Copy shared_libs and system_shared_libs to module snapshot

This change ensures that the runtime dependencies between a
binary/shared library are correctly specified in the snapshot so that
the build can ensure that shared libraries are built before the targets
that use them.

It adds support for differentiating between references that are
required to refer to another sdk member (required) and those that may
refer to either an sdk member or a non-sdk member (optional). The
latter is used for shared library references as the libraries used by
an sdk member may be provided from outside the sdk. e.g. liblog is not
part of the ART module but is used by some members of the ART sdk.

Bug: 142935992
Bug: 153306490
Test: m nothing
Merged-In: Ia8509ffe79b208c23beba1880fe9c8a92b732685
Change-Id: Ia8509ffe79b208c23beba1880fe9c8a92b732685

android/sdk.go

@@ -186,9 +186,33 @@ type SnapshotBuilder interface {
 	// is correctly output for both versioned and unversioned prebuilts in the
 	// snapshot.
 	//
+	// "required: true" means that the property must only contain references
+	// to other members of the sdk. Passing a reference to a module that is not a
+	// member of the sdk will result in a build error.
+	//
+	// "required: false" means that the property can contain references to modules
+	// that are either members or not members of the sdk. If a reference is to a
+	// module that is a non member then the reference is left unchanged, i.e. it
+	// is not transformed as references to members are.
+	//
+	// The handling of the member names is dependent on whether it is an internal or
+	// exported member. An exported member is one whose name is specified in one of
+	// the member type specific properties. An internal member is one that is added
+	// due to being a part of an exported (or other internal) member and is not itself
+	// an exported member.
+	//
+	// Member names are handled as follows:
+	// * When creating the unversioned form of the module the name is left unchecked
+	//   unless the member is internal in which case it is transformed into an sdk
+	//   specific name, i.e. by prefixing with the sdk name.
+	//
+	// * When creating the versioned form of the module the name is transformed into
+	//   a versioned sdk specific name, i.e. by prefixing with the sdk name and
+	//   suffixing with the version.
+	//
 	// e.g.
-	// bpPropertySet.AddPropertyWithTag("libs", []string{"member1", "member2"}, builder.SdkMemberReferencePropertyTag())
+	// bpPropertySet.AddPropertyWithTag("libs", []string{"member1", "member2"}, builder.SdkMemberReferencePropertyTag(true))
-	SdkMemberReferencePropertyTag() BpPropertyTag
+	SdkMemberReferencePropertyTag(required bool) BpPropertyTag
 }
 
 type BpPropertyTag interface{}

cc/binary_sdk_member.go

@@ -95,6 +95,16 @@ type nativeBinaryInfoProperties struct {
 
 	// outputFile is not exported as it is always arch specific.
 	outputFile android.Path
+
+	// The set of shared libraries
+	//
+	// This field is exported as its contents may not be arch specific.
+	SharedLibs []string
+
+	// The set of system shared libraries
+	//
+	// This field is exported as its contents may not be arch specific.
+	SystemSharedLibs []string
 }
 
 func (p *nativeBinaryInfoProperties) PopulateFromVariant(variant android.SdkAware) {
@@ -102,6 +112,14 @@ func (p *nativeBinaryInfoProperties) PopulateFromVariant(variant android.SdkAwar
 
 	p.archType = ccModule.Target().Arch.ArchType.String()
 	p.outputFile = ccModule.OutputFile().Path()
+
+	if ccModule.linker != nil {
+		specifiedDeps := specifiedDeps{}
+		specifiedDeps = ccModule.linker.linkerSpecifiedDeps(specifiedDeps)
+
+		p.SharedLibs = specifiedDeps.sharedLibs
+		p.SystemSharedLibs = specifiedDeps.systemSharedLibs
+	}
 }
 
 func (p *nativeBinaryInfoProperties) AddToPropertySet(sdkModuleContext android.ModuleContext, builder android.SnapshotBuilder, propertySet android.BpPropertySet) {
@@ -114,4 +132,12 @@ func (p *nativeBinaryInfoProperties) AddToPropertySet(sdkModuleContext android.M
 
