diff --git a/Android.bp b/Android.bp
index 45e661e..d6260b4 100644
--- a/Android.bp
+++ b/Android.bp
@@ -116,3 +116,13 @@
 dex_bootjars {
     name: "dex_bootjars",
 }
+
+// Pseudo-test that's run on checkbuilds to ensure that get_clang_version can
+// parse cc/config/global.go.
+genrule {
+    name: "get_clang_version_test",
+    cmd: "$(location get_clang_version) > $(out)",
+    tools: ["get_clang_version"],
+    srcs: ["cc/config/global.go"],
+    out: ["clang-prebuilts-version.txt"],
+}
diff --git a/README.md b/README.md
index b7e93f4..10ddd73 100644
--- a/README.md
+++ b/README.md
@@ -213,8 +213,8 @@
 
 A module name's **scope** is the smallest namespace containing it. Suppose a
 source tree has `device/my` and `device/my/display` namespaces. If `libfoo`
-module is defined in `device/co/display/lib/Android.bp`, its namespace is
-`device/co/display`.
+module is defined in `device/my/display/lib/Android.bp`, its namespace is
+`device/my/display`.
 
 The name uniqueness thus means that module's name is unique within its scope. In
 other words, "//_scope_:_name_" is globally unique module reference, e.g,
diff --git a/apex/prebuilt.go b/apex/prebuilt.go
index f783172..1bb0fb5 100644
--- a/apex/prebuilt.go
+++ b/apex/prebuilt.go
@@ -376,6 +376,12 @@
 			}
 		}
 
+		// Ignore any modules that do not implement ApexModule as they cannot have an APEX specific
+		// variant.
+		if _, ok := child.(android.ApexModule); !ok {
+			return false
+		}
+
 		// Strip off the prebuilt_ prefix if present before storing content to ensure consistent
 		// behavior whether there is a corresponding source module present or not.
 		depName = android.RemoveOptionalPrebuiltPrefix(depName)
diff --git a/cc/cc.go b/cc/cc.go
index 15cb39a..0aa1014 100644
--- a/cc/cc.go
+++ b/cc/cc.go
@@ -571,7 +571,8 @@
 	sharedLibs []string
 	// Note nil and [] are semantically distinct. [] prevents linking against the defaults (usually
 	// libc, libm, etc.)
-	systemSharedLibs []string
+	systemSharedLibs  []string
+	defaultSharedLibs []string
 }
 
 // installer is the interface for an installer helper object. This helper is responsible for
diff --git a/cc/cc_test.go b/cc/cc_test.go
index 401fd6f..0a74e58 100644
--- a/cc/cc_test.go
+++ b/cc/cc_test.go
@@ -4046,12 +4046,12 @@
 		"${config.ArmToolchainClangCflags}",
 		"${config.ArmClangArmv7ANeonCflags}",
 		"${config.ArmClangGenericCflags}",
-		"export_include_dirs",
-		"linux_export_include_dirs",
-		"android_export_include_dirs",
-		"arm_export_include_dirs",
-		"lib32_export_include_dirs",
 		"android_arm_export_include_dirs",
+		"lib32_export_include_dirs",
+		"arm_export_include_dirs",
+		"android_export_include_dirs",
+		"linux_export_include_dirs",
+		"export_include_dirs",
 		"android_arm_local_include_dirs",
 		"lib32_local_include_dirs",
 		"arm_local_include_dirs",
diff --git a/cc/compiler.go b/cc/compiler.go
index 78a5a5d..69ead30 100644
--- a/cc/compiler.go
+++ b/cc/compiler.go
@@ -92,7 +92,7 @@
 
 	// list of generated headers to add to the include path. These are the names
 	// of genrule modules.
-	Generated_headers []string `android:"arch_variant"`
+	Generated_headers []string `android:"arch_variant,variant_prepend"`
 
 	// pass -frtti instead of -fno-rtti
 	Rtti *bool
diff --git a/cc/library.go b/cc/library.go
index 95f9b0a..4fd7c74 100644
--- a/cc/library.go
+++ b/cc/library.go
@@ -147,11 +147,12 @@
 
 	Cflags []string `android:"arch_variant"`
 
-	Enabled            *bool    `android:"arch_variant"`
-	Whole_static_libs  []string `android:"arch_variant"`
-	Static_libs        []string `android:"arch_variant"`
-	Shared_libs        []string `android:"arch_variant"`
-	System_shared_libs []string `android:"arch_variant"`
+	Enabled             *bool    `android:"arch_variant"`
+	Whole_static_libs   []string `android:"arch_variant"`
+	Static_libs         []string `android:"arch_variant"`
+	Shared_libs         []string `android:"arch_variant"`
+	System_shared_libs  []string `android:"arch_variant"`
+	Default_shared_libs []string `android:"arch_variant"`
 
 	Export_shared_lib_headers []string `android:"arch_variant"`
 	Export_static_lib_headers []string `android:"arch_variant"`
@@ -184,11 +185,11 @@
 	// be added to the include path (using -I) for this module and any module that links
 	// against this module.  Directories listed in export_include_dirs do not need to be
 	// listed in local_include_dirs.
-	Export_include_dirs []string `android:"arch_variant"`
+	Export_include_dirs []string `android:"arch_variant,variant_prepend"`
 
 	// list of directories that will be added to the system include path
 	// using -isystem for this module and any module that links against this module.
-	Export_system_include_dirs []string `android:"arch_variant"`
+	Export_system_include_dirs []string `android:"arch_variant,variant_prepend"`
 
