address comments on code

doc/README.md

@@ -229,7 +229,7 @@ the output are relative to the total of samples in the diff base profile.
 * **-base= _profile_:** useful for subtracting a cumulative profile, like a
 [golang block profile](https://golang.org/doc/diagnostics.html#profiling),
 from another cumulative profile collected from the same program at a later time.
-When comparing cumulative profiles collected on the same profile, percentages in
+When comparing cumulative profiles collected on the same program, percentages in
 the output are relative to the difference between the total for the source
 profile and the total for the base profile.
 

internal/driver/cli.go

@@ -142,7 +142,7 @@ func parseFlags(o *plugin.Options) (*source, []string, error) {
 		Comment:      *flagAddComment,
 	}
 
-	if err := source.addBaseProfiles(flagBase, flagDiffBase); err != nil {
+	if err := source.addBaseProfiles(*flagBase, *flagDiffBase); err != nil {
 		return nil, nil, err
 	}
 
@@ -161,9 +161,9 @@ func parseFlags(o *plugin.Options) (*source, []string, error) {
 // addBaseProfiles adds the list of base profiles or diff base profiles to
 // the source. This function will return an error if both base and diff base
 // profiles are specified.
-func (source *source) addBaseProfiles(flagBase, flagDiffBase *[]*string) error {
-	base := parseStringListFlag(flagBase)
-	diffBase := parseStringListFlag(flagDiffBase)
+func (source *source) addBaseProfiles(flagBase, flagDiffBase []*string) error {
+	base := dropEmpty(flagBase)
+	diffBase := dropEmpty(flagDiffBase)
 
 	if len(base) > 0 && len(diffBase) > 0 {
 		return fmt.Errorf("-base and -diff_base flags cannot both be specified")
@@ -177,11 +177,11 @@ func (source *source) addBaseProfiles(flagBase, flagDiffBase *[]*string) error {
 	return nil
 }
 
-// parseStringListFlag list takes a StringList flag, and outputs an array of non-empty
+// dropEmpty list takes a StringList flag, and outputs an array of non-empty
 // strings associated with the flag.
-func parseStringListFlag(list *[]*string) []string {
+func dropEmpty(list []*string) []string {
 	var l []string
-	for _, s := range *list {
+	for _, s := range list {
 		if *s != "" {
 			l = append(l, *s)
 		}

internal/driver/fetch.go

@@ -57,12 +57,15 @@ func fetchProfiles(s *source, o *plugin.Options) (*profile.Profile, error) {
 		})
 	}
 
-	p, pbase, m, mbase, save, err := grabSourcesAndBases(sources, bases, s.DiffBase, o.Fetch, o.Obj, o.UI)
+	p, pbase, m, mbase, save, err := grabSourcesAndBases(sources, bases, o.Fetch, o.Obj, o.UI)
 	if err != nil {
 		return nil, err
 	}
 
 	if pbase != nil {
+		if s.DiffBase {
+			pbase.SetLabel("pprof::base", []string{"true"})
+		}
 		if s.Normalize {
 			err := p.Normalize(pbase)
 			if err != nil {
@@ -120,7 +123,7 @@ func fetchProfiles(s *source, o *plugin.Options) (*profile.Profile, error) {
 	return p, nil
 }
 
-func grabSourcesAndBases(sources, bases []profileSource, isDiffBase bool, fetch plugin.Fetcher, obj plugin.ObjTool, ui plugin.UI) (*profile.Profile, *profile.Profile, plugin.MappingSources, plugin.MappingSources, bool, error) {
+func grabSourcesAndBases(sources, bases []profileSource, fetch plugin.Fetcher, obj plugin.ObjTool, ui plugin.UI) (*profile.Profile, *profile.Profile, plugin.MappingSources, plugin.MappingSources, bool, error) {
 	wg := sync.WaitGroup{}
 	wg.Add(2)
 	var psrc, pbase *profile.Profile
@@ -135,9 +138,6 @@ func grabSourcesAndBases(sources, bases []profileSource, isDiffBase bool, fetch
 	go func() {
 		defer wg.Done()
 		pbase, mbase, savebase, countbase, errbase = chunkedGrab(bases, fetch, obj, ui)
-		if pbase != nil && isDiffBase {
-			pbase.SetTag("pprof::base", []string{"true"})
-		}
 	}()
 	wg.Wait()
 	save := savesrc || savebase

internal/report/report.go

@@ -266,7 +266,7 @@ func (rpt *Report) newGraph(nodes graph.NodeSet) *graph.Graph {
 
 	// Remove tag marking samples from the base profiles, so it does not appear
 	// as a nodelet in the graph view.
-	prof.SetTag("pprof::base", []string{})
+	prof.RemoveLabel("pprof::base")
 
 	formatTag := func(v int64, key string) string {
 		return measurement.ScaledLabel(v, key, o.OutputUnit)
@@ -1232,7 +1232,7 @@ func computeTotal(prof *profile.Profile, value, meanDiv func(v []int64) int64) i
 		}
 		total += v
 		div += d
-		if sample.HasTag("pprof::base", "true") {
+		if sample.HasLabel("pprof::base", "true") {
 			diffTotal += v
 			diffDiv += d
 		}

profile/profile.go

@@ -674,9 +674,9 @@ func numLabelsToString(numLabels map[string][]int64, numUnits map[string][]strin
 	return strings.Join(ls, " ")
 }
 
-// SetTag sets the specified key to the specified value for all samples in the
+// SetLabel sets the specified key to the specified value for all samples in the
 // profile.
-func (p *Profile) SetTag(key string, value []string) {
+func (p *Profile) SetLabel(key string, value []string) {
 	for _, sample := range p.Sample {
 		if sample.Label == nil {
 			sample.Label = map[string][]string{}
@@ -685,8 +685,18 @@ func (p *Profile) SetTag(key string, value []string) {
 	}
 }
 
-// HasTag returns true if a sample has a tag with indicated key and value.
-func (s *Sample) HasTag(key, value string) bool {
+// RemoveLabel removes all labels associated with the specified key for all
+// samples in the profile.
+func (p *Profile) RemoveLabel(key string) {
+	for _, sample := range p.Sample {
+		if _, ok := sample.Label[key]; ok {
+			delete(sample.Label, key)
+		}
+	}
+}
+
+// HasLabel returns true if a sample has a label with indicated key and value.
+func (s *Sample) HasLabel(key, value string) bool {
 	if values, ok := s.Label[key]; ok {
 		for _, v := range values {
 			if v == value {