirectory, of course: but more importantly, which/what index files should be updated?)]

### Allow for lots of testing

We should never release a main version without testing it as a subversion first.

### Test popular applications and modules.

We should never release a main version without testing whether or not it breaks various popular modules and applications. A partial list of such things would include majordomo, metaconfig, apache, Tk, CGI, libnet, and libwww, to name just a few. Of course it's quite possible that some of those things will be just plain broken and need to be fixed, but, in general, we ought to try to avoid breaking widely-installed things.

### Automated generation of derivative files

The `embed.h`, `keywords.h`, `opcode.h`, and `perltoc.pod` files are all automatically generated by perl scripts. In general, don't patch these directly; patch the data files instead.

`Configure` and `config_h.SH` are also automatically generated by metaconfig. In general, you should patch the metaconfig units instead of patching these files directly. However, very minor changes to `Configure` may be made in between major sync-ups with the metaconfig units, which tends to be complicated operations. But be careful, this can quickly spiral out of control. Running metaconfig is not really hard.

Also `Makefile` is automatically produced from `Makefile.SH`. In general, look out for all `*.SH` files.

Finally, the sample files in the `Porting/` subdirectory are generated automatically by the script `U/mksample` included with the metaconfig units. See the section on run metaconfig elsewhere in this document below for information on obtaining the metaconfig units.

## How to Make a Distribution

There really ought to be a 'make dist' target, but there isn't. The 'dist' suite of tools also contains a number of tools that I haven't learned how to use yet. Some of them may make this all a bit easier.

Here are the steps I go through to prepare a patch & distribution.

Lots of it could doubtless be automated but isn't. The Porting/makerel (make release) perl script does now help automate some parts of it.

### Announce your intentions

First, you should volunteer out loud to take the patch pumpkin. It's generally counter-productive to have multiple people working in secret on the same thing.

At the same time, announce what you plan to do with the patch pumpkin, to allow folks a chance to object or suggest alternatives, or do it for you. Naturally, the patch pumpkin holder ought to incorporate various bug fixes and documentation improvements that are posted while he or she has the pumpkin, but there might also be larger issues at stake.

One of the precepts of the subversion idea is that we shouldn't give the patch pumpkin to anyone unless we have some idea what he or she is going to do with it.

### refresh pod/perltoc.pod

Presumably, you have done a full `make` in your working source directory. Before you `make spotless` (if you do), and if you have changed any documentation in any module or pod file, change to the `pod` directory and run `make toc`.

### run installhtml to check the validity of the pod files

### update patchlevel.h

Don't be shy about using the subversion number, even for a relatively modest patch. We've never even come close to using all 99 subversions, and it's better to have a distinctive number for your patch. If you need feedback on your patch, go ahead and issue it and promise to incorporate that feedback quickly (e.g. within 1 week) and send out a second patch.

### run metaconfig

    If you need to make changes to Configure or config_h.SH, it may be best to
    change the appropriate metaconfig units instead, and regenerate Configure.

    	metaconfig -m

will regenerate Configure and config_h.SH. Much more information on obtaining and running metaconfig is in the `U/README` file that comes with Perl's metaconfig units. Perl's metaconfig units should be available on CPAN. A set of units that will work with perl5.005 is in the file `mc_units-5.005_00-01.tar.gz` under http://www.perl.com/CPAN/authors/id/ANDYD/ . The mc_units tar file should be unpacked in your main perl source directory. Note: those units were for use with 5.005. There may have been changes since then. Check for later versions or contact perl5-porters@perl.org to obtain a pointer to the current version.

Alternatively, do consider if the `*ish.h` files might be a better place for your changes.

### MANIFEST

    Make sure the MANIFEST is up-to-date.  You can use dist's manicheck
    program for this.  You can also use

        perl -w -MExtUtils::Manifest=fullcheck -e fullcheck

Both commands will also list extra files in the directory that are not listed in MANIFEST.

The MANIFEST is normally sorted.

If you are using metaconfig to regenerate Configure, then you should note that metaconfig actually uses MANIFEST.new, so you want to be sure MANIFEST.new is up-to-date too. I haven't found the MANIFEST/MANIFEST.new distinction particularly useful, but that's probably because I still haven't learned how to use the full suite of tools in the dist distribution.

### Check permissions

All the tests in the t/ directory ought to be executable. The main makefile used to do a 'chmod t/*/*.t', but that resulted in a self-modifying distribution--something some users would strongly prefer to avoid. The `t/TEST` script will check for this and do the chmod if needed, but the tests still ought to be executable.