 	Target struct {
 		Vendor, Product struct {
@@ -1156,11 +1157,17 @@
 		if library.StaticProperties.Static.System_shared_libs != nil {
 			library.baseLinker.Properties.System_shared_libs = library.StaticProperties.Static.System_shared_libs
 		}
+		if library.StaticProperties.Static.Default_shared_libs != nil {
+			library.baseLinker.Properties.Default_shared_libs = library.StaticProperties.Static.Default_shared_libs
+		}
 	} else if library.shared() {
 		// Compare with nil because an empty list needs to be propagated.
 		if library.SharedProperties.Shared.System_shared_libs != nil {
 			library.baseLinker.Properties.System_shared_libs = library.SharedProperties.Shared.System_shared_libs
 		}
+		if library.SharedProperties.Shared.Default_shared_libs != nil {
+			library.baseLinker.Properties.Default_shared_libs = library.SharedProperties.Shared.Default_shared_libs
+		}
 	}
 
 	deps = library.baseLinker.linkerDeps(ctx, deps)
@@ -1242,6 +1249,11 @@
 	} else {
 		specifiedDeps.systemSharedLibs = append(specifiedDeps.systemSharedLibs, properties.System_shared_libs...)
 	}
+	if specifiedDeps.defaultSharedLibs == nil {
+		specifiedDeps.defaultSharedLibs = properties.Default_shared_libs
+	} else {
+		specifiedDeps.defaultSharedLibs = append(specifiedDeps.defaultSharedLibs, properties.Default_shared_libs...)
+	}
 
 	specifiedDeps.sharedLibs = android.FirstUniqueStrings(specifiedDeps.sharedLibs)
 	if len(specifiedDeps.systemSharedLibs) > 0 {
@@ -1249,6 +1261,11 @@
 		// retained.
 		specifiedDeps.systemSharedLibs = android.FirstUniqueStrings(specifiedDeps.systemSharedLibs)
 	}
+	if len(specifiedDeps.defaultSharedLibs) > 0 {
+		// Skip this if defaultSharedLibs is either nil or [], to ensure they are
+		// retained.
+		specifiedDeps.defaultSharedLibs = android.FirstUniqueStrings(specifiedDeps.defaultSharedLibs)
+	}
 	return specifiedDeps
 }
 
diff --git a/cc/library_sdk_member.go b/cc/library_sdk_member.go
index 9010a1a..9ad2742 100644
--- a/cc/library_sdk_member.go
+++ b/cc/library_sdk_member.go
@@ -258,6 +258,12 @@
 		outputProperties.AddPropertyWithTag("system_shared_libs", libInfo.SystemSharedLibs, builder.SdkMemberReferencePropertyTag(false))
 	}
 
+	// SystemSharedLibs needs to be propagated if it's a list, even if it's empty,
+	// so check for non-nil instead of nonzero length.
+	if libInfo.DefaultSharedLibs != nil {
+		outputProperties.AddPropertyWithTag("default_shared_libs", libInfo.DefaultSharedLibs, builder.SdkMemberReferencePropertyTag(false))
+	}
+
 	// Map from property name to the include dirs to add to the prebuilt module in the snapshot.
 	includeDirs := make(map[string][]string)
 
@@ -387,6 +393,12 @@
 	// This field is exported as its contents may not be arch specific.
 	SystemSharedLibs []string `android:"arch_variant"`
 
+	// The set of default shared libraries. Note nil and [] are semantically
+	// distinct - see BaseLinkerProperties.Default_shared_libs.
+	//
+	// This field is exported as its contents may not be arch specific.
+	DefaultSharedLibs []string `android:"arch_variant"`
+
 	// The specific stubs version for the lib variant, or empty string if stubs
 	// are not in use.
 	//
@@ -462,6 +474,7 @@
 			}
 		}
 		p.SystemSharedLibs = specifiedDeps.systemSharedLibs
+		p.DefaultSharedLibs = specifiedDeps.defaultSharedLibs
 	}
 	p.ExportedGeneratedHeaders = exportedInfo.GeneratedHeaders
 
diff --git a/cc/linker.go b/cc/linker.go
index 7b16b40..13df232 100644
--- a/cc/linker.go
+++ b/cc/linker.go
@@ -45,11 +45,18 @@
 	// list of module-specific flags that will be used for all link steps
 	Ldflags []string `android:"arch_variant"`
 
-	// list of system libraries that will be dynamically linked to
-	// shared library and executable modules.  If unset, generally defaults to libc,
-	// libm, and libdl.  Set to [] to prevent linking against the defaults.
+	// list of system libraries that will be dynamically linked to shared library and executable
+	// modules that build against bionic (device or Linux bionic modules).  If unset, generally
+	// defaults to libc, libm, and libdl.  Set to [] to prevent linking against the defaults.
+	// Equivalent to default_shared_libs for modules that build against bionic, and ignored on
+	// modules that do not build against bionic.
 	System_shared_libs []string `android:"arch_variant"`
 
+	// list of system libraries that will be dynamically linked to shared library and executable
+	// modules.  If unset, generally defaults to libc, libm, and libdl.  Set to [] to prevent
+	// linking against the defaults.  Equivalent to system_shared_libs, but applies to all modules.
+	Default_shared_libs []string `android:"arch_variant"`
+
 	// allow the module to contain undefined symbols.  By default,
 	// modules cannot contain undefined symbols that are not satisified by their immediate
 	// dependencies.  Set this flag to true to remove --no-undefined from the linker flags.
@@ -231,6 +238,19 @@
 	linker.Properties.Ldflags = append(linker.Properties.Ldflags, flags...)
 }
 
