*: support "continue" to label within for-loop

code/failpoint.go

@@ -27,6 +27,10 @@ type Failpoint struct {
 
 	// whitespace for padding
 	ws string
+
+	// if true, do not acquire read lock on failpoints
+	// useful for "continue"
+	eval bool
 }
 
 // newFailpoint makes a new failpoint based on the a line containing a
@@ -38,10 +42,11 @@ func newFailpoint(l string) (*Failpoint, error) {
 	}
 	cmd := strings.SplitAfter(l, "// gofail:")[1]
 	fields := strings.Fields(cmd)
-	if len(fields) != 3 || fields[0] != "var" {
+	if len(fields) < 3 || fields[0] != "var" {
 		return nil, fmt.Errorf("failpoint: malformed comment header %q", l)
 	}
-	return &Failpoint{name: fields[1], varType: fields[2], ws: strings.Split(l, "//")[0]}, nil
+	eval := len(fields) == 4 && fields[3] == "eval"
+	return &Failpoint{name: fields[1], varType: fields[2], ws: strings.Split(l, "//")[0], eval: eval}, nil
 }
 
 // flush writes the failpoint code to a buffer
@@ -53,14 +58,19 @@ func (fp *Failpoint) flush(dst io.Writer) error {
 }
 
 func (fp *Failpoint) hdr(varname string) string {
-	hdr := fp.ws + "if v" + fp.name + ", __fpErr := " + fp.Runtime() + ".Acquire(); __fpErr == nil { "
-	hdr = hdr + "defer " + fp.Runtime() + ".Release(); "
+	hdr := fp.ws + "if v" + fp.name + ", __fpErr := "
+	if !fp.eval {
+		hdr += fp.Runtime() + ".Acquire(); __fpErr == nil { "
+		hdr += "defer " + fp.Runtime() + ".Release(); "
+	} else {
+		hdr += fp.Runtime() + ".Eval(); __fpErr == nil { "
+	}
 	if fp.varType == "struct{}" {
 		// unused
 		varname = "_"
 	}
 	return hdr + varname + ", __fpTypeOK := v" + fp.name +
-		".(" + fp.varType + "); if !__fpTypeOK { goto __badType" + fp.name + "} "
+		".(" + fp.varType + "); if !__fpTypeOK { goto __badType" + fp.name + " } else { continue __fp_" + fp.name + " }"
 }
 
 func (fp *Failpoint) footer() string {
@@ -69,6 +79,10 @@ func (fp *Failpoint) footer() string {
 }
 
 func (fp *Failpoint) flushSingle(dst io.Writer) error {
+	if fp.varType == "continue" {
+		_, cerr := io.WriteString(dst, "__fp_"+fp.name+":\n")
+		return cerr
+	}
 	if _, err := io.WriteString(dst, fp.hdr("_")); err != nil {
 		return err
 	}

code/rewrite.go

@@ -48,7 +48,9 @@ func ToFailpoints(wdst io.Writer, rsrc io.Reader) (fps []*Failpoint, err error)
 				continue
 			} else {
 				curfp.flush(dst)
-				fps = append(fps, curfp)
+				if curfp.varType != "continue" {
+					fps = append(fps, curfp)
+				}
 				curfp = nil
 			}
 		} else {
@@ -81,6 +83,14 @@ func ToComments(wdst io.Writer, rsrc io.Reader) (fps []*Failpoint, err error) {
 		err = rerr
 		lTrim := strings.TrimSpace(l)
 
+		isContinue := strings.HasPrefix(lTrim, "__fp_") && lTrim[len(lTrim)-1] == ':'
+		if isContinue {
+			n := strings.Split(strings.Split(lTrim, "__fp_")[1], ":")[0]
+			dst.WriteString("\t// gofail: var " + n + " continue" + "\n")
+			fps = append(fps, &Failpoint{name: n, varType: "continue"})
+			continue
+		}
+
 		if unmatchedBraces > 0 {
 			opening, closing := numBraces(l)
 			unmatchedBraces += opening - closing
@@ -98,6 +108,9 @@ func ToComments(wdst io.Writer, rsrc io.Reader) (fps []*Failpoint, err error) {
 			ws = strings.Split(l, "i")[0]
 			n := strings.Split(strings.Split(l, "__fp_")[1], ".")[0]
 			t := strings.Split(strings.Split(l, ".(")[1], ")")[0]
+			if strings.Contains(lTrim, n+"."+"Eval();") {
+				t += " eval"
+			}
 			dst.WriteString(ws + "// gofail: var " + n + " " + t + "\n")
 			if !strings.Contains(l, "; __badType") {
 				// not single liner

runtime/failpoint.go

@@ -30,6 +30,21 @@ func NewFailpoint(pkg, name string) *Failpoint {
 	return fp
 }
 
+// Eval merely evaluates the failpoint terms without
+// acquiring the read lock.
+func (fp *Failpoint) Eval() (interface{}, error) {
+	fp.mu.RLock()
+	defer fp.mu.RUnlock()
+	if fp.t == nil {
+		return nil, ErrDisabled
+	}
+	v, err := fp.t.eval()
+	if v == nil {
+		err = ErrDisabled
+	}
+	return v, err
+}
+
 // Acquire gets evalutes the failpoint terms; if the failpoint
 // is active, it will return a value. Otherwise, returns a non-nil error.
 func (fp *Failpoint) Acquire() (interface{}, error) {