    In all, the following files should probably be executable:

        Configure
        configpm
        configure.gnu
        embed.pl
        installperl
        installman
        keywords.pl
        myconfig
        opcode.pl
        perly.fixer
        t/TEST
        t/*/*.t
        *.SH
        vms/ext/Stdio/test.pl
        vms/ext/filespec.t
        x2p/*.SH

Other things ought to be readable, at least :-).

Probably, the permissions for the files could be encoded in MANIFEST somehow, but I'm reluctant to change MANIFEST itself because that could break old scripts that use MANIFEST.

I seem to recall that some SVR3 systems kept some sort of file that listed permissions for system files; something like that might be appropriate.

### Run Configure

    This will build a config.sh and config.h.  You can skip this if you haven't
    changed Configure or config_h.SH at all.  I use the following command

        sh Configure -Dprefix=/opt/perl -Doptimize=-O -Dusethreads \
    	-Dcf_by='yourname' \
    	-Dcf_email='yourname@yourhost.yourplace.com' \
    	-Dperladmin='yourname@yourhost.yourplace.com' \
    	-Dmydomain='.yourplace.com' \
    	-Dmyhostname='yourhost' \
    	-des

### Update Porting/config.sh and Porting/config_H

[XXX This section needs revision. We're currently working on easing the task of keeping the vms, win32, and plan9 config.sh info up-to-date. The plan is to use keep up-to-date 'canned' config.sh files in the appropriate subdirectories and then generate 'canned' config.h files for vms, win32, etc. from the generic config.sh file. This is to ease maintenance. When Configure gets updated, the parts sometimes get scrambled around, and the changes in config_H can sometimes be very hard to follow. config.sh, on the other hand, can safely be sorted, so it's easy to track (typically very small) changes to config.sh and then propoagate them to a canned 'config.h' by any number of means, including a perl script in win32/ or carrying config.sh and config_h.SH to a Unix system and running sh config_h.SH.) Vms uses configure.com to generate its own config.sh and config.h. If you want to add a new variable to config.sh check with vms folk how to add it to configure.com too. XXX]

The Porting/config.sh and Porting/config_H files are provided to help those folks who can't run Configure. It is important to keep them up-to-date. If you have changed config_h.SH, those changes must be reflected in config_H as well. (The name config_H was chosen to distinguish the file from config.h even on case-insensitive file systems.) Simply edit the existing config_H file; keep the first few explanatory lines and then copy your new config.h below.

It may also be necessary to update win32/config.?c, and plan9/config.plan9, though you should be quite careful in doing so if you are not familiar with those systems. You might want to issue your patch with a promise to quickly issue a follow-up that handles those directories.

### make run_byacc

If you have byacc-1.8.2 (available from CPAN), and if there have been changes to `perly.y`, you can regenerate the `perly.c` file. The run_byacc makefile target does this by running byacc and then applying some patches so that byacc dynamically allocates space, rather than having fixed limits. This patch is handled by the `perly.fixer` script. Depending on the nature of the changes to `perly.y`, you may or may not have to hand-edit the patch to apply correctly. If you do, you should include the edited patch in the new distribution. If you have byacc-1.9, the patch won't apply cleanly. Changes to the printf output statements mean the patch won't apply cleanly. Long ago I started to fix `perly.fixer` to detect this, but I never completed the task.

If `perly.c` or `perly.h` changes, make sure you run `perl vms/vms_yfix.pl` to update the corresponding VMS files. This could be taken care of by the regen_all target in the Unix Makefile. See also the VMS-specific updates entry elsewhere in this document.

Some additional notes from Larry on this:

    Don't forget to regenerate perly_c.diff.

        byacc -d perly.y
        mv y.tab.c perly.c
        patch perly.c <perly_c.diff
        # manually apply any failed hunks
        diff -c2 perly.c.orig perly.c >perly_c.diff

    One chunk of lines that often fails begins with

        #line 29 "perly.y"

    and ends one line before

        #define YYERRCODE 256

This only happens when you add or remove a token type. I suppose this could be automated, but it doesn't happen very often nowadays.

Larry

### make regen_all

This target takes care of the PERLYVMS, regen_headers, and regen_pods targets.

### make regen_headers

The `embed.h`, `keywords.h`, and `opcode.h` files are all automatically generated by perl scripts. Since the user isn't guaranteed to have a working perl, we can't require the user to generate them. Hence you have to, if you're making a distribution.

