[PATCH v3 0/2] MR9306: msvcrt: Use the correct arguments when a WinRT exception is thrown with _CxxThrowException.

[Vibhav Pant (＠vibhavp)]

Another dependency for !9209.

When C++/CX applications manually throw exceptions (i.e, by calling `_CxxThrowException` and not `__abi_WinRTraise*`), msvcrt/ucrt will still use the `cxx_exception_type` RTTI data from `vccorlib`, and not the one passed by the user. It also invokes a callback inside `exception_info`, which likely performs the necessary RoOriginateError/RoOriginateLanguageException bookkeeping and sets the `IRestrictedErrorInfo` field.

--
  v3: msvcrt: Update WinRT exception type info in _CxxThrowException.
      msvcrt: Rename exception *IUNKNOWN flags to *WINRT.

https://gitlab.winehq.org/wine/wine/-/merge_requests/9306

[PATCH v3 1/2] msvcrt: Rename exception *IUNKNOWN flags to *WINRT.

[Piotr Caban]

From: Piotr Caban

It's only used for WinRT exceptions (not for other COM objects).
---
 dlls/msvcrt/cppexcept.h | 8 ++++----
 dlls/msvcrt/except.c    | 2 +-
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/dlls/msvcrt/cppexcept.h b/dlls/msvcrt/cppexcept.h
index 21a7e6a8009..61267add740 100644
--- a/dlls/msvcrt/cppexcept.h
+++ b/dlls/msvcrt/cppexcept.h
@@ -135,12 +135,12 @@ typedef struct

#define CLASS_IS_SIMPLE_TYPE          1
 #define CLASS_HAS_VIRTUAL_BASE_CLASS  4
-#define CLASS_IS_IUNKNOWN             8
+#define CLASS_IS_WINRT                8

#define TYPE_FLAG_CONST      1
 #define TYPE_FLAG_VOLATILE   2
 #define TYPE_FLAG_REFERENCE  8
-#define TYPE_FLAG_IUNKNOWN  16
+#define TYPE_FLAG_WINRT     16

void WINAPI DECLSPEC_NORETURN _CxxThrowException(void*,const cxx_exception_type*);

@@ -248,7 +248,7 @@ static inline void copy_exception( void *object, void **dest, UINT catch_flags,
     }
     else if (type->flags & CLASS_IS_SIMPLE_TYPE)
     {
-        if (type->flags & CLASS_IS_IUNKNOWN && *(IUnknown**)object)
+        if (type->flags & CLASS_IS_WINRT && *(IUnknown**)object)
             IUnknown_AddRef(*(IUnknown**)object);
         memmove( dest, object, type->size );
         /* if it is a pointer, adjust it */
@@ -264,7 +264,7 @@ static inline void copy_exception( void *object, void **dest, UINT catch_flags,
         }
         else
         {
-            if (type->flags & CLASS_IS_IUNKNOWN && *(IUnknown**)object)
+            if (type->flags & CLASS_IS_WINRT && *(IUnknown**)object)
                 IUnknown_AddRef(*(IUnknown**)object);
             memmove( dest, get_this_pointer( &type->offsets, object ), type->size );
         }
diff --git a/dlls/msvcrt/except.c b/dlls/msvcrt/except.c
index bed1df0276e..383c67f7437 100644
--- a/dlls/msvcrt/except.c
+++ b/dlls/msvcrt/except.c
@@ -964,7 +964,7 @@ void CDECL __DestructExceptionObject(EXCEPTION_RECORD *rec)

if (info->destructor)
         call_dtor( cxx_rva( info->destructor, rec->ExceptionInformation[3] ), object );
-    else if (info->flags & TYPE_FLAG_IUNKNOWN && *(IUnknown**)object)
+    else if (info->flags & TYPE_FLAG_WINRT && *(IUnknown**)object)
         IUnknown_Release( *(IUnknown**)object );
 }

[PATCH v3 2/2] msvcrt: Update WinRT exception type info in _CxxThrowException.

[Vibhav Pant]

From: Vibhav Pant

---
 dlls/msvcrt/cpp.c       | 10 ++++++++++
 dlls/msvcrt/cppexcept.h | 13 +++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/dlls/msvcrt/cpp.c b/dlls/msvcrt/cpp.c
index c30fd4994a6..c8537bda8f4 100644
--- a/dlls/msvcrt/cpp.c
+++ b/dlls/msvcrt/cpp.c
@@ -903,6 +903,16 @@ void WINAPI _CxxThrowException( void *object, const cxx_exception_type *type )
 {
     ULONG_PTR args[CXX_EXCEPTION_PARAMS];

+    if (type && type->flags & TYPE_FLAG_WINRT)
+    {
+        /* This is a WinRT exception, which contains a pointer to winrt_exception_info just before the object.
+         * We use the exception_type field inside that struct as the actual value for exception type. */
+         winrt_exception_info **info = *(winrt_exception_info ***)object - 1;
+
+         type = (*info)->exception_type;
+         (*info)->set_exception_info( info );
+    }
+
     args[0] = CXX_FRAME_MAGIC_VC6;
     args[1] = (ULONG_PTR)object;
     args[2] = (ULONG_PTR)type;
diff --git a/dlls/msvcrt/cppexcept.h b/dlls/msvcrt/cppexcept.h
index 61267add740..0f64f97dd20 100644
--- a/dlls/msvcrt/cppexcept.h
+++ b/dlls/msvcrt/cppexcept.h
@@ -142,6 +142,19 @@ typedef struct
 #define TYPE_FLAG_REFERENCE  8
 #define TYPE_FLAG_WINRT     16

+typedef struct winrt_exception_info
+{
+    BSTR description;
+    BSTR restricted_desc;
+    void *unknown1;
+    void *unknown2;
+    HRESULT hr;
+    void *error_info; /* IRestrictedErrorInfo */
+    const cxx_exception_type *exception_type;
+    UINT32 unknown3;
+    void (*WINAPI set_exception_info)(struct winrt_exception_info **);
+} winrt_exception_info;
+
 void WINAPI DECLSPEC_NORETURN _CxxThrowException(void*,const cxx_exception_type*);

static inline BOOL is_cxx_exception( EXCEPTION_RECORD *rec )

[Piotr Caban (＠piotr)]

I've pushed a version with some minor style changes. Thank you.

[Vibhav Pant (＠vibhavp)]

On Wed Oct 29 14:40:07 2025 +0000, Piotr Caban wrote:
> I've pushed a version with some minor style changes. Thank you.

Thanks.

[PATCH v3 0/2] MR9306: msvcrt: Use the correct arguments when a WinRT exception is thrown with _CxxThrowException. - approved

[Piotr Caban (＠piotr)]

This merge request was approved by Piotr Caban.