 		builder.CopyToSnapshot(p.outputFile, nativeBinaryPathFor(*p))
 	}
+
+	if len(p.SharedLibs) > 0 {
+		propertySet.AddPropertyWithTag("shared_libs", p.SharedLibs, builder.SdkMemberReferencePropertyTag(false))
+	}
+
+	if len(p.SystemSharedLibs) > 0 {
+		propertySet.AddPropertyWithTag("system_shared_libs", p.SystemSharedLibs, builder.SdkMemberReferencePropertyTag(false))
+	}
 }

cc/cc.go

@@ -370,6 +370,15 @@ type linker interface {
 
 	nativeCoverage() bool
 	coverageOutputFilePath() android.OptionalPath
+
+	// Get the deps that have been explicitly specified in the properties.
+	// Only updates the
+	linkerSpecifiedDeps(specifiedDeps specifiedDeps) specifiedDeps
+}
+
+type specifiedDeps struct {
+	sharedLibs       []string
+	systemSharedLibs []string
 }
 
 type installer interface {

cc/library.go

@@ -817,6 +817,23 @@ func (library *libraryDecorator) linkerDeps(ctx DepsContext, deps Deps) Deps {
 	return deps
 }
 
+func (library *libraryDecorator) linkerSpecifiedDeps(specifiedDeps specifiedDeps) specifiedDeps {
+	specifiedDeps = library.baseLinker.linkerSpecifiedDeps(specifiedDeps)
+	var properties StaticOrSharedProperties
+	if library.static() {
+		properties = library.StaticProperties.Static
+	} else if library.shared() {
+		properties = library.SharedProperties.Shared
+	}
+
+	specifiedDeps.sharedLibs = append(specifiedDeps.sharedLibs, properties.Shared_libs...)
+	specifiedDeps.systemSharedLibs = append(specifiedDeps.systemSharedLibs, properties.System_shared_libs...)
+
+	specifiedDeps.sharedLibs = android.FirstUniqueStrings(specifiedDeps.sharedLibs)
+	specifiedDeps.systemSharedLibs = android.FirstUniqueStrings(specifiedDeps.systemSharedLibs)
+	return specifiedDeps
+}
+
 func (library *libraryDecorator) linkStatic(ctx ModuleContext,
 	flags Flags, deps PathDeps, objs Objects) android.Path {
 

cc/library_sdk_member.go

@@ -19,6 +19,7 @@ import (
 
 	"android/soong/android"
 	"github.com/google/blueprint"
+	"github.com/google/blueprint/proptools"
 )
 
 // This file contains support for using cc library modules within an sdk.
@@ -108,8 +109,11 @@ func (mt *librarySdkMemberType) AddPrebuiltModule(sdkModuleContext android.Modul
 }
 
 func (mt *librarySdkMemberType) FinalizeModule(sdkModuleContext android.ModuleContext, builder android.SnapshotBuilder, member android.SdkMember, bpModule android.BpModule) {
-	bpModule.AddProperty("stl", "none")
+	ccModule := (member.Variants()[0]).(*Module)
-	bpModule.AddProperty("system_shared_libs", []string{})
+	stl := ccModule.stl.Properties.Stl
+	if stl != nil {
+		bpModule.AddProperty("stl", proptools.String(stl))
+	}
 }
 
 func (mt *librarySdkMemberType) CreateVariantPropertiesStruct() android.SdkMemberProperties {
@@ -193,6 +197,14 @@ func addPossiblyArchSpecificProperties(sdkModuleContext android.ModuleContext, b
 		outputProperties.AddProperty("srcs", []string{nativeLibraryPath})
 	}
 
+	if len(libInfo.SharedLibs) > 0 {
+		outputProperties.AddPropertyWithTag("shared_libs", libInfo.SharedLibs, builder.SdkMemberReferencePropertyTag(false))
+	}
+
+	if len(libInfo.SystemSharedLibs) > 0 {
+		outputProperties.AddPropertyWithTag("system_shared_libs", libInfo.SystemSharedLibs, 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)
 