    I used to include rules like the following in the makefile:

        # The following three header files are generated automatically
        # The correct versions should be already supplied with the perl kit,
        # in case you don't have perl or 'sh' available.
        # The - is to ignore error return codes in case you have the source
        # installed read-only or you don't have perl yet.
        keywords.h: keywords.pl
    	    @echo "Don't worry if this fails."
    	    - perl keywords.pl

However, I got lots of mail consisting of people worrying because the command failed. I eventually decided that I would save myself time and effort by manually running `make regen_headers` myself rather than answering all the questions and complaints about the failing command.

### make regen_pods

Will run `make regen_pods` in the pod directory for indexing.

### global.sym, interp.sym and perlio.sym

Make sure these files are up-to-date. Read the comments in these files and in perl_exp.SH to see what to do.

### Binary compatibility

If you do change `global.sym` or `interp.sym`, think carefully about what you are doing. To the extent reasonable, we'd like to maintain source and binary compatibility with older releases of perl. That way, extensions built under one version of perl will continue to work with new versions of perl.

Of course, some incompatible changes may well be necessary. I'm just suggesting that we not make any such changes without thinking carefully about them first. If possible, we should provide backwards-compatibility stubs. There's a lot of XS code out there. Let's not force people to keep changing it.

### Changes

Be sure to update the `Changes` file. Try to include both an overall summary as well as detailed descriptions of the changes. Your audience will include other developers and users, so describe user-visible changes (if any) in terms they will understand, not in code like "initialize foo variable in bar function".

There are differing opinions on whether the detailed descriptions ought to go in the Changes file or whether they ought to be available separately in the patch file (or both). There is no disagreement that detailed descriptions ought to be easily available somewhere.

### Todo

The `Todo` file contains a roughly-catgorized unordered list of aspects of Perl that could use enhancement, features that could be added, areas that could be cleaned up, and so on. During your term as pumpkin-holder, you will probably address some of these issues, and perhaps identify others which, while you decide not to address them this time around, may be tackled in the future. Update the file reflect the situation as it stands when you hand over the pumpkin.

You might like, early in your pumpkin-holding career, to see if you can find champions for partiticular issues on the to-do list: an issue owned is an issue more likely to be resolved.

There are also some more porting-specific the Todo manpage items later in this file.

### OS/2-specific updates

In the os2 directory is `diff.configure`, a set of OS/2-specific diffs against Configure. If you make changes to Configure, you may want to consider regenerating this diff file to save trouble for the OS/2 maintainer.

You can also consider the OS/2 diffs as reminders of portability things that need to be fixed in Configure.

### VMS-specific updates

If you have changed `perly.y` or `perly.c`, then you most probably want to update `vms/perly_{h,c}.vms` by running `perl vms/vms_yfix.pl`, or by running `make regen_all` which will run that script for you.

The Perl revision number appears as "perl5" in configure.com. It is courteous to update that if necessary.

### Making the new distribution

    Suppose, for example, that you want to make version 5.004_08.  Then you can
    do something like the following

    	mkdir ../perl5.004_08
    	awk '{print $1}' MANIFEST | cpio -pdm ../perl5.004_08
    	cd ../
    	tar cf perl5.004_08.tar perl5.004_08
    	gzip --best perl5.004_08.tar

These steps, with extra checks, are automated by the Porting/makerel script.

### Making a new patch

    I find the makepatch utility quite handy for making patches.
    You can obtain it from any CPAN archive under
    http://www.perl.com/CPAN/authors/Johan_Vromans/ .  There are a couple
    of differences between my version and the standard one. I have mine do
    a

    	# Print a reassuring "End of Patch" note so people won't
    	# wonder if their mailer truncated patches.
    	print "\n\nEnd of Patch.\n";

at the end. That's because I used to get questions from people asking if their mail was truncated.

It also writes Index: lines which include the new directory prefix (change Index: print, approx line 294 or 310 depending on the version, to read: print PATCH ("Index: $newdir$new\n");). That helps patches work with more POSIX conformant patch programs.

    Here's how I generate a new patch.  I'll use the hypothetical
    5.004_07 to 5.004_08 patch as an example.

    	# unpack perl5.004_07/
    	gzip -d -c perl5.004_07.tar.gz | tar -xof -
    	# unpack perl5.004_08/
    	gzip -d -c perl5.004_08.tar.gz | tar -xof -
    	makepatch perl5.004_07 perl5.004_08 > perl5.004_08.pat

    Makepatch will automatically generate appropriate rm commands to remove
    deleted files.  Unfortunately, it will not correctly set permissions
    for newly created files, so you may have to do so manually.  For example,
    patch 5.003_04 created a new test t/op/gv.t which needs to be executable,
    so at the top of the patch, I inserted the following lines:

    	# Make a new test
    	touch t/op/gv.t
    	chmod +x t/opt/gv.t

Now, of course, my patch is now wrong because makepatch didn't know I was going to do that command, and it patched against /dev/null.

