</section>
-</chapter>
+ <section>
+ <title>Overriding construction variables when calling a Builder</title>
+
+ <para>
+
+ It is possible to override or add construction variables
+ when calling a builder method by passing additional keyword arguments.
+ These overridden or added variables will only be in effect when
+ building the target, so they will not affect other parts of the build.
+ For example, if you want to add additional libraries for just one program:
+
+ </para>
+
+ <programlisting>
+env.Program('hello', 'hello.c', LIBS=['gl', 'glut'])
+ </programlisting>
+
+ <para>
+
+ or generate a shared library with a non-standard suffix:
+
+ </para>
+
+ <programlisting>
+env.SharedLibrary('word', 'word.cpp',
+ SHLIBSUFFIX='.ocx',
+ LIBSUFFIXES=['.ocx'])
+ </programlisting>
+
+ <para>
+
+ It is also possible to use the <literal>parse_flags</literal> keyword argument in an
+ override:
+
+ </para>
+
+ <para>
+
+ This example adds 'include' to &cv-link-CPPPATH;,
+ 'EBUG' to &cv-link-CPPDEFINES;, and 'm' to &cv-link-LIBS;.
+
+ </para>
+
+ <programlisting>
+env = Program('hello', 'hello.c', parse_flags = '-Iinclude -DEBUG -lm')
+ </programlisting>
+
+ <para>
+
+ Within the call to the builder action the environment is not cloned,
+ instead an OverrideEnvironment() is created which is more
+ light weight than a whole Environment()
+
+ </para>
+
+ </section>
+
+</chapter>
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This is important since many files get scanned in a typical build.
</para>
- </section>
+ </section>
+
+ <section>
+ <title>Using scanners with Builders</title>
+
+ <para>
+
+ One approach for the use of scanners is with builders.
+ There are two optional parameters we can use with a builder
+ <literal>source_scanner</literal> and <literal>target_scanner</literal>.
+
+ </para>
+
+ <scons_example name="scanners_builders">
+ <file name="SConstruct" printme="1">
+
+def kfile_scan(node, env, path, arg):
+ contents = node.get_text_contents()
+ return env.File(include_re.findall(contents))
+
+kscan = Scanner(function = kfile_scan,
+ skeys = ['.k'],
+ path_function = FindPathDirs('KPATH'))
+
+def build_function(target, source, env):
+ # Code to build "target" from "source"
+ return None
+
+bld = Builder(action = build_function,
+ suffix = '.foo',
+ source_scanner = kscan
+ src_suffix = '.input')
+env = Environment(BUILDERS = {'Foo' : bld})
+env.Foo('file')
+
+ </file>
+ </scons_example>
+
+ <para>
+
+ An emiter function can modify the list of sources or targets
+ passed to the action function when the builder is triggered.
+
+ </para>
+
+ <para>
+
+ A scanner function will not affect the list of sources or targets
+ seen by the builder during the build action. The scanner function
+ will however affect if the builder should be rebuilt (if any of
+ the files sourced by the scanner have changed for example).
+
+ </para>
+ </section>
-</chapter>
+</chapter>
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