@@ -299,6 +311,16 @@ type nativeLibInfoProperties struct {
 	// This field is exported as its contents may not be arch specific.
 	ExportedFlags []string
 
+	// The set of shared libraries
+	//
+	// This field is exported as its contents may not be arch specific.
+	SharedLibs []string
+
+	// The set of system shared libraries
+	//
+	// This field is exported as its contents may not be arch specific.
+	SystemSharedLibs []string
+
 	// outputFile is not exported as it is always arch specific.
 	outputFile android.Path
 }
@@ -323,6 +345,13 @@ func (p *nativeLibInfoProperties) PopulateFromVariant(variant android.SdkAware)
 	p.exportedGeneratedIncludeDirs = exportedGeneratedIncludeDirs
 	p.ExportedSystemIncludeDirs = ccModule.ExportedSystemIncludeDirs()
 	p.ExportedFlags = ccModule.ExportedFlags()
+	if ccModule.linker != nil {
+		specifiedDeps := specifiedDeps{}
+		specifiedDeps = ccModule.linker.linkerSpecifiedDeps(specifiedDeps)
+
+		p.SharedLibs = specifiedDeps.sharedLibs
+		p.SystemSharedLibs = specifiedDeps.systemSharedLibs
+	}
 	p.exportedGeneratedHeaders = ccModule.ExportedGeneratedHeaders()
 }
 

cc/linker.go

@@ -490,6 +490,12 @@ func (linker *baseLinker) link(ctx ModuleContext,
 	panic(fmt.Errorf("baseLinker doesn't know how to link"))
 }
 
+func (linker *baseLinker) linkerSpecifiedDeps(specifiedDeps specifiedDeps) specifiedDeps {
+	specifiedDeps.sharedLibs = append(specifiedDeps.sharedLibs, linker.Properties.Shared_libs...)
+	specifiedDeps.systemSharedLibs = append(specifiedDeps.systemSharedLibs, linker.Properties.System_shared_libs...)
+	return specifiedDeps
+}
+
 // Injecting version symbols
 // Some host modules want a version number, but we don't want to rebuild it every time.  Optionally add a step
 // after linking that injects a constant placeholder with the current version number.

java/system_modules.go

@@ -255,5 +255,5 @@ func (mt *systemModulesSdkMemberType) BuildSnapshot(sdkModuleContext android.Mod
 
 	pbm := builder.AddPrebuiltModule(member, "java_system_modules_import")
 	// Add the references to the libraries that form the system module.
-	pbm.AddPropertyWithTag("libs", systemModule.properties.Libs, builder.SdkMemberReferencePropertyTag())
+	pbm.AddPropertyWithTag("libs", systemModule.properties.Libs, builder.SdkMemberReferencePropertyTag(true))
 }

sdk/cc_sdk_test.go

@@ -309,7 +309,6 @@ cc_prebuilt_library_shared {
         },
     },
     stl: "none",
-    system_shared_libs: [],
 }
 
 cc_prebuilt_library_shared {
@@ -326,7 +325,6 @@ cc_prebuilt_library_shared {
         },
     },
     stl: "none",
-    system_shared_libs: [],
 }
 
 sdk_snapshot {
@@ -555,7 +553,6 @@ cc_prebuilt_library_shared {
         },
     },
     stl: "none",
-    system_shared_libs: [],
 }
 
 cc_prebuilt_library_shared {
@@ -577,7 +574,6 @@ cc_prebuilt_library_shared {
         },
     },
     stl: "none",
-    system_shared_libs: [],
 }
 
 sdk_snapshot {
@@ -599,6 +595,189 @@ include/Test.h -> include/include/Test.h
 	)
 }
 
