Support prebuilt shared libs end with versions

This commit changes how `cc/androidmk.go` generates LOCAL_MODULE_STEM,
LOCAL_MODULE_SUFFIX, and LOCAL_BUILT_MODULE_STEM.  Now, `splitFileExt()`
takes a file name and a list of expected file extensions.
`splitFileExt()` searches the first occurrence of expected file
extensions in the file name.  If it can not find any, it will simply
return the last file extension.

Before this commit, `cc/androidmk.go` simply extracts the last file
extension (e.g. `.so`).  However, if the prebuilt shared libs end with
version numbers (e.g. `libc++.so.1`), it will use `$(LOCAL_MODULE).1` as
LOCAL_BUILT_MODULE_STEM and this will lead to missing target ninja
error.

Bug: 111579848
Test: Build a program that links libc++_host (from prebuilts/clang)
Change-Id: Id96726c69705d518ea725bb6abd8ff4527ca0cbc
diff --git a/cc/androidmk.go b/cc/androidmk.go
index 228b64a..c510d98 100644
--- a/cc/androidmk.go
+++ b/cc/androidmk.go
@@ -192,7 +192,9 @@
 			}
 		}
 
-		fmt.Fprintln(w, "LOCAL_BUILT_MODULE_STEM := $(LOCAL_MODULE)"+outputFile.Ext())
+		_, _, ext := splitFileExt(outputFile.Base())
+
+		fmt.Fprintln(w, "LOCAL_BUILT_MODULE_STEM := $(LOCAL_MODULE)"+ext)
 
 		fmt.Fprintln(w, "LOCAL_SYSTEM_SHARED_LIBRARIES :=")
 
@@ -286,7 +288,8 @@
 func (library *toolchainLibraryDecorator) AndroidMk(ctx AndroidMkContext, ret *android.AndroidMkData) {
 	ret.Class = "STATIC_LIBRARIES"
 	ret.Extra = append(ret.Extra, func(w io.Writer, outputFile android.Path) {
-		fmt.Fprintln(w, "LOCAL_MODULE_SUFFIX := "+outputFile.Ext())
+		_, suffix, _ := splitFileExt(outputFile.Base())
+		fmt.Fprintln(w, "LOCAL_MODULE_SUFFIX := "+suffix)
 		fmt.Fprintln(w, "LOCAL_SYSTEM_SHARED_LIBRARIES :=")
 	})
 }
@@ -327,8 +330,8 @@
 	ret.Extra = append(ret.Extra, func(w io.Writer, outputFile android.Path) {
 		path := installer.path.RelPathString()
 		dir, file := filepath.Split(path)
-		stem := strings.TrimSuffix(file, filepath.Ext(file))
-		fmt.Fprintln(w, "LOCAL_MODULE_SUFFIX := "+filepath.Ext(file))
+		stem, suffix, _ := splitFileExt(file)
+		fmt.Fprintln(w, "LOCAL_MODULE_SUFFIX := "+suffix)
 		fmt.Fprintln(w, "LOCAL_MODULE_PATH := $(OUT_DIR)/"+filepath.Clean(dir))
 		fmt.Fprintln(w, "LOCAL_MODULE_STEM := "+stem)
 	})
@@ -340,9 +343,9 @@
 
 	ret.Extra = append(ret.Extra, func(w io.Writer, outputFile android.Path) {
 		path, file := filepath.Split(c.installPath.String())
-		stem := strings.TrimSuffix(file, filepath.Ext(file))
+		stem, suffix, _ := splitFileExt(file)
 		fmt.Fprintln(w, "LOCAL_SYSTEM_SHARED_LIBRARIES :=")
-		fmt.Fprintln(w, "LOCAL_MODULE_SUFFIX := "+outputFile.Ext())
+		fmt.Fprintln(w, "LOCAL_MODULE_SUFFIX := "+suffix)
 		fmt.Fprintln(w, "LOCAL_MODULE_PATH := "+path)
 		fmt.Fprintln(w, "LOCAL_MODULE_STEM := "+stem)
 		fmt.Fprintln(w, "LOCAL_NO_NOTICE_FILE := true")
@@ -360,8 +363,9 @@
 
 	ret.Extra = append(ret.Extra, func(w io.Writer, outputFile android.Path) {
 		c.libraryDecorator.androidMkWriteExportedFlags(w)
+		_, _, ext := splitFileExt(outputFile.Base())
 
-		fmt.Fprintln(w, "LOCAL_BUILT_MODULE_STEM := $(LOCAL_MODULE)"+outputFile.Ext())
+		fmt.Fprintln(w, "LOCAL_BUILT_MODULE_STEM := $(LOCAL_MODULE)"+ext)
 		fmt.Fprintln(w, "LOCAL_STRIP_MODULE := false")
 		fmt.Fprintln(w, "LOCAL_SYSTEM_SHARED_LIBRARIES :=")
 		fmt.Fprintln(w, "LOCAL_UNINSTALLABLE_MODULE := true")
@@ -380,12 +384,12 @@
 
