Creation of C Flags Build Variables

Modifications made to soong/cc to look for specific C Flags used by
Android modules and store name of module into a build variable array.

Bug: 140442588
Test: Executed m dist and presubmit
Change-Id: If46a11462369c43bbcd445156aff0641514c58b1

Android.bp

@@ -172,6 +172,7 @@ bootstrap_go_package {
         "cc/vndk_prebuilt.go",
         "cc/xom.go",
 
+        "cc/cflag_artifacts.go",
         "cc/cmakelists.go",
         "cc/compdb.go",
         "cc/compiler.go",

cc/cflag_artifacts.go

@@ -0,0 +1,188 @@
+package cc
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+
+	"github.com/google/blueprint/proptools"
+
+	"android/soong/android"
+)
+
+func init() {
+	android.RegisterSingletonType("cflag_artifacts_text", cflagArtifactsTextFactory)
+}
+
+var (
+	TrackedCFlags = []string{
+		"-Wall",
+		"-Werror",
+		"-Wextra",
+		"-Wthread-safety",
+		"-O3",
+	}
+
+	TrackedCFlagsDir = []string{
+		"device/google/",
+		"vendor/google/",
+	}
+)
+
+const FileBP = 50
+
+// Stores output files.
+type cflagArtifactsText struct {
+	interOutputs map[string]android.WritablePaths
+	outputs      android.WritablePaths
+}
+
+// allowedDir verifies if the directory/project is part of the TrackedCFlagsDir
+// filter.
+func allowedDir(subdir string) bool {
+	subdir += "/"
+	for _, prefix := range TrackedCFlagsDir {
+		if strings.HasPrefix(subdir, prefix) {
+			return true
+		}
+	}
+	return false
+}
+
+func (s *cflagArtifactsText) genFlagFilename(flag string) string {
+	return fmt.Sprintf("module_cflags%s.txt", flag)
+}
+
+// incrementFile is used to generate an output path object with the passed in flag
+// and part number.
+// e.g. FLAG + part # -> out/soong/cflags/module_cflags-FLAG.txt.0
+func (s *cflagArtifactsText) incrementFile(ctx android.SingletonContext,
+	flag string, part int) (string, android.OutputPath) {
+
+	filename := fmt.Sprintf("%s.%d", s.genFlagFilename(flag), part)
+	filepath := android.PathForOutput(ctx, "cflags", filename)
+	s.interOutputs[flag] = append(s.interOutputs[flag], filepath)
+	return filename, filepath
+}
+
+// GenCFlagArtifactParts is used to generate the build rules which produce the
+// intermediary files for each desired C Flag artifact
+// e.g. module_cflags-FLAG.txt.0, module_cflags-FLAG.txt.1, ...
+func (s *cflagArtifactsText) GenCFlagArtifactParts(ctx android.SingletonContext,
+	flag string, using bool, modules []string, part int) int {
+
+	cleanedName := strings.Replace(flag, "=", "_", -1)
+	filename, filepath := s.incrementFile(ctx, cleanedName, part)
+	rule := android.NewRuleBuilder()
+	rule.Command().Textf("rm -f %s", filepath.String())
+
+	if using {
+		rule.Command().
+			Textf("echo '# Modules using %s'", flag).
+			FlagWithOutput(">> ", filepath)
+	} else {
+		rule.Command().
+			Textf("echo '# Modules not using %s'", flag).
+			FlagWithOutput(">> ", filepath)
+	}
+
+	length := len(modules)
+
+	if length == 0 {
+		rule.Build(pctx, ctx, filename, "gen "+filename)
+		part++
+	}
+
+	// Following loop splits the module list for each tracked C Flag into
+	// chunks of length FileBP (file breakpoint) and generates a partial artifact
+	// (intermediary file) build rule for each split.
+	moduleShards := android.ShardStrings(modules, FileBP)
+	for index, shard := range moduleShards {
