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[perl5.git] / lib / ExtUtils / MakeMaker / FAQ.pod
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1package ExtUtils::MakeMaker::FAQ;
2
5e719f03 3(our $VERSION) = sprintf "%03d", q$Revision: 1.9 $ =~ /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
e3aa3ecb 64=item How do I keep my $VERSION up to date without resetting it manually?
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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:
2530b651 77
5e719f03 78 $VERSION = sprintf "%d.%03d", q$Revision: 1.9 $ =~ /(\d+)/g;
2530b651 79
c2990482 80Every time the file is checked in the $Z<>Revision$ will be updated,
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81updating your $VERSION.
82
83In CVS version 1.9 is followed by 1.10. Since CPAN compares version
84numbers numerically we use a sprintf() to convert 1.9 to 1.009 and
851.10 to 1.010 which compare properly.
86
c2990482 87If branches are involved (ie. $Z<>Revision: 1.5.3.4) its a little more
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88complicated.
89
90 # must be all on one line or MakeMaker will get confused.
5e719f03 91 $VERSION = do { my @r = (q$Revision: 1.9 $ =~ /\d+/g); sprintf "%d."."%03d" x $#r, @r };
2530b651 92
e3aa3ecb 93=item What's this F<META.yml> thing and how did it get in my F<MANIFEST>?!
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94
95F<META.yml> is a module meta-data file pioneered by Module::Build and
96automatically generated as part of the 'distdir' target (and thus
97'dist'). See L<ExtUtils::MakeMaker/"Module Meta-Data">.
98
99To shut off its generation, pass the C<NO_META> flag to C<WriteMakefile()>.
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100
101=back
102
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103=head2 XS
104
105=over 4
106
e3aa3ecb 107=item How to I prevent "object version X.XX does not match bootstrap parameter Y.YY" errors?
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108
109XS code is very sensitive to the module version number and will
110complain if the version number in your Perl module doesn't match. If
111you change your module's version # without reruning Makefile.PL the old
112version number will remain in the Makefile causing the XS code to be built
113with the wrong number.
114
115To avoid this, you can force the Makefile to be rebuilt whenever you
116change the module containing the version number by adding this to your
117WriteMakefile() arguments.
118
119 depend => { '$(FIRST_MAKEFILE)' => '$(VERSION_FROM)' }
120
121
e3aa3ecb 122=item How do I make two or more XS files coexist in the same directory?
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123
124Sometimes you need to have two and more XS files in the same package.
125One way to go is to put them into separate directories, but sometimes
126this is not the most suitable solution. The following technique allows
127you to put two (and more) XS files in the same directory.
128
129Let's assume that we have a package C<Cool::Foo>, which includes
130C<Cool::Foo> and C<Cool::Bar> modules each having a separate XS
131file. First we use the following I<Makefile.PL>:
132
133 use ExtUtils::MakeMaker;
134
135 WriteMakefile(
136 NAME => 'Cool::Foo',
137 VERSION_FROM => 'Foo.pm',
138 OBJECT => q/$(O_FILES)/,
139 # ... other attrs ...
140 );
141
142Notice the C<OBJECT> attribute. MakeMaker generates the following
143variables in I<Makefile>:
144
145 # Handy lists of source code files:
146 XS_FILES= Bar.xs \
147 Foo.xs
148 C_FILES = Bar.c \
149 Foo.c
150 O_FILES = Bar.o \
151 Foo.o
152
153Therefore we can use the C<O_FILES> variable to tell MakeMaker to use
154these objects into the shared library.
155
156That's pretty much it. Now write I<Foo.pm> and I<Foo.xs>, I<Bar.pm>
157and I<Bar.xs>, where I<Foo.pm> bootstraps the shared library and
158I<Bar.pm> simply loading I<Foo.pm>.
159
160The only issue left is to how to bootstrap I<Bar.xs>. This is done
161from I<Foo.xs>:
162
163 MODULE = Cool::Foo PACKAGE = Cool::Foo
164
165 BOOT:
166 # boot the second XS file
167 boot_Cool__Bar(aTHX_ cv);
168
169If you have more than two files, this is the place where you should
170boot extra XS files from.
171
172The following four files sum up all the details discussed so far.
173
174 Foo.pm:
175 -------
176 package Cool::Foo;
177
178 require DynaLoader;
179
180 our @ISA = qw(DynaLoader);
181 our $VERSION = '0.01';
182 bootstrap Cool::Foo $VERSION;
183
184 1;
185
186 Bar.pm:
187 -------
188 package Cool::Bar;
189
190 use Cool::Foo; # bootstraps Bar.xs
191
192 1;
193
194 Foo.xs:
195 -------
196 #include "EXTERN.h"
197 #include "perl.h"
198 #include "XSUB.h"
199
200 MODULE = Cool::Foo PACKAGE = Cool::Foo
201
202 BOOT:
203 # boot the second XS file
204 boot_Cool__Bar(aTHX_ cv);
205
206 MODULE = Cool::Foo PACKAGE = Cool::Foo PREFIX = cool_foo_
207
208 void
209 cool_foo_perl_rules()
210
211 CODE:
212 fprintf(stderr, "Cool::Foo says: Perl Rules\n");
213
214 Bar.xs:
215 -------
216 #include "EXTERN.h"
217 #include "perl.h"
218 #include "XSUB.h"
219
220 MODULE = Cool::Bar PACKAGE = Cool::Bar PREFIX = cool_bar_
221
222 void
223 cool_bar_perl_rules()
224
225 CODE:
226 fprintf(stderr, "Cool::Bar says: Perl Rules\n");
227
228And of course a very basic test:
229
230 test.pl:
231 --------
232 use Test;
233 BEGIN { plan tests => 1 };
234 use Cool::Foo;
235 use Cool::Bar;
236 Cool::Foo::perl_rules();
237 Cool::Bar::perl_rules();
238 ok 1;
239
240This tip has been brought to you by Nick Ing-Simmons and Stas Bekman.
241
242=back
243
244=head1 PATCHING
245
246If you have a question you'd like to see added to the FAQ (whether or
247not you have the answer) please send it to makemaker@perl.org.
248
249=head1 AUTHOR
250
251The denizens of makemaker@perl.org.
252
253=head1 SEE ALSO
254
255L<ExtUtils::MakeMaker>
256
257=cut