ExtUtil...er::FAQ(3)

📦 version 7.70, in opensuse-leap 16.0

✨ NAME ✨

ExtUtils::MakeMaker::FAQ — Frequently Asked Questions About MakeMaker 💅

okay so this is the section 3 man page, user contributed perl documentation, and bestie it's part 1 of 3 🫶

🦋 DESCRIPTION 🦋

FAQs, tricks and tips for ExtUtils::MakeMaker. That's the whole vibe. ✨

🎀 Module Installation 🎀

💖 How do I install a module into your home directory?

ok so if you're not the Perl administrator you probably don't have permission to install a module to its default location. The ways of handling this with a lot less manual effort on your part are perlbrew and local::lib. iconic.

Otherwise, you can install it for your own use into your home directory like so:

# Non-unix folks, replace ~ with /path/to/your/home/dir
perl Makefile.PL INSTALL_BASE=~

This will put modules into ~/lib/perl5, man pages into ~/man and programs into ~/bin.

To ensure your Perl programs can see these newly installed modules, set your PERL5LIB environment variable to ~/lib/perl5 or tell each of your programs to look in that directory with the following:

use lib "$ENV{HOME}/lib/perl5";

or if $ENV{HOME} isn't set and you don't want to set it for some reason, do it the long way.

use lib "/path/to/your/home/dir/lib/perl5";

🌸 How do I get MakeMaker and Module::Build to install to the same place?

Module::Build, as of 0.28, supports two ways to install to the same location as MakeMaker.

We highly recommend the install_base method, its the simplest and most closely approximates the expected behavior of an installation prefix.

1) Use INSTALL_BASE / --install_base

MakeMaker (as of 6.31) and Module::Build (as of 0.28) both can install to the same locations using the install_base concept. See INSTALL_BASE in ExtUtils::MakeMaker for details. To get MM and MB to install to the same location simply set INSTALL_BASE in MM and --install_base in MB to the same location.

perl Makefile.PL INSTALL_BASE=/whatever
perl Build.PL    --install_base /whatever

This works most like other language's behavior when you specify a prefix. We recommend this method. 👑

2) Use PREFIX / --prefix

Module::Build 0.28 added support for --prefix which works like MakeMaker's PREFIX.

perl Makefile.PL PREFIX=/whatever
perl Build.PL    --prefix /whatever

We highly discourage this method. It should only be used if you know what you're doing and specifically need the PREFIX behavior. The PREFIX algorithm is complicated and focused on matching the system installation. 💀

🧚 How do I keep from installing man pages?

Recent versions of MakeMaker will only install man pages on Unix-like operating systems by default. To generate manpages on non-Unix operating systems, make the manifypods target.

For an individual module:

perl Makefile.PL INSTALLMAN1DIR=none INSTALLMAN3DIR=none

If you want to suppress man page installation for all modules you have to reconfigure Perl and tell it 'none' when it asks where to install man pages.

🍓 How do I use a module without installing it?

Two ways. One is to build the module normally...

perl Makefile.PL
make
make test

...and then use blib to point Perl at the built but uninstalled module:

perl -Mblib script.pl
perl -Mblib -e '...'

The other is to install the module in a temporary location.

perl Makefile.PL INSTALL_BASE=~/tmp
make
make test
make install

And then set PERL5LIB to ~/tmp/lib/perl5. This works well when you have multiple modules to work with. It also ensures that the module goes through its full installation process which may modify it. Again, local::lib may assist you here. 💜

🌈 How can I organize tests into subdirectories and have them run?

Let's take the following test directory structure:

t/foo/sometest.t
t/bar/othertest.t
t/bar/baz/anothertest.t

Now, inside of the WriteMakefile() function in your Makefile.PL, specify where your tests are located with the test directive:

test => {TESTS => 't/*.t t/*/*.t t/*/*/*.t'}

The first entry in the string will run all tests in the top-level t/ directory. The second will run all test files located in any subdirectory under t/. The third, runs all test files within any subdirectory within any other subdirectory located under t/.