 		path := c.path.RelPathString()
 		dir, file := filepath.Split(path)
-		stem := strings.TrimSuffix(file, filepath.Ext(file))
+		stem, suffix, ext := splitFileExt(file)
 		fmt.Fprintln(w, "LOCAL_STRIP_MODULE := false")
 		fmt.Fprintln(w, "LOCAL_SYSTEM_SHARED_LIBRARIES :=")
 		fmt.Fprintln(w, "LOCAL_USE_VNDK := true")
-		fmt.Fprintln(w, "LOCAL_BUILT_MODULE_STEM := $(LOCAL_MODULE)"+outputFile.Ext())
-		fmt.Fprintln(w, "LOCAL_MODULE_SUFFIX := "+filepath.Ext(file))
+		fmt.Fprintln(w, "LOCAL_BUILT_MODULE_STEM := $(LOCAL_MODULE)"+ext)
+		fmt.Fprintln(w, "LOCAL_MODULE_SUFFIX := "+suffix)
 		fmt.Fprintln(w, "LOCAL_MODULE_PATH := $(OUT_DIR)/"+filepath.Clean(dir))
 		fmt.Fprintln(w, "LOCAL_MODULE_STEM := "+stem)
 	})
@@ -408,8 +412,9 @@
 
 	ret.Extra = append(ret.Extra, func(w io.Writer, outputFile android.Path) {
 		c.libraryDecorator.androidMkWriteExportedFlags(w)
+		_, _, ext := splitFileExt(outputFile.Base())
 
-		fmt.Fprintln(w, "LOCAL_BUILT_MODULE_STEM := $(LOCAL_MODULE)"+outputFile.Ext())
+		fmt.Fprintln(w, "LOCAL_BUILT_MODULE_STEM := $(LOCAL_MODULE)"+ext)
 		fmt.Fprintln(w, "LOCAL_STRIP_MODULE := false")
 		fmt.Fprintln(w, "LOCAL_SYSTEM_SHARED_LIBRARIES :=")
 		fmt.Fprintln(w, "LOCAL_UNINSTALLABLE_MODULE := true")
diff --git a/cc/util.go b/cc/util.go
index 1e4a0c0..8de4210 100644
--- a/cc/util.go
+++ b/cc/util.go
@@ -16,6 +16,7 @@
 
 import (
 	"fmt"
+	"path/filepath"
 	"regexp"
 	"strings"
 
@@ -102,3 +103,29 @@
 	}
 	return list
 }
+
+var shlibVersionPattern = regexp.MustCompile("(?:\\.\\d+)+")
+
+// splitFileExt splits a file name into root, suffix and ext. root stands for the file name without
+// the file extension and the version number (e.g. "libexample"). suffix stands for the
+// concatenation of the file extension and the version number (e.g. ".so.1.0"). ext stands for the
+// file extension after the version numbers are trimmed (e.g. ".so").
+func splitFileExt(name string) (string, string, string) {
+	// Extract and trim the shared lib version number if the file name ends with dot digits.
+	suffix := ""
+	matches := shlibVersionPattern.FindAllStringIndex(name, -1)
+	if len(matches) > 0 {
+		lastMatch := matches[len(matches)-1]
+		if lastMatch[1] == len(name) {
+			suffix = name[lastMatch[0]:lastMatch[1]]
+			name = name[0:lastMatch[0]]
+		}
+	}
+
+	// Extract the file name root and the file extension.
+	ext := filepath.Ext(name)
+	root := strings.TrimSuffix(name, ext)
+	suffix = ext + suffix
+
+	return root, suffix, ext
+}
diff --git a/cc/util_test.go b/cc/util_test.go
new file mode 100644
index 0000000..3108294
--- /dev/null
+++ b/cc/util_test.go
@@ -0,0 +1,68 @@
+// Copyright 2018 Google Inc. All rights reserved.
+//
+// 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.
+
+package cc
+
+import (
+	"testing"
+)
+
+func TestSplitFileExt(t *testing.T) {
+	t.Run("soname with version", func(t *testing.T) {
+		root, suffix, ext := splitFileExt("libtest.so.1.0.30")
+		expected := "libtest"
+		if root != expected {
+			t.Errorf("root should be %q but got %q", expected, root)
+		}
+		expected = ".so.1.0.30"
+		if suffix != expected {
+			t.Errorf("suffix should be %q but got %q", expected, suffix)
+		}
+		expected = ".so"
+		if ext != expected {
+			t.Errorf("ext should be %q but got %q", expected, ext)
+		}
+	})
+
+	t.Run("version numbers in the middle should be ignored", func(t *testing.T) {
+		root, suffix, ext := splitFileExt("libtest.1.0.30.so")
+		expected := "libtest.1.0.30"
+		if root != expected {
+			t.Errorf("root should be %q but got %q", expected, root)
+		}
+		expected = ".so"
+		if suffix != expected {
+			t.Errorf("suffix should be %q but got %q", expected, suffix)
+		}
+		expected = ".so"
+		if ext != expected {
+			t.Errorf("ext should be %q but got %q", expected, ext)
+		}
+	})
+
+	t.Run("no known file extension", func(t *testing.T) {
+		root, suffix, ext := splitFileExt("test.exe")
+		expected := "test"
+		if root != expected {
+			t.Errorf("root should be %q but got %q", expected, root)
+		}
+		expected = ".exe"
+		if suffix != expected {
+			t.Errorf("suffix should be %q but got %q", expected, suffix)
+		}
+		if ext != expected {
+			t.Errorf("ext should be %q but got %q", expected, ext)
+		}
+	})
+}