diff --git a/core/binary.mk b/core/binary.mk
index 0c6d8e8..c2e3069 100644
--- a/core/binary.mk
+++ b/core/binary.mk
@@ -1412,8 +1412,7 @@
     # Set up global default checks
     my_tidy_checks := $(WITH_TIDY_CHECKS)
     ifeq ($(my_tidy_checks),)
-      # AOSP source did not follow Google readability rules.
-      my_tidy_checks := -*,google*,-google-readability*
+      my_tidy_checks := $(call default_global_tidy_checks,$(LOCAL_PATH))
     endif
     # Append local clang-tidy checks.
     ifneq ($(LOCAL_TIDY_CHECKS),)
diff --git a/core/ccache.mk b/core/ccache.mk
index 5c2ae23..d67bce6 100644
--- a/core/ccache.mk
+++ b/core/ccache.mk
@@ -17,7 +17,7 @@
 ifneq ($(filter-out false,$(USE_CCACHE)),)
   # The default check uses size and modification time, causing false misses
   # since the mtime depends when the repo was checked out
-  export CCACHE_COMPILERCHECK := content
+  export CCACHE_COMPILERCHECK ?= content
 
   # See man page, optimizations to get more cache hits
   # implies that __DATE__ and __TIME__ are not critical for functionality.
diff --git a/core/clang/config.mk b/core/clang/config.mk
index 39862be..4ae0bc5 100644
--- a/core/clang/config.mk
+++ b/core/clang/config.mk
@@ -177,3 +177,5 @@
 # We don't have 32-bit prebuilt libLLVM/libclang, so force to build them from source.
 FORCE_BUILD_LLVM_COMPONENTS := true
 endif
+
+include $(BUILD_SYSTEM)/clang/tidy.mk
diff --git a/core/clang/tidy.mk b/core/clang/tidy.mk
new file mode 100644
index 0000000..e8a69ef
--- /dev/null
+++ b/core/clang/tidy.mk
@@ -0,0 +1,57 @@
+#
+# Copyright (C) 2016 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+# Most Android source files are not clang-tidy clean yet.
+# Global tidy checks include only google* minus google-readability*.
+DEFAULT_GLOBAL_TIDY_CHECKS := \
+  -*,google*,-google-readability*
+
+# Disable google style rules usually not followed by external projects.
+# Every word in DEFAULT_LOCAL_TIDY_CHECKS list has the following format:
+#   <local_path_prefix>:,<tidy-check-pattern>
+# The tidy-check-patterns of all matching local_path_prefixes will be used.
+# For example, external/google* projects will have:
+#   ,-google-build-using-namespace,-google-explicit-constructor
+#   ,-google-runtime-int,google-runtime-int
+# where google-runtime-int is enabled at the end.
+DEFAULT_LOCAL_TIDY_CHECKS := \
+  external/:,-google-build-using-namespace \
+  external/:,-google-explicit-constructor \
+  external/:,-google-runtime-int \
+  external/google:,google-runtime-int \
+  external/webrtc/:,google-runtime-int \
+
+# Returns 2nd word of $(1) if $(2) has prefix of the 1st word of $(1).
+define find_default_local_tidy_check2
+$(if $(filter $(word 1,$(1))%,$(2)/),$(word 2,$(1)))
+endef
+
+# Returns 2nd part of $(1) if $(2) has prefix of the 1st part of $(1).
+define find_default_local_tidy_check
+$(call find_default_local_tidy_check2,$(subst :,$(space),$(1)),$(2))
+endef
+
+# Returns concatenated tidy check patterns from the
+# DEFAULT_GLOBAL_TIDY_CHECKS and all matched patterns
+# in DEFAULT_LOCAL_TIDY_CHECKS based on given directory path $(1).
+define default_global_tidy_checks
+$(subst $(space),, \
+  $(DEFAULT_GLOBAL_TIDY_CHECKS) \
+  $(foreach pattern,$(DEFAULT_LOCAL_TIDY_CHECKS), \
+    $(call find_default_local_tidy_check,$(pattern),$(1)) \
+  ) \
+)
+endef
diff --git a/core/dynamic_binary.mk b/core/dynamic_binary.mk
index f11803d..58f76b0 100644
--- a/core/dynamic_binary.mk
+++ b/core/dynamic_binary.mk
@@ -116,8 +116,17 @@
   $(LOCAL_STRIP_MODULE_$($(my_prefix)$(LOCAL_2ND_ARCH_VAR_PREFIX)ARCH)) \
   $(LOCAL_STRIP_MODULE))
 ifeq ($(my_strip_module),)
+  my_strip_module := mini-debug-info
+endif
+
+ifeq ($(my_strip_module),mini-debug-info)
+# Don't use mini-debug-info on mips (both 32-bit and 64-bit). objcopy checks that all
+# SH_MIPS_DWARF sections having name prefix .debug_ or .zdebug_, so there seems no easy
+# way using objcopy to remove all debug sections except .debug_frame on mips.
+ifneq ($(filter mips mips64,$($(my_prefix)$(LOCAL_2ND_ARCH_VAR_PREFIX)ARCH)),)
   my_strip_module := true
 endif
+endif
 
 $(strip_output): PRIVATE_STRIP := $($(LOCAL_2ND_ARCH_VAR_PREFIX)TARGET_STRIP)
 $(strip_output): PRIVATE_OBJCOPY := $($(LOCAL_2ND_ARCH_VAR_PREFIX)TARGET_OBJCOPY)
diff --git a/core/java_common.mk b/core/java_common.mk
index e17691b..1b12ea2 100644
--- a/core/java_common.mk
+++ b/core/java_common.mk
@@ -133,6 +133,15 @@
   extra_jar_args :=
 endif # java_resource_file_groups
 
+#####################################
+## Warn if there is unrecognized file in LOCAL_SRC_FILES.
+my_unknown_src_files := $(filter-out \
+  %.java %.aidl %.proto %.logtags %.fs %.rs, \
+  $(LOCAL_SRC_FILES) $(LOCAL_INTERMEDIATE_SOURCES) $(LOCAL_GENERATED_SOURCES))
+ifneq ($(my_unknown_src_files),)
+$(warning $(LOCAL_MODULE_MAKEFILE): $(LOCAL_MODULE): Unused source files: $(my_unknown_src_files))
+endif
+
 ######################################
 ## PRIVATE java vars
 # LOCAL_SOURCE_FILES_ALL_GENERATED is set only if the module does not have static source files,