1 files changed, 39 insertions, 10 deletions

diff --git a/src/cmd/vendor/github.com/google/pprof/internal/driver/cli.go b/src/cmd/vendor/github.com/google/pprof/internal/driver/cli.go
index c3c22e7c96..a5153e1511 100644
--- a/src/cmd/vendor/github.com/google/pprof/internal/driver/cli.go
+++ b/src/cmd/vendor/github.com/google/pprof/internal/driver/cli.go
@@ -15,6 +15,7 @@
 package driver
 
 import (
+	"errors"
 	"fmt"
 	"os"
 	"strings"
@@ -28,6 +29,7 @@ type source struct {
 	ExecName  string
 	BuildID   string
 	Base      []string
+	DiffBase  bool
 	Normalize bool
 
 	Seconds      int
@@ -43,7 +45,8 @@ type source struct {
 func parseFlags(o *plugin.Options) (*source, []string, error) {
 	flag := o.Flagset
 	// Comparisons.
-	flagBase := flag.StringList("base", "", "Source for base profile for comparison")
+	flagBase := flag.StringList("base", "", "Source for base profile for profile subtraction")
+	flagDiffBase := flag.StringList("diff_base", "", "Source for diff base profile for comparison")
 	// Source options.
 	flagSymbolize := flag.String("symbolize", "", "Options for profile symbolization")
 	flagBuildID := flag.String("buildid", "", "Override build id for first mapping")
@@ -85,7 +88,7 @@ func parseFlags(o *plugin.Options) (*source, []string, error) {
 			usageMsgVars)
 	})
 	if len(args) == 0 {
-		return nil, nil, fmt.Errorf("no profile source specified")
+		return nil, nil, errors.New("no profile source specified")
 	}
 
 	var execName string
@@ -112,7 +115,7 @@ func parseFlags(o *plugin.Options) (*source, []string, error) {
 		return nil, nil, err
 	}
 	if cmd != nil && *flagHTTP != "" {
-		return nil, nil, fmt.Errorf("-http is not compatible with an output format on the command line")
+		return nil, nil, errors.New("-http is not compatible with an output format on the command line")
 	}
 
 	si := pprofVariables["sample_index"].value
@@ -140,15 +143,13 @@ func parseFlags(o *plugin.Options) (*source, []string, error) {
 		Comment:      *flagAddComment,
 	}
 
-	for _, s := range *flagBase {
-		if *s != "" {
-			source.Base = append(source.Base, *s)
-		}
+	if err := source.addBaseProfiles(*flagBase, *flagDiffBase); err != nil {
+		return nil, nil, err
 	}
 
 	normalize := pprofVariables["normalize"].boolValue()
 	if normalize && len(source.Base) == 0 {
-		return nil, nil, fmt.Errorf("Must have base profile to normalize by")
+		return nil, nil, errors.New("must have base profile to normalize by")
 	}
 	source.Normalize = normalize
 
@@ -158,6 +159,34 @@ func parseFlags(o *plugin.Options) (*source, []string, error) {
 	return source, cmd, nil
 }
 
+// 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, diffBase := dropEmpty(flagBase), dropEmpty(flagDiffBase)
+	if len(base) > 0 && len(diffBase) > 0 {
+		return errors.New("-base and -diff_base flags cannot both be specified")
+	}
+
+	source.Base = base
+	if len(diffBase) > 0 {
+		source.Base, source.DiffBase = diffBase, true
+	}
+	return nil
+}
+
+// dropEmpty list takes a slice of string pointers, and outputs a slice of
+// non-empty strings associated with the flag.
+func dropEmpty(list []*string) []string {
+	var l []string
+	for _, s := range list {
+		if *s != "" {
+			l = append(l, *s)
+		}
+	}
+	return l
+}
+
 // installFlags creates command line flags for pprof variables.
 func installFlags(flag plugin.FlagSet) flagsInstalled {
 	f := flagsInstalled{
@@ -240,7 +269,7 @@ func outputFormat(bcmd map[string]*bool, acmd map[string]*string) (cmd []string,
 	for n, b := range bcmd {
 		if *b {
 			if cmd != nil {
-				return nil, fmt.Errorf("must set at most one output format")
+				return nil, errors.New("must set at most one output format")
 			}
 			cmd = []string{n}
 		}
@@ -248,7 +277,7 @@ func outputFormat(bcmd map[string]*bool, acmd map[string]*string) (cmd []string,
 	for n, s := range acmd {
 		if *s != "" {
 			if cmd != nil {
-				return nil, fmt.Errorf("must set at most one output format")
+				return nil, errors.New("must set at most one output format")
 			}
 			cmd = []string{n, *s}
 		}