cmd/protoc-gen-go: unexport implementation-specific XXX fields
We modify protoc-gen-go to stop generating exported XXX fields.
The unsafe implementation is unaffected by this change since unsafe
can access fields regardless of visibility. However, for the purego
implementation, we need to respect Go visibility rules as enforced
by the reflect package.
We work around this by generating a exporter function that given
a reference to the message and the field to export, returns a reference
to the unexported field value. This exporter function is protected by
a constant such that it is not linked into the final binary in non-purego
build environment.
Updates golang/protobuf#276
Change-Id: Idf5c1f158973fa1c61187ff41440acb21c5dac94
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/185141
Reviewed-by: Damien Neil <dneil@google.com>
diff --git a/internal/impl/codec_message.go b/internal/impl/codec_message.go
index 2d5b376..e4e3706 100644
--- a/internal/impl/codec_message.go
+++ b/internal/impl/codec_message.go
@@ -19,8 +19,8 @@
type coderMessageInfo struct {
orderedCoderFields []*coderFieldInfo
sizecacheOffset offset
- extensionOffset offset
unknownOffset offset
+ extensionOffset offset
needsInitCheck bool
}
@@ -55,7 +55,7 @@
}
mi.orderedCoderFields = append(mi.orderedCoderFields, &coderFieldInfo{
num: fd.Number(),
- offset: offsetOf(fs),
+ offset: offsetOf(fs, mi.Exporter),
wiretag: wiretag,
tagsize: wire.SizeVarint(wiretag),
funcs: fieldCoder(fd, ft),
@@ -71,7 +71,7 @@
fs := si.oneofsByName[od.Name()]
mi.orderedCoderFields = append(mi.orderedCoderFields, &coderFieldInfo{
num: od.Fields().Get(0).Number(),
- offset: offsetOf(fs),
+ offset: offsetOf(fs, mi.Exporter),
funcs: makeOneofFieldCoder(fs, od, si.fieldsByNumber, si.oneofWrappersByNumber),
isPointer: true,
})