+func TestSnapshotWithCcSharedLibrarySharedLibs(t *testing.T) {
+	result := testSdkWithCc(t, `
+		sdk {
+			name: "mysdk",
+			native_shared_libs: [
+				"mynativelib",
+				"myothernativelib",
+				"mysystemnativelib",
+			],
+		}
+
+		cc_library {
+			name: "mysystemnativelib",
+			srcs: [
+				"Test.cpp",
+			],
+			system_shared_libs: [],
+			stl: "none",
+		}
+
+		cc_library_shared {
+			name: "myothernativelib",
+			srcs: [
+				"Test.cpp",
+			],
+			system_shared_libs: [
+				// A reference to a library that is not an sdk member. Uses libm as that
+				// is in the default set of modules available to this test and so is available
+				// both here and also when the generated Android.bp file is tested in
+				// CheckSnapshot(). This ensures that the system_shared_libs property correctly
+				// handles references to modules that are not sdk members.
+				"libm",
+			],
+			stl: "none",
+		}
+
+		cc_library {
+			name: "mynativelib",
+			srcs: [
+				"Test.cpp",
+			],
+			shared_libs: [
+				// A reference to another sdk member.
+				"myothernativelib",
+			],
+			target: {
+				android: {
+					shared: {
+						shared_libs: [
+							// A reference to a library that is not an sdk member. The libc library
+							// is used here to check that the shared_libs property is handled correctly
+							// in a similar way to how libm is used to check system_shared_libs above.
+							"libc",
+						],
+					},
+				},
+			},
+			system_shared_libs: [],
+			stl: "none",
+		}
+	`)
+
+	result.CheckSnapshot("mysdk", "",
+		checkAndroidBpContents(`
+// This is auto-generated. DO NOT EDIT.
+
+cc_prebuilt_library_shared {
+    name: "mysdk_mynativelib@current",
+    sdk_member_name: "mynativelib",
+    installable: false,
+    shared_libs: [
+        "mysdk_myothernativelib@current",
+        "libc",
+    ],
+    arch: {
+        arm64: {
+            srcs: ["arm64/lib/mynativelib.so"],
+        },
+        arm: {
+            srcs: ["arm/lib/mynativelib.so"],
+        },
+    },
+    stl: "none",
+}
+
+cc_prebuilt_library_shared {
+    name: "mynativelib",
+    prefer: false,
+    shared_libs: [
+        "myothernativelib",
+        "libc",
+    ],
+    arch: {
+        arm64: {
+            srcs: ["arm64/lib/mynativelib.so"],
+        },
+        arm: {
+            srcs: ["arm/lib/mynativelib.so"],
+        },
+    },
+    stl: "none",
+}
+
+cc_prebuilt_library_shared {
+    name: "mysdk_myothernativelib@current",
+    sdk_member_name: "myothernativelib",
+    installable: false,
+    system_shared_libs: ["libm"],
+    arch: {
+        arm64: {
+            srcs: ["arm64/lib/myothernativelib.so"],
+        },
+        arm: {
+            srcs: ["arm/lib/myothernativelib.so"],
+        },
+    },
+    stl: "none",
+}
+
+cc_prebuilt_library_shared {
+    name: "myothernativelib",
+    prefer: false,
+    system_shared_libs: ["libm"],
+    arch: {
+        arm64: {
+            srcs: ["arm64/lib/myothernativelib.so"],
+        },
+        arm: {
+            srcs: ["arm/lib/myothernativelib.so"],
+        },
+    },
+    stl: "none",
+}
+
+cc_prebuilt_library_shared {
+    name: "mysdk_mysystemnativelib@current",
+    sdk_member_name: "mysystemnativelib",
+    installable: false,
+    arch: {
+        arm64: {
+            srcs: ["arm64/lib/mysystemnativelib.so"],
+        },
+        arm: {
+            srcs: ["arm/lib/mysystemnativelib.so"],
+        },
+    },
+    stl: "none",
+}
+
+cc_prebuilt_library_shared {
+    name: "mysystemnativelib",
+    prefer: false,
+    arch: {
+        arm64: {
+            srcs: ["arm64/lib/mysystemnativelib.so"],
+        },
+        arm: {
+            srcs: ["arm/lib/mysystemnativelib.so"],
+        },
+    },
+    stl: "none",
+}
+
+sdk_snapshot {
+    name: "mysdk@current",
+    native_shared_libs: [
+        "mysdk_mynativelib@current",
+        "mysdk_myothernativelib@current",
+        "mysdk_mysystemnativelib@current",
+    ],
+}
+`),
+		checkAllCopyRules(`
+.intermediates/mynativelib/android_arm64_armv8-a_shared/mynativelib.so -> arm64/lib/mynativelib.so
+.intermediates/mynativelib/android_arm_armv7-a-neon_shared/mynativelib.so -> arm/lib/mynativelib.so
+.intermediates/myothernativelib/android_arm64_armv8-a_shared/myothernativelib.so -> arm64/lib/myothernativelib.so
+.intermediates/myothernativelib/android_arm_armv7-a-neon_shared/myothernativelib.so -> arm/lib/myothernativelib.so
+.intermediates/mysystemnativelib/android_arm64_armv8-a_shared/mysystemnativelib.so -> arm64/lib/mysystemnativelib.so
+.intermediates/mysystemnativelib/android_arm_armv7-a-neon_shared/mysystemnativelib.so -> arm/lib/mysystemnativelib.so
+`),
+	)
+}
+
 func TestHostSnapshotWithCcSharedLibrary(t *testing.T) {
 	// b/145598135 - Generating host snapshots for anything other than linux is not supported.
 	SkipIfNotLinux(t)
@@ -652,7 +831,6 @@ cc_prebuilt_library_shared {
         },
     },
     stl: "none",
-    system_shared_libs: [],
 }
 
