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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
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64=item
65
66How do I keep my $VERSION up to date without resetting it manually?
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67
68Often you want to manually set the $VERSION in the main module
69distribution because this is the version that everybody sees on CPAN
70and maybe you want to customize it a bit. But for all the other
71modules in your dist, $VERSION is really just bookkeeping and all that's
72important is it goes up every time the module is changed. Doing this
73by hand is a pain and you often forget.
74
75Simplest way to do it automatically is to use your version control
76system's revision number (you are using version control, right?).
77
c2990482 78In CVS and RCS you use $Z<>Revision$ writing it like so:
2530b651 79
c2990482 80 $VERSION = sprintf "%d.%03d", q$Revision$ =~ /(\d+)/g;
2530b651 81
c2990482 82On your next check in, $Z<>Revision$ will magically be expanded to contain
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83the current revision #.
84
c2990482 85 $VERSION = sprintf "%d.%03d", q$Revision: 1.7 $ =~ /(\d+)/g;
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c2990482 87Every time the file is checked in the $Z<>Revision$ will be updated,
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88updating your $VERSION.
89
90In CVS version 1.9 is followed by 1.10. Since CPAN compares version
91numbers numerically we use a sprintf() to convert 1.9 to 1.009 and
921.10 to 1.010 which compare properly.
93
c2990482 94If branches are involved (ie. $Z<>Revision: 1.5.3.4) its a little more
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95complicated.
96
97 # must be all on one line or MakeMaker will get confused.
c2990482 98 $VERSION = do { my @r = (q$Revision$ =~ /\d+/g); sprintf "%d."."%03d" x $#r, @r };
2530b651 99
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100=item
101
102What's this F<META.yml> thing and how did it get in my F<MANIFEST>?!
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103
104F<META.yml> is a module meta-data file pioneered by Module::Build and
105automatically generated as part of the 'distdir' target (and thus
106'dist'). See L<ExtUtils::MakeMaker/"Module Meta-Data">.
107
108To shut off its generation, pass the C<NO_META> flag to C<WriteMakefile()>.
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109
110=back
111
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112=head2 XS
113
114=over 4
115
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116=item
117
118How to I prevent "object version X.XX does not match bootstrap parameter Y.YY"
119errors?
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120
121XS code is very sensitive to the module version number and will
122complain if the version number in your Perl module doesn't match. If
123you change your module's version # without reruning Makefile.PL the old
124version number will remain in the Makefile causing the XS code to be built
125with the wrong number.
126
127To avoid this, you can force the Makefile to be rebuilt whenever you
128change the module containing the version number by adding this to your
129WriteMakefile() arguments.
130
131 depend => { '$(FIRST_MAKEFILE)' => '$(VERSION_FROM)' }
132
133
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134=item
135
136How do I make two or more XS files coexist in the same directory?
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137
138Sometimes you need to have two and more XS files in the same package.
139One way to go is to put them into separate directories, but sometimes
140this is not the most suitable solution. The following technique allows
141you to put two (and more) XS files in the same directory.
142
143Let's assume that we have a package C<Cool::Foo>, which includes
144C<Cool::Foo> and C<Cool::Bar> modules each having a separate XS
145file. First we use the following I<Makefile.PL>:
146
147 use ExtUtils::MakeMaker;
148
149 WriteMakefile(
150 NAME => 'Cool::Foo',
151 VERSION_FROM => 'Foo.pm',
152 OBJECT => q/$(O_FILES)/,
153 # ... other attrs ...
154 );
155
156Notice the C<OBJECT> attribute. MakeMaker generates the following
157variables in I<Makefile>:
158
159 # Handy lists of source code files:
160 XS_FILES= Bar.xs \
161 Foo.xs
162 C_FILES = Bar.c \
163 Foo.c
164 O_FILES = Bar.o \
165 Foo.o
166
167Therefore we can use the C<O_FILES> variable to tell MakeMaker to use
168these objects into the shared library.
169
170That's pretty much it. Now write I<Foo.pm> and I<Foo.xs>, I<Bar.pm>
171and I<Bar.xs>, where I<Foo.pm> bootstraps the shared library and
172I<Bar.pm> simply loading I<Foo.pm>.
173
174The only issue left is to how to bootstrap I<Bar.xs>. This is done
175from I<Foo.xs>:
176
177 MODULE = Cool::Foo PACKAGE = Cool::Foo
178
179 BOOT:
180 # boot the second XS file
181 boot_Cool__Bar(aTHX_ cv);
182
183If you have more than two files, this is the place where you should
184boot extra XS files from.
185
186The following four files sum up all the details discussed so far.
187
188 Foo.pm:
189 -------
190 package Cool::Foo;
191
192 require DynaLoader;
193
194 our @ISA = qw(DynaLoader);
195 our $VERSION = '0.01';
196 bootstrap Cool::Foo $VERSION;
197
198 1;
199
200 Bar.pm:
201 -------
202 package Cool::Bar;
203
204 use Cool::Foo; # bootstraps Bar.xs
205
206 1;
207
208 Foo.xs:
209 -------
210 #include "EXTERN.h"
211 #include "perl.h"
212 #include "XSUB.h"
213
214 MODULE = Cool::Foo PACKAGE = Cool::Foo
215
216 BOOT:
217 # boot the second XS file
218 boot_Cool__Bar(aTHX_ cv);
219
220 MODULE = Cool::Foo PACKAGE = Cool::Foo PREFIX = cool_foo_
221
222 void
223 cool_foo_perl_rules()
224
225 CODE:
226 fprintf(stderr, "Cool::Foo says: Perl Rules\n");
227
228 Bar.xs:
229 -------
230 #include "EXTERN.h"
231 #include "perl.h"
232 #include "XSUB.h"
233
234 MODULE = Cool::Bar PACKAGE = Cool::Bar PREFIX = cool_bar_
235
236 void
237 cool_bar_perl_rules()
238
239 CODE:
240 fprintf(stderr, "Cool::Bar says: Perl Rules\n");
241
242And of course a very basic test:
243
244 test.pl:
245 --------
246 use Test;
247 BEGIN { plan tests => 1 };
248 use Cool::Foo;
249 use Cool::Bar;
250 Cool::Foo::perl_rules();
251 Cool::Bar::perl_rules();
252 ok 1;
253
254This tip has been brought to you by Nick Ing-Simmons and Stas Bekman.
255
256=back
257
258=head1 PATCHING
259
260If you have a question you'd like to see added to the FAQ (whether or
261not you have the answer) please send it to makemaker@perl.org.
262
263=head1 AUTHOR
264
265The denizens of makemaker@perl.org.
266
267=head1 SEE ALSO
268
269L<ExtUtils::MakeMaker>
270
271=cut