internal/impl: fix size cache semantics with lazy decoding
When a message (within an extension) is lazily decoded, its size cache is
initialized to 0 (the zero value for an int32). This doesn’t mean the size cache
reads 0, but rather that it was not initialized.
This fixes TestExtensionGetRace being flaky since CL 580015.
related to golang/protobuf#1609
Change-Id: Ia305badadd300679975f230005c3e33c94050e4a
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/586396
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Lasse Folger <lassefolger@google.com>
diff --git a/internal/impl/encode.go b/internal/impl/encode.go
index 7769a54..febd212 100644
--- a/internal/impl/encode.go
+++ b/internal/impl/encode.go
@@ -49,8 +49,11 @@
return 0
}
if opts.UseCachedSize() && mi.sizecacheOffset.IsValid() {
- if size := atomic.LoadInt32(p.Apply(mi.sizecacheOffset).Int32()); size >= 0 {
- return int(size)
+ // The size cache contains the size + 1, to allow the
+ // zero value to be invalid, while also allowing for a
+ // 0 size to be cached.
+ if size := atomic.LoadInt32(p.Apply(mi.sizecacheOffset).Int32()); size > 0 {
+ return int(size - 1)
}
}
return mi.sizePointerSlow(p, opts)
@@ -60,7 +63,7 @@
if flags.ProtoLegacy && mi.isMessageSet {
size = sizeMessageSet(mi, p, opts)
if mi.sizecacheOffset.IsValid() {
- atomic.StoreInt32(p.Apply(mi.sizecacheOffset).Int32(), int32(size))
+ atomic.StoreInt32(p.Apply(mi.sizecacheOffset).Int32(), int32(size+1))
}
return size
}
@@ -84,13 +87,16 @@
}
}
if mi.sizecacheOffset.IsValid() {
- if size > math.MaxInt32 {
+ if size > (math.MaxInt32 - 1) {
// The size is too large for the int32 sizecache field.
// We will need to recompute the size when encoding;
// unfortunately expensive, but better than invalid output.
- atomic.StoreInt32(p.Apply(mi.sizecacheOffset).Int32(), -1)
+ atomic.StoreInt32(p.Apply(mi.sizecacheOffset).Int32(), 0)
} else {
- atomic.StoreInt32(p.Apply(mi.sizecacheOffset).Int32(), int32(size))
+ // The size cache contains the size + 1, to allow the
+ // zero value to be invalid, while also allowing for a
+ // 0 size to be cached.
+ atomic.StoreInt32(p.Apply(mi.sizecacheOffset).Int32(), int32(size+1))
}
}
return size
