PATCHING   [plain text]

"The easy way is always mined.
 The important things are always simple.
 The simple things are always hard."
        -- Some of Murphy's Laws of Combat

This is a short set of guidelines for those patching
ExtUtils::MakeMaker.  Its not an iron-clad set of rules, but just
things which make life easier when reading and integrating a patch.

Lots of information can be found in

MakerMaker is being maintained until something else can replace it.
Bugs will be fixed and compatibility improved, but I would like to
avoid new features.  If you want to add something to MakeMaker,
consider instead working on Module::Build, MakeMaker's heir apparent.

Reporting bugs

- Often the only information we have for fixing a bug is contained in your
  report.  So...

- Please report your bugs via or by mailing to  RT is preferred.

- Please report your bug immediately upon encountering it.  Do not wait
  until you have a patch to fix the bug.  Patches are good, but not at
  the expense of timely bug reports.

- Please be as verbose as possible.  Include the complete output of
  your 'make test' or even 'make test TEST_VERBOSE=1' and a copy of the 
  generated Makefile.  Err on the side of verbosity.  The more data we
  have to work with, the faster we can diagnose the problem.

- If you find an undocumented feature, or if a feature has changed/been
  added which causes a problem, report it.  Do not assume it was done
  deliberately.  Even if it was done deliberately, we still want to hear
  if it caused problems.

- If you're testing MakeMaker against a development version of Perl,
  please also check it against the latest stable version.  This makes it
  easier to figure out if its MakeMaker or Perl at fault.

Patching details

- Please use unified diffs.  (diff -u)

- Patches against the latest development snapshot from are 
  preferred.  Patches against the latest CPAN version are ok, too.

- Post your patch to

Code formatting

- No literal tabs (except where necessary inside Makefile code, obviously).

- 4 character indentation.

- this_style is prefered instead of studlyCaps.

- Private subroutine names (ie. those used only in the same package
  they're declared in) should start with an underscore (_sekret_method).

- Protected subroutines (ie. ones intended to be used by other modules in
  ExtUtils::*) should be named normally (no leading underscore) but
  documented as protected (see Documentation below).

- Do not use indirect object syntax (ie. new Foo::Bar (@args))

- make variables use dollar signs like Perl scalars.  This causes problems
  when you have to mix them both in a string.  If you find yourself
  backwacking lots of dollar signs because you have one interpolated
  perl variable, like this:

    return <<EOT;
subdirs ::
	\$(NOECHO)cd $subdir && \$(MAKE) -f \$(FIRST_MAKEFILE) all \$(PASTHRU)


  or are switching quoting contexts:

    return q{
subdirs ::
	$(NOECHO)cd }.$subdir.q{ && $(MAKE) -f $(FIRST_MAKEFILE) all $(PASTHRU)


  consider using sprintf instead.

    return sprintf <<'EOT', $subdir;
subdirs ::
	$(NOECHO)cd %s && $(MAKE) -f $(FIRST_MAKEFILE) all $(PASTHRU)


Refactoring and Cleanup

- MakeMaker is a mess.  We like patches which clean things up.

Backwards Compatibility

- MakeMaker must be backwards compatible to 5.5.4 (5.005_04).  Avoid any
  obvious 5.6-isms (threads,, Unicode, our, v1.2.3, attributes
  open my $fh, lvalue subroutines, qr//, any new core modules, etc...).

- MakeMaker should avoid having module dependencies.  Avoid using modules
  which didn't come with 5.5.4 and avoid using features from newer 
  versions.  Sometimes this is unavoidable.

Cross-Platform Compatibility

- With the exception of MacOS Classic, MakeMaker must work on all 
  architectures Perl works on (see perlport.pod).  This means all Unixen 
  (including Cygwin and MacOS X), Windows (including Win9x and DOS), and VMS.

- Use the available macros rather than shell commands $(MV), $(CP),
  $(TOUCH), etc...

- MakeMaker must work on many makes.  GNU, BSD, Solaris, nmake, dmake, MMS
  and MMK to name the most common.  Keep your make code as simple as 

- Avoid special make variables (even $@).  

- Format targets as "target : dependency", the spacing is important.  

- Use $(NOECHO) instead of @.

- Use - to tell make to ignore the exit code of a command.  (Unfortunately,
  some make variants don't honor an $(IGNORE) macro).

- Always put a space between $(NOECHO) and the command.

- Always put a space between - (ignore) and the command.

- Always put $(NOECHO) and - together, no space between them.

        # Right
        -$(NOECHO) command
        $(NOECHO) command
        - command

- Often when you patch ExtUtils::MM_Unix, similar patches must be done
  to the other MM_* modules.  If you can, please do this extra work
  otherwise I have to.  If you can't, that's ok.  We can help.

- If possible, please test your patch on two Very Different architectures.
  Unix, Windows and VMS being Very Different.  Note: Cygwin and OS X are 
  Unixen for our purposes.

- If nothing else, at least try it on two different Unixen or Windows
  machines (ie. Linux and IRIX or WinNT and Win95).

- HP's TestDrive ( and SourceForge's
  compile farm ( are good sources of testing
  machines of many different architectures and platforms.  Accounts are 

- If you find yourself writing "do_this if $^O eq 'That'" (ie. checks on
  the OS type) perhaps your code belongs in one of the non-Unix MM_*
  modules (ie. MM_Win32, MM_VMS, etc...).  If one does not exist, consider
  creating one.  Its ok to have an MM_* module with only one method.

- Some shells have very small buffers.  This means command lines must
  be as small as possible.  If your command is just too long, consider
  making it an ExtUtils::Command::MM function.  If your command might
  receive many arguments (such as pod2man or pm_to_blib) consider
  using split_command() to split it into several, shorter calls.

- Most shells quote differently.  If you need to put a perl one-liner
  in the Makefile, please use oneliner() to generate it.


- Tests would be nice, but I'm not going to pretend testing MakeMaker
  is easy.  If nothing else, let us know how you tested your patch by


- Documentation would be nice.

- If the new feature/method is private, please document it with POD
  wrapped in "=begin/end private" tags.  That way it will be documented,
  but won't be displayed (future versions of perldoc may have options
  to display).

    =begin private

    =head3 _foo_bar


    Blah blah blah

    =end private


    sub _foo_bar {

- If you're overriding a method, document that its an override and
  *why* its being overridden.  Don't repeat the original documentation.