+// overrideDefaultSharedLibraries returns the contents of the default_shared_libs or
+// system_shared_libs properties, and records an error if both are set.
+func (linker *baseLinker) overrideDefaultSharedLibraries(ctx BaseModuleContext) []string {
+	if linker.Properties.System_shared_libs != nil && linker.Properties.Default_shared_libs != nil {
+		ctx.PropertyErrorf("system_shared_libs", "cannot be specified if default_shared_libs is also specified")
+	}
+	if ctx.toolchain().Bionic() && linker.Properties.System_shared_libs != nil {
+		// system_shared_libs is only honored when building against bionic.
+		return linker.Properties.System_shared_libs
+	}
+	return linker.Properties.Default_shared_libs
+}
+
 // linkerInit initializes dynamic properties of the linker (such as runpath).
 func (linker *baseLinker) linkerInit(ctx BaseModuleContext) {
 	if ctx.toolchain().Is64Bit() {
@@ -331,22 +351,22 @@
 		deps.SharedLibs = append(deps.SharedLibs, linker.Properties.Target.Platform.Shared_libs...)
 	}
 
+	deps.SystemSharedLibs = linker.overrideDefaultSharedLibraries(ctx)
+	// In Bazel conversion mode, variations have not been specified, so SystemSharedLibs may
+	// inaccuarately appear unset, which can cause issues with circular dependencies.
+	if deps.SystemSharedLibs == nil && !ctx.BazelConversionMode() {
+		// Provide a default set of shared libraries if default_shared_libs and system_shared_libs
+		// are unspecified.  Note: If an empty list [] is specified, it implies that the module
+		// declines the default shared libraries.
+		deps.SystemSharedLibs = append(deps.SystemSharedLibs, ctx.toolchain().DefaultSharedLibraries()...)
+	}
+
 	if ctx.toolchain().Bionic() {
 		// libclang_rt.builtins has to be last on the command line
 		if !Bool(linker.Properties.No_libcrt) && !ctx.header() {
 			deps.LateStaticLibs = append(deps.LateStaticLibs, config.BuiltinsRuntimeLibrary(ctx.toolchain()))
 		}
 
-		deps.SystemSharedLibs = linker.Properties.System_shared_libs
-		// In Bazel conversion mode, variations have not been specified, so SystemSharedLibs may
-		// inaccuarately appear unset, which can cause issues with circular dependencies.
-		if deps.SystemSharedLibs == nil && !ctx.BazelConversionMode() {
-			// Provide a default system_shared_libs if it is unspecified. Note: If an
-			// empty list [] is specified, it implies that the module declines the
-			// default system_shared_libs.
-			deps.SystemSharedLibs = append(deps.SystemSharedLibs, ctx.toolchain().DefaultSharedLibraries()...)
-		}
-
 		if inList("libdl", deps.SharedLibs) {
 			// If system_shared_libs has libc but not libdl, make sure shared_libs does not
 			// have libdl to avoid loading libdl before libc.
@@ -573,6 +593,11 @@
 	} else {
 		specifiedDeps.systemSharedLibs = append(specifiedDeps.systemSharedLibs, linker.Properties.System_shared_libs...)
 	}
+	if specifiedDeps.defaultSharedLibs == nil {
+		specifiedDeps.defaultSharedLibs = linker.Properties.Default_shared_libs
+	} else {
+		specifiedDeps.defaultSharedLibs = append(specifiedDeps.defaultSharedLibs, linker.Properties.Default_shared_libs...)
+	}
 
 	return specifiedDeps
 }
diff --git a/java/base.go b/java/base.go
index 77f6fc6..6b81196 100644
--- a/java/base.go
+++ b/java/base.go
@@ -870,6 +870,7 @@
 	if aaptSrcJar != nil {
 		srcJars = append(srcJars, aaptSrcJar)
 	}
+	srcFiles = srcFiles.FilterOutByExt(".srcjar")
 
 	if j.properties.Jarjar_rules != nil {
 		j.expandJarjarRules = android.PathForModuleSrc(ctx, *j.properties.Jarjar_rules)
diff --git a/java/bootclasspath_fragment_test.go b/java/bootclasspath_fragment_test.go
index b469886..3d0e155 100644
--- a/java/bootclasspath_fragment_test.go
+++ b/java/bootclasspath_fragment_test.go
@@ -197,7 +197,7 @@
 				],
 			},
 			core_platform_api: {
-				stub_libs: ["mycoreplatform"],
+				stub_libs: ["mycoreplatform.stubs"],
 			},
 		}
 
diff --git a/java/hiddenapi_modular.go b/java/hiddenapi_modular.go
index 7e10fab..c4832d2 100644
--- a/java/hiddenapi_modular.go
+++ b/java/hiddenapi_modular.go
@@ -586,6 +586,13 @@
 // addStubDexJar adds a stub dex jar path provided by the specified module for the specified scope.
 func (s StubDexJarsByModule) addStubDexJar(ctx android.ModuleContext, module android.Module, scope *HiddenAPIScope, stubDexJar android.Path) {
 	name := android.RemoveOptionalPrebuiltPrefix(module.Name())
+
+	// Each named module provides one dex jar for each scope. However, in some cases different API
+	// versions of a single classes are provided by separate modules. e.g. the core platform
+	// version of java.lang.Object is provided by the legacy.art.module.platform.api module but the
+	// public version is provided by the art.module.public.api module. In those cases it is necessary
+	// to treat all those modules as they were the same name, otherwise it will result in multiple
+	// definitions of a single class being passed to hidden API processing which will cause an error.
 	if name == scope.nonUpdatablePrebuiltModule || name == scope.nonUpdatableSourceModule {
 		// Treat all *android-non-updatable* modules as if they were part of an android-non-updatable
 		// java_sdk_library.
@@ -606,6 +613,14 @@
 		// conscrypt.module.public.api java_sdk_library which will be the case once the former has been
 		// migrated to a module_lib API.
 		name = "conscrypt.module.public.api"
+	} else if d, ok := module.(SdkLibraryComponentDependency); ok {
+		sdkLibraryName := d.SdkLibraryName()
+		if sdkLibraryName != nil {
+			// The module is a component of a java_sdk_library so use the name of the java_sdk_library.
+			// e.g. if this module is `foo.system.stubs` and is part of the `foo` java_sdk_library then
+			// use `foo` as the name.
+			name = *sdkLibraryName
+		}
 	}
 	stubDexJarsByScope := s[name]
 	if stubDexJarsByScope == nil {
diff --git a/java/jacoco.go b/java/jacoco.go
index 9162161..e11c2ce 100644
--- a/java/jacoco.go
+++ b/java/jacoco.go
@@ -94,7 +94,7 @@
 	if len(includes) > 0 {
 		specs += strings.Join(includes, " ")
 	} else {
-		specs += "**/*.class"
+		specs += "'**/*.class'"
 	}
 	return specs
 }
diff --git a/java/jacoco_test.go b/java/jacoco_test.go
index 91f0553..1882908 100644
--- a/java/jacoco_test.go
+++ b/java/jacoco_test.go
@@ -74,7 +74,7 @@
 		{
 			name:     "implicit wildcard",
 			includes: []string{},
-			out:      "**/*.class",
+			out:      "'**/*.class'",
 		},
 		{
 			name:     "only include",
diff --git a/java/lint_defaults.txt b/java/lint_defaults.txt
index 2de05b0..75de7dc 100644
--- a/java/lint_defaults.txt
+++ b/java/lint_defaults.txt
@@ -78,3 +78,7 @@
 --disable_check HardcodedDebugMode
 