    So, what I do is sort out all such shell commands that need to be in the
    patch (including possible mv-ing of files, if needed) and put that in the
    shell commands at the top of the patch.  Next, I delete all the patch parts
    of perl5.004_08.pat, leaving just the shell commands.  Then, I do the
    following:

    	cd perl5.004_07
    	sh ../perl5.004_08.pat
    	cd ..
    	makepatch perl5.004_07 perl5.004_08 >> perl5.004_08.pat

(Note the append to preserve my shell commands.) Now, my patch will line up with what the end users are going to do.

### Testing your patch

    It seems obvious, but be sure to test your patch.  That is, verify that
    it produces exactly the same thing as your full distribution.

    	rm -rf perl5.004_07
    	gzip -d -c perl5.004_07.tar.gz | tar -xf -
    	cd perl5.004_07
    	sh ../perl5.004_08.pat
    	patch -p1 -N < ../perl5.004_08.pat
    	cd ..
    	gdiff -r perl5.004_07 perl5.004_08

where gdiff is GNU diff. Other diff's may also do recursive checking.

### More testing

Again, it's obvious, but you should test your new version as widely as you can. You can be sure you'll hear about it quickly if your version doesn't work on both ANSI and pre-ANSI compilers, and on common systems such as SunOS 4.1.[34], Solaris, and Linux.

    If your changes include conditional code, try to test the different
    branches as thoroughly as you can.  For example, if your system
    supports dynamic loading, you can also test static loading with

    	sh Configure -Uusedl

You can also hand-tweak your config.h to try out different #ifdef branches.

### Other tests

CHECK_FORMAT
  To test the correct use of printf-style arguments, `Configure` with -Dccflags='-DCHECK_FORMAT -Wformat' and run `make`. The compiler will produce warning of incorrect use of format arguments. CHECK_FORMAT changes perl-defined formats to common formats, so DO NOT USE the executable produced by this process.

      A more accurate approach is the following commands:

          sh Configure -des -Dccflags=-Wformat ...
          make miniperl		# without -DCHECK_FORMAT
          perl -i.orig -pwe 's/-Wformat/-DCHECK_FORMAT $&/' config.sh
          sh Configure -S
          make >& make.log		# build from correct miniperl
          make clean
          make miniperl >& mini.log	# build miniperl with -DCHECK_FORMAT
          perl -nwe 'print if /^\S+:/ and not /^make\b/' mini.log make.log
          make clean

  (-Wformat support by Robin Barker.)

## Running Purify

Purify is a commercial tool that is helpful in identifying memory overruns, wild pointers, memory leaks and other such badness. Perl must be compiled in a specific way for optimal testing with Purify.

    Use the following commands to test perl with Purify:

    	sh Configure -des -Doptimize=-g -Uusemymalloc -Dusemultiplicity \
    	    -Accflags=-DPURIFY
    	setenv PURIFYOPTIONS "-chain-length=25"
    	make all pureperl
    	cd t
    	ln -s ../pureperl perl
    	setenv PERL_DESTRUCT_LEVEL 5
    	./perl TEST

Disabling Perl's malloc allows Purify to monitor allocations and leaks more closely; using Perl's malloc will make Purify report most leaks in the "potential" leaks category. Enabling the multiplicity option allows perl to clean up thoroughly when the interpreter shuts down, which reduces the number of bogus leak reports from Purify. The -DPURIFY enables any Purify-specific debugging code in the sources.

    Purify outputs messages in "Viewer" windows by default.  If you don't have
    a windowing environment or if you simply want the Purify output to
    unobtrusively go to a log file instead of to the interactive window,
    use the following options instead:

    	setenv PURIFYOPTIONS "-chain-length=25 -windows=no -log-file=perl.log \
    	    -append-logfile=yes"

The only currently known leaks happen when there are compile-time errors within eval or require. (Fixing these is non-trivial, unfortunately, but they must be fixed eventually.)

## Common Gotcha's

#elif
  The '#elif' preprocessor directive is not understood on all systems. Specifically, I know that Pyramids don't understand it. Thus instead of the simple

      	#if defined(I_FOO)
      	#  include <foo.h>
      	#elif defined(I_BAR)
      	#  include <bar.h>
      	#else
      	#  include <fubar.h>
      	#endif

      You have to do the more Byzantine

      	#if defined(I_FOO)
      	#  include <foo.h>
      	#else
      	#  if defined(I_BAR)
      	#    include <bar.h>
      	#  else
      	#    include <fubar.h>
      	#  endif
      	#endif

  Incidentally, whitespace between the leading '#' and the preprocessor command is not guaranteed, but is very portable and you may use it freely. I think it makes things a bit more readable, especially once things get rather deeply nested. I also think that things should almost never get too deeply nested, so it ought to be a moot point :-)

Probably Prefer POSIX
  It's often the case that you'll need to choose whether to do something the BSD-ish way or the POSIX-ish way. It's usually not a big problem when the two systems use different names for similar functions, such as memcmp() and bcmp(). The perl.h header file handles these by appropriate #defines, selecting the POSIX mem*() functions if available, but falling back on the b*() functions, if need be.

      More serious is the case where some brilliant person decided to
      use the same function name but give it a different meaning or
      calling sequence :-).  getpgrp() and setpgrp() come to mind.
      These are a real problem on systems that aim for conformance to
      one standard (e.g. POSIX), but still try to support the other way
      of doing things (e.g. BSD).  My general advice (still not really
      implemented in the source) is to do something like the following.
      Suppose there are two alternative versions, fooPOSIX() and
      fooBSD().

          #ifdef HAS_FOOPOSIX
      	/* use fooPOSIX(); */
          #else
          #  ifdef HAS_FOOBSD
      	/* try to emulate fooPOSIX() with fooBSD();
      	   perhaps with the following:  */
          #    define fooPOSIX fooBSD
          #  else
          #  /* Uh, oh.  We have to supply our own. */
          #    define fooPOSIX Perl_fooPOSIX
          #  endif
          #endif

Think positively
  If you need to add an #ifdef test, it is usually easier to follow if you think positively, e.g.

      	#ifdef HAS_NEATO_FEATURE
      	    /* use neato feature */
      	#else
      	    /* use some fallback mechanism */
      	#endif

      rather than the more impenetrable

      	#ifndef MISSING_NEATO_FEATURE
      	    /* Not missing it, so we must have it, so use it */
      	#else
      	    /* Are missing it, so fall back on something else. */
      	#endif

      Of course for this toy example, there's not much difference.  But when
      the #ifdef's start spanning a couple of screen fulls, and the #else's
      are marked something like

      	#else /* !MISSING_NEATO_FEATURE */

  I find it easy to get lost.

Providing Missing Functions -- Problem
  Not all systems have all the neat functions you might want or need, so you might decide to be helpful and provide an emulation. This is sound in theory and very kind of you, but please be careful about what you name the function. Let me use the `pause()` function as an illustration.

      Perl5.003 has the following in perl.h

          #ifndef HAS_PAUSE
          #define pause() sleep((32767<<16)+32767)
          #endif

  Configure sets HAS_PAUSE if the system has the pause() function, so this #define only kicks in if the pause() function is missing. Nice idea, right?

  Unfortunately, some systems apparently have a prototype for pause() in `unistd.h`, but don't actually have the function in the library. (Or maybe they do have it in a library we're not using.)

      Thus, the compiler sees something like

          extern int pause(void);
          /* . . . */
          #define pause() sleep((32767<<16)+32767)

  and dies with an error message. (Some compilers don't mind this; others apparently do.)

      To work around this, 5.003_03 and later have the following in perl.h:

          /* Some unistd.h's give a prototype for pause() even though
             HAS_PAUSE ends up undefined.  This causes the #define
             below to be rejected by the compiler.  Sigh.
          */
          #ifdef HAS_PAUSE
          #  define Pause	pause
          #else
          #  define Pause() sleep((32767<<16)+32767)
          #endif

  This works.

      The curious reader may wonder why I didn't do the following in
      util.c instead:

          #ifndef HAS_PAUSE
          void pause()
          {
          sleep((32767<<16)+32767);
          }
          #endif

  That is, since the function is missing, just provide it. Then things would probably be been alright, it would seem.

  Well, almost. It could be made to work. The problem arises from the conflicting needs of dynamic loading and namespace protection.

  For dynamic loading to work on AIX (and VMS) we need to provide a list of symbols to be exported. This is done by the script `perl_exp.SH`, which reads `global.sym` and `interp.sym`. Thus, the `pause` symbol would have to be added to `global.sym` So far, so good.

      On the other hand, one of the goals of Perl5 is to make it easy to
      either extend or embed perl and link it with other libraries.  This
      means we have to be careful to keep the visible namespace "clean".
      That is, we don't want perl's global variables to conflict with
      those in the other application library.  Although this work is still
      in progress, the way it is currently done is via the embed.h file.
      This file is built from the global.sym and interp.sym files,
      since those files already list the globally visible symbols.  If we
      had added pause to global.sym, then embed.h would contain the
      line

          #define pause	Perl_pause

  and calls to `pause` in the perl sources would now point to `Perl_pause`. Now, when ld is run to build the `perl` executable, it will go looking for `perl_pause`, which probably won't exist in any of the standard libraries. Thus the build of perl will fail.

