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<!--
Copyright (c) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 The SCons Foundation
Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:
The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
-->
<!--
=head1 Variant builds
=head2 Variations on a theme
Other variations of this model are possible. For example, you might decide
that you want to separate out your include files into platform dependent and
platform independent files. In this case, you'd have to define an
alternative to C<$INCLUDE> for platform-dependent files. Most F<Conscript>
files, generating purely platform-independent include files, would not have
to change.
You might also want to be able to compile your whole system with debugging
or profiling, for example, enabled. You could do this with appropriate
command line options, such as C<DEBUG=on>. This would then be translated
into the appropriate platform-specific requirements to enable debugging
(this might include turning off optimization, for example). You could
optionally vary the name space for these different types of systems, but, as
we'll see in the next section, it's not B<essential> to do this, since Cons
is pretty smart about rebuilding things when you change options.
-->
<para>
The &variant_dir; keyword argument of
the &SConscript; function provides everything
we need to show how easy it is to create
variant builds using &SCons;.
Suppose, for example, that we want to
build a program for both Windows and Linux platforms,
but that we want to build it in a shared directory
with separate side-by-side build directories
for the Windows and Linux versions of the program.
</para>
<scons_example name="ex_variants">
<file name="SConstruct" printme="1">
platform = ARGUMENTS.get('OS', Platform())
include = "#export/$PLATFORM/include"
lib = "#export/$PLATFORM/lib"
bin = "#export/$PLATFORM/bin"
env = Environment(PLATFORM = platform,
BINDIR = bin,
INCDIR = include,
LIBDIR = lib,
CPPPATH = [include],
LIBPATH = [lib],
LIBS = 'world')
Export('env')
env.SConscript('src/SConscript', variant_dir='build/$PLATFORM')
</file>
<directory name="src"></directory>
<directory name="src/hello"></directory>
<directory name="src/world"></directory>
<file name="src/SConscript">
Import('env')
SConscript('hello/SConscript')
SConscript('world/SConscript')
</file>
<file name="src/hello/SConscript">
Import('env')
hello = env.Program('hello.c')
env.Install('$BINDIR', hello)
</file>
<file name="src/hello/hello.c">
#include "world.h"
int main(int argc, char *argv[]) { printf "hello.c\n"; world(); }
</file>
<file name="src/world/SConscript">
Import('env')
world = env.Library('world.c')
env.Install('$LIBDIR', world)
env.Install('$INCDIR', 'world.h')
</file>
<file name="src/world/world.h">
#define STRING "world.h"
extern int world();
</file>
<file name="src/world/world.c">
int world() { printf "world.c\n"; }
</file>
</scons_example>
<para>
This SConstruct file,
when run on a Linux system, yields:
</para>
<scons_output example="ex_variants" os="posix">
<scons_output_command>scons -Q OS=linux</scons_output_command>
</scons_output>
<para>
The same SConstruct file on Windows would build:
</para>
<scons_output example="ex_variants" os="win32">
<scons_output_command>scons -Q OS=windows</scons_output_command>
</scons_output>
<!--
<scons_example name="ex_var2">
<file name="SConstruct" printme="1">
env = Environment(OS = ARGUMENTS.get('OS'))
for os in ['newell', 'post']:
SConscript('src/SConscript', variant_dir='build/' + os)
</file>
</scons_example>
<scons_output example="ex_var2">
<scons_output_command>scons -Q</scons_output_command>
</scons_output>
-->
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