 --warning_check QueryAllPackagesPermission
+
+--warning_check CoarseFineLocation
+--warning_check IntentFilterExportedReceiver
+--warning_check RemoteViewLayout
diff --git a/java/sdk.go b/java/sdk.go
index cbd873d..d1b899e 100644
--- a/java/sdk.go
+++ b/java/sdk.go
@@ -175,10 +175,24 @@
 		}
 	case android.SdkModule:
 		// TODO(146757305): provide .apk and .aidl that have more APIs for modules
-		return toModule([]string{"android_module_lib_stubs_current"}, "framework-res", nonUpdatableFrameworkAidlPath(ctx))
+		return sdkDep{
+			useModule:          true,
+			bootclasspath:      []string{"android_module_lib_stubs_current", config.DefaultLambdaStubsLibrary},
+			systemModules:      "core-module-lib-stubs-system-modules",
+			java9Classpath:     []string{"android_module_lib_stubs_current"},
+			frameworkResModule: "framework-res",
+			aidl:               android.OptionalPathForPath(nonUpdatableFrameworkAidlPath(ctx)),
+		}
 	case android.SdkSystemServer:
 		// TODO(146757305): provide .apk and .aidl that have more APIs for modules
-		return toModule([]string{"android_system_server_stubs_current"}, "framework-res", sdkFrameworkAidlPath(ctx))
+		return sdkDep{
+			useModule:          true,
+			bootclasspath:      []string{"android_system_server_stubs_current", config.DefaultLambdaStubsLibrary},
+			systemModules:      "core-module-lib-stubs-system-modules",
+			java9Classpath:     []string{"android_system_server_stubs_current"},
+			frameworkResModule: "framework-res",
+			aidl:               android.OptionalPathForPath(sdkFrameworkAidlPath(ctx)),
+		}
 	default:
 		panic(fmt.Errorf("invalid sdk %q", sdkVersion.Raw))
 	}
diff --git a/java/sdk_library.go b/java/sdk_library.go
index 567e292..ed9aeff 100644
--- a/java/sdk_library.go
+++ b/java/sdk_library.go
@@ -675,10 +675,13 @@
 		return false
 	}
 
+	namePtr := proptools.StringPtr(c.module.BaseModuleName())
+	c.sdkLibraryComponentProperties.SdkLibraryName = namePtr
+
 	// Only track this sdk library if this can be used as a shared library.
 	if c.sharedLibrary() {
 		// Use the name specified in the module definition as the owner.
-		c.sdkLibraryComponentProperties.SdkLibraryToImplicitlyTrack = proptools.StringPtr(c.module.BaseModuleName())
+		c.sdkLibraryComponentProperties.SdkLibraryToImplicitlyTrack = namePtr
 	}
 
 	return true
@@ -922,15 +925,19 @@
 
 func (c *commonToSdkLibraryAndImport) sdkComponentPropertiesForChildLibrary() interface{} {
 	componentProps := &struct {
+		SdkLibraryName              *string
 		SdkLibraryToImplicitlyTrack *string
 	}{}
 
+	namePtr := proptools.StringPtr(c.module.BaseModuleName())
+	componentProps.SdkLibraryName = namePtr
+
 	if c.sharedLibrary() {
 		// Mark the stubs library as being components of this java_sdk_library so that
 		// any app that includes code which depends (directly or indirectly) on the stubs
 		// library will have the appropriate <uses-library> invocation inserted into its
 		// manifest if necessary.
-		componentProps.SdkLibraryToImplicitlyTrack = proptools.StringPtr(c.module.BaseModuleName())
+		componentProps.SdkLibraryToImplicitlyTrack = namePtr
 	}
 
 	return componentProps
@@ -949,6 +956,8 @@
 
 // Properties related to the use of a module as an component of a java_sdk_library.
 type SdkLibraryComponentProperties struct {
+	// The name of the java_sdk_library/_import module.
+	SdkLibraryName *string `blueprint:"mutated"`
 
 	// The name of the java_sdk_library/_import to add to a <uses-library> entry
 	// in the AndroidManifest.xml of any Android app that includes code that references
@@ -967,6 +976,11 @@
 }
 
 // to satisfy SdkLibraryComponentDependency
+func (e *EmbeddableSdkLibraryComponent) SdkLibraryName() *string {
+	return e.sdkLibraryComponentProperties.SdkLibraryName
+}
+
+// to satisfy SdkLibraryComponentDependency
 func (e *EmbeddableSdkLibraryComponent) OptionalImplicitSdkLibrary() *string {
 	return e.sdkLibraryComponentProperties.SdkLibraryToImplicitlyTrack
 }
@@ -982,6 +996,9 @@
 type SdkLibraryComponentDependency interface {
 	UsesLibraryDependency
 