 cc_prebuilt_library_shared {
@@ -673,7 +851,6 @@ cc_prebuilt_library_shared {
         },
     },
     stl: "none",
-    system_shared_libs: [],
 }
 
 sdk_snapshot {
@@ -753,7 +930,6 @@ cc_prebuilt_library_shared {
         },
     },
     stl: "none",
-    system_shared_libs: [],
 }
 
 cc_prebuilt_library_shared {
@@ -773,7 +949,6 @@ cc_prebuilt_library_shared {
         },
     },
     stl: "none",
-    system_shared_libs: [],
 }
 
 sdk_snapshot {
@@ -833,7 +1008,6 @@ cc_prebuilt_library_static {
         },
     },
     stl: "none",
-    system_shared_libs: [],
 }
 
 cc_prebuilt_library_static {
@@ -851,7 +1025,6 @@ cc_prebuilt_library_static {
         },
     },
     stl: "none",
-    system_shared_libs: [],
 }
 
 module_exports_snapshot {
@@ -924,7 +1097,6 @@ cc_prebuilt_library_static {
         },
     },
     stl: "none",
-    system_shared_libs: [],
 }
 
 cc_prebuilt_library_static {
@@ -944,7 +1116,6 @@ cc_prebuilt_library_static {
         },
     },
     stl: "none",
-    system_shared_libs: [],
 }
 
 module_exports_snapshot {
@@ -1020,7 +1191,6 @@ cc_prebuilt_library_static {
         },
     },
     stl: "none",
-    system_shared_libs: [],
 }
 
 cc_prebuilt_library_static {
@@ -1036,7 +1206,6 @@ cc_prebuilt_library_static {
         },
     },
     stl: "none",
-    system_shared_libs: [],
 }
 
 module_exports_snapshot {
@@ -1084,7 +1253,6 @@ cc_prebuilt_library_headers {
     sdk_member_name: "mynativeheaders",
     export_include_dirs: ["include/include"],
     stl: "none",
-    system_shared_libs: [],
 }
 
 cc_prebuilt_library_headers {
@@ -1092,7 +1260,6 @@ cc_prebuilt_library_headers {
     prefer: false,
     export_include_dirs: ["include/include"],
     stl: "none",
-    system_shared_libs: [],
 }
 
 sdk_snapshot {
@@ -1139,7 +1306,6 @@ cc_prebuilt_library_headers {
     host_supported: true,
     export_include_dirs: ["include/include"],
     stl: "none",
-    system_shared_libs: [],
 }
 
 cc_prebuilt_library_headers {
@@ -1149,7 +1315,6 @@ cc_prebuilt_library_headers {
     host_supported: true,
     export_include_dirs: ["include/include"],
     stl: "none",
-    system_shared_libs: [],
 }
 
