raft: Add TestProtoMemorySizes test

This test checks the in-memory size of each proto struct to detect
unexpected changes to their memory representation.

raft/raftpb/raft_test.go

@@ -0,0 +1,64 @@
+// Copyright 2021 The etcd Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package raftpb
+
+import (
+	"math/bits"
+	"testing"
+	"unsafe"
+)
+
+func TestProtoMemorySizes(t *testing.T) {
+	assert := func(size, exp uintptr, name string) {
+		t.Helper()
+		if size != exp {
+			t.Errorf("expected size of %s proto to be %d bytes, found %d bytes", name, exp, size)
+		}
+	}
+
+	if64Bit := func(yes, no uintptr) uintptr {
+		if bits.UintSize == 64 {
+			return yes
+		}
+		return no
+	}
+
+	var e Entry
+	assert(unsafe.Sizeof(e), if64Bit(80, 48), "Entry")
+
+	var sm SnapshotMetadata
+	assert(unsafe.Sizeof(sm), if64Bit(184, 100), "SnapshotMetadata")
+
+	var s Snapshot
+	assert(unsafe.Sizeof(s), if64Bit(240, 128), "Snapshot")
+
+	var m Message
+	assert(unsafe.Sizeof(m), if64Bit(392, 232), "Message")
+
+	var hs HardState
+	assert(unsafe.Sizeof(hs), if64Bit(56, 40), "HardState")
+
+	var cs ConfState
+	assert(unsafe.Sizeof(cs), if64Bit(136, 68), "ConfState")
+
+	var cc ConfChange
+	assert(unsafe.Sizeof(cc), if64Bit(80, 48), "ConfChange")
+
+	var ccs ConfChangeSingle
+	assert(unsafe.Sizeof(ccs), if64Bit(48, 28), "ConfChangeSingle")
+
+	var ccv2 ConfChangeV2
+	assert(unsafe.Sizeof(ccv2), if64Bit(88, 44), "ConfChangeV2")
+}