+	// SdkLibraryName returns the name of the java_sdk_library/_import module.
+	SdkLibraryName() *string
+
 	// The optional name of the sdk library that should be implicitly added to the
 	// AndroidManifest of an app that contains code which references the sdk library.
 	//
diff --git a/java/sdk_test.go b/java/sdk_test.go
index 2b18465..bb595a5 100644
--- a/java/sdk_test.go
+++ b/java/sdk_test.go
@@ -219,7 +219,7 @@
 			name:           "module_current",
 			properties:     `sdk_version: "module_current",`,
 			bootclasspath:  []string{"android_module_lib_stubs_current", "core-lambda-stubs"},
-			system:         "core-current-stubs-system-modules",
+			system:         "core-module-lib-stubs-system-modules",
 			java9classpath: []string{"android_module_lib_stubs_current"},
 			aidl:           "-pout/soong/framework_non_updatable.aidl",
 		},
@@ -227,7 +227,7 @@
 			name:           "system_server_current",
 			properties:     `sdk_version: "system_server_current",`,
 			bootclasspath:  []string{"android_system_server_stubs_current", "core-lambda-stubs"},
-			system:         "core-current-stubs-system-modules",
+			system:         "core-module-lib-stubs-system-modules",
 			java9classpath: []string{"android_system_server_stubs_current"},
 			aidl:           "-pout/soong/framework.aidl",
 		},
diff --git a/java/testing.go b/java/testing.go
index c3803c8..e2ff5cd 100644
--- a/java/testing.go
+++ b/java/testing.go
@@ -312,6 +312,7 @@
 
 	systemModules := []string{
 		"core-current-stubs-system-modules",
+		"core-module-lib-stubs-system-modules",
 		"legacy-core-platform-api-stubs-system-modules",
 		"stable-core-platform-api-stubs-system-modules",
 	}
diff --git a/scripts/Android.bp b/scripts/Android.bp
index 1c02bd0..635be10 100644
--- a/scripts/Android.bp
+++ b/scripts/Android.bp
@@ -265,3 +265,19 @@
         "linker_config_proto",
     ],
 }
+
+python_binary_host {
+    name: "get_clang_version",
+    main: "get_clang_version.py",
+    srcs: [
+        "get_clang_version.py",
+    ],
+    version: {
+        py2: {
+            enabled: false,
+        },
+        py3: {
+            enabled: true,
+        },
+    },
+}
diff --git a/scripts/get_clang_version.py b/scripts/get_clang_version.py
new file mode 100755
index 0000000..622fca1
--- /dev/null
+++ b/scripts/get_clang_version.py
@@ -0,0 +1,46 @@
+#!/usr/bin/env python
+#
+# Copyright (C) 2021 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.
+"""A tool to report the current clang version used during build"""
+
+import os
+import re
+import sys
+
+
+ANDROID_BUILD_TOP = os.environ.get("ANDROID_BUILD_TOP", ".")
+
+def get_clang_prebuilts_version(global_go):
+  # TODO(b/187231324): Get clang version from the json file once it is no longer
+  # hard-coded in global.go
+  if global_go is None:
+      global_go = ANDROID_BUILD_TOP + '/build/soong/cc/config/global.go'
+  with open(global_go) as infile:
+    contents = infile.read()
+
+  regex_rev = r'\tClangDefaultVersion\s+= "clang-(?P<rev>r\d+[a-z]?\d?)"'
+  match_rev = re.search(regex_rev, contents)
+  if match_rev is None:
+    raise RuntimeError('Parsing clang info failed')
+  return match_rev.group('rev')
+
+
+def main():
+  global_go = sys.argv[1] if len(sys.argv) > 1 else None
+  print(get_clang_prebuilts_version(global_go));
+
+
+if __name__ == '__main__':
+  main()
diff --git a/scripts/get_clang_version_test.py b/scripts/get_clang_version_test.py
new file mode 100644
index 0000000..e57df6c
--- /dev/null
+++ b/scripts/get_clang_version_test.py
@@ -0,0 +1,32 @@
+#!/usr/bin/env python
+#
+# Copyright (C) 2021 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.
+#
+"""Unit tests for get_clang_version.py."""
+
+import unittest
+
+import get_clang_version
+
+class GetClangVersionTest(unittest.TestCase):
+  """Unit tests for get_clang_version."""
+
+  def test_get_clang_version(self):
+    """Test parsing of clang prebuilts version."""
+    self.assertIsNotNone(get_clang_version.get_clang_prebuilts_version())
+
+
+if __name__ == '__main__':
+  unittest.main(verbosity=2)
diff --git a/sdk/cc_sdk_test.go b/sdk/cc_sdk_test.go
index 31555c0..98697dc 100644
--- a/sdk/cc_sdk_test.go
+++ b/sdk/cc_sdk_test.go
@@ -2189,7 +2189,7 @@
 	result := testSdkWithCc(t, `
 		sdk {
 			name: "mysdk",
-			native_shared_libs: ["sslnil", "sslempty", "sslnonempty"],
+			native_shared_libs: ["sslnil", "sslempty", "sslnonempty", "dslnil", "dslempty", "dslnonempty"],
 		}
 
 		cc_library {
@@ -2206,6 +2206,21 @@
 			name: "sslnonempty",
 			system_shared_libs: ["sslnil"],
 		}
+
+		cc_library {
+			name: "dslnil",
+			host_supported: true,
+		}
+
+		cc_library {
+			name: "dslempty",
+			default_shared_libs: [],
+		}
+
+		cc_library {
+			name: "dslnonempty",
+			default_shared_libs: ["sslnil"],
+		}
 	`)
 
 	CheckSnapshot(t, result, "mysdk", "",
@@ -2261,13 +2276,62 @@
         },
     },
 }
-`))
+
+cc_prebuilt_library_shared {
+    name: "dslnil",
+    prefer: false,
+    visibility: ["//visibility:public"],
+    apex_available: ["//apex_available:platform"],
+    compile_multilib: "both",
+    arch: {
+        arm64: {
+            srcs: ["arm64/lib/dslnil.so"],
+        },
+        arm: {
+            srcs: ["arm/lib/dslnil.so"],
+        },
+    },
+}
+
+cc_prebuilt_library_shared {
+    name: "dslempty",
+    prefer: false,
+    visibility: ["//visibility:public"],
+    apex_available: ["//apex_available:platform"],
+    compile_multilib: "both",
+    default_shared_libs: [],
+    arch: {
+        arm64: {
+            srcs: ["arm64/lib/dslempty.so"],
+        },
+        arm: {
+            srcs: ["arm/lib/dslempty.so"],
+        },
+    },
+}
+
+cc_prebuilt_library_shared {
+    name: "dslnonempty",
+    prefer: false,
+    visibility: ["//visibility:public"],
+    apex_available: ["//apex_available:platform"],
+    compile_multilib: "both",
+    default_shared_libs: ["sslnil"],
+    arch: {
+        arm64: {
+            srcs: ["arm64/lib/dslnonempty.so"],
+        },
+        arm: {
+            srcs: ["arm/lib/dslnonempty.so"],
+        },
+    },
+}`))
 
 	result = testSdkWithCc(t, `
 		sdk {
 			name: "mysdk",
 			host_supported: true,
-			native_shared_libs: ["sslvariants"],
+			native_shared_libs: ["sslvariants", "dslvariants"],
 		}
 
 		cc_library {
@@ -2279,6 +2343,16 @@
 				},
 			},
 		}
+
+		cc_library {
+			name: "dslvariants",
+			host_supported: true,
+			target: {
+				android: {
+					default_shared_libs: [],
+				},
+			},
+		}
 	`)
 
 	CheckSnapshot(t, result, "mysdk", "",
@@ -2315,6 +2389,37 @@
         },
     },
 }
+
+cc_prebuilt_library_shared {
+    name: "dslvariants",
+    prefer: false,
+    visibility: ["//visibility:public"],
+    apex_available: ["//apex_available:platform"],
+    host_supported: true,
+    compile_multilib: "both",
+    target: {
+        host: {
+            enabled: false,
+        },
+        android: {
+            default_shared_libs: [],
+        },
+        android_arm64: {
+            srcs: ["android/arm64/lib/dslvariants.so"],
+        },
+        android_arm: {
+            srcs: ["android/arm/lib/dslvariants.so"],
+        },
+        linux_glibc_x86_64: {
+            enabled: true,
+            srcs: ["linux_glibc/x86_64/lib/dslvariants.so"],
+        },
+        linux_glibc_x86: {
+            enabled: true,
+            srcs: ["linux_glibc/x86/lib/dslvariants.so"],
+        },
+    },
+}
 `),
 		checkVersionedAndroidBpContents(`
 // This is auto-generated. DO NOT EDIT.
@@ -2351,11 +2456,46 @@
     },
 }
 
+cc_prebuilt_library_shared {
+    name: "mysdk_dslvariants@current",
+    sdk_member_name: "dslvariants",
+    visibility: ["//visibility:public"],
+    apex_available: ["//apex_available:platform"],
+    host_supported: true,
+    installable: false,
+    compile_multilib: "both",
+    target: {
+        host: {
+            enabled: false,
+        },
+        android: {
+            default_shared_libs: [],
+        },
+        android_arm64: {
+            srcs: ["android/arm64/lib/dslvariants.so"],
+        },
+        android_arm: {
+            srcs: ["android/arm/lib/dslvariants.so"],
+        },
+        linux_glibc_x86_64: {
+            enabled: true,
+            srcs: ["linux_glibc/x86_64/lib/dslvariants.so"],
+        },
+        linux_glibc_x86: {
+            enabled: true,
+            srcs: ["linux_glibc/x86/lib/dslvariants.so"],
+        },
+    },
+}
+
 sdk_snapshot {
     name: "mysdk@current",
     visibility: ["//visibility:public"],
     host_supported: true,
-    native_shared_libs: ["mysdk_sslvariants@current"],
+    native_shared_libs: [
+        "mysdk_sslvariants@current",
+        "mysdk_dslvariants@current",
+    ],
     target: {
         host: {
             enabled: false,
diff --git a/sh/sh_binary.go b/sh/sh_binary.go
index 4805846..1647428 100644
--- a/sh/sh_binary.go
+++ b/sh/sh_binary.go
@@ -495,6 +495,10 @@
 	module := &ShTest{}
 	InitShBinaryModule(&module.ShBinary)
 	module.AddProperties(&module.testProperties)
+	// Default sh_test_host to unit_tests = true
+	if module.testProperties.Test_options.Unit_test == nil {
+		module.testProperties.Test_options.Unit_test = proptools.BoolPtr(true)
+	}
 
 	android.InitAndroidArchModule(module, android.HostSupported, android.MultilibFirst)
 	return module
diff --git a/tests/bootstrap_test.sh b/tests/bootstrap_test.sh
index 8c8dc82..1258684 100755
--- a/tests/bootstrap_test.sh
+++ b/tests/bootstrap_test.sh
@@ -486,6 +486,39 @@
   fi
 }
 
