Native Coverage support in Soong (gcov)

This is configured the same as make -- a global NATIVE_COVERAGE=true
flag to allow native coverage, then COVERAGE_PATHS=path1,path2,... to
turn it on for certain paths.

There are .gcnodir files exported to Make and saved in $OUT/coverage/...
files which are `ar` archives containing all of the compiler-produced
.gcno files for a particular executable / shared library.

Unlike the Make implementation, this only passes links the helper
library (automatically through --coverage) when one of the object files
or static libraries being used actually has coverage enabled.

Host support is currently disabled, since we set -nodefaultlibs, which
prevents libclang_rt.profile-*.a from being picked up automatically.

Bug: 32749731
Test: NATIVE_COVERAGE=true COVERAGE_PATHS=system/core/libcutils m -j libbacktrace libutils tombstoned
      $OUT/coverage/system/lib*/libcutils.gcnodir looks correct (self)
      $OUT/coverage/system/lib*/libbacktrace.gcnodir looks correct (static)
      $OUT/coverage/system/lib*/libutils.gcnodir doesn't exist (shared)
      $OUT/coverage/system/bin/tombstoned.gcnodir looks correct (executable)
Test: NATIVE_COVERAGE=true COVERAGE_PATHS=external/libcxxabi m -j libc++
      Confirm that $OUT/coverage/system/lib*/libc++.gcnodir looks correct (whole_static_libs)
Change-Id: I48aaa0ba8d76e50e9c2d1151421c0c6dc8ed79a9

7 files changed, 236 insertions, 20 deletions

diff --git a/cc/androidmk.go b/cc/androidmk.go
index a5a625fe..198c6106 100644
--- a/cc/androidmk.go
+++ b/cc/androidmk.go
@@ -111,6 +111,10 @@ func (library *libraryDecorator) AndroidMk(ctx AndroidMkContext, ret *android.An
 
 		fmt.Fprintln(w, "LOCAL_SYSTEM_SHARED_LIBRARIES :=")
 
+		if library.coverageOutputFile.Valid() {
+			fmt.Fprintln(w, "LOCAL_PREBUILT_COVERAGE_ARCHIVE :=", library.coverageOutputFile.String())
+		}
+
 		return nil
 	})
 
@@ -145,6 +149,9 @@ func (binary *binaryDecorator) AndroidMk(ctx AndroidMkContext, ret *android.Andr
 			fmt.Fprintln(w, "LOCAL_MODULE_SYMLINKS := "+strings.Join(binary.symlinks, " "))
 		}
 
+		if binary.coverageOutputFile.Valid() {
+			fmt.Fprintln(w, "LOCAL_PREBUILT_COVERAGE_ARCHIVE :=", binary.coverageOutputFile.String())
+		}
 		return nil
 	})
 }
diff --git a/cc/binary.go b/cc/binary.go
index afc8a990..521ccb70 100644
--- a/cc/binary.go
+++ b/cc/binary.go
@@ -79,6 +79,9 @@ type binaryDecorator struct {
 
 	// Names of symlinks to be installed for use in LOCAL_MODULE_SYMLINKS
 	symlinks []string
+
+	// Output archive of gcno coverage information
+	coverageOutputFile android.OptionalPath
 }
 
 var _ linker = (*binaryDecorator)(nil)
@@ -299,6 +302,10 @@ func (binary *binaryDecorator) link(ctx ModuleContext,
 		deps.LateStaticLibs, deps.WholeStaticLibs, linkerDeps, deps.CrtBegin, deps.CrtEnd, true,
 		builderFlags, outputFile)
 
+	objs.coverageFiles = append(objs.coverageFiles, deps.StaticLibObjs.coverageFiles...)
+	objs.coverageFiles = append(objs.coverageFiles, deps.WholeStaticLibObjs.coverageFiles...)
+	binary.coverageOutputFile = TransformCoverageFilesToLib(ctx, objs, builderFlags, binary.getStem(ctx))
+
 	return ret
 }
 
diff --git a/cc/builder.go b/cc/builder.go
index c9a6722b..9a871d55 100644
--- a/cc/builder.go
+++ b/cc/builder.go
@@ -198,6 +198,7 @@ type builderFlags struct {
 	toolchain   config.Toolchain
 	clang       bool
 	tidy        bool
+	coverage    bool
 