  Those systems where `HAS_PAUSE` is not defined would be ok, however, since they would get a `Perl_pause` function in util.c. The rest of the world would be in trouble.

      And yes, this scenario has happened.  On SCO, the function chsize
      is available.  (I think it's in -lx, the Xenix compatibility
      library.)  Since the perl4 days (and possibly before), Perl has
      included a chsize function that gets called something akin to

          #ifndef HAS_CHSIZE
          I32 chsize(fd, length)
          /*  . . . */
          #endif

      When 5.003 added

          #define chsize	Perl_chsize

  to `embed.h`, the compile started failing on SCO systems.

      The "fix" is to give the function a different name.  The one
      implemented in 5.003_05 isn't optimal, but here's what was done:

          #ifdef HAS_CHSIZE
          # ifdef my_chsize  /* Probably #defined to Perl_my_chsize in embed.h */
          #   undef my_chsize
          # endif
          # define my_chsize chsize
          #endif

      My explanatory comment in patch 5.003_05 said:

           Undef and then re-define my_chsize from Perl_my_chsize to
           just plain chsize if this system HAS_CHSIZE.  This probably only
           applies to SCO.  This shows the perils of having internal
           functions with the same name as external library functions :-).

  Now, we can safely put `my_chsize` in `global.sym`, export it, and hide it with `embed.h`.

  To be consistent with what I did for `pause`, I probably should have called the new function `Chsize`, rather than `my_chsize`. However, the perl sources are quite inconsistent on this (Consider New, Mymalloc, and Myremalloc, to name just a few.)

  There is a problem with this fix, however, in that `Perl_chsize` was available as a `libperl.a` library function in 5.003, but it isn't available any more (as of 5.003_07). This means that we've broken binary compatibility. This is not good.

Providing missing functions -- some ideas
  We currently don't have a standard way of handling such missing function names. Right now, I'm effectively thinking aloud about a solution. Some day, I'll try to formally propose a solution.

      Part of the problem is that we want to have some functions listed as
      exported but not have their names mangled by embed.h or possibly
      conflict with names in standard system headers.  We actually already
      have such a list at the end of perl_exp.SH (though that list is
      out-of-date):

          # extra globals not included above.
          cat <<END >> perl.exp
          perl_init_ext
          perl_init_fold
          perl_init_i18nl14n
          perl_alloc
          perl_construct
          perl_destruct
          perl_free
          perl_parse
          perl_run
          perl_get_sv
          perl_get_av
          perl_get_hv
          perl_get_cv
          perl_call_argv
          perl_call_pv
          perl_call_method
          perl_call_sv
          perl_requirepv
          safecalloc
          safemalloc
          saferealloc
          safefree

  This still needs much thought, but I'm inclined to think that one possible solution is to prefix all such functions with `perl_` in the source and list them along with the other `perl_*` functions in `perl_exp.SH`.

      Thus, for chsize, we'd do something like the following:

          /* in perl.h */
          #ifdef HAS_CHSIZE
          #  define perl_chsize chsize
          #endif

      then in some file (e.g. util.c or doio.c) do

          #ifndef HAS_CHSIZE
          I32 perl_chsize(fd, length)
          /* implement the function here . . . */
          #endif

  Alternatively, we could just always use `chsize` everywhere and move `chsize` from `global.sym` to the end of `perl_exp.SH`. That would probably be fine as long as our `chsize` function agreed with all the `chsize` function prototypes in the various systems we'll be using. As long as the prototypes in actual use don't vary that much, this is probably a good alternative. (As a counter-example, note how Configure and perl have to go through hoops to find and use get Malloc_t and Free_t for `malloc` and `free`.)

  At the moment, this latter option is what I tend to prefer.

All the world's a VAX
  Sorry, showing my age:-). Still, all the world is not BSD 4.[34], SVR4, or POSIX. Be aware that SVR3-derived systems are still quite common (do you have any idea how many systems run SCO?) If you don't have a bunch of v7 manuals handy, the metaconfig units (by default installed in `/usr/local/lib/dist/U`) are a good resource to look at for portability.

## Miscellaneous Topics

### Autoconf

Why does perl use a metaconfig-generated Configure script instead of an autoconf-generated configure script?

