android: Don't use cpp to strip comments in jni_generator.

base/android/jni_generator/jni_generator.py

 #!/usr/bin/env python
 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Extracts native methods from a Java file and generates the JNI bindings.
 If you change this, please run and update the tests."""
 
 import collections
 import errno
@@ skipping 563 matching lines @@
                          stderr=subprocess.PIPE)
     stdout, _ = p.communicate()
     jni_from_javap = JNIFromJavaP(stdout.split('\n'), options)
     return jni_from_javap
 
 
 class JNIFromJavaSource(object):
   """Uses the given java source file to generate the JNI header file."""
 
   def __init__(self, contents, fully_qualified_class, options):
-    contents = self._RemoveComments(contents, options)
+    contents = self._RemoveComments(contents)
     JniParams.SetFullyQualifiedClass(fully_qualified_class)
     JniParams.ExtractImportsAndInnerClasses(contents)
     jni_namespace = ExtractJNINamespace(contents) or options.namespace
     natives = ExtractNatives(contents, options.ptr_type)
     called_by_natives = ExtractCalledByNatives(contents)
     if len(natives) == 0 and len(called_by_natives) == 0:
       raise SyntaxError('Unable to find any JNI methods for %s.' %
                         fully_qualified_class)
     inl_header_file_generator = InlHeaderFileGenerator(
         jni_namespace, fully_qualified_class, natives, called_by_natives,
         [], options)
     self.content = inl_header_file_generator.GetContent()
 
-  def _RemoveComments(self, contents, options):
+  # Match single line comments, multiline comments, character literals, and
+  # double-quoted strings.
+  _comment_remover_regex = re.compile(

[bulach, 2014/04/14 11:30:44]

nit: maybe move this before __init__ ? it took me a couple of seconds to
understand the scope :)

[Torne, 2014/04/14 11:41:06]

Done.

+      r'//.*?$|/\*.*?\*/|\'(?:\\.|[^\\\'])*\'|"(?:\\.|[^\\"])*"',
+      re.DOTALL | re.MULTILINE)
+
+  def _RemoveComments(self, contents):

[bulach, 2014/04/14 11:30:44]

...and then perhaps make this @staticmethod?

[Torne, 2014/04/14 11:41:06]

Static methods can't access members of the class, but I can make it a class
method.

     # We need to support both inline and block comments, and we need to handle
-    # strings that contain '//' or '/*'. Rather than trying to do all that with
-    # regexps, we just pipe the contents through the C preprocessor. We tell cpp
-    # the file has already been preprocessed, so it just removes comments and
-    # doesn't try to parse #include, #pragma etc.
-    #
-    # TODO(husky): This is a bit hacky. It would be cleaner to use a real Java
+    # strings that contain '//' or '/*'.
+    # TODO(bulach): This is a bit hacky. It would be cleaner to use a real Java
     # parser. Maybe we could ditch JNIFromJavaSource and just always use
     # JNIFromJavaP; or maybe we could rewrite this script in Java and use APT.
     # http://code.google.com/p/chromium/issues/detail?id=138941
-    p = subprocess.Popen(args=[options.cpp, '-fpreprocessed'],
-                         stdin=subprocess.PIPE,
-                         stdout=subprocess.PIPE,
-                         stderr=subprocess.PIPE)
-    stdout, _ = p.communicate(contents)
-    return stdout
+    def replacer(match):
+      # Replace matches that are comments with nothing; return literals/strings
+      # unchanged.
+      s = match.group(0)
+      if s.startswith('/'):
+        return ""

[bulach, 2014/04/14 11:30:44]

nit: s/""/''/

[Torne, 2014/04/14 11:41:06]

Done.

+      else:
+        return s
+    return self._comment_remover_regex.sub(replacer, contents)
 
   def GetContent(self):
     return self.content
 
   @staticmethod
   def CreateFromFile(java_file_name, options):
     contents = file(java_file_name).read()
     fully_qualified_class = ExtractFullyQualifiedJavaClassName(java_file_name,
                                                                contents)
     return JNIFromJavaSource(contents, fully_qualified_class, options)
@@ skipping 712 matching lines @@
     root_name = os.path.splitext(os.path.basename(input_file))[0]
     output_file = os.path.join(options.output_dir, root_name) + '_jni.h'
   if options.jarjar:
     with open(options.jarjar) as f:
       JniParams.SetJarJarMappings(f.read())
   GenerateJNIHeader(input_file, output_file, options)
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv))