1 files changed, 58 insertions, 46 deletions

diff --git a/src/runtime/debug/mod.go b/src/runtime/debug/mod.go
index 11f995ba75..8c6c48089b 100644
--- a/src/runtime/debug/mod.go
+++ b/src/runtime/debug/mod.go
@@ -7,7 +7,6 @@ package debug
 import (
 	"bytes"
 	"fmt"
-	"strings"
 )
 
 // exported from runtime
@@ -17,11 +16,19 @@ func modinfo() string
 // in the running binary. The information is available only
 // in binaries built with module support.
 func ReadBuildInfo() (info *BuildInfo, ok bool) {
-	return readBuildInfo(modinfo())
+	data := modinfo()
+	if len(data) < 32 {
+		return nil, false
+	}
+	data = data[16 : len(data)-16]
+	bi := &BuildInfo{}
+	if err := bi.UnmarshalText([]byte(data)); err != nil {
+		return nil, false
+	}
+	return bi, true
 }
 
-// BuildInfo represents the build information read from
-// the running binary.
+// BuildInfo represents the build information read from a Go binary.
 type BuildInfo struct {
 	Path string    // The main package path
 	Main Module    // The module containing the main package
@@ -71,80 +78,85 @@ func (bi *BuildInfo) MarshalText() ([]byte, error) {
 	return buf.Bytes(), nil
 }
 
-func readBuildInfo(data string) (*BuildInfo, bool) {
-	if len(data) < 32 {
-		return nil, false
-	}
-	data = data[16 : len(data)-16]
+func (bi *BuildInfo) UnmarshalText(data []byte) (err error) {
+	*bi = BuildInfo{}
+	lineNum := 1
+	defer func() {
+		if err != nil {
+			err = fmt.Errorf("could not parse Go build info: line %d: %w", lineNum, err)
+		}
+	}()
 
-	const (
-		pathLine = "path\t"
-		modLine  = "mod\t"
-		depLine  = "dep\t"
-		repLine  = "=>\t"
+	var (
+		pathLine = []byte("path\t")
+		modLine  = []byte("mod\t")
+		depLine  = []byte("dep\t")
+		repLine  = []byte("=>\t")
+		newline  = []byte("\n")
+		tab      = []byte("\t")
 	)
 
-	readEntryFirstLine := func(elem []string) (Module, bool) {
+	readModuleLine := func(elem [][]byte) (Module, error) {
 		if len(elem) != 2 && len(elem) != 3 {
-			return Module{}, false
+			return Module{}, fmt.Errorf("expected 2 or 3 columns; got %d", len(elem))
 		}
 		sum := ""
 		if len(elem) == 3 {
-			sum = elem[2]
+			sum = string(elem[2])
 		}
 		return Module{
-			Path:    elem[0],
-			Version: elem[1],
+			Path:    string(elem[0]),
+			Version: string(elem[1]),
 			Sum:     sum,
-		}, true
+		}, nil
 	}
 
 	var (
-		info = &BuildInfo{}
 		last *Module
-		line string
+		line []byte
 		ok   bool
 	)
-	// Reverse of cmd/go/internal/modload.PackageBuildInfo
+	// Reverse of BuildInfo.String()
 	for len(data) > 0 {
-		line, data, ok = strings.Cut(data, "\n")
+		line, data, ok = bytes.Cut(data, newline)
 		if !ok {
 			break
 		}
 		switch {
-		case strings.HasPrefix(line, pathLine):
+		case bytes.HasPrefix(line, pathLine):
 			elem := line[len(pathLine):]
-			info.Path = elem
-		case strings.HasPrefix(line, modLine):
-			elem := strings.Split(line[len(modLine):], "\t")
-			last = &info.Main
-			*last, ok = readEntryFirstLine(elem)
-			if !ok {
-				return nil, false
+			bi.Path = string(elem)
+		case bytes.HasPrefix(line, modLine):
+			elem := bytes.Split(line[len(modLine):], tab)
+			last = &bi.Main
+			*last, err = readModuleLine(elem)
+			if err != nil {
+				return err
 			}
-		case strings.HasPrefix(line, depLine):
-			elem := strings.Split(line[len(depLine):], "\t")
+		case bytes.HasPrefix(line, depLine):
+			elem := bytes.Split(line[len(depLine):], tab)
 			last = new(Module)
-			info.Deps = append(info.Deps, last)
-			*last, ok = readEntryFirstLine(elem)
-			if !ok {
-				return nil, false
+			bi.Deps = append(bi.Deps, last)
+			*last, err = readModuleLine(elem)
+			if err != nil {
+				return err
 			}
-		case strings.HasPrefix(line, repLine):
-			elem := strings.Split(line[len(repLine):], "\t")
+		case bytes.HasPrefix(line, repLine):
+			elem := bytes.Split(line[len(repLine):], tab)
 			if len(elem) != 3 {
-				return nil, false
+				return fmt.Errorf("expected 3 columns for replacement; got %d", len(elem))
 			}
 			if last == nil {
-				return nil, false
+				return fmt.Errorf("replacement with no module on previous line")
 			}
 			last.Replace = &Module{
-				Path:    elem[0],
-				Version: elem[1],
-				Sum:     elem[2],
+				Path:    string(elem[0]),
+				Version: string(elem[1]),
+				Sum:     string(elem[2]),
 			}
 			last = nil
 		}
+		lineNum++
 	}
-	return info, true
+	return nil
 }