runtime: use real type size in map keys and values functions

We were using the size stored in the map, which is the smaller
of the real type size and 128.

As of CL 61538 we don't use these functions, but we expect to
use them again in the future after #61626 is resolved.

Change-Id: I7bfb4af5f0e3a56361d4019a8ed7c1ec59ff31fd
Reviewed-on: https://go-review.googlesource.com/c/go/+/535215
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Keith Randall <khr@google.com>

src/runtime/export_test.go

@@ -53,6 +53,9 @@ var CgoCheckPointer = cgoCheckPointer
 const TracebackInnerFrames = tracebackInnerFrames
 const TracebackOuterFrames = tracebackOuterFrames
 
+var MapKeys = keys
+var MapValues = values
+
 var LockPartialOrder = lockPartialOrder
 
 type LockRank lockRank

src/runtime/map.go

@@ -1651,7 +1651,7 @@ func copyKeys(t *maptype, h *hmap, b *bmap, s *slice, offset uint8) {
 			if s.len >= s.cap {
 				fatal("concurrent map read and map write")
 			}
-			typedmemmove(t.Key, add(s.array, uintptr(s.len)*uintptr(t.KeySize)), k)
+			typedmemmove(t.Key, add(s.array, uintptr(s.len)*uintptr(t.Key.Size())), k)
 			s.len++
 		}
 		b = b.overflow(t)
@@ -1716,7 +1716,7 @@ func copyValues(t *maptype, h *hmap, b *bmap, s *slice, offset uint8) {
 			if s.len >= s.cap {
 				fatal("concurrent map read and map write")
 			}
-			typedmemmove(t.Elem, add(s.array, uintptr(s.len)*uintptr(t.ValueSize)), ele)
+			typedmemmove(t.Elem, add(s.array, uintptr(s.len)*uintptr(t.Elem.Size())), ele)
 			s.len++
 		}
 		b = b.overflow(t)

src/runtime/map_test.go

@@ -1434,3 +1434,33 @@ func TestLoadFactor(t *testing.T) {
 		}
 	}
 }
+
+func TestMapKeys(t *testing.T) {
+	type key struct {
+		s   string
+		pad [128]byte // sizeof(key) > abi.MapMaxKeyBytes
+	}
+	m := map[key]int{{s: "a"}: 1, {s: "b"}: 2}
+	keys := make([]key, 0, len(m))
+	runtime.MapKeys(m, unsafe.Pointer(&keys))
+	for _, k := range keys {
+		if len(k.s) != 1 {
+			t.Errorf("len(k.s) == %d, want 1", len(k.s))
+		}
+	}
+}
+
+func TestMapValues(t *testing.T) {
+	type val struct {
+		s   string
+		pad [128]byte // sizeof(val) > abi.MapMaxElemBytes
+	}
+	m := map[int]val{1: {s: "a"}, 2: {s: "b"}}
+	vals := make([]val, 0, len(m))
+	runtime.MapValues(m, unsafe.Pointer(&vals))
+	for _, v := range vals {
+		if len(v.s) != 1 {
+			t.Errorf("len(v.s) == %d, want 1", len(v.s))
+		}
+	}
+}