2 files changed, 44 insertions, 2 deletions
diff --git a/src/runtime/string.go b/src/runtime/string.go
index 9ec6f320eb..58198d0e1b 100644
--- a/src/runtime/string.go
+++ b/src/runtime/string.go
@@ -185,8 +185,15 @@ type stringStruct struct {
 	len int
 }
 
-func intstring(v int64) string {
-	s, b := rawstring(4)
+func intstring(buf *[4]byte, v int64) string {
+	var s string
+	var b []byte
+	if buf != nil {
+		b = buf[:]
+		s = slicebytetostringtmp(b)
+	} else {
+		s, b = rawstring(4)
+	}
 	n := runetochar(b, rune(v))
 	return s[:n]
 }
diff --git a/src/runtime/string_test.go b/src/runtime/string_test.go
index 249f431e18..27a44ad645 100644
--- a/src/runtime/string_test.go
+++ b/src/runtime/string_test.go
@@ -186,3 +186,38 @@ func TestStringOnStack(t *testing.T) {
 		t.Fatalf("want: '%v', got '%v'", want, s)
 	}
 }
+
+func TestIntString(t *testing.T) {
+	// Non-escaping result of intstring.
+	s := ""
+	for i := 0; i < 4; i++ {
+		s += string(i+'0') + string(i+'0'+1)
+	}
+	if want := "01122334"; s != want {
+		t.Fatalf("want '%v', got '%v'", want, s)
+	}
+
+	// Escaping result of intstring.
+	var a [4]string
+	for i := 0; i < 4; i++ {
+		a[i] = string(i + '0')
+	}
+	s = a[0] + a[1] + a[2] + a[3]
+	if want := "0123"; s != want {
+		t.Fatalf("want '%v', got '%v'", want, s)
+	}
+}
+
+func TestIntStringAllocs(t *testing.T) {
+	unknown := '0'
+	n := testing.AllocsPerRun(1000, func() {
+		s1 := string(unknown)
+		s2 := string(unknown + 1)
+		if s1 == s2 {
+			t.Fatalf("bad")
+		}
+	})
+	if n != 0 {
+		t.Fatalf("want 0 allocs, got %v", n)
+	}
+}