Note that you do not have to use wildcards. You can specify explicitly which subdirectories to run tests in:

test => {TESTS => 't/*.t t/foo/*.t t/bar/baz/*.t'}

🦋 PREFIX vs INSTALL_BASE from Module::Build::Cookbook

The behavior of PREFIX is complicated and depends closely on how your Perl is configured. The resulting installation locations will vary from machine to machine and even different installations of Perl on the same machine. Because of this, its difficult to document where prefix will place your modules.

In contrast, INSTALL_BASE has predictable, easy to explain installation locations. Now that Module::Build and MakeMaker both have INSTALL_BASE there is little reason to use PREFIX other than to preserve your existing installation locations. If you are starting a fresh Perl installation we encourage you to use INSTALL_BASE. If you have an existing installation installed via PREFIX, consider moving it to an installation structure matching INSTALL_BASE and using that instead.

⭐ Generating *.pm files with substitutions eg of $VERSION

If you want to configure your module files for local conditions, or to automatically insert a version number, you can use EUMM's PL_FILES capability, where it will automatically run each *.PL it finds to generate its basename. For instance:

# Makefile.PL:
require 'common.pl';
my $version = get_version();
my @pms = qw(Foo.pm);
WriteMakefile(
  NAME => 'Foo',
  VERSION => $version,
  PM => { map { ($_ => "\$(INST_LIB)/$_") } @pms },
  clean => { FILES => join ' ', @pms },
);

# common.pl:
sub get_version { '0.04' }
sub process { my $v = get_version(); s/__VERSION__/$v/g; }
1;

# Foo.pm.PL:
require 'common.pl';
$_ = join '', <DATA>;
process();
my $file = shift;
open my $fh, '>', $file or die "$file: $!";
print $fh $_;
__DATA__
package Foo;
our $VERSION = '__VERSION__';
1;

You may notice that PL_FILES is not specified above, since the default of mapping each .PL file to its basename works well.

If the generated module were architecture-specific, you could replace $(INST_LIB) above with $(INST_ARCHLIB), although if you locate modules under lib, that would involve ensuring any lib/ in front of the module location were removed.

😭 Common errors and problems 😭

💀 No rule to make target ...

The exact error, no cap:

No rule to make target `/usr/lib/perl5/CORE/config.h', needed by `Makefile'

Just what it says, you're missing that file. MakeMaker uses it to determine if perl has been rebuilt since the Makefile was made. It's a bit of a bug that it halts installation.

Some operating systems don't ship the CORE directory with their base perl install. To solve the problem, you likely need to install a perl development package such as perl-devel (CentOS, Fedora and other Redhat systems) or perl (Ubuntu and other Debian systems).

👑 Philosophy and History 👑

🤔 Why not just use <insert other build config tool here>?

Why did MakeMaker reinvent the build configuration wheel? Why not just use autoconf or automake or ppm or Ant or ...

There are many reasons, but the major one is cross-platform compatibility.

Perl is one of the most ported pieces of software ever. It works on operating systems I've never even heard of (see perlport for details). It needs a build tool that can work on all those platforms and with any wacky C compilers and linkers they might have.

No such build tool exists. Even make itself has wildly different dialects. So we have to build our own. periodt. 🔥

🌟 What is Module::Build and how does it relate to MakeMaker?

Module::Build is a project by Ken Williams to supplant MakeMaker. Its primary advantages are:

  • pure perl. no make, no shell commands
  • easier to customize
  • cleaner internals
  • less cruft

Module::Build was long the official heir apparent to MakeMaker. The rate of both its development and adoption has slowed in recent years, though, and it is unclear what the future holds for it. That said, Module::Build set the stage for something to become the heir to MakeMaker. MakeMaker's maintainers have long said that it is a dead end and should be kept functioning, while being cautious about extending with new features.

💅 Module Writing 💅

💖 How do I keep my $VERSION up to date without resetting it manually?

Often you want to manually set the $VERSION in the main module distribution because this is the version that everybody sees on CPAN and maybe you want to customize it a bit. But for all the other modules in your dist, $VERSION is really just bookkeeping and all that's important is it goes up every time the module is changed. Doing this by hand is a pain and you often forget. 😭

Probably the easiest way to do this is using perl-reversion in Perl::Version:

perl-reversion -bump

If your version control system supports revision numbers (git doesn't easily), the simplest way to do it automatically is to use its revision number (you are using version control, right?).

