Diff source dump and previous version dump for Cross-Version ABI Check

Created a function to determine the current finalization stage by
environment variable and the existence of a version folder
prebuilt/abi-dumps/<lib_type>/<platform_sdk_version>/.
Assign the corresponding prevVersion with the current stage and generate
mk commands to diff source and previous dump to
{fileName}.{prevVersion}.abidiff with diff flag --allow-extension and
--advice-only
The test is verified in all stages. lsdumps should be prepared in
advance.
For stage 1: current/ and PLATFORM_SDK_VERSION/
For stage 2: current/ and {PLATFORM_SDK_VERSION-1}/
For stage 3: PLATFORM_SDK_VERSION/ and {PLATFORM_SDK_VERSION-1}/
The definition of stages could be found at
"go/cross-version-abi-check#bookmark=id.vpflkul2z968"

Test: make libbinder_ndk
Bug: 238387082
Change-Id: Ic29456113a541650c75fa38c5c4f2d6d2e76a877
diff --git a/cc/androidmk.go b/cc/androidmk.go
index ff5ba45..47fb919 100644
--- a/cc/androidmk.go
+++ b/cc/androidmk.go
@@ -226,17 +226,27 @@
 	}
 }
 
-func (library *libraryDecorator) androidMkEntriesWriteAdditionalDependenciesForSourceAbiDiff(entries *android.AndroidMkEntries) {
-	if library.sAbiDiff.Valid() && !library.static() {
-		entries.AddStrings("LOCAL_ADDITIONAL_DEPENDENCIES", library.sAbiDiff.String())
+func (library *libraryDecorator) getAbiDiffsForAndroidMkDeps() []string {
+	if library.static() {
+		return nil
 	}
+	var abiDiffs []string
+	if library.sAbiDiff.Valid() {
+		abiDiffs = append(abiDiffs, library.sAbiDiff.String())
+	}
+	if library.prevSAbiDiff.Valid() {
+		abiDiffs = append(abiDiffs, library.prevSAbiDiff.String())
+	}
+	return abiDiffs
+}
+
+func (library *libraryDecorator) androidMkEntriesWriteAdditionalDependenciesForSourceAbiDiff(entries *android.AndroidMkEntries) {
+	entries.AddStrings("LOCAL_ADDITIONAL_DEPENDENCIES", library.getAbiDiffsForAndroidMkDeps()...)
 }
 
 // TODO(ccross): remove this once apex/androidmk.go is converted to AndroidMkEntries
 func (library *libraryDecorator) androidMkWriteAdditionalDependenciesForSourceAbiDiff(w io.Writer) {
-	if library.sAbiDiff.Valid() && !library.static() {
-		fmt.Fprintln(w, "LOCAL_ADDITIONAL_DEPENDENCIES +=", library.sAbiDiff.String())
-	}
+	fmt.Fprintln(w, "LOCAL_ADDITIONAL_DEPENDENCIES +=", strings.Join(library.getAbiDiffsForAndroidMkDeps(), " "))
 }
 
 func (library *libraryDecorator) AndroidMkEntries(ctx AndroidMkContext, entries *android.AndroidMkEntries) {
diff --git a/cc/builder.go b/cc/builder.go
index ab2b80a..f3faca8 100644
--- a/cc/builder.go
+++ b/cc/builder.go
@@ -920,10 +920,15 @@
 
 // sourceAbiDiff registers a build statement to compare linked sAbi dump files (.lsdump).
 func sourceAbiDiff(ctx android.ModuleContext, inputDump android.Path, referenceDump android.Path,
-	baseName, exportedHeaderFlags string, diffFlags []string,
-	checkAllApis, isLlndk, isNdk, isVndkExt bool) android.OptionalPath {
+	baseName, prevVersion, exportedHeaderFlags string, diffFlags []string,
+	checkAllApis, isLlndk, isNdk, isVndkExt, previousVersionDiff bool) android.OptionalPath {
 
-	outputFile := android.PathForModuleOut(ctx, baseName+".abidiff")
+	var outputFile android.ModuleOutPath
+	if prevVersion == "" {
+		outputFile = android.PathForModuleOut(ctx, baseName+".abidiff")
+	} else {
+		outputFile = android.PathForModuleOut(ctx, baseName+"."+prevVersion+".abidiff")
+	}
 	libName := strings.TrimSuffix(baseName, filepath.Ext(baseName))
 
 	var extraFlags []string
@@ -935,10 +940,15 @@
 			"-allow-unreferenced-elf-symbol-changes")
 	}
 
