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Clarify main rule/type declaration

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[SVN r26451]
This commit is contained in:
Vladimir Prus
2004-12-06 14:07:55 +00:00
parent 648b30b73c
commit bedd7e8ac5
1 changed files with 33 additions and 33 deletions
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66
v2/doc/src/extending.xml
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@@ -630,16 +630,34 @@ feature.compose <parallelism>fake : <library>/mpi//fake/<parallel
<section id="bbv2.extending.rules">
<title>Main target rules</title>
<para>
The main target rule is what creates a top-level target, for example "exe" or
"lib". It's quite likely that you'll want to declare your own and
there are as many as three ways to do that.
A main target rule is what creates a top-level target, for example "exe"
or "lib". It's quite likely that you'll want to declare your own and
there are two ways to do this.
</para>
<para id="bbv2.extending.rules.main-type">The first way applies then when
your target rule should just produce a target of specific type. Then, a
rule is already defined for you! When you define a new type, Boost.Build
automatically defines a corresponding rule. The name of the rule is
obtained from the name of the type, by downcasing all letters and
replacing underscores with slashes. For example, if you create a module
"obfuscate.jam" containing:
<programlisting>
import type ;
type.register OBFUSCATED_CPP : ocpp ;
import generators ;
generators.register-standard obfuscate.file : CPP : OBFUSCATED_CPP ;
</programlisting>
and import that module, you'll be able to use the rule "obfuscated-cpp"
in Jamfiles, which will convert source to the OBFUSCATED_CPP type.
</para>
<para>The first is the simplest, but is sufficient in a number of
cases. Just write a wrapper rule, which will redirect to any of the
existing rules. For example, you have only one library per directory and
want all cpp files in the directory to be compiled. You can achieve this
effect with:
<para>The second way is to write a wrapper rule, which will redirect to
any of the existing rules. For example, you have only one library per
directory and want all cpp files in the directory to be compiled. You
can achieve this effect with:
<programlisting>
lib codegen : [ glob *.cpp ] ;
</programlisting>
@@ -657,33 +675,15 @@ glib codegen ;
</programlisting>
</para>
<para id="bbv2.extending.rules.main-type">The second approach is suitable
when your target rule should just produce a target of specific
type. Then, when declaring a type you should tell Boost.Build that a
main target rule should be created. For example, if you create a module
"obfuscate.jam" containing:
<programlisting>
import type ;
type.register OBFUSCATED_CPP : ocpp : : main ;
import generators ;
generators.register-standard obfuscate.file : CPP : OBFUSCATED_CPP ;
</programlisting>
and import that module, you'll be able to use the rule "obfuscated-cpp"
in Jamfiles, which will convert source to the OBFUSCATED_CPP type.
</para>
<para>
The remaining method is to declare your own main target class. The
simplest example of this can be found in "build/alias.jam" file. The
current V2 uses this method when transformations are relatively
complex. However, we might deprecate this approach. If you find that you
need to use it (that is, the first two approaches are not sufficient),
please let us know by posting to the mailing list.
Note that because you can associate custom generator with a target
type, the logic of building can be rather compiler. For example, the
<code>boostbook</code> module declares a target type
<code>BOOSTBOOK_MAIN</code> and a custom generator for that type,
which implements pretty complex logic. You can use that as example if
your main target rule is non-trivial.
</para>
</section>
<section id="bbv2.extending.toolset_modules">