In CVS, RCS and SVN you use $Revision$ (see the documentation of your version control system for details). Every time the file is checked in the $Revision$ will be updated, updating your $VERSION.

SVN uses a simple integer for $Revision$ so you can adapt it for your $VERSION like so:

($VERSION) = q$Revision$ =~ /(\d+)/;

In CVS and RCS version 1.9 is followed by 1.10. Since CPAN compares version numbers numerically we use a sprintf() to convert 1.9 to 1.009 and 1.10 to 1.010 which compare properly.

$VERSION = sprintf "%d.%03d", q$Revision$ =~ /(\d+)\.(\d+)/g;

If branches are involved (ie. $Revision: 1.5.3.4$) it's a little more complicated.

okay bestie so your $VERSION line has to be a one-liner or MakeMaker gets all confused and starts acting up 😭:

# must be all on one line or MakeMaker will get confused.
$VERSION = do { my @r = (q$Revision$ =~ /\d+/g); sprintf "%d."."%03d" x $#r, @r };

So like, in SVN, $Revision$ is literally the same for every single file in the project, so they'd all end up with the same $VERSION — cute, matching outfits 💅. But CVS and RCS? Different $Revision$ per file, so each file gets its own different $VERSION. And distributed version control systems like SVK might give you a different $Revision$ depending on who checked out the file, which means a different $VERSION on each machine — chaos, not the fun kind 💀. And finally, some distributed systems like darcs have no concept of a revision number at all. Zero. Nada. 🫠

🎀 What's this META.yml thing and how did it get in my MANIFEST?!

META.yml is a module meta-data file pioneered by Module::Build, and it gets automatically generated as part of the 'distdir' target (and thus 'dist' too). Slay. See "Module Meta-Data" in ExtUtils::MakeMaker for the lore 📖.

Wanna shut off its generation? Just pass the "NO_META" flag to WriteMakefile(). Done and dusted ✨.

🗑️ How do I delete everything not in my MANIFEST?

Okay so this trips people up constantly ngl. Some folks are surprised that make distclean does not delete everything not listed in their MANIFEST (which, yes, would make a clean distribution) — it only tells them what they need to delete. And why? Because it's considered too dangerous 😳. Think about it: you're developing your module, you write a new file, you forget to add it to the MANIFEST, you run a "distclean"… and bestie, your new work is gone. Deleted. Sadness. 💔

But if you truly, genuinely wanna do this, you can use ExtUtils::Manifest::manifind() to read the MANIFEST and File::Find to delete the files. You just have to be careful. Here's a script that does exactly that:

Use at your own risk. Have fun blowing holes in your foot. 🙈
#!/usr/bin/perl -w

use strict;

use File::Spec;
use File::Find;
use ExtUtils::Manifest qw(maniread);

my %manifest = map  {( $_ => 1 )}
               grep { File::Spec->canonpath($_) }
                    keys %{ maniread() };

if( !keys %manifest ) {
    print "No files found in MANIFEST.  Stopping.\n";
    exit;
}

find({
      wanted   => sub {
          my $path = File::Spec->canonpath($_);

          return unless -f $path;
          return if exists $manifest{ $path };

          print "unlink $path\n";
          unlink $path;
      },
      no_chdir => 1
     },
     "."
);

🧸 Which tar should I use on Windows?

We recommend ptar from Archive::Tar, not older than 1.66, with the -C option. That's the vibe check ✅.

📦 Which zip should I use on Windows for '[ndg]make zipdist'?

We recommend InfoZIP: <http://www.info-zip.org/Zip.html> — iconic, no notes 🌈.

🧬 XS 🧬

😱 How do I prevent "object version X.XX does not match bootstrap parameter Y.YY" errors?

So real talk: XS code is very sensitive to the module version number and will absolutely complain if the version number in your Perl module doesn't match. And the sneaky part? If you change your module's version # without rerunning Makefile.PL, the old version number just… stays in the Makefile, chilling there, and now your XS code gets built with the wrong number. Betrayal 😭.

