Added 'preprocess()' method to CCompiler interface, and implemented
it in UnixCCompiler.  Still needs to be implemented in MSVCCompiler (and
whatever other compiler classes are lurking out there, waiting to be
checked in).
diff --git a/Lib/distutils/ccompiler.py b/Lib/distutils/ccompiler.py
index b146f89..53d4fa5 100644
--- a/Lib/distutils/ccompiler.py
+++ b/Lib/distutils/ccompiler.py
@@ -414,6 +414,22 @@
     # -- Worker methods ------------------------------------------------
     # (must be implemented by subclasses)
 
+    def preprocess (self,
+                    source,
+                    output_file=None,
+                    macros=None,
+                    include_dirs=None,
+                    extra_preargs=None,
+                    extra_postargs=None):
+        """Preprocess a single C/C++ source file, named in 'source'.
+        Output will be written to file named 'output_file', or stdout if
+        'output_file' not supplied.  'macros' is a list of macro
+        definitions as for 'compile()', which will augment the macros set
+        with 'define_macro()' and 'undefine_macro()'.  'include_dirs' is a
+        list of directory names that will be added to the default list.
+        """
+        pass
+
     def compile (self,
                  sources,
                  output_dir=None,
diff --git a/Lib/distutils/unixccompiler.py b/Lib/distutils/unixccompiler.py
index 4d38e4d..47d8ad6 100644
--- a/Lib/distutils/unixccompiler.py
+++ b/Lib/distutils/unixccompiler.py
@@ -21,6 +21,7 @@
 from types import *
 from copy import copy
 from distutils import sysconfig
+from distutils.dep_util import newer
 from distutils.ccompiler import \
      CCompiler, gen_preprocess_options, gen_lib_options
 from distutils.errors import \
@@ -104,6 +105,37 @@
     # __init__ ()
 
 
+    def preprocess (self,
+                    source,
+                    output_file=None,
+                    macros=None,
+                    include_dirs=None,
+                    extra_preargs=None,
+                    extra_postargs=None):
+
+        (_, macros, include_dirs) = \
+            self._fix_compile_args (None, macros, include_dirs)
+        pp_opts = gen_preprocess_options (macros, include_dirs)
+        cc_args = ['-E'] + pp_opts
+        if output_file:
+            cc_args.extend(['-o', output_file])
+        if extra_preargs:
+            cc_args[:0] = extra_preargs
+        if extra_postargs:
+            extra_postargs.extend(extra_postargs)
+
+        # We need to preprocess: either we're being forced to, or the
+        # source file is newer than the target (or the target doesn't
+        # exist).
+        if self.force or (output_file and newer(source, output_file)):
+            if output_file:
+                self.mkpath(os.path.dirname(output_file))
+            try:
+                self.spawn ([self.cc] + cc_args)
+            except DistutilsExecError, msg:
+                raise CompileError, msg
+
+
     def compile (self,
                  sources,
                  output_dir=None,