+		rule.Command().
+			Textf("for m in %s; do echo $m",
+				strings.Join(proptools.ShellEscapeList(shard), " ")).
+			FlagWithOutput(">> ", filepath).
+			Text("; done")
+		rule.Build(pctx, ctx, filename, "gen "+filename)
+
+		if index+1 != len(moduleShards) {
+			filename, filepath = s.incrementFile(ctx, cleanedName, part+index+1)
+			rule = android.NewRuleBuilder()
+			rule.Command().Textf("rm -f %s", filepath.String())
+		}
+	}
+
+	return part + len(moduleShards)
+}
+
+// GenCFlagArtifacts is used to generate build rules which combine the
+// intermediary files of a specific tracked flag into a single C Flag artifact
+// for each tracked flag.
+// e.g. module_cflags-FLAG.txt.0 + module_cflags-FLAG.txt.1 = module_cflags-FLAG.txt
+func (s *cflagArtifactsText) GenCFlagArtifacts(ctx android.SingletonContext) {
+	// Scans through s.interOutputs and creates a build rule for each tracked C
+	// Flag that concatenates the associated intermediary file into a single
+	// artifact.
+	for _, flag := range TrackedCFlags {
+		// Generate build rule to combine related intermediary files into a
+		// C Flag artifact
+		rule := android.NewRuleBuilder()
+		filename := s.genFlagFilename(flag)
+		outputpath := android.PathForOutput(ctx, "cflags", filename)
+		rule.Command().
+			Text("cat").
+			Inputs(s.interOutputs[flag].Paths()).
+			FlagWithOutput("> ", outputpath)
+		rule.Build(pctx, ctx, filename, "gen "+filename)
+		s.outputs = append(s.outputs, outputpath)
+	}
+}
+
+func (s *cflagArtifactsText) GenerateBuildActions(ctx android.SingletonContext) {
+	modulesWithCFlag := make(map[string][]string)
+
+	// Scan through all modules, selecting the ones that are part of the filter,
+	// and then storing into a map which tracks whether or not tracked C flag is
+	// used or not.
+	ctx.VisitAllModules(func(module android.Module) {
+		if ccModule, ok := module.(*Module); ok {
+			if allowedDir(ctx.ModuleDir(ccModule)) {
+				cflags := ccModule.flags.CFlags
+				cppflags := ccModule.flags.CppFlags
+				module := fmt.Sprintf("%s:%s (%s)",
+					ctx.BlueprintFile(ccModule),
+					ctx.ModuleName(ccModule),
+					ctx.ModuleSubDir(ccModule))
+				for _, flag := range TrackedCFlags {
+					if inList(flag, cflags) || inList(flag, cppflags) {
+						modulesWithCFlag[flag] = append(modulesWithCFlag[flag], module)
+					} else {
+						modulesWithCFlag["!"+flag] = append(modulesWithCFlag["!"+flag], module)
+					}
+				}
+			}
+		}
+	})
+
+	// Traversing map and setting up rules to produce intermediary files which
+	// contain parts of each expected C Flag artifact.
+	for _, flag := range TrackedCFlags {
+		sort.Strings(modulesWithCFlag[flag])
+		part := s.GenCFlagArtifactParts(ctx, flag, true, modulesWithCFlag[flag], 0)
+		sort.Strings(modulesWithCFlag["!"+flag])
+		s.GenCFlagArtifactParts(ctx, flag, false, modulesWithCFlag["!"+flag], part)
+	}
+
+	// Combine intermediary files into a single C Flag artifact.
+	s.GenCFlagArtifacts(ctx)
+}
+
+func cflagArtifactsTextFactory() android.Singleton {
+	return &cflagArtifactsText{
+		interOutputs: make(map[string]android.WritablePaths),
+	}
+}
+
+func (s *cflagArtifactsText) MakeVars(ctx android.MakeVarsContext) {
+	ctx.Strict("SOONG_MODULES_CFLAG_ARTIFACTS", strings.Join(s.outputs.Strings(), " "))
+}