Add "WITH_SYNTAX_CHECK=1 make ..."

The new option WITH_SYNTAX_CHECK=1 instructs build system to invoke
"clang -fsyntax-only" to utilize clang's better diagnostics before calling
LOCAL_CC/LOCAL_CXX for code generation.  The compilation time is slightly
longer, and the generated object file should be the same as w/o WITH_SYNTAX_CHECK

Project use lots of GCC extensions (eg. nested function) not supported
by clang may opt out by adding LOCAL_NO_SYNTAX_CHECK:=true

Change-Id: I5689586788ef049bd967364f71f31f1e359bd121

core/binary.mk

@@ -170,6 +170,16 @@ $(LOCAL_INTERMEDIATE_TARGETS): PRIVATE_TARGET_GLOBAL_CPPFLAGS := $(TARGET_GLOBAL
 $(LOCAL_INTERMEDIATE_TARGETS): PRIVATE_NO_DEFAULT_COMPILER_FLAGS := \
     $(strip $(LOCAL_NO_DEFAULT_COMPILER_FLAGS))
 
+ifeq ($(strip $(WITH_SYNTAX_CHECK)),)
+  LOCAL_NO_SYNTAX_CHECK := true
+endif
+
+ifneq ($(strip $(LOCAL_IS_HOST_MODULE)),)
+  my_syntax_arch := host
+else
+  my_syntax_arch := $(TARGET_ARCH)
+endif
+
 ifeq ($(strip $(LOCAL_CC)),)
   ifeq ($(strip $(LOCAL_CLANG)),true)
     LOCAL_CC := $(CLANG)
@@ -177,6 +187,9 @@ ifeq ($(strip $(LOCAL_CC)),)
     LOCAL_CC := $($(my_prefix)CC)
   endif
 endif
+ifneq ($(LOCAL_NO_SYNTAX_CHECK),true)
+  LOCAL_CC := $(SYNTAX_TOOLS_PREFIX)/ccc-syntax $(my_syntax_arch) "$(LOCAL_CC)"
+endif
 $(LOCAL_INTERMEDIATE_TARGETS): PRIVATE_CC := $(LOCAL_CC)
 
 ifeq ($(strip $(LOCAL_CXX)),)
@@ -186,6 +199,9 @@ ifeq ($(strip $(LOCAL_CXX)),)
     LOCAL_CXX := $($(my_prefix)CXX)
   endif
 endif
+ifneq ($(LOCAL_NO_SYNTAX_CHECK),true)
+  LOCAL_CXX := $(SYNTAX_TOOLS_PREFIX)/cxx-syntax $(my_syntax_arch) "$(LOCAL_CXX)"
+endif
 $(LOCAL_INTERMEDIATE_TARGETS): PRIVATE_CXX := $(LOCAL_CXX)
 
 # TODO: support a mix of standard extensions so that this isn't necessary

core/clear_vars.mk

@@ -137,6 +137,7 @@ LOCAL_ADDITIONAL_CERTIFICATES:=
 LOCAL_PREBUILT_MODULE_FILE:=
 LOCAL_POST_INSTALL_CMD:=
 LOCAL_DIST_BUNDLED_BINARIES:=
+LOCAL_NO_SYNTAX_CHECK:=
 
 # Trim MAKEFILE_LIST so that $(call my-dir) doesn't need to
 # iterate over thousands of entries every time.

core/config.mk

@@ -247,6 +247,15 @@ TARGET_TOOLCHAIN_ROOT := $(patsubst %/, %, $(dir $(TARGET_TOOLCHAIN_ROOT)))
 TARGET_TOOLCHAIN_ROOT := $(wildcard $(TARGET_TOOLCHAIN_ROOT))
 endif
 
+# Disable WITH_SYNTAX_CHECK if tool can't be found
+SYNTAX_TOOLS_PREFIX := prebuilts/clang/$(HOST_PREBUILT_TAG)/host/3.3/bin
+ifneq ($(strip $(WITH_SYNTAX_CHECK)),)
+  ifeq ($(wildcard $(SYNTAX_TOOLS_PREFIX)/ccc-syntax),)
+    $(warning *** Disable WITH_SYNTAX_CHECK because $(SYNTAX_TOOLS_PREFIX)/ccc-syntax does not exist)
+    WITH_SYNTAX_CHECK :=
+  endif
+endif
+
 # Pick a Java compiler.
 include $(BUILD_SYSTEM)/combo/javac.mk