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[perl5.git] / lib / ExtUtils / MakeMaker / FAQ.pod
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1package ExtUtils::MakeMaker::FAQ;
2
c2990482 3(our $VERSION) = sprintf "%03d", q$Revision: 1.7 $ =~ /Revision:\s+(\S+)/;
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4
51;
6__END__
7
8=head1 NAME
9
10ExtUtils::MakeMaker::FAQ - Frequently Asked Questions About MakeMaker
11
12=head1 DESCRIPTION
13
14FAQs, tricks and tips for C<ExtUtils::MakeMaker>.
15
16=head2 Philosophy and History
17
18=over 4
19
20=item Why not just use <insert other build config tool here>?
21
22Why did MakeMaker reinvent the build configuration wheel? Why not
23just use autoconf or automake or ppm or Ant or ...
24
25There are many reasons, but the major one is cross-platform
26compatibility.
27
28Perl is one of the most ported pieces of software ever. It works on
29operating systems I've never even heard of (see perlport for details).
30It needs a build tool that can work on all those platforms and with
31any wacky C compilers they might have.
32
33No such build tool existed at the time and I only know of one now
34(Module::Build).
35
36
37=item What's Module::Build and how does it relate to MakeMaker?
38
39Module::Build is a project by Ken Williams to supplant MakeMaker.
40Its primary advantages are:
41
42=over 8
43
44=item * pure perl. no make, no shell commands
45
46=item * easier to customize
47
48=item * cleaner internals
49
50=item * less cruft
51
52=back
53
54Module::Build is the official heir apparent to MakeMaker and we
55encourage people to work on M::B rather than spending time improving
56MakeMaker.
57
58=back
59
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60=head2 Module Writing
61
62=over 4
63
64=item How do I keep my $VERSION up to date without resetting it manually?
65
66Often you want to manually set the $VERSION in the main module
67distribution because this is the version that everybody sees on CPAN
68and maybe you want to customize it a bit. But for all the other
69modules in your dist, $VERSION is really just bookkeeping and all that's
70important is it goes up every time the module is changed. Doing this
71by hand is a pain and you often forget.
72
73Simplest way to do it automatically is to use your version control
74system's revision number (you are using version control, right?).
75
c2990482 76In CVS and RCS you use $Z<>Revision$ writing it like so:
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c2990482 78 $VERSION = sprintf "%d.%03d", q$Revision$ =~ /(\d+)/g;
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c2990482 80On your next check in, $Z<>Revision$ will magically be expanded to contain
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81the current revision #.
82
c2990482 83 $VERSION = sprintf "%d.%03d", q$Revision: 1.7 $ =~ /(\d+)/g;
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c2990482 85Every time the file is checked in the $Z<>Revision$ will be updated,
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86updating your $VERSION.
87
88In CVS version 1.9 is followed by 1.10. Since CPAN compares version
89numbers numerically we use a sprintf() to convert 1.9 to 1.009 and
901.10 to 1.010 which compare properly.
91
c2990482 92If branches are involved (ie. $Z<>Revision: 1.5.3.4) its a little more
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93complicated.
94
95 # must be all on one line or MakeMaker will get confused.
c2990482 96 $VERSION = do { my @r = (q$Revision$ =~ /\d+/g); sprintf "%d."."%03d" x $#r, @r };
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98=item What's this F<META.yml> thing and how did it get in my F<MANIFEST>?!
99
100F<META.yml> is a module meta-data file pioneered by Module::Build and
101automatically generated as part of the 'distdir' target (and thus
102'dist'). See L<ExtUtils::MakeMaker/"Module Meta-Data">.
103
104To shut off its generation, pass the C<NO_META> flag to C<WriteMakefile()>.
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105
106=back
107
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108=head2 XS
109
110=over 4
111
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112=item How to I prevent "object version X.XX does not match bootstrap parameter Y.YY" errors?
113
114XS code is very sensitive to the module version number and will
115complain if the version number in your Perl module doesn't match. If
116you change your module's version # without reruning Makefile.PL the old
117version number will remain in the Makefile causing the XS code to be built
118with the wrong number.
119
120To avoid this, you can force the Makefile to be rebuilt whenever you
121change the module containing the version number by adding this to your
122WriteMakefile() arguments.