The fix: force the Makefile to be rebuilt whenever you change the module containing the version number, by adding this to your WriteMakefile() arguments:

depend => { '$(FIRST_MAKEFILE)' => '$(VERSION_FROM)' }

Periodt. That's the whole trick 💖.

🫶 How do I make two or more XS files coexist in the same directory?

Sometimes you genuinely need two or more XS files in the same package. There are three ways to do it: "XSMULTI", separate directories, and bootstrapping one XS from another. Let's go 🕺

  • XSMULTI — Structure your modules so they're all located under lib, such that Foo::Bar is in lib/Foo/Bar.pm and lib/Foo/Bar.xs, etc. Have your top-level WriteMakefile set the variable XSMULTI to a true value.

Er, that's it. 💅

  • Separate directories — Put each XS file into separate directories, each with their own Makefile.PL. Make sure each of those Makefile.PLs has the correct CFLAGS, INC, LIBS, etc. You'll need to make sure the top-level Makefile.PL refers to each of these using DIR.
  • Bootstrapping — so let's assume we have a package Cool::Foo, which includes Cool::Foo and Cool::Bar modules, each having a separate XS file. First we use the following Makefile.PL:
use ExtUtils::MakeMaker;

WriteMakefile(
    NAME              => 'Cool::Foo',
    VERSION_FROM      => 'Foo.pm',
    OBJECT              => q/$(O_FILES)/,
    # ... other attrs ...
);

Notice the OBJECT attribute 👀. MakeMaker generates the following variables in the Makefile:

# Handy lists of source code files:
XS_FILES= Bar.xs \
      Foo.xs
C_FILES = Bar.c \
      Foo.c
O_FILES = Bar.o \
      Foo.o

So we can use the O_FILES variable to tell MakeMaker to use these objects into the shared library. 🎯

That's pretty much it. Now write Foo.pm and Foo.xs, Bar.pm and Bar.xs, where Foo.pm bootstraps the shared library and Bar.pm simply loads Foo.pm.

The only issue left is how to bootstrap Bar.xs. This is done from Foo.xs:

MODULE = Cool::Foo PACKAGE = Cool::Foo

BOOT:
# boot the second XS file
boot_Cool__Bar(aTHX_ cv);

If you have more than two files, this is the place where you should boot extra XS files from. 🚀

The following four files sum up all the details discussed so far.

Foo.pm:

package Cool::Foo;

require DynaLoader;

our @ISA = qw(DynaLoader);
our $VERSION = '0.01';
bootstrap Cool::Foo $VERSION;

1;

Bar.pm:

package Cool::Bar;

use Cool::Foo; # bootstraps Bar.xs

1;

Foo.xs:

#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"

MODULE = Cool::Foo  PACKAGE = Cool::Foo

BOOT:
# boot the second XS file
boot_Cool__Bar(aTHX_ cv);

MODULE = Cool::Foo  PACKAGE = Cool::Foo  PREFIX = cool_foo_

void
cool_foo_perl_rules()

    CODE:
    fprintf(stderr, "Cool::Foo says: Perl Rules\n");

Bar.xs:

#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"

MODULE = Cool::Bar  PACKAGE = Cool::Bar PREFIX = cool_bar_

void
cool_bar_perl_rules()

    CODE:
    fprintf(stderr, "Cool::Bar says: Perl Rules\n");

And of course a very basic test 🧪:

t/cool.t:

use Test::More tests => 1;
use Cool::Foo;
use Cool::Bar;
Cool::Foo::perl_rules();
Cool::Bar::perl_rules();
ok 1;

This tip has been brought to you by Nick Ing-Simmons and Stas Bekman. Legends, honestly 👑.