 sdk_snapshot {
@@ -1211,7 +1376,6 @@ cc_prebuilt_library_headers {
         },
     },
     stl: "none",
-    system_shared_libs: [],
 }
 
 cc_prebuilt_library_headers {
@@ -1228,7 +1392,6 @@ cc_prebuilt_library_headers {
         },
     },
     stl: "none",
-    system_shared_libs: [],
 }
 
 sdk_snapshot {

sdk/sdk.go

@@ -50,9 +50,6 @@ type sdk struct {
 	// list properties, e.g. java_libs.
 	dynamicMemberTypeListProperties interface{}
 
-	// The set of exported members.
-	exportedMembers map[string]struct{}
-
 	// Information about the OsType specific member variants associated with this variant.
 	//
 	// Set by OsType specific variants when their GenerateAndroidBuildActions is invoked
@@ -233,26 +230,19 @@ func (s *sdk) memberListProperties() []*sdkMemberListProperty {
 }
 
 func (s *sdk) getExportedMembers() map[string]struct{} {
-	if s.exportedMembers == nil {
+	// Collect all the exported members.
-		// Collect all the exported members.
+	exportedMembers := make(map[string]struct{})
-		s.exportedMembers = make(map[string]struct{})
 
-		for _, memberListProperty := range s.memberListProperties() {
+	for _, memberListProperty := range s.memberListProperties() {
-			names := memberListProperty.getter(s.dynamicMemberTypeListProperties)
+		names := memberListProperty.getter(s.dynamicMemberTypeListProperties)
 
-			// Every member specified explicitly in the properties is exported by the sdk.
+		// Every member specified explicitly in the properties is exported by the sdk.
-			for _, name := range names {
+		for _, name := range names {
-				s.exportedMembers[name] = struct{}{}
+			exportedMembers[name] = struct{}{}
-			}
 		}
 	}
 
-	return s.exportedMembers
+	return exportedMembers
-}
-
-func (s *sdk) isInternalMember(memberName string) bool {
-	_, ok := s.getExportedMembers()[memberName]
-	return !ok
 }
 
 func (s *sdk) snapshot() bool {

sdk/update.go

@@ -226,17 +226,23 @@ func versionedSdkMemberName(ctx android.ModuleContext, memberName string, versio
 // the contents (header files, stub libraries, etc) into the zip file.
 func (s *sdk) buildSnapshot(ctx android.ModuleContext, sdkVariants []*sdk) android.OutputPath {
 
-	exportedMembers := make(map[string]struct{})
+	allMembersByName := make(map[string]struct{})
+	exportedMembersByName := make(map[string]struct{})
 	var memberRefs []sdkMemberRef
 	for _, sdkVariant := range sdkVariants {
 		memberRefs = append(memberRefs, sdkVariant.memberRefs...)
 
+		// Record the names of all the members, both explicitly specified and implicitly
+		// included.
+		for _, memberRef := range sdkVariant.memberRefs {
+			allMembersByName[memberRef.variant.Name()] = struct{}{}
+		}
+
 		// Merge the exported member sets from all sdk variants.
 		for key, _ := range sdkVariant.getExportedMembers() {
-			exportedMembers[key] = struct{}{}
+			exportedMembersByName[key] = struct{}{}
 		}
 	}
-	s.exportedMembers = exportedMembers
 
 	snapshotDir := android.PathForModuleOut(ctx, "snapshot")
 
@@ -247,14 +253,16 @@ func (s *sdk) buildSnapshot(ctx android.ModuleContext, sdkVariants []*sdk) andro
 	}
 
 	builder := &snapshotBuilder{
-		ctx:             ctx,
+		ctx:                   ctx,
-		sdk:             s,
+		sdk:                   s,
-		version:         "current",
+		version:               "current",
-		snapshotDir:     snapshotDir.OutputPath,
+		snapshotDir:           snapshotDir.OutputPath,
-		copies:          make(map[string]string),
+		copies:                make(map[string]string),
-		filesToZip:      []android.Path{bp.path},
+		filesToZip:            []android.Path{bp.path},
-		bpFile:          bpFile,
+		bpFile:                bpFile,
-		prebuiltModules: make(map[string]*bpModule),
+		prebuiltModules:       make(map[string]*bpModule),
+		allMembersByName:      allMembersByName,
+		exportedMembersByName: exportedMembersByName,
 	}
 	s.builderForTests = builder
 
