cmd/link: handle types as converted to interface when dynlink

When using plugins, a type (whose value) may be pass to a plugin
and get converted to interface there, or vice versa. We need to
treat the type as potentially converted to interface, and retain
its methods.

Should fix #44586.

Change-Id: I80dd35e68baedaa852a317543ccd78d94628d13b
Reviewed-on: https://go-review.googlesource.com/c/go/+/296709
Trust: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/cmd/link/internal/ld/deadcode.go b/src/cmd/link/internal/ld/deadcode.go
index 1874103b93..ebde41499e 100644
--- a/src/cmd/link/internal/ld/deadcode.go
+++ b/src/cmd/link/internal/ld/deadcode.go
@@ -24,6 +24,7 @@ type deadcodePass struct {
 	ifaceMethod     map[methodsig]bool // methods declared in reached interfaces
 	markableMethods []methodref        // methods of reached types
 	reflectSeen     bool               // whether we have seen a reflect method call
+	dynlink         bool
 
 	methodsigstmp []methodsig // scratch buffer for decoding method signatures
 }
@@ -34,6 +35,7 @@ func (d *deadcodePass) init() {
 	if objabi.Fieldtrack_enabled != 0 {
 		d.ldr.Reachparent = make([]loader.Sym, d.ldr.NSym())
 	}
+	d.dynlink = d.ctxt.DynlinkingGo()
 
 	if d.ctxt.BuildMode == BuildModeShared {
 		// Mark all symbols defined in this library as reachable when
@@ -115,6 +117,11 @@ func (d *deadcodePass) flood() {
 		var usedInIface bool
 
 		if isgotype {
+			if d.dynlink {
+				// When dynaamic linking, a type may be passed across DSO
+				// boundary and get converted to interface at the other side.
+				d.ldr.SetAttrUsedInIface(symIdx, true)
+			}
 			usedInIface = d.ldr.AttrUsedInIface(symIdx)
 		}