1 files changed, 48 insertions, 13 deletions

diff --git a/libgo/go/cmd/vet/buildtag.go b/libgo/go/cmd/vet/buildtag.go
index 80d8f819240..ba3a361b911 100644
--- a/libgo/go/cmd/vet/buildtag.go
+++ b/libgo/go/cmd/vet/buildtag.go
@@ -18,12 +18,39 @@ var (
 	plusBuild  = []byte("+build")
 )
 
+func badfLine(f *File, line int, format string, args ...interface{}) {
+	msg := fmt.Sprintf(format, args...)
+	fmt.Fprintf(os.Stderr, "%s:%d: %s\n", f.name, line, msg)
+	setExit(1)
+}
+
 // checkBuildTag checks that build tags are in the correct location and well-formed.
-func checkBuildTag(name string, data []byte) {
+func checkBuildTag(f *File) {
 	if !vet("buildtags") {
 		return
 	}
-	lines := bytes.SplitAfter(data, nl)
+
+	// we must look at the raw lines, as build tags may appear in non-Go
+	// files such as assembly files.
+	lines := bytes.SplitAfter(f.content, nl)
+
+	// lineWithComment reports whether a line corresponds to a comment in
+	// the source file. If the source file wasn't Go, the function always
+	// returns true.
+	lineWithComment := func(line int) bool {
+		if f.file == nil {
+			// Current source file is not Go, so be conservative.
+			return true
+		}
+		for _, group := range f.file.Comments {
+			startLine := f.fset.Position(group.Pos()).Line
+			endLine := f.fset.Position(group.End()).Line
+			if startLine <= line && line <= endLine {
+				return true
+			}
+		}
+		return false
+	}
 
 	// Determine cutpoint where +build comments are no longer valid.
 	// They are valid in leading // comments in the file followed by
@@ -46,18 +73,29 @@ func checkBuildTag(name string, data []byte) {
 		if !bytes.HasPrefix(line, slashSlash) {
 			continue
 		}
+		if !bytes.Contains(line, plusBuild) {
+			// Check that the comment contains "+build" early, to
+			// avoid unnecessary lineWithComment calls that may
+			// incur linear searches.
+			continue
+		}
+		if !lineWithComment(i + 1) {
+			// This is a line in a Go source file that looks like a
+			// comment, but actually isn't - such as part of a raw
+			// string.
+			continue
+		}
+
 		text := bytes.TrimSpace(line[2:])
 		if bytes.HasPrefix(text, plusBuild) {
 			fields := bytes.Fields(text)
 			if !bytes.Equal(fields[0], plusBuild) {
 				// Comment is something like +buildasdf not +build.
-				fmt.Fprintf(os.Stderr, "%s:%d: possible malformed +build comment\n", name, i+1)
-				setExit(1)
+				badfLine(f, i+1, "possible malformed +build comment")
 				continue
 			}
 			if i >= cutoff {
-				fmt.Fprintf(os.Stderr, "%s:%d: +build comment must appear before package clause and be followed by a blank line\n", name, i+1)
-				setExit(1)
+				badfLine(f, i+1, "+build comment must appear before package clause and be followed by a blank line")
 				continue
 			}
 			// Check arguments.
@@ -65,15 +103,13 @@ func checkBuildTag(name string, data []byte) {
 			for _, arg := range fields[1:] {
 				for _, elem := range strings.Split(string(arg), ",") {
 					if strings.HasPrefix(elem, "!!") {
-						fmt.Fprintf(os.Stderr, "%s:%d: invalid double negative in build constraint: %s\n", name, i+1, arg)
-						setExit(1)
+						badfLine(f, i+1, "invalid double negative in build constraint: %s", arg)
 						break Args
 					}
 					elem = strings.TrimPrefix(elem, "!")
 					for _, c := range elem {
 						if !unicode.IsLetter(c) && !unicode.IsDigit(c) && c != '_' && c != '.' {
-							fmt.Fprintf(os.Stderr, "%s:%d: invalid non-alphanumeric build constraint: %s\n", name, i+1, arg)
-							setExit(1)
+							badfLine(f, i+1, "invalid non-alphanumeric build constraint: %s", arg)
 							break Args
 						}
 					}
@@ -82,9 +118,8 @@ func checkBuildTag(name string, data []byte) {
 			continue
 		}
 		// Comment with +build but not at beginning.
-		if bytes.Contains(line, plusBuild) && i < cutoff {
-			fmt.Fprintf(os.Stderr, "%s:%d: possible malformed +build comment\n", name, i+1)
-			setExit(1)
+		if i < cutoff {
+			badfLine(f, i+1, "possible malformed +build comment")
 			continue
 		}
 	}