 	groupStaticLibs bool
 
@@ -207,21 +208,24 @@ type builderFlags struct {
 }
 
 type Objects struct {
-	objFiles  android.Paths
-	tidyFiles android.Paths
+	objFiles      android.Paths
+	tidyFiles     android.Paths
+	coverageFiles android.Paths
 }
 
 func (a Objects) Copy() Objects {
 	return Objects{
-		objFiles:  append(android.Paths{}, a.objFiles...),
-		tidyFiles: append(android.Paths{}, a.tidyFiles...),
+		objFiles:      append(android.Paths{}, a.objFiles...),
+		tidyFiles:     append(android.Paths{}, a.tidyFiles...),
+		coverageFiles: append(android.Paths{}, a.coverageFiles...),
 	}
 }
 
 func (a Objects) Append(b Objects) Objects {
 	return Objects{
-		objFiles:  append(a.objFiles, b.objFiles...),
-		tidyFiles: append(a.tidyFiles, b.tidyFiles...),
+		objFiles:      append(a.objFiles, b.objFiles...),
+		tidyFiles:     append(a.tidyFiles, b.tidyFiles...),
+		coverageFiles: append(a.coverageFiles, b.coverageFiles...),
 	}
 }
 
@@ -234,6 +238,10 @@ func TransformSourceToObj(ctx android.ModuleContext, subdir string, srcFiles and
 	if flags.tidy && flags.clang {
 		tidyFiles = make(android.Paths, 0, len(srcFiles))
 	}
+	var coverageFiles android.Paths
+	if flags.coverage {
+		coverageFiles = make(android.Paths, 0, len(srcFiles))
+	}
 
 	cflags := flags.globalFlags + " " + flags.cFlags + " " + flags.conlyFlags
 	cppflags := flags.globalFlags + " " + flags.cFlags + " " + flags.cppFlags
@@ -268,12 +276,14 @@ func TransformSourceToObj(ctx android.ModuleContext, subdir string, srcFiles and
 		var moduleCflags string
 		var ccCmd string
 		tidy := flags.tidy && flags.clang
+		coverage := flags.coverage
 
 		switch srcFile.Ext() {
 		case ".S", ".s":
 			ccCmd = "gcc"
 			moduleCflags = asflags
 			tidy = false
+			coverage = false
 		case ".c":
 			ccCmd = "gcc"
 			moduleCflags = cflags
@@ -300,11 +310,19 @@ func TransformSourceToObj(ctx android.ModuleContext, subdir string, srcFiles and
 			ccCmd = gccCmd(flags.toolchain, ccCmd)
 		}
 
+		var implicitOutputs android.WritablePaths
+		if coverage {
+			gcnoFile := android.ObjPathWithExt(ctx, subdir, srcFile, "gcno")
+			implicitOutputs = append(implicitOutputs, gcnoFile)
+			coverageFiles = append(coverageFiles, gcnoFile)
+		}
+
 		ctx.ModuleBuild(pctx, android.ModuleBuildParams{
-			Rule:      cc,
-			Output:    objFile,
-			Input:     srcFile,
-			OrderOnly: deps,
+			Rule:            cc,
+			Output:          objFile,
+			ImplicitOutputs: implicitOutputs,
+			Input:           srcFile,
+			OrderOnly:       deps,
 			Args: map[string]string{
 				"cFlags": moduleCflags,
 				"ccCmd":  ccCmd,
@@ -332,8 +350,9 @@ func TransformSourceToObj(ctx android.ModuleContext, subdir string, srcFiles and
 	}
 
 	return Objects{
-		objFiles:  objFiles,
-		tidyFiles: tidyFiles,
+		objFiles:      objFiles,
+		tidyFiles:     tidyFiles,
+		coverageFiles: coverageFiles,
 	}
 }
 
@@ -341,6 +360,11 @@ func TransformSourceToObj(ctx android.ModuleContext, subdir string, srcFiles and
 func TransformObjToStaticLib(ctx android.ModuleContext, objFiles android.Paths,
 	flags builderFlags, outputFile android.ModuleOutPath, deps android.Paths) {
 
