Enable Invoke and GetValue for ref-returning members (#17732)

* Reapply https://github.com/dotnet/coreclr/pull/17639

* tryagain-wip 4/23/2018 7:27:37 AM - Fix Invoke of enum-returning methods

* Assert for refbufargs implying valuetype

* Catch ref to void in managed layer

1 files changed, 16 insertions, 41 deletions

diff --git a/src/vm/invokeutil.cpp b/src/vm/invokeutil.cpp
index 170b0da6d6..a45e81b262 100644
--- a/src/vm/invokeutil.cpp
+++ b/src/vm/invokeutil.cpp
@@ -649,9 +649,14 @@ void InvokeUtil::ValidField(TypeHandle th, OBJECTREF* value)
         COMPlusThrow(kArgumentException,W("Arg_ObjObj"));
 }
 
-// InternalCreateObject
-// This routine will create the specified object from the value
-OBJECTREF InvokeUtil::CreateObject(TypeHandle th, void * pValue) {
+//
+// CreateObjectAfterInvoke
+// This routine will create the specified object from the value returned by the Invoke target. 
+//
+// This does not handle the ELEMENT_TYPE_VALUETYPE case. The caller must preallocate the box object and
+// copy the value type into it afterward.
+//
+OBJECTREF InvokeUtil::CreateObjectAfterInvoke(TypeHandle th, void * pValue) {
     CONTRACTL {
         THROWS;
         GC_TRIGGERS;
@@ -663,9 +668,11 @@ OBJECTREF InvokeUtil::CreateObject(TypeHandle th, void * pValue) {
     CONTRACTL_END;
 
     CorElementType type = th.GetSignatureCorElementType();
-    MethodTable *pMT = NULL;
     OBJECTREF obj = NULL;
 
+    // WARNING: pValue can be an inner reference into a managed object and it is not protected from GC. You must do nothing that
+    // triggers a GC until the all the data it points to has been captured in a GC-protected location.
+
     // Handle the non-table types
     switch (type) {
     case ELEMENT_TYPE_VOID:
@@ -677,18 +684,6 @@ OBJECTREF InvokeUtil::CreateObject(TypeHandle th, void * pValue) {
         break;
     }
 
-    case ELEMENT_TYPE_FNPTR:
-        pMT = MscorlibBinder::GetElementType(ELEMENT_TYPE_I);
-        goto PrimitiveType;
-
-    case ELEMENT_TYPE_VALUETYPE:
-    {
-        _ASSERTE(!th.IsTypeDesc());
-        pMT = th.AsMethodTable();
-        obj = pMT->Box(pValue);
-        break;
-    }
-
     case ELEMENT_TYPE_CLASS:        // Class
     case ELEMENT_TYPE_SZARRAY:      // Single Dim, Zero
     case ELEMENT_TYPE_ARRAY:        // General Array
@@ -698,35 +693,15 @@ OBJECTREF InvokeUtil::CreateObject(TypeHandle th, void * pValue) {
         obj = *(OBJECTREF *)pValue;
         break;
     
-    case ELEMENT_TYPE_BOOLEAN:      // boolean
-    case ELEMENT_TYPE_I1:           // byte
-    case ELEMENT_TYPE_U1:
-    case ELEMENT_TYPE_I2:           // short
-    case ELEMENT_TYPE_U2:           
-    case ELEMENT_TYPE_CHAR:         // char
-    case ELEMENT_TYPE_I4:           // int
-    case ELEMENT_TYPE_U4:
-    case ELEMENT_TYPE_I8:           // long
-    case ELEMENT_TYPE_U8:       
-    case ELEMENT_TYPE_R4:           // float
-    case ELEMENT_TYPE_R8:           // double
-    case ELEMENT_TYPE_I:
-    case ELEMENT_TYPE_U:
-        _ASSERTE(!th.IsTypeDesc());
-        pMT = th.AsMethodTable();
-    PrimitiveType:
+    case ELEMENT_TYPE_FNPTR:
         {
-            // Don't use MethodTable::Box here for perf reasons
-            PREFIX_ASSUME(pMT != NULL);
-            obj = AllocateObject(pMT);
-            DWORD size = pMT->GetNumInstanceFieldBytes();
-            memcpyNoGCRefs(obj->UnBox(), pValue, size);
+            LPVOID capturedValue = *(LPVOID*)pValue;
+            INDEBUG(pValue = (LPVOID)0xcccccccc); // We're about to allocate a GC object - can no longer trust pValue
+            obj = AllocateObject(MscorlibBinder::GetElementType(ELEMENT_TYPE_I));
+            *(LPVOID*)(obj->UnBox()) = capturedValue;
         }
         break;
     
-    case ELEMENT_TYPE_BYREF:
-        COMPlusThrow(kNotSupportedException, W("NotSupported_ByRefReturn"));
-    case ELEMENT_TYPE_END:
     default:
         _ASSERTE(!"Unknown Type");
         COMPlusThrow(kNotSupportedException);