scons_gd/scons/doc/user/variants.xml

<?xml version='1.0'?>
<!DOCTYPE sconsdoc [
    <!ENTITY % scons SYSTEM "../scons.mod">
    %scons;
    
    <!ENTITY % builders-mod SYSTEM "../generated/builders.mod">
    %builders-mod;
    <!ENTITY % functions-mod SYSTEM "../generated/functions.mod">
    %functions-mod;
    <!ENTITY % tools-mod SYSTEM "../generated/tools.mod">
    %tools-mod;
    <!ENTITY % variables-mod SYSTEM "../generated/variables.mod">
    %variables-mod;
]>

<section id="sect-variants"
         xmlns="http://www.scons.org/dbxsd/v1.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://www.scons.org/dbxsd/v1.0 http://www.scons.org/dbxsd/v1.0/scons.xsd">
<title>Variant Build Examples</title>

<!--

  __COPYRIGHT__

  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.

-->

  <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 directory on a network share
  with separate side-by-side build directories
  for the Windows and Linux versions of the program.
  We have to do a little bit of work to construct paths,
  to make sure unwanted location dependencies don't creep in.
  The top-relative path reference can be useful here.
  To avoid writing conditional code based on platform,
  we can build the <parameter>variant_dir</parameter>
  path dynamically:

  </para>

  <scons_example name="variants_ex">
    <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="variants_ex" os="posix" suffix="1">
    <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="variants_ex" os="win32" suffix="2">
    <scons_output_command>scons -Q OS=windows</scons_output_command>
  </scons_output>

  <para>

  In order to build several variants at once when using the
  <parameter>variant_dir</parameter> argument to &SConscript;,
  you can call the function repeatedely - this example
  does so in a loop. Note that the &f-link-SConscript; trick of
  passing a list of script files, or a list of source directories,
  does not work with <parameter>variant_dir</parameter>,
  &SCons; allows only a single &SConscript; to be given if
  <parameter>variant_dir</parameter> is used.

  </para>

  <scons_example name="variants_ex2">
    <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="variants_ex2" suffix="1">
    <scons_output_command>scons -Q</scons_output_command>
  </scons_output>

  -->

</section>