Android: Don't require RegisterNatives if there are none

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 830 matching lines @@
     if self.options.native_exports_optional:
       early_exit = """\
   if (base::android::IsManualJniRegistrationDisabled()) return true;
 """
 
     natives = self.GetRegisterNativesImplString()
     values = {'REGISTER_NATIVES_SIGNATURE': signature,
               'EARLY_EXIT': early_exit,
               'NATIVES': natives,
              }
-    return template.substitute(values)
+
+    func_declaration = ''
+    if not natives:
+      func_declaration = Template("""\
+${REGISTER_NATIVES_SIGNATURE} __attribute__((unused));

[no sievers, 2016/08/01 21:42:41]

This can only be used on the declaration, not the definition :/

[Torne, 2016/08/02 12:23:13]

Yeah attributes are annoying :)

+""").substitute(values)
+
+    return func_declaration + template.substitute(values)
 
   def GetRegisterNativesImplString(self):
     """Returns the shared implementation for RegisterNatives."""
     if not self.options.native_exports_optional:
       return ''
 
     template = Template("""\
   const int kMethods${JAVA_CLASS}Size = arraysize(kMethods${JAVA_CLASS});
 
   if (env->RegisterNatives(${JAVA_CLASS}_clazz(env),
@@ skipping 232 matching lines @@
 static ${RETURN_TYPE} Java_${JAVA_CLASS}_${METHOD_ID_VAR_NAME}(\
 JNIEnv* env${FIRST_PARAM_IN_DECLARATION}${PARAMS_IN_DECLARATION})""")
     function_header_template = Template("""\
 ${FUNCTION_SIGNATURE} {""")
     function_header_with_unused_template = Template("""\
 ${FUNCTION_SIGNATURE} __attribute__ ((unused));
 ${FUNCTION_SIGNATURE} {""")
     template = Template("""
 static base::subtle::AtomicWord g_${JAVA_CLASS}_${METHOD_ID_VAR_NAME} = 0;
 ${FUNCTION_HEADER}
-  /* Must call RegisterNativesImpl()  */
   CHECK_CLAZZ(env, ${FIRST_PARAM_IN_CALL},
       ${JAVA_CLASS}_clazz(env)${OPTIONAL_ERROR_RETURN});
   jmethodID method_id =
     ${GET_METHOD_ID_IMPL}
   ${RETURN_DECLARATION}
      ${PRE_CALL}env->${ENV_CALL}(${FIRST_PARAM_IN_CALL},
           method_id${PARAMS_IN_CALL})${POST_CALL};
   ${CHECK_EXCEPTION}
   ${RETURN_CLAUSE}
 }""")
@@ skipping 242 matching lines @@
   GenerateJNIHeader(input_file, output_file, options)
 
   if options.depfile:
     build_utils.WriteDepfile(
         options.depfile,
         build_utils.GetPythonDependencies())
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv))