internal/legacy: guarantee one-to-one generation of wrapper types
When concurrent requests to wrap a type occurs, it is possible that
two different descriptors are created for the same Go type.
Add sufficient synchronization to ensure that one descriptor is ever
returned for one Go type.
Change-Id: Idbbca4c1877a70317b39900ae83bfc3085d4a9c5
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/168398
Reviewed-by: Herbie Ong <herbie@google.com>
diff --git a/internal/legacy/file.go b/internal/legacy/file.go
index 5c79810..c438c1d 100644
--- a/internal/legacy/file.go
+++ b/internal/legacy/file.go
@@ -42,12 +42,12 @@
// File descriptors generated by protoc-gen-go do not rely on that property.
func loadFileDesc(b []byte) *descriptorpb.FileDescriptorProto {
// Fast-path: check whether we already have a cached file descriptor.
- if v, ok := fileDescCache.Load(&b[0]); ok {
- return v.(*descriptorpb.FileDescriptorProto)
+ if fd, ok := fileDescCache.Load(&b[0]); ok {
+ return fd.(*descriptorpb.FileDescriptorProto)
}
// Slow-path: decompress and unmarshal the file descriptor proto.
- m := new(descriptorpb.FileDescriptorProto)
+ fd := new(descriptorpb.FileDescriptorProto)
zr, err := gzip.NewReader(bytes.NewReader(b))
if err != nil {
panic(err)
@@ -56,12 +56,14 @@
if err != nil {
panic(err)
}
- err = proto.UnmarshalOptions{DiscardUnknown: true}.Unmarshal(b, m)
+ err = proto.UnmarshalOptions{DiscardUnknown: true}.Unmarshal(b, fd)
if err != nil {
panic(err)
}
- fileDescCache.Store(&b[0], m)
- return m
+ if fd, ok := fileDescCache.LoadOrStore(&b[0], fd); ok {
+ return fd.(*descriptorpb.FileDescriptorProto)
+ }
+ return fd
}
// parentFileDescriptor returns the parent protoreflect.FileDescriptor for the