Fix nested structs on 32bit archs

Not entirely sure why this fails, but this fixes it in the meanwhile.

Fixes #314

encode.go

@@ -411,7 +411,17 @@ func (enc *Encoder) eStruct(key Key, rv reflect.Value, inline bool) {
 			if typeIsHash(tomlTypeOfGo(frv)) {
 				fieldsSub = append(fieldsSub, append(start, f.Index...))
 			} else {
-				fieldsDirect = append(fieldsDirect, append(start, f.Index...))
+				// Copy so it works correct on 32bit archs; not clear why this
+				// is needed. See #314, and https://www.reddit.com/r/golang/comments/pnx8v4
+				// This also works fine on 64bit, but 32bit archs are somewhat
+				// rare and this is a wee bit faster.
+				if math.MaxInt == math.MaxInt32 {
+					copyStart := make([]int, len(start))
+					copy(copyStart, start)
+					fieldsDirect = append(fieldsDirect, append(copyStart, f.Index...))
+				} else {
+					fieldsDirect = append(fieldsDirect, append(start, f.Index...))
+				}
 			}
 		}
 	}

encode_test.go

@@ -396,6 +396,21 @@ Fun = "why would you do this?"
 	}
 }
 
+// Would previously fail on 32bit architectures; can test with:
+//   GOARCH=386         go test -c &&  ./toml.test
+//   GOARCH=arm GOARM=7 go test -c && qemu-arm ./toml.test
+func TestEncode32bit(t *testing.T) {
+	type Inner struct {
+		A, B, C string
+	}
+	type Outer struct{ Inner }
+
+	encodeExpected(t, "embedded anonymous untagged struct",
+		Outer{Inner{"a", "b", "c"}},
+		"A = \"a\"\nB = \"b\"\nC = \"c\"\n",
+		nil)
+}
+
 func encodeExpected(t *testing.T, label string, val interface{}, want string, wantErr error) {
 	t.Helper()
 
@@ -420,8 +435,6 @@ func encodeExpected(t *testing.T, label string, val interface{}, want string, wa
 		want = strings.TrimSpace(want)
 		if want != have {
 			t.Errorf("\nhave:\n%s\nwant:\n%s\n", have, want)
-			// v, _ := json.MarshalIndent(val, "", "  ")
-			// t.Log(string(v))
 		}
 	})
 }