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SCons / CrossCompilingMingw

I wanted to write a scons build system which can build my project on both Windows and POSIX platforms. Since my project ultimately builds Windows executables, it needs some cross-compiling. Since SCons doesn't have built-in support for it, I had to add it myself. For this purpose, I wrote this tool definition for MinGW. It's based on the original MinGW tool definition which comes with SCons 0.96.90. My windres patch is also applied.

On top of what the original tool definition does, this tool searches for MinGW using more than one common prefixes and sets Windows prefixes and suffixes for output files.

To use it, save in a directory called scons-tools and use:

env.Tool('crossmingw', toolpath = ['scons-tools'])

A complete usage example can be found in NSIS CVS repository. The tool is located under SCons/Tools. It's used in SCons/Config/gnu.

import os
import os.path

import SCons.Action
import SCons.Builder
import SCons.Tool
import SCons.Util

# This is what we search for to find mingw:
prefixes = SCons.Util.Split("""

def find(env):
  for prefix in prefixes:
    # First search in the SCons path and then the OS path:
    if env.WhereIs(prefix + 'gcc') or SCons.Util.WhereIs(prefix + 'gcc'):
      return prefix

  return ''

def shlib_generator(target, source, env, for_signature):
  cmd = SCons.Util.CLVar(['$SHLINK', '$SHLINKFLAGS'])

  dll = env.FindIxes(target, 'SHLIBPREFIX', 'SHLIBSUFFIX')
  if dll: cmd.extend(['-o', dll])

  cmd.extend(['$SOURCES', '$_LIBDIRFLAGS', '$_LIBFLAGS'])

  implib = env.FindIxes(target, 'LIBPREFIX', 'LIBSUFFIX')
  if implib: cmd.append('-Wl,--out-implib,'+implib.get_string(for_signature))

  def_target = env.FindIxes(target, 'WIN32DEFPREFIX', 'WIN32DEFSUFFIX')
  if def_target: cmd.append('-Wl,--output-def,'+def_target.get_string(for_signature))

  return [cmd]

def shlib_emitter(target, source, env):
  dll = env.FindIxes(target, 'SHLIBPREFIX', 'SHLIBSUFFIX')
  no_import_lib = env.get('no_import_lib', 0)

  if not dll:
    raise SCons.Errors.UserError, "A shared library should have exactly one target with the suffix: %s" % env.subst("$SHLIBSUFFIX")

  if not no_import_lib and \
     not env.FindIxes(target, 'LIBPREFIX', 'LIBSUFFIX'):

    # Append an import library to the list of targets.
                    'SHLIBPREFIX', 'SHLIBSUFFIX',
                    'LIBPREFIX', 'LIBSUFFIX'))

  # Append a def file target if there isn't already a def file target
  # or a def file source. There is no option to disable def file
  # target emitting, because I can't figure out why someone would ever
  # want to turn it off.
  def_source = env.FindIxes(source, 'WIN32DEFPREFIX', 'WIN32DEFSUFFIX')
  def_target = env.FindIxes(target, 'WIN32DEFPREFIX', 'WIN32DEFSUFFIX')
  if not def_source and not def_target:
                  'SHLIBPREFIX', 'SHLIBSUFFIX',
                  'WIN32DEFPREFIX', 'WIN32DEFSUFFIX'))

  return (target, source)

shlib_action = SCons.Action.CommandGenerator(shlib_generator)
# in Scons 2.1 the line above needs to be replace with:
#shlib_action = SCons.Action.Action(shlib_generator, generator=1)

res_action = SCons.Action.Action('$RCCOM', '$RCCOMSTR')

res_builder = SCons.Builder.Builder(action=res_action, suffix='.o',
SCons.Tool.SourceFileScanner.add_scanner('.rc', SCons.Defaults.CScan)

def generate(env):
  mingw_prefix = find(env)

  if mingw_prefix:
    dir = os.path.dirname(env.WhereIs(mingw_prefix + 'gcc') or SCons.Util.WhereIs(mingw_prefix + 'gcc'))

    # The mingw bin directory must be added to the path:
    path = env['ENV'].get('PATH', [])
    if not path:
      path = []
    if SCons.Util.is_String(path):
      path = path.split(os.pathsep)

    env['ENV']['PATH'] = os.pathsep.join([dir] + path)

  # Most of mingw is the same as gcc and friends...
  gnu_tools = ['gcc', 'g++', 'gnulink', 'ar', 'gas']
  for tool in gnu_tools:

  #... but a few things differ:
  env['CC'] = mingw_prefix + 'gcc'
  env['SHCCFLAGS'] = SCons.Util.CLVar('$CCFLAGS')
  env['CXX'] = mingw_prefix + 'g++'
  env['SHCXXFLAGS'] = SCons.Util.CLVar('$CXXFLAGS')
  env['SHLINKFLAGS'] = SCons.Util.CLVar('$LINKFLAGS -shared')
  env['SHLINKCOM']   = shlib_action
  env.Append(SHLIBEMITTER = [shlib_emitter])
  # This line isn't required and breaks C++ linking
  #env['LINK'] = mingw_prefix + 'g++'
  env['AS'] = mingw_prefix + 'as'
  env['AR'] = mingw_prefix + 'ar'
  env['RANLIB'] = mingw_prefix + 'ranlib'
  env['WIN32DEFPREFIX']    = ''
  env['WIN32DEFSUFFIX']    = '.def'
  env['SHOBJSUFFIX'] = '.o'

  env['RC'] = mingw_prefix + 'windres'
  env['RCFLAGS'] = SCons.Util.CLVar('')
  env['RCINCFLAGS'] = '$( ${_concat(RCINCPREFIX, CPPPATH, RCINCSUFFIX, __env__, RDirs, TARGET)} $)'
  env['RCINCPREFIX'] = '--include-dir '
  env['RCINCSUFFIX'] = ''
  env['BUILDERS']['RES'] = res_builder

  # Some setting from the platform also have to be overridden:
  env['OBJPREFIX']    = ''
  env['OBJSUFFIX']    = '.o'
  env['LIBPREFIX']    = 'lib'
  env['LIBSUFFIX']    = '.a'
  env['PROGPREFIX']   = ''
  env['PROGSUFFIX']   = '.exe'
  env['LIBPREFIX']    = ''
  env['LIBSUFFIX']    = '.lib'
  env['SHLIBPREFIX']  = ''
  env['SHLIBSUFFIX']  = '.dll'
  env['LIBPREFIXES']  = [ '$LIBPREFIX' ]
  env['LIBSUFFIXES']  = [ '$LIBSUFFIX' ]

def exists(env):
  return find(env)