+function test_write_to_source_tree {
+  setup
+  mkdir -p a
+  cat > a/Android.bp <<EOF
+genrule {
+  name: "write_to_source_tree",
+  out: ["write_to_source_tree"],
+  cmd: "touch file_in_source_tree && touch \$(out)",
+}
+EOF
+  readonly EXPECTED_OUT=out/soong/.intermediates/a/write_to_source_tree/gen/write_to_source_tree
+  readonly ERROR_LOG=${MOCK_TOP}/out/error.log
+  readonly ERROR_MSG="Read-only file system"
+  readonly ERROR_HINT_PATTERN="BUILD_BROKEN_SRC_DIR"
+  # Test in ReadOnly source tree
+  run_ninja BUILD_BROKEN_SRC_DIR_IS_WRITABLE=false ${EXPECTED_OUT} &> /dev/null && \
+    fail "Write to source tree should not work in a ReadOnly source tree"
+
+  if grep -q "${ERROR_MSG}" ${ERROR_LOG} && grep -q "${ERROR_HINT_PATTERN}" ${ERROR_LOG} ; then
+    echo Error message and error hint found in logs >/dev/null
+  else
+    fail "Did not find Read-only error AND error hint in error.log"
+  fi
+
+  # Test in ReadWrite source tree
+  run_ninja BUILD_BROKEN_SRC_DIR_IS_WRITABLE=true ${EXPECTED_OUT} &> /dev/null || \
+    fail "Write to source tree did not succeed in a ReadWrite source tree"
+
+  if  grep -q "${ERROR_MSG}\|${ERROR_HINT_PATTERN}" ${ERROR_LOG} ; then
+    fail "Found read-only error OR error hint in error.log"
+  fi
+}
+
 function test_bp2build_smoke {
   setup
   GENERATE_BAZEL_FILES=1 run_soong
@@ -692,6 +725,7 @@
 test_glob_during_bootstrapping
 test_soong_build_rerun_iff_environment_changes
 test_dump_json_module_graph
+test_write_to_source_tree
 test_bp2build_smoke
 test_bp2build_generates_fake_ninja_file
 test_bp2build_null_build
diff --git a/tests/lib.sh b/tests/lib.sh
index 35ccea9..f1e1efa 100644
--- a/tests/lib.sh
+++ b/tests/lib.sh
@@ -126,6 +126,10 @@
   GENERATE_BAZEL_FILES=true build/soong/soong_ui.bash --make-mode --skip-ninja --skip-make --skip-soong-tests nothing
 }
 
+run_ninja() {
+  build/soong/soong_ui.bash --make-mode --skip-make --skip-soong-tests "$@"
+}
+
 info "Starting Soong integration test suite $(basename $0)"
 info "Mock top: $MOCK_TOP"
 
diff --git a/ui/build/build.go b/ui/build/build.go
index 1187aa2..1ed9014 100644
--- a/ui/build/build.go
+++ b/ui/build/build.go
@@ -28,16 +28,20 @@
 func SetupOutDir(ctx Context, config Config) {
 	ensureEmptyFileExists(ctx, filepath.Join(config.OutDir(), "Android.mk"))
 	ensureEmptyFileExists(ctx, filepath.Join(config.OutDir(), "CleanSpec.mk"))
-	if !config.SkipKati() {
-		// Run soong_build with Kati for a hybrid build, e.g. running the
-		// AndroidMk singleton and postinstall commands. Communicate this to
-		// soong_build by writing an empty .soong.kati_enabled marker file in the
-		// soong_build output directory for the soong_build primary builder to
-		// know if the user wants to run Kati after.
-		//
-		// This does not preclude running Kati for *product configuration purposes*.
-		ensureEmptyFileExists(ctx, filepath.Join(config.SoongOutDir(), ".soong.kati_enabled"))
+
+	// Potentially write a marker file for whether kati is enabled. This is used by soong_build to
+	// potentially run the AndroidMk singleton and postinstall commands.
+	// Note that the absence of the  file does not not preclude running Kati for product
+	// configuration purposes.
+	katiEnabledMarker := filepath.Join(config.SoongOutDir(), ".soong.kati_enabled")
+	if config.SkipKatiNinja() {
+		os.Remove(katiEnabledMarker)
+		// Note that we can not remove the file for SkipKati builds yet -- some continuous builds
+		// --skip-make builds rely on kati targets being defined.
+	} else if !config.SkipKati() {
+		ensureEmptyFileExists(ctx, katiEnabledMarker)
 	}
+
 	// The ninja_build file is used by our buildbots to understand that the output
 	// can be parsed as ninja output.
 	ensureEmptyFileExists(ctx, filepath.Join(config.OutDir(), "ninja_build"))
diff --git a/ui/build/config.go b/ui/build/config.go
index 4806721..7370627 100644
--- a/ui/build/config.go
+++ b/ui/build/config.go
@@ -161,6 +161,10 @@
 		ret.distDir = filepath.Join(ret.OutDir(), "dist")
 	}
 
+	if srcDirIsWritable, ok := ret.environ.Get("BUILD_BROKEN_SRC_DIR_IS_WRITABLE"); ok {
+		ret.sandboxConfig.SetSrcDirIsRO(srcDirIsWritable == "false")
+	}
+
 	ret.environ.Unset(
 		// We're already using it
 		"USE_SOONG_UI",
diff --git a/ui/build/sandbox_linux.go b/ui/build/sandbox_linux.go
index b0a6748..5b2046e 100644
--- a/ui/build/sandbox_linux.go
+++ b/ui/build/sandbox_linux.go
@@ -97,8 +97,11 @@
 			"-u", "nobody",
 			"-g", sandboxConfig.group,
 			"-R", "/",
-			"-B", sandboxConfig.srcDir,
+			// Mount tmp before srcDir
+			// srcDir is /tmp/.* in integration tests, which is a child dir of /tmp
+			// nsjail throws an error if a child dir is mounted before its parent
 			"-B", "/tmp",
+			"-B", sandboxConfig.srcDir,
 			"-B", sandboxConfig.outDir,
 		}
 
diff --git a/ui/status/ninja.go b/ui/status/ninja.go
index 765679f..2445972 100644
--- a/ui/status/ninja.go
+++ b/ui/status/ninja.go
@@ -19,6 +19,8 @@
 	"fmt"
 	"io"
 	"os"
+	"regexp"
+	"strings"
 	"syscall"
 	"time"
 