+	if ctx.Darwin() {
+		transformDarwinObjToStaticLib(ctx, objFiles, flags, outputFile, deps)
+		return
+	}
+
 	arCmd := gccCmd(flags.toolchain, "ar")
 	arFlags := "crsPD"
 
@@ -360,7 +384,7 @@ func TransformObjToStaticLib(ctx android.ModuleContext, objFiles android.Paths,
 // darwin.  The darwin ar tool doesn't support @file for list files, and has a
 // very small command line length limit, so we have to split the ar into multiple
 // steps, each appending to the previous one.
-func TransformDarwinObjToStaticLib(ctx android.ModuleContext, objFiles android.Paths,
+func transformDarwinObjToStaticLib(ctx android.ModuleContext, objFiles android.Paths,
 	flags builderFlags, outputPath android.ModuleOutPath, deps android.Paths) {
 
 	arFlags := "cqs"
@@ -599,6 +623,20 @@ func TransformDarwinStrip(ctx android.ModuleContext, inputFile android.Path,
 	})
 }
 
+func TransformCoverageFilesToLib(ctx android.ModuleContext,
+	inputs Objects, flags builderFlags, baseName string) android.OptionalPath {
+
+	if len(inputs.coverageFiles) > 0 {
+		outputFile := android.PathForModuleOut(ctx, baseName+".gcnodir")
+
+		TransformObjToStaticLib(ctx, inputs.coverageFiles, flags, outputFile, nil)
+
+		return android.OptionalPathForPath(outputFile)
+	}
+
+	return android.OptionalPath{}
+}
+
 func CopyGccLib(ctx android.ModuleContext, libName string,
 	flags builderFlags, outputFile android.WritablePath) {
 
diff --git a/cc/cc.go b/cc/cc.go
index 3824b451..d486db3f 100644
--- a/cc/cc.go
+++ b/cc/cc.go
@@ -46,6 +46,8 @@ func init() {
 
 		ctx.TopDown("tsan_deps", sanitizerDepsMutator(tsan))
 		ctx.BottomUp("tsan", sanitizerMutator(tsan)).Parallel()
+
+		ctx.BottomUp("coverage", coverageLinkingMutator).Parallel()
 	})
 
 	pctx.Import("android/soong/cc/config")
@@ -78,6 +80,7 @@ type PathDeps struct {
 
 	// Paths to .o files
 	Objs               Objects
+	StaticLibObjs      Objects
 	WholeStaticLibObjs Objects
 
 	// Paths to generated source files
@@ -108,6 +111,7 @@ type Flags struct {
 	Toolchain config.Toolchain
 	Clang     bool
 	Tidy      bool
+	Coverage  bool
 
 	RequiredInstructionSet string
 	DynamicLinker          string
@@ -144,8 +148,7 @@ type BaseProperties struct {
 }
 
 type UnusedProperties struct {
-	Native_coverage *bool
-	Tags            []string
+	Tags []string
 }
 
 type ModuleContextIntf interface {
@@ -261,6 +264,7 @@ type Module struct {
 	installer installer
 	stl       *stl
 	sanitize  *sanitize
+	coverage  *coverage
 
 	androidMkSharedLibDeps []string
 
@@ -291,6 +295,9 @@ func (c *Module) Init() (blueprint.Module, []interface{}) {
 	if c.sanitize != nil {
 		props = append(props, c.sanitize.props()...)
 	}
+	if c.coverage != nil {
+		props = append(props, c.coverage.props()...)
+	}
 	for _, feature := range c.features {
 		props = append(props, feature.props()...)
 	}
@@ -411,6 +418,7 @@ func newModule(hod android.HostOrDeviceSupported, multilib android.Multilib) *Mo
 	}
 	module.stl = &stl{}
 	module.sanitize = &sanitize{}
+	module.coverage = &coverage{}
 	return module
 }
 