Metaconfig and autoconf are two tools with very similar purposes. Metaconfig is actually the older of the two, and was originally written by Larry Wall, while autoconf is probably now used in a wider variety of packages. The autoconf info file discusses the history of autoconf and how it came to be. The curious reader is referred there for further information.

Overall, both tools are quite good, I think, and the choice of which one to use could be argued either way. In March, 1994, when I was just starting to work on Configure support for Perl5, I considered both autoconf and metaconfig, and eventually decided to use metaconfig for the following reasons:

Compatibility with Perl4
  Perl4 used metaconfig, so many of the #ifdef's were already set up for metaconfig. Of course metaconfig had evolved some since Perl4's days, but not so much that it posed any serious problems.
Metaconfig worked for me
  My system at the time was Interactive 2.2, a SVR3.2/386 derivative that also had some POSIX support. Metaconfig-generated Configure scripts worked fine for me on that system. On the other hand, autoconf-generated scripts usually didn't. (They did come quite close, though, in some cases.) At the time, I actually fetched a large number of GNU packages and checked. Not a single one configured and compiled correctly out-of-the-box with the system's cc compiler.
Configure can be interactive
  With both autoconf and metaconfig, if the script works, everything is fine. However, one of my main problems with autoconf-generated scripts was that if it guessed wrong about something, it could be very hard to go back and fix it. For example, autoconf always insisted on passing the -Xp flag to cc (to turn on POSIX behavior), even when that wasn't what I wanted or needed for that package. There was no way short of editing the configure script to turn this off. You couldn't just edit the resulting Makefile at the end because the -Xp flag influenced a number of other configure tests.

  Metaconfig's Configure scripts, on the other hand, can be interactive. Thus if Configure is guessing things incorrectly, you can go back and fix them. This isn't as important now as it was when we were actively developing Configure support for new features such as dynamic loading, but it's still useful occasionally.

GPL
  At the time, autoconf-generated scripts were covered under the GNU Public License, and hence weren't suitable for inclusion with Perl, which has a different licensing policy. (Autoconf's licensing has since changed.)
Modularity
  Metaconfig builds up Configure from a collection of discrete pieces called "units". You can override the standard behavior by supplying your own unit. With autoconf, you have to patch the standard files instead. I find the metaconfig "unit" method easier to work with. Others may find metaconfig's units clumsy to work with.

### Why isn't there a directory to override Perl's library?

Mainly because no one's gotten around to making one. Note that "making one" involves changing perl.c, Configure, config_h.SH (and associated files, see above), and documenting it all in the INSTALL file.

Apparently, most folks who want to override one of the standard library files simply do it by overwriting the standard library files.

### APPLLIB

    In the perl.c sources, you'll find an undocumented APPLLIB_EXP
    variable, sort of like PRIVLIB_EXP and ARCHLIB_EXP (which are
    documented in config_h.SH).  Here's what APPLLIB_EXP is for, from
    a mail message from Larry:

        The main intent of APPLLIB_EXP is for folks who want to send out a
        version of Perl embedded in their product.  They would set the symbol
        to be the name of the library containing the files needed to run or to
        support their particular application.  This works at the "override"
        level to make sure they get their own versions of any library code that
        they absolutely must have configuration control over.

        As such, I don't see any conflict with a sysadmin using it for a
        override-ish sort of thing, when installing a generic Perl.  It should
        probably have been named something to do with overriding though.  Since
        it's undocumented we could still change it...  :-)

    Given that it's already there, you can use it to override
    distribution modules.  If you do

    	sh Configure -Dccflags='-DAPPLLIB_EXP=/my/override'

then perl.c will put /my/override ahead of ARCHLIB and PRIVLIB.

### Shared libperl.so location

    Why isn't the shared libperl.so installed in /usr/lib/ along
    with "all the other" shared libraries?  Instead, it is installed
    in $archlib, which is typically something like

    	/usr/local/lib/perl5/archname/5.00404

and is architecture- and version-specific.

The basic reason why a shared libperl.so gets put in $archlib is so that you can have more than one version of perl on the system at the same time, and have each refer to its own libperl.so.

Three examples might help. All of these work now; none would work if you put libperl.so in /usr/lib.