+	// TODO(b/241496591): Remove -advice-only after b/239792343 and b/239790286 are reolved.
+	if previousVersionDiff {
+		extraFlags = append(extraFlags, "-advice-only")
+	}
+
 	if isLlndk || isNdk {
 		extraFlags = append(extraFlags, "-consider-opaque-types-different")
 	}
-	if isVndkExt {
+	if isVndkExt || previousVersionDiff {
 		extraFlags = append(extraFlags, "-allow-extensions")
 	}
 	// TODO(b/232891473): Simplify the above logic with diffFlags.
diff --git a/cc/library.go b/cc/library.go
index ff485cf..28cdc85 100644
--- a/cc/library.go
+++ b/cc/library.go
@@ -613,6 +613,9 @@
 	// Source Abi Diff
 	sAbiDiff android.OptionalPath
 
+	// Source Abi Diff against previous SDK version
+	prevSAbiDiff android.OptionalPath
+
 	// Location of the static library in the sysroot. Empty if the library is
 	// not included in the NDK.
 	ndkSysrootPath android.Path
@@ -1614,9 +1617,39 @@
 	return nil
 }
 
+func prevDumpRefVersion(ctx ModuleContext) string {
+	sdkVersionInt := ctx.Config().PlatformSdkVersion().FinalInt()
+	sdkVersionStr := ctx.Config().PlatformSdkVersion().String()
+
+	if ctx.Config().PlatformSdkFinal() {
+		return strconv.Itoa(sdkVersionInt - 1)
+	} else {
+		var dirName string
+
+		isNdk := ctx.isNdk(ctx.Config())
+		if isNdk {
+			dirName = "ndk"
+		} else {
+			dirName = "platform"
+		}
+
+		// The platform SDK version can be upgraded before finalization while the corresponding abi dumps hasn't
+		// been generated. Thus the Cross-Version Check chooses PLATFORM_SDK_VERION - 1 as previous version.
+		// This situation could be identified by checking the existence of the PLATFORM_SDK_VERION dump directory.
+		refDumpDir := android.ExistentPathForSource(ctx, "prebuilts", "abi-dumps", dirName, sdkVersionStr)
+		if refDumpDir.Valid() {
+			return sdkVersionStr
+		} else {
+			return strconv.Itoa(sdkVersionInt - 1)
+		}
+	}
+}
+
 func (library *libraryDecorator) linkSAbiDumpFiles(ctx ModuleContext, objs Objects, fileName string, soFile android.Path) {
 	if library.sabi.shouldCreateSourceAbiDump() {
 		var version string
+		var prevVersion string
+
 		if ctx.useVndk() {
 			// For modules linking against vndk, follow its vndk version
 			version = ctx.Module().(*Module).VndkVersion()
@@ -1628,6 +1661,7 @@
 			} else {
 				version = "current"
 			}
+			prevVersion = prevDumpRefVersion(ctx)
 		}
 
 		exportIncludeDirs := library.flagExporter.exportedIncludes(ctx)
@@ -1646,13 +1680,24 @@
 
 		addLsdumpPath(classifySourceAbiDump(ctx) + ":" + library.sAbiOutputFile.String())
 
+		if prevVersion != "" {
+			prevRefAbiDumpFile := getRefAbiDumpFile(ctx, prevVersion, fileName)
+			if prevRefAbiDumpFile != nil {
+				library.prevSAbiDiff = sourceAbiDiff(ctx, library.sAbiOutputFile.Path(),
+					prevRefAbiDumpFile, fileName, prevVersion, exportedHeaderFlags,
+					library.Properties.Header_abi_checker.Diff_flags,
+					Bool(library.Properties.Header_abi_checker.Check_all_apis),
+					ctx.IsLlndk(), ctx.isNdk(ctx.Config()), ctx.IsVndkExt(), true)
+			}
+		}
+
 		refAbiDumpFile := getRefAbiDumpFile(ctx, version, fileName)
 		if refAbiDumpFile != nil {
 			library.sAbiDiff = sourceAbiDiff(ctx, library.sAbiOutputFile.Path(),
-				refAbiDumpFile, fileName, exportedHeaderFlags,
+				refAbiDumpFile, fileName, "", exportedHeaderFlags,
 				library.Properties.Header_abi_checker.Diff_flags,
 				Bool(library.Properties.Header_abi_checker.Check_all_apis),
-				ctx.IsLlndk(), ctx.isNdk(ctx.Config()), ctx.IsVndkExt())
+				ctx.IsLlndk(), ctx.isNdk(ctx.Config()), ctx.IsVndkExt(), false)
 		}
 	}
 }