@@ -402,7 +410,7 @@ func (s *sdk) addMemberPropertiesToPropertySet(builder *snapshotBuilder, propert
 	for _, memberListProperty := range s.memberListProperties() {
 		names := memberListProperty.getter(dynamicMemberTypeListProperties)
 		if len(names) > 0 {
-			propertySet.AddProperty(memberListProperty.propertyName(), builder.versionedSdkMemberNames(names))
+			propertySet.AddProperty(memberListProperty.propertyName(), builder.versionedSdkMemberNames(names, false))
 		}
 	}
 }
@@ -415,7 +423,13 @@ type propertyTag struct {
 //
 // This will cause the references to be rewritten to a versioned reference in the version
 // specific instance of a snapshot module.
-var sdkMemberReferencePropertyTag = propertyTag{"sdkMemberReferencePropertyTag"}
+var requiredSdkMemberReferencePropertyTag = propertyTag{"requiredSdkMemberReferencePropertyTag"}
+
+// A BpPropertyTag to add to a property that contains references to other sdk members.
+//
+// This will cause the references to be rewritten to a versioned reference in the version
+// specific instance of a snapshot module.
+var optionalSdkMemberReferencePropertyTag = propertyTag{"optionalSdkMemberReferencePropertyTag"}
 
 // A BpPropertyTag that indicates the property should only be present in the versioned
 // module.
@@ -433,14 +447,15 @@ func (t unversionedToVersionedTransformation) transformModule(module *bpModule)
 	// Use a versioned name for the module but remember the original name for the
 	// snapshot.
 	name := module.getValue("name").(string)
-	module.setProperty("name", t.builder.versionedSdkMemberName(name))
+	module.setProperty("name", t.builder.versionedSdkMemberName(name, true))
 	module.insertAfter("name", "sdk_member_name", name)
 	return module
 }
 
 func (t unversionedToVersionedTransformation) transformProperty(name string, value interface{}, tag android.BpPropertyTag) (interface{}, android.BpPropertyTag) {
-	if tag == sdkMemberReferencePropertyTag {
+	if tag == requiredSdkMemberReferencePropertyTag || tag == optionalSdkMemberReferencePropertyTag {
-		return t.builder.versionedSdkMemberNames(value.([]string)), tag
+		required := tag == requiredSdkMemberReferencePropertyTag
+		return t.builder.versionedSdkMemberNames(value.([]string), required), tag
 	} else {
 		return value, tag
 	}
@@ -454,7 +469,7 @@ type unversionedTransformation struct {
 func (t unversionedTransformation) transformModule(module *bpModule) *bpModule {
 	// If the module is an internal member then use a unique name for it.
 	name := module.getValue("name").(string)
-	module.setProperty("name", t.builder.unversionedSdkMemberName(name))
+	module.setProperty("name", t.builder.unversionedSdkMemberName(name, true))
 
 	// Set prefer: false - this is not strictly required as that is the default.
 	module.insertAfter("name", "prefer", false)
@@ -463,8 +478,9 @@ func (t unversionedTransformation) transformModule(module *bpModule) *bpModule {
 }
 
 func (t unversionedTransformation) transformProperty(name string, value interface{}, tag android.BpPropertyTag) (interface{}, android.BpPropertyTag) {
-	if tag == sdkMemberReferencePropertyTag {
+	if tag == requiredSdkMemberReferencePropertyTag || tag == optionalSdkMemberReferencePropertyTag {
-		return t.builder.unversionedSdkMemberNames(value.([]string)), tag
+		required := tag == requiredSdkMemberReferencePropertyTag
+		return t.builder.unversionedSdkMemberNames(value.([]string), required), tag
 	} else if tag == sdkVersionedOnlyPropertyTag {
 		// The property is not allowed in the unversioned module so remove it.
 		return nil, nil
@@ -559,6 +575,12 @@ type snapshotBuilder struct {
 