@@ -454,6 +462,9 @@ func (c *Module) GenerateAndroidBuildActions(actx android.ModuleContext) {
 	if c.sanitize != nil {
 		flags = c.sanitize.flags(ctx, flags)
 	}
+	if c.coverage != nil {
+		flags = c.coverage.flags(ctx, flags)
+	}
 	for _, feature := range c.features {
 		flags = feature.flags(ctx, flags)
 	}
@@ -525,6 +536,9 @@ func (c *Module) begin(ctx BaseModuleContext) {
 	if c.sanitize != nil {
 		c.sanitize.begin(ctx)
 	}
+	if c.coverage != nil {
+		c.coverage.begin(ctx)
+	}
 	for _, feature := range c.features {
 		feature.begin(ctx)
 	}
@@ -563,6 +577,9 @@ func (c *Module) deps(ctx DepsContext) Deps {
 	if c.sanitize != nil {
 		deps = c.sanitize.deps(ctx, deps)
 	}
+	if c.coverage != nil {
+		deps = c.coverage.deps(ctx, deps)
+	}
 	for _, feature := range c.features {
 		deps = feature.deps(ctx, deps)
 	}
@@ -951,6 +968,20 @@ func (c *Module) depsToPaths(ctx android.ModuleContext) PathDeps {
 			depPaths.CrtEnd = linkFile
 		}
 
+		switch tag {
+		case staticDepTag, staticExportDepTag, lateStaticDepTag:
+			staticLib, ok := cc.linker.(libraryInterface)
+			if !ok || !staticLib.static() {
+				ctx.ModuleErrorf("module %q not a static library", name)
+				return
+			}
+
+			// When combining coverage files for shared libraries and executables, coverage files
+			// in static libraries act as if they were whole static libraries.
+			depPaths.StaticLibObjs.coverageFiles = append(depPaths.StaticLibObjs.coverageFiles,
+				staticLib.objs().coverageFiles...)
+		}
+
 		if ptr != nil {
 			if !linkFile.Valid() {
 				ctx.ModuleErrorf("module %q missing output file", name)
@@ -1024,6 +1055,7 @@ func DefaultsFactory(props ...interface{}) (blueprint.Module, []interface{}) {
 		&StripProperties{},
 		&InstallerProperties{},
 		&TidyProperties{},
+		&CoverageProperties{},
 	)
 
 	return android.InitDefaultsModule(module, module, props...)
diff --git a/cc/coverage.go b/cc/coverage.go
new file mode 100644
index 00000000..b1c87837
--- /dev/null
+++ b/cc/coverage.go
@@ -0,0 +1,124 @@
+// Copyright 2017 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 (
+	"android/soong/android"
+	"github.com/google/blueprint"
+)
+
+type CoverageProperties struct {
+	Native_coverage *bool
+
+	CoverageEnabled bool `blueprint:"mutated"`
+}
+
+type coverage struct {
+	Properties CoverageProperties
+
+	// Whether binaries containing this module need --coverage added to their ldflags
+	linkCoverage bool
+}
+
+func (cov *coverage) props() []interface{} {
+	return []interface{}{&cov.Properties}
+}
+
+func (cov *coverage) begin(ctx BaseModuleContext) {}
+
+func (cov *coverage) deps(ctx BaseModuleContext, deps Deps) Deps {
+	return deps
+}
+
+func (cov *coverage) flags(ctx ModuleContext, flags Flags) Flags {
+	if !ctx.DeviceConfig().NativeCoverageEnabled() {
+		return flags
+	}
+
+	if cov.Properties.CoverageEnabled {
+		flags.Coverage = true
+		flags.GlobalFlags = append(flags.GlobalFlags, "--coverage", "-O0")
+		cov.linkCoverage = true
+	}
+
+	// Even if we don't have coverage enabled, if any of our object files were compiled
+	// with coverage, then we need to add --coverage to our ldflags.
+	if !cov.linkCoverage {
+		if ctx.static() && !ctx.staticBinary() {
+			// For static libraries, the only thing that changes our object files
+			// are included whole static libraries, so check to see if any of
+			// those have coverage enabled.
+			ctx.VisitDirectDeps(func(m blueprint.Module) {
+				if ctx.OtherModuleDependencyTag(m) != wholeStaticDepTag {
+					return
+				}
+
+				if cc, ok := m.(*Module); ok && cc.coverage != nil {
+					if cc.coverage.linkCoverage {
+						cov.linkCoverage = true
+					}
+				}
+			})
+		} else {
+			// For executables and shared libraries, we need to check all of
+			// our static dependencies.
+			ctx.VisitDirectDeps(func(m blueprint.Module) {
+				cc, ok := m.(*Module)
+				if !ok || cc.coverage == nil {
+					return
+				}
+
+				if static, ok := cc.linker.(libraryInterface); !ok || !static.static() {
+					return
+				}
+
+				if cc.coverage.linkCoverage {
+					cov.linkCoverage = true
+				}
+			})
+		}
+	}
+
+	if cov.linkCoverage {
+		flags.LdFlags = append(flags.LdFlags, "--coverage")
+	}
+
+	return flags
+}
+
+func coverageLinkingMutator(mctx android.BottomUpMutatorContext) {
+	if c, ok := mctx.Module().(*Module); ok && c.coverage != nil {
+		var enabled bool
+
+		if !mctx.DeviceConfig().NativeCoverageEnabled() {
+			// Coverage is disabled globally
+		} else if mctx.Host() {
+			// TODO(dwillemsen): because of -nodefaultlibs, we must depend on libclang_rt.profile-*.a
+			// Just turn off for now.
+		} else if c.coverage.Properties.Native_coverage != nil {
+			enabled = *c.coverage.Properties.Native_coverage
+		} else {
+			enabled = mctx.DeviceConfig().CoverageEnabledForPath(mctx.ModuleDir())
+		}
+
+		if enabled {
+			// Create a variation so that we don't need to recompile objects
+			// when turning on or off coverage. We'll still relink the necessary
+			// binaries, since we don't know which ones those are until later.
+			m := mctx.CreateLocalVariations("cov")
+			m[0].(*Module).coverage.Properties.CoverageEnabled = true
+		}
+	}
+}
diff --git a/cc/library.go b/cc/library.go
index 8474f969..efaf4408 100644
--- a/cc/library.go
+++ b/cc/library.go
@@ -199,6 +199,9 @@ type libraryDecorator struct {
 
