diff --git a/cc/compiler.go b/cc/compiler.go
index 8f119cf..10cec8c 100644
--- a/cc/compiler.go
+++ b/cc/compiler.go
@@ -392,6 +392,12 @@
 			fmt.Sprintf("${config.%sGlobalCflags}", hod))
 	}
 
+	if flags.Clang {
+		if strings.HasPrefix(android.PathForModuleSrc(ctx).String(), "external/") {
+			flags.GlobalFlags = append([]string{"${config.ClangExternalCflags}"}, flags.GlobalFlags...)
+		}
+	}
+
 	if ctx.Device() {
 		if Bool(compiler.Properties.Rtti) {
 			flags.CppFlags = append(flags.CppFlags, "-frtti")
diff --git a/cc/config/clang.go b/cc/config/clang.go
index ba1cd3c..22e428f 100644
--- a/cc/config/clang.go
+++ b/cc/config/clang.go
@@ -182,6 +182,11 @@
 		// compatibility.
 		"-Wno-c++98-compat-extra-semi",
 	}, " "))
+
+	// Extra cflags for projects under external/ directory
+	pctx.StaticVariable("ClangExtraExternalCflags", strings.Join([]string{
+		// TODO(yikong): Move -Wno flags here
+	}, " "))
 }
 
 func ClangFilterUnknownCflags(cflags []string) []string {
diff --git a/cc/config/global.go b/cc/config/global.go
index 06f6f9a..c734c2e 100644
--- a/cc/config/global.go
+++ b/cc/config/global.go
@@ -170,6 +170,8 @@
 	pctx.StaticVariable("CommonClangGlobalCppflags",
 		strings.Join(append(ClangFilterUnknownCflags(commonGlobalCppflags), "${ClangExtraCppflags}"), " "))
 
+	pctx.StaticVariable("ClangExternalCflags", "${ClangExtraExternalCflags}")
+
 	// Everything in these lists is a crime against abstraction and dependency tracking.
 	// Do not add anything to this list.
 	pctx.PrefixedExistentPathsForSourcesVariable("CommonGlobalIncludes", "-I",
diff --git a/cc/makevars.go b/cc/makevars.go
index c95bad2..d036bb6 100644
--- a/cc/makevars.go
+++ b/cc/makevars.go
@@ -83,6 +83,7 @@
 	ctx.Strict("RS_LLVM_AS", "${config.RSLLVMPrebuiltsPath}/llvm-as")
 	ctx.Strict("RS_LLVM_LINK", "${config.RSLLVMPrebuiltsPath}/llvm-link")
 
+	ctx.Strict("CLANG_EXTERNAL_CFLAGS", "${config.ClangExternalCflags}")
 	ctx.Strict("GLOBAL_CFLAGS_NO_OVERRIDE", "${config.NoOverrideGlobalCflags}")
 	ctx.Strict("GLOBAL_CLANG_CFLAGS_NO_OVERRIDE", "${config.ClangExtraNoOverrideCflags}")
 	ctx.Strict("GLOBAL_CPPFLAGS_NO_OVERRIDE", "")