An alternative way to achieve this can be seen in Gtk2::CodeGen and Glib::CodeGen — go peek if you're curious, iykyk 👀✨

🦋 DESIGN 🦋

okay bestie this is the part where we look at how MakeMaker is actually built, and ngl it is a lot. but stay with me, it's kind of iconic once you see it 💅

✨ MakeMaker object hierarchy (simplified) ✨

here's the version you actually need in your life — superclasses on top, kween behavior:

               ExtUtils::MM_Any
                       |
               ExtUtils::MM_Unix
                       |
               ExtUtils::MM_{Current OS}
                       |
               ExtUtils::MakeMaker
                       |
                      MY

so the object you're actually using? that's of the class MY, and it exists so you can override little bits of MakeMaker right inside your Makefile.PL by declaring MY::foo() methods. it's giving main character energy, honestly 🫶

🌸 MakeMaker object hierarchy (real) 🌸

and here's how it really works, no filter, no cap:

                                           ExtUtils::MM_Any
                                                   |
                                           ExtUtils::MM_Unix
                                                   |
           ExtUtils::Liblist::Kid          ExtUtils::MM_{Current OS} (if necessary)
                 |                                          |
           ExtUtils::Liblist     ExtUtils::MakeMaker        |
                           |     |                          |
                           |     |   |-----------------------
                          ExtUtils::MM
                          |          |
               ExtUtils::MY         MM (created by ExtUtils::MM)
               |                                   |
               MY (created by ExtUtils::MY)        |
                           .                       |
                        (mixin)                    |
                           .                       |
                      PACK### (created each call to ExtUtils::MakeMaker->new)
NOTE: yes, this is a mess. 😭 see http://archive.develooper.com/makemaker@perl.org/msg00134.html for some history. it's giving lore drop.
NOTE: when ExtUtils::MM gets loaded, it chooses a superclass for MM from amongst the ExtUtils::MM_* modules based on the current operating system. iykyk 🧚
NOTE: ExtUtils::MM_{Current OS} represents one of the ExtUtils::MM_* modules except ExtUtils::MM_Any, chosen based on your operating system.
NOTE: the main object used by MakeMaker is a PACK### object, not ExtUtils::MakeMaker. it is, effectively, a subclass of MY, ExtUtils::MakeMaker, ExtUtils::Liblist and ExtUtils::MM_{Current OS}. literally the whole squad in one object 💀
NOTE: the methods in MY are simply copied into PACK### rather than MY being a superclass of PACK###. the docs are like "i don't remember the rationale" and honestly? respect for the honesty 🙈
NOTE: ExtUtils::Liblist should be removed from the inheritance hiearchy and simply be called as functions. it's on the "we should fix this" list, bestie.
NOTE: modules like File::Spec and Exporter have been omitted for clarity. you're welcome 🎀

⭐ The MM_* hierarchy ⭐

one more diagram, this one's the family tree for the MM_* kids:

                                       MM_Win95   MM_NW5
                                            \      /
        MM_BeOS  MM_Cygwin  MM_OS2  MM_VMS  MM_Win32  MM_DOS  MM_UWIN
              \        |      |         |        /      /      /
               ------------------------------------------------
                                  |       |
                               MM_Unix    |
                                     |    |
                                     MM_Any
NOTE: each direct MM_Unix subclass is also an MM_Any subclass. this is a temporary hack because MM_Unix overrides some MM_Any methods with Unix specific code. it lets the non-Unix modules see the original MM_Any implementations. lowkey clever, highkey a hack 💜
NOTE: modules like File::Spec and Exporter have been omitted for clarity. again. still omitted. still clear. 🦋

🎀 PATCHING 🎀

got a question you'd love to see added to the FAQ? (whether or not you have the answer, and honestly same bestie) — please either:

  • make a pull request on the MakeMaker github repository
  • raise a issue on the MakeMaker github repository
  • file an RT ticket
  • email makemaker@perl.org

pick your fighter, all four are valid 🌈

👑 AUTHOR 👑

the denizens of makemaker@perl.org. iconic, mysterious, presumably caffeinated ✨

🌸 SEE ALSO 🌸

  • ExtUtils::MakeMaker

and that's a wrap, bestie!! 💖 you just read the whole ExtUtil...er::FAQ(3) page — this little number is from perl v5.42.0, dated 2023-04-04, so give it some love. go forth and Make that Makefile, you absolute legend 🫶✨🍓

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