123
124 depend => { '$(FIRST_MAKEFILE)' => '$(VERSION_FROM)' }
125
126
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127=item How do I make two or more XS files coexist in the same directory?
128
129Sometimes you need to have two and more XS files in the same package.
130One way to go is to put them into separate directories, but sometimes
131this is not the most suitable solution. The following technique allows
132you to put two (and more) XS files in the same directory.
133
134Let's assume that we have a package C<Cool::Foo>, which includes
135C<Cool::Foo> and C<Cool::Bar> modules each having a separate XS
136file. First we use the following I<Makefile.PL>:
137
138 use ExtUtils::MakeMaker;
139
140 WriteMakefile(
141 NAME => 'Cool::Foo',
142 VERSION_FROM => 'Foo.pm',
143 OBJECT => q/$(O_FILES)/,
144 # ... other attrs ...
145 );
146
147Notice the C<OBJECT> attribute. MakeMaker generates the following
148variables in I<Makefile>:
149
150 # Handy lists of source code files:
151 XS_FILES= Bar.xs \
152 Foo.xs
153 C_FILES = Bar.c \
154 Foo.c
155 O_FILES = Bar.o \
156 Foo.o
157
158Therefore we can use the C<O_FILES> variable to tell MakeMaker to use
159these objects into the shared library.
160
161That's pretty much it. Now write I<Foo.pm> and I<Foo.xs>, I<Bar.pm>
162and I<Bar.xs>, where I<Foo.pm> bootstraps the shared library and
163I<Bar.pm> simply loading I<Foo.pm>.
164
165The only issue left is to how to bootstrap I<Bar.xs>. This is done
166from I<Foo.xs>:
167
168 MODULE = Cool::Foo PACKAGE = Cool::Foo
169
170 BOOT:
171 # boot the second XS file
172 boot_Cool__Bar(aTHX_ cv);
173
174If you have more than two files, this is the place where you should
175boot extra XS files from.
176
177The following four files sum up all the details discussed so far.
178
179 Foo.pm:
180 -------
181 package Cool::Foo;
182
183 require DynaLoader;
184
185 our @ISA = qw(DynaLoader);
186 our $VERSION = '0.01';
187 bootstrap Cool::Foo $VERSION;
188
189 1;
190
191 Bar.pm:
192 -------
193 package Cool::Bar;
194
195 use Cool::Foo; # bootstraps Bar.xs
196
197 1;
198
199 Foo.xs:
200 -------
201 #include "EXTERN.h"
202 #include "perl.h"
203 #include "XSUB.h"
204
205 MODULE = Cool::Foo PACKAGE = Cool::Foo
206
207 BOOT:
208 # boot the second XS file
209 boot_Cool__Bar(aTHX_ cv);
210
211 MODULE = Cool::Foo PACKAGE = Cool::Foo PREFIX = cool_foo_
212
213 void
214 cool_foo_perl_rules()
215
216 CODE:
217 fprintf(stderr, "Cool::Foo says: Perl Rules\n");
218
219 Bar.xs:
220 -------
221 #include "EXTERN.h"
222 #include "perl.h"
223 #include "XSUB.h"
224
225 MODULE = Cool::Bar PACKAGE = Cool::Bar PREFIX = cool_bar_
226
227 void
228 cool_bar_perl_rules()
229
230 CODE:
231 fprintf(stderr, "Cool::Bar says: Perl Rules\n");
232
233And of course a very basic test:
234
235 test.pl:
236 --------
237 use Test;
238 BEGIN { plan tests => 1 };
239 use Cool::Foo;
240 use Cool::Bar;
241 Cool::Foo::perl_rules();
242 Cool::Bar::perl_rules();
243 ok 1;
244
245This tip has been brought to you by Nick Ing-Simmons and Stas Bekman.
246
247=back
248
249=head1 PATCHING
250
251If you have a question you'd like to see added to the FAQ (whether or
252not you have the answer) please send it to makemaker@perl.org.
253
254=head1 AUTHOR
255
256The denizens of makemaker@perl.org.
257
258=head1 SEE ALSO
259
260L<ExtUtils::MakeMaker>
261
262=cut