1 files changed, 58 insertions, 2 deletions
diff --git a/src/strconv/atof_test.go b/src/strconv/atof_test.go
index 545d989c41..3c058b9be5 100644
--- a/src/strconv/atof_test.go
+++ b/src/strconv/atof_test.go
@@ -303,6 +303,12 @@ var atoftests = []atofTest{
 	{"1.00000000000000033306690738754696212708950042724609375", "1.0000000000000004", nil},
 	{"0x1.00000000000018p0", "1.0000000000000004", nil},
 
+	// Halfway between 1090544144181609278303144771584 and 1090544144181609419040633126912
+	// (15497564393479157p+46, should round to even 15497564393479156p+46, issue 36657)
+	{"1090544144181609348671888949248", "1.0905441441816093e+30", nil},
+	// slightly above, rounds up
+	{"1090544144181609348835077142190", "1.0905441441816094e+30", nil},
+
 	// Underscores.
 	{"1_23.50_0_0e+1_2", "1.235e+14", nil},
 	{"-_123.5e+12", "0", ErrSyntax},
@@ -628,6 +634,23 @@ func TestRoundTrip32(t *testing.T) {
 	t.Logf("tested %d float32's", count)
 }
 
+// Issue 42297: a lot of code in the wild accidentally calls ParseFloat(s, 10)
+// or ParseFloat(s, 0), so allow bitSize values other than 32 and 64.
+func TestParseFloatIncorrectBitSize(t *testing.T) {
+	const s = "1.5e308"
+	const want = 1.5e308
+
+	for _, bitSize := range []int{0, 10, 100, 128} {
+		f, err := ParseFloat(s, bitSize)
+		if err != nil {
+			t.Fatalf("ParseFloat(%q, %d) gave error %s", s, bitSize, err)
+		}
+		if f != want {
+			t.Fatalf("ParseFloat(%q, %d) = %g (expected %g)", s, bitSize, f, want)
+		}
+	}
+}
+
 func BenchmarkAtof64Decimal(b *testing.B) {
 	for i := 0; i < b.N; i++ {
 		ParseFloat("33909", 64)
@@ -653,17 +676,38 @@ func BenchmarkAtof64Big(b *testing.B) {
 }
 
 func BenchmarkAtof64RandomBits(b *testing.B) {
+	initAtof()
+	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
 		ParseFloat(benchmarksRandomBits[i%1024], 64)
 	}
 }
 
 func BenchmarkAtof64RandomFloats(b *testing.B) {
+	initAtof()
+	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
 		ParseFloat(benchmarksRandomNormal[i%1024], 64)
 	}
 }
 
+func BenchmarkAtof64RandomLongFloats(b *testing.B) {
+	initAtof()
+	samples := make([]string, len(atofRandomTests))
+	for i, t := range atofRandomTests {
+		samples[i] = FormatFloat(t.x, 'g', 20, 64)
+	}
+	b.ResetTimer()
+	idx := 0
+	for i := 0; i < b.N; i++ {
+		ParseFloat(samples[idx], 64)
+		idx++
+		if idx == len(samples) {
+			idx = 0
+		}
+	}
+}
+
 func BenchmarkAtof32Decimal(b *testing.B) {
 	for i := 0; i < b.N; i++ {
 		ParseFloat("33909", 32)
@@ -682,10 +726,9 @@ func BenchmarkAtof32FloatExp(b *testing.B) {
 	}
 }
 
-var float32strings [4096]string
-
 func BenchmarkAtof32Random(b *testing.B) {
 	n := uint32(997)
+	var float32strings [4096]string
 	for i := range float32strings {
 		n = (99991*n + 42) % (0xff << 23)
 		float32strings[i] = FormatFloat(float64(math.Float32frombits(n)), 'g', -1, 32)
@@ -695,3 +738,16 @@ func BenchmarkAtof32Random(b *testing.B) {
 		ParseFloat(float32strings[i%4096], 32)
 	}
 }
+
+func BenchmarkAtof32RandomLong(b *testing.B) {
+	n := uint32(997)
+	var float32strings [4096]string
+	for i := range float32strings {
+		n = (99991*n + 42) % (0xff << 23)
+		float32strings[i] = FormatFloat(float64(math.Float32frombits(n)), 'g', 20, 32)
+	}
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		ParseFloat(float32strings[i%4096], 32)
+	}
+}