 	prebuiltModules map[string]*bpModule
 	prebuiltOrder   []*bpModule
+
+	// The set of all members by name.
+	allMembersByName map[string]struct{}
+
+	// The set of exported members by name.
+	exportedMembersByName map[string]struct{}
 }
 
 func (s *snapshotBuilder) CopyToSnapshot(src android.Path, dest string) {
@@ -612,7 +634,7 @@ func (s *snapshotBuilder) AddPrebuiltModule(member android.SdkMember, moduleType
 
 	variant := member.Variants()[0]
 
-	if s.sdk.isInternalMember(name) {
+	if s.isInternalMember(name) {
 		// An internal member is only referenced from the sdk snapshot which is in the
 		// same package so can be marked as private.
 		m.AddProperty("visibility", []string{"//visibility:private"})
@@ -676,40 +698,66 @@ func addHostDeviceSupportedProperties(deviceSupported bool, hostSupported bool,
 	}
 }
 
-func (s *snapshotBuilder) SdkMemberReferencePropertyTag() android.BpPropertyTag {
+func (s *snapshotBuilder) SdkMemberReferencePropertyTag(required bool) android.BpPropertyTag {
-	return sdkMemberReferencePropertyTag
+	if required {
+		return requiredSdkMemberReferencePropertyTag
+	} else {
+		return optionalSdkMemberReferencePropertyTag
+	}
+}
+
+func (s *snapshotBuilder) OptionalSdkMemberReferencePropertyTag() android.BpPropertyTag {
+	return optionalSdkMemberReferencePropertyTag
 }
 
 // Get a versioned name appropriate for the SDK snapshot version being taken.
-func (s *snapshotBuilder) versionedSdkMemberName(unversionedName string) string {
+func (s *snapshotBuilder) versionedSdkMemberName(unversionedName string, required bool) string {
+	if _, ok := s.allMembersByName[unversionedName]; !ok {
+		if required {
+			s.ctx.ModuleErrorf("Required member reference %s is not a member of the sdk", unversionedName)
+		}
+		return unversionedName
+	}
 	return versionedSdkMemberName(s.ctx, unversionedName, s.version)
 }
 
-func (s *snapshotBuilder) versionedSdkMemberNames(members []string) []string {
+func (s *snapshotBuilder) versionedSdkMemberNames(members []string, required bool) []string {
 	var references []string = nil
 	for _, m := range members {
-		references = append(references, s.versionedSdkMemberName(m))
+		references = append(references, s.versionedSdkMemberName(m, required))
 	}
 	return references
 }
 
 // Get an internal name unique to the sdk.
-func (s *snapshotBuilder) unversionedSdkMemberName(unversionedName string) string {
+func (s *snapshotBuilder) unversionedSdkMemberName(unversionedName string, required bool) string {
-	if s.sdk.isInternalMember(unversionedName) {
+	if _, ok := s.allMembersByName[unversionedName]; !ok {
+		if required {
+			s.ctx.ModuleErrorf("Required member reference %s is not a member of the sdk", unversionedName)
+		}
+		return unversionedName
+	}
+
+	if s.isInternalMember(unversionedName) {
 		return s.ctx.ModuleName() + "_" + unversionedName
 	} else {
 		return unversionedName
 	}
 }
 
-func (s *snapshotBuilder) unversionedSdkMemberNames(members []string) []string {
+func (s *snapshotBuilder) unversionedSdkMemberNames(members []string, required bool) []string {
 	var references []string = nil
 	for _, m := range members {
-		references = append(references, s.unversionedSdkMemberName(m))
+		references = append(references, s.unversionedSdkMemberName(m, required))
 	}
 	return references
 }
 
+func (s *snapshotBuilder) isInternalMember(memberName string) bool {
+	_, ok := s.exportedMembersByName[memberName]
+	return !ok
+}
+
 type sdkMemberRef struct {
 	memberType android.SdkMemberType
 	variant    android.SdkAware