From c3869236b814241948b23d2ba8f48469870ece3b Mon Sep 17 00:00:00 2001
From: hugo-fc-visions <220964862+hugo-fc-visions@users.noreply.github.com>
Date: Mon, 20 Jul 2026 12:36:10 -0300
Subject: [PATCH] Fix x64 cross-apartment marshaling of IScriptError (Error
 cast -> E_NOINTERFACE)

On x64, casting ScriptControl.Error to the strongly-typed IScriptError/Error
interface fails with E_NOINTERFACE when the object is consumed from a COM MTA
thread (e.g. a .NET host whose main thread is MTA):

  Unable to cast COM object ... to interface type 'MSScriptControl.Error' ...
  QueryInterface ... IID '{70841C78-067D-11D0-95D8-00A02463AB28}' ...
  E_NOINTERFACE (0x80004002)

Root cause: the control is registered ThreadingModel=Apartment (STA). When it
is created from an MTA thread, COM returns a proxy, and QueryInterface on that
proxy for the IScriptError vtable interface needs marshaling metadata. The
type library only declared IScriptControl, never IScriptError, so there was no
proxy/stub nor type-library marshaler registered for {70841C78-...} on x64 and
the cross-apartment QI failed. (Late-bound/IDispatch access still works because
IDispatch is always marshalable; only the strongly-typed vtable cast breaks.)

Fix: declare IScriptError in the .idl (dual + oleautomation, with the exact
vtable order and dispids CTScriptError already implements) so it becomes part
of the type library. The existing DllRegisterServer -> RegisterTypeLib call
then registers an oleautomation marshaler for the interface, and the
cross-apartment QueryInterface (and the managed cast) succeed.

No C++ change: CTScriptError already implements the interface (it uses the
#import-ed IScriptError, same IID); tsc64.cpp does not include the MIDL header,
so there is no type clash.
---
 tsc64/tsc64.idl | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/tsc64/tsc64.idl b/tsc64/tsc64.idl
index 55b5668..1bf2581 100644
--- a/tsc64/tsc64.idl
+++ b/tsc64/tsc64.idl
@@ -70,6 +70,40 @@ interface IScriptControl : IDispatch
                     [out, retval] VARIANT* pvarResult);
 };
 
+// Error object. Declared here (with its real msscript.ocx IID) so the type
+// library describes it. RegisterTypeLib then registers an oleautomation
+// marshaler for {70841C78-...}, which lets the strongly-typed IScriptError /
+// Error interface be marshaled across COM apartments (e.g. an STA-created
+// object consumed from a host running on an MTA thread). Members are listed in
+// the exact vtable order implemented by CTScriptError.
+[
+	object,
+	uuid(70841C78-067D-11D0-95D8-00A02463AB28),
+	dual,
+	oleautomation
+]
+interface IScriptError : IDispatch
+{
+	[id(0x000000c9), propget]
+	HRESULT Number([out, retval] long* plNumber);
+	[id(0x000000ca), propget]
+	HRESULT Source([out, retval] BSTR* pbstrSource);
+	[id(0x000000cb), propget]
+	HRESULT Description([out, retval] BSTR* pbstrDescription);
+	[id(0x000000cc), propget]
+	HRESULT HelpFile([out, retval] BSTR* pbstrHelpFile);
+	[id(0x000000cd), propget]
+	HRESULT HelpContext([out, retval] long* plHelpContext);
+	[id(0xfffffdfb), propget]
+	HRESULT Text([out, retval] BSTR* pbstrText);
+	[id(0x000000ce), propget]
+	HRESULT Line([out, retval] long* plLine);
+	[id(0xfffffdef), propget]
+	HRESULT Column([out, retval] long* plColumn);
+	[id(0x000000d0)]
+	HRESULT Clear();
+};
+
 // Type library
 [
     version(1.0),
@@ -79,4 +113,5 @@ library IScriptControl
 {
 	importlib("stdole32.tlb");
 	interface IScriptControl;
+	interface IScriptError;
 };
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