 	sanitize *sanitize
 
+	// Output archive of gcno coverage information files
+	coverageOutputFile android.OptionalPath
+
 	// Decorated interafaces
 	*baseCompiler
 	*baseLinker
@@ -393,12 +396,12 @@ func (library *libraryDecorator) linkStatic(ctx ModuleContext,
 
 	outputFile := android.PathForModuleOut(ctx,
 		ctx.ModuleName()+library.Properties.VariantName+staticLibraryExtension)
+	builderFlags := flagsToBuilderFlags(flags)
 
-	if ctx.Darwin() {
-		TransformDarwinObjToStaticLib(ctx, library.objects.objFiles, flagsToBuilderFlags(flags), outputFile, objs.tidyFiles)
-	} else {
-		TransformObjToStaticLib(ctx, library.objects.objFiles, flagsToBuilderFlags(flags), outputFile, objs.tidyFiles)
-	}
+	TransformObjToStaticLib(ctx, library.objects.objFiles, builderFlags, outputFile, objs.tidyFiles)
+
+	library.coverageOutputFile = TransformCoverageFilesToLib(ctx, library.objects, builderFlags,
+		ctx.ModuleName()+library.Properties.VariantName)
 
 	library.wholeStaticMissingDeps = ctx.GetMissingDependencies()
 
@@ -506,6 +509,10 @@ func (library *libraryDecorator) linkShared(ctx ModuleContext,
 		deps.StaticLibs, deps.LateStaticLibs, deps.WholeStaticLibs,
 		linkerDeps, deps.CrtBegin, deps.CrtEnd, false, builderFlags, outputFile)
 
+	objs.coverageFiles = append(objs.coverageFiles, deps.StaticLibObjs.coverageFiles...)
+	objs.coverageFiles = append(objs.coverageFiles, deps.WholeStaticLibObjs.coverageFiles...)
+	library.coverageOutputFile = TransformCoverageFilesToLib(ctx, objs, builderFlags, library.getLibName(ctx))
+
 	return ret
 }
 
diff --git a/cc/util.go b/cc/util.go
index 466266c3..570052ea 100644
--- a/cc/util.go
+++ b/cc/util.go
@@ -101,6 +101,7 @@ func flagsToBuilderFlags(in Flags) builderFlags {
 		yasmFlags:   strings.Join(in.YasmFlags, " "),
 		toolchain:   in.Toolchain,
 		clang:       in.Clang,
+		coverage:    in.Coverage,
 		tidy:        in.Tidy,
 
 		groupStaticLibs: in.GroupStaticLibs,