1. Suppose you want to have both threaded and non-threaded perl versions around. Configure will name both perl libraries "libperl.so" (so that you can link to them with -lperl). The perl binaries tell them apart by having looking in the appropriate $archlib directories.
2. Suppose you have perl5.004_04 installed and you want to try to compile it again, perhaps with different options or after applying a patch. If you already have libperl.so installed in /usr/lib/, then it may be either difficult or impossible to get ld.so to find the new libperl.so that you're trying to build. If, instead, libperl.so is tucked away in $archlib, then you can always just change $archlib in the current perl you're trying to build so that ld.so won't find your old libperl.so. (The INSTALL file suggests you do this when building a debugging perl.)
3. The shared perl library is not a "well-behaved" shared library with proper major and minor version numbers, so you can't necessarily have perl5.004_04 and perl5.004_05 installed simultaneously. Suppose perl5.004_04 were to install /usr/lib/libperl.so.4.4, and perl5.004_05 were to install /usr/lib/libperl.so.4.5. Now, when you try to run perl5.004_04, ld.so might try to load libperl.so.4.5, since it has the right "major version" number. If this works at all, it almost certainly defeats the reason for keeping perl5.004_04 around. Worse, with development subversions, you certaily can't guarantee that libperl.so.4.4 and libperl.so.4.55 will be compatible.

   Anyway, all this leads to quite obscure failures that are sure to drive casual users crazy. Even experienced users will get confused :-). Upon reflection, I'd say leave libperl.so in $archlib.

## Upload Your Work to CPAN

You can upload your work to CPAN if you have a CPAN id. Check out http://www.perl.com/CPAN/modules/04pause.html for information on _PAUSE_, the Perl Author's Upload Server.

I typically upload both the patch file, e.g. `perl5.004_08.pat.gz` and the full tar file, e.g. `perl5.004_08.tar.gz`.

If you want your patch to appear in the `src/5.0/unsupported` directory on CPAN, send e-mail to the CPAN master librarian. (Check out http://www.perl.com/CPAN/CPAN.html ).

## Help Save the World

You should definitely announce your patch on the perl5-porters list. You should also consider announcing your patch on comp.lang.perl.announce, though you should make it quite clear that a subversion is not a production release, and be prepared to deal with people who will not read your disclaimer.

## Todo

Here, in no particular order, are some Configure and build-related items that merit consideration. This list isn't exhaustive, it's just what I came up with off the top of my head.

### Good ideas waiting for round tuits

Configure -Dsrc=/blah/blah
  We should be able to emulate configure --srcdir. Tom Tromey tromey@creche.cygnus.com has submitted some patches to the dist-users mailing list along these lines. They have been folded back into the main distribution, but various parts of the perl Configure/build/install process still assume src='.'.
Hint file fixes
  Various hint files work around Configure problems. We ought to fix Configure so that most of them aren't needed.
Hint file information
  Some of the hint file information (particularly dynamic loading stuff) ought to be fed back into the main metaconfig distribution.

### Probably good ideas waiting for round tuits

GNU configure --options
  I've received sensible suggestions for --exec_prefix and other GNU configure --options. It's not always obvious exactly what is intended, but this merits investigation.
make clean
  Currently, make clean isn't all that useful, though make realclean and make distclean are. This needs a bit of thought and documentation before it gets cleaned up.
Try gcc if cc fails
  Currently, we just give up.
bypassing safe*alloc wrappers
  On some systems, it may be safe to call the system malloc directly without going through the util.c safe* layers. (Such systems would accept free(0), for example.) This might be a time-saver for systems that already have a good malloc. (Recent Linux libc's apparently have a nice malloc that is well-tuned for the system.)

### Vague possibilities

MacPerl
  Get some of the Macintosh stuff folded back into the main distribution.
gconvert replacement
  Maybe include a replacement function that doesn't lose data in rare cases of coercion between string and numerical values.
Improve makedepend
  The current makedepend process is clunky and annoyingly slow, but it works for most folks. Alas, it assumes that there is a filename $firstmakefile that the make command will try to use before it uses `Makefile`. Such may not be the case for all make commands, particularly those on non-Unix systems.

  Probably some variant of the BSD `.depend` file will be useful. We ought to check how other packages do this, if they do it at all. We could probably pre-generate the dependencies (with the exception of malloc.o, which could probably be determined at `Makefile.SH` extraction time.

GNU Makefile standard targets
  GNU software generally has standardized Makefile targets. Unless we have good reason to do otherwise, I see no reason not to support them.
File locking
  Somehow, straighten out, document, and implement lockf(), flock(), and/or fcntl() file locking. It's a mess. See $d_fcntl_can_lock in recent config.sh files though.

## AUTHORS

Original author: Andy Dougherty doughera@lafcol.lafayette.edu . Additions by Chip Salzenberg chip@perl.com and Tim Bunce Tim.Bunce@ig.co.uk .

All opinions expressed herein are those of the author(s).

## LAST MODIFIED

$Id: pumpkin.pod,v 1.23 2000/01/13 19:45:13 doughera Released $

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