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Edits in "Conditions and alternatives" section.

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[SVN r31071]
This commit is contained in:
Vladimir Prus
2005-09-21 14:43:44 +00:00
parent 238f1c9068
commit 8335fb2851
1 changed files with 13 additions and 12 deletions
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v2/doc/src/tutorial.xml
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@@ -572,12 +572,11 @@ exe app : app.cpp core ;</programlisting>
<title>Conditions and alternatives</title>
<para>Sometimes, particular relationships need to be maintained
among a target's build properties. This can be achieved with
<firstterm>conditional
requirement</firstterm>. For example, you might want to set
specific <code>#defines</code> when a library is built as shared,
or when a target's <code>release</code> variant is built in
release mode.
among a target's build properties. For example, you might want to set
specific <code>#define</code> when a library is built as shared,
or when a target's <code>release</code> variant is built.
This can be achieved with <firstterm>conditional requirements</firstterm>.
<programlisting>
lib network : network.cpp
: <emphasis role="bold">&lt;link&gt;shared:&lt;define&gt;NEWORK_LIB_SHARED</emphasis>
@@ -588,7 +587,8 @@ lib network : network.cpp
In the example above, whenever <filename>network</filename> is
built with <code>&lt;link&gt;shared</code>,
<code>&lt;define&gt;NEWORK_LIB_SHARED</code> will be in its
properties, too.
properties, too. Also, whenever its release variant is built,
<code>&lt;define&gt;EXTRA_FAST</code> will appear in its properties.
</para>
<para>
@@ -603,11 +603,12 @@ lib demangler : dummy_demangler.cpp ; # alternative 1
lib demangler : demangler_gcc.cpp : &lt;toolset&gt;gcc ; # alternative 2
lib demangler : demangler_msvc.cpp : &lt;toolset&gt;msvc ; # alternative 3
</programlisting>
In the example above, when built with <literal>gcc</literal>
or <literal>msvc</literal>, <filename>demangler</filename>
will use a source file specific to the toolset. Otherwise, it
will use a generic source file,
<filename>dummy_demangler.cpp</filename>.
When building <filename>demangler</filename>, Boost.Build will compare
requirements for each alternative with build properties to find the best match.
For example, when building with with <code>&lt;toolset&gt;gcc</code>
alternative 2, will be selected, and when building with
<code>&lt;toolset&gt;msvc</code> alternative 3 will be selected. In all other
cases, the most generic alternative 1 will be built.
</para>
</section>