Set __<libname>_API__ macro when building against stubs

When building against libFoo#ver, __LIBFOO_API__ macro is set to ver so
that headers from libFoo can be conditionally compiled (e.g., hide APIs
that are not available for the version, etc.)

Bug: 112672359
Test: m (cc_test added)
Change-Id: I863ef95b385cdd842eec1bf34e81f44b5e3b58b3

cc/cc_test.go

@@ -1738,13 +1738,16 @@ func TestVersionedStubs(t *testing.T) {
 	ctx := testCc(t, `
 		cc_library_shared {
 			name: "libFoo",
+			srcs: ["foo.c"],
 			stubs: {
 				symbol_file: "foo.map.txt",
 				versions: ["1", "2", "3"],
 			},
 		}
+
 		cc_library_shared {
 			name: "libBar",
+			srcs: ["bar.c"],
 			shared_libs: ["libFoo#1"],
 		}`)
 
@@ -1786,4 +1789,11 @@ func TestVersionedStubs(t *testing.T) {
 	if !strings.Contains(libFlags, libFoo1StubPath) {
 		t.Errorf("%q is not found in %q", libFoo1StubPath, libFlags)
 	}
+
+	libBarCompileRule := ctx.ModuleForTests("libBar", "android_arm64_armv8-a_core_shared").Rule("cc")
+	cFlags := libBarCompileRule.Args["cFlags"]
+	libFoo1VersioningMacro := "-D__LIBFOO_API__=1"
+	if !strings.Contains(cFlags, libFoo1VersioningMacro) {
+		t.Errorf("%q is not found in %q", libFoo1VersioningMacro, cFlags)
+	}
 }

cc/library.go

@@ -15,7 +15,9 @@
 package cc
 
 import (
+	"regexp"
 	"strings"
+	"sync"
 
 	"github.com/google/blueprint"
 	"github.com/google/blueprint/pathtools"
@@ -443,6 +445,8 @@ func (library *libraryDecorator) getLibName(ctx ModuleContext) string {
 	return name + library.MutatedProperties.VariantName
 }
 
+var versioningMacroNamesListMutex sync.Mutex
+
 func (library *libraryDecorator) linkerInit(ctx BaseModuleContext) {
 	location := InstallInSystem
 	if library.baseLinker.sanitize.inSanitizerDir() {
@@ -453,6 +457,18 @@ func (library *libraryDecorator) linkerInit(ctx BaseModuleContext) {
 	// Let baseLinker know whether this variant is for stubs or not, so that
 	// it can omit things that are not required for linking stubs.
 	library.baseLinker.dynamicProperties.BuildStubs = library.buildStubs()
+
+	if library.buildStubs() {
+		macroNames := versioningMacroNamesList(ctx.Config())
+		myName := versioningMacroName(ctx.ModuleName())
+		versioningMacroNamesListMutex.Lock()
+		defer versioningMacroNamesListMutex.Unlock()
+		if (*macroNames)[myName] == "" {
+			(*macroNames)[myName] = ctx.ModuleName()
+		} else if (*macroNames)[myName] != ctx.ModuleName() {
+			ctx.ModuleErrorf("Macro name %q for versioning conflicts with macro name from module %q ", myName, (*macroNames)[myName])
+		}
+	}
 }
 
 func (library *libraryDecorator) linkerDeps(ctx DepsContext, deps Deps) Deps {
@@ -715,6 +731,10 @@ func (library *libraryDecorator) link(ctx ModuleContext,
 		library.reuseExportedFlags = append(library.reuseExportedFlags, flags...)
 	}
 
+	if library.buildStubs() {
+		library.reexportFlags([]string{"-D" + versioningMacroName(ctx.ModuleName()) + "=" + library.stubsVersion()})
+	}
+
 	return out
 }
 
@@ -823,6 +843,23 @@ func (library *libraryDecorator) stubsVersion() string {
 	return library.MutatedProperties.StubsVersion
 }
 
+func versioningMacroNamesList(config android.Config) *map[string]string {
+	return config.Once("versioningMacroNamesList", func() interface{} {
+		m := make(map[string]string)
+		return &m
+	}).(*map[string]string)
+}
+
+// alphanumeric and _ characters are preserved.
+// other characters are all converted to _
+var charsNotForMacro = regexp.MustCompile("[^a-zA-Z0-9_]+")
+
+func versioningMacroName(moduleName string) string {
+	macroName := charsNotForMacro.ReplaceAllString(moduleName, "_")
+	macroName = strings.ToUpper(moduleName)
+	return "__" + macroName + "_API__"
+}
+
 func NewLibrary(hod android.HostOrDeviceSupported) (*Module, *libraryDecorator) {
 	module := newModule(hod, android.MultilibBoth)