@@ -158,9 +160,10 @@
 					err = fmt.Errorf("exited with code: %d", exitCode)
 				}
 
+				outputWithErrorHint := errorHintGenerator.GetOutputWithErrorHint(msg.EdgeFinished.GetOutput(), exitCode)
 				n.status.FinishAction(ActionResult{
 					Action: started,
-					Output: msg.EdgeFinished.GetOutput(),
+					Output: outputWithErrorHint,
 					Error:  err,
 					Stats: ActionResultStats{
 						UserTime:                   msg.EdgeFinished.GetUserTime(),
@@ -219,3 +222,53 @@
 
 	return ret, nil
 }
+
+// key is pattern in stdout/stderr
+// value is error hint
+var allErrorHints = map[string]string{
+	"Read-only file system": `\nWrite to a read-only file system detected. Possible fixes include
+1. Generate file directly to out/ which is ReadWrite, #recommend solution
+2. BUILD_BROKEN_SRC_DIR_RW_ALLOWLIST := <my/path/1> <my/path/2> #discouraged, subset of source tree will be RW
+3. BUILD_BROKEN_SRC_DIR_IS_WRITABLE := true #highly discouraged, entire source tree will be RW
+`,
+}
+var errorHintGenerator = *newErrorHintGenerator(allErrorHints)
+
+type ErrorHintGenerator struct {
+	allErrorHints                map[string]string
+	allErrorHintPatternsCompiled *regexp.Regexp
+}
+
+func newErrorHintGenerator(allErrorHints map[string]string) *ErrorHintGenerator {
+	var allErrorHintPatterns []string
+	for errorHintPattern, _ := range allErrorHints {
+		allErrorHintPatterns = append(allErrorHintPatterns, errorHintPattern)
+	}
+	allErrorHintPatternsRegex := strings.Join(allErrorHintPatterns[:], "|")
+	re := regexp.MustCompile(allErrorHintPatternsRegex)
+	return &ErrorHintGenerator{
+		allErrorHints:                allErrorHints,
+		allErrorHintPatternsCompiled: re,
+	}
+}
+
+func (errorHintGenerator *ErrorHintGenerator) GetOutputWithErrorHint(rawOutput string, buildExitCode int) string {
+	if buildExitCode == 0 {
+		return rawOutput
+	}
+	errorHint := errorHintGenerator.getErrorHint(rawOutput)
+	if errorHint == nil {
+		return rawOutput
+	}
+	return rawOutput + *errorHint
+}
+
+// Returns the error hint corresponding to the FIRST match in raw output
+func (errorHintGenerator *ErrorHintGenerator) getErrorHint(rawOutput string) *string {
+	firstMatch := errorHintGenerator.allErrorHintPatternsCompiled.FindString(rawOutput)
+	if _, found := errorHintGenerator.allErrorHints[firstMatch]; found {
+		errorHint := errorHintGenerator.allErrorHints[firstMatch]
+		return &errorHint
+	}
+	return nil
+}
diff --git a/ui/status/ninja_test.go b/ui/status/ninja_test.go
index c400c97..f3638b3 100644
--- a/ui/status/ninja_test.go
+++ b/ui/status/ninja_test.go
@@ -43,3 +43,53 @@
 		t.Errorf("nr.Close timed out, %s > %s", g, w)
 	}
 }
+
+// Test that error hint is added to output if available
+func TestNinjaReader_CorrectErrorHint(t *testing.T) {
+	errorPattern1 := "pattern-1 in input"
+	errorHint1 := "\n Fix by doing task 1"
+	errorPattern2 := "pattern-2 in input"
+	errorHint2 := "\n Fix by doing task 2"
+	mockErrorHints := make(map[string]string)
+	mockErrorHints[errorPattern1] = errorHint1
+	mockErrorHints[errorPattern2] = errorHint2
+
+	errorHintGenerator := *newErrorHintGenerator(mockErrorHints)
+	testCases := []struct {
+		rawOutput            string
+		buildExitCode        int
+		expectedFinalOutput  string
+		testCaseErrorMessage string
+	}{
+		{
+			rawOutput:            "ninja build was successful",
+			buildExitCode:        0,
+			expectedFinalOutput:  "ninja build was successful",
+			testCaseErrorMessage: "raw output changed when build was successful",
+		},
+		{
+			rawOutput:            "ninja build failed",
+			buildExitCode:        1,
+			expectedFinalOutput:  "ninja build failed",
+			testCaseErrorMessage: "raw output changed even when no error hint pattern was found",
+		},
+		{
+			rawOutput:            "ninja build failed: " + errorPattern1 + "some footnotes",
+			buildExitCode:        1,
+			expectedFinalOutput:  "ninja build failed: " + errorPattern1 + "some footnotes" + errorHint1,
+			testCaseErrorMessage: "error hint not added despite pattern match",
+		},
+		{
+			rawOutput:            "ninja build failed: " + errorPattern2 + errorPattern1,
+			buildExitCode:        1,
+			expectedFinalOutput:  "ninja build failed: " + errorPattern2 + errorPattern1 + errorHint2,
+			testCaseErrorMessage: "error hint should be added for first pattern match in raw output",
+		},
+	}
+	for _, testCase := range testCases {
+		actualFinalOutput := errorHintGenerator.GetOutputWithErrorHint(testCase.rawOutput, testCase.buildExitCode)
+		if actualFinalOutput != testCase.expectedFinalOutput {
+			t.Errorf(testCase.testCaseErrorMessage+"\nexpected: %s\ngot: %s", testCase.expectedFinalOutput, actualFinalOutput)
+		}
+	}
+}