telegraphing the unsafeness (#3806)

Author: stevewhims

uwp/cpp-and-winrt-apis/interop-winrt-abi.md

@@ -1,7 +1,7 @@
 ---
 description: This topic shows how to convert between application binary interface (ABI) and C++/WinRT objects.
 title: Interop between C++/WinRT and the ABI
-ms.date: 11/30/2018
+ms.date: 09/29/2023
 ms.topic: article
 keywords: windows 10, uwp, standard, c++, cpp, winrt, projection, port, migrate, interop, ABI
 ms.localizationpriority: medium
@@ -13,6 +13,9 @@ This topic shows how to convert between SDK application binary interface (ABI) a
 
 In general, C++/WinRT exposes ABI types as **void\***, so that you don't need to include platform header files.
 
+> [!NOTE]
+> In the code examples, we use `reinterpret_cast` (rather than `static_cast`) in an effort to *telegraph* what are inherently unsafe casts.
+
 ## What is the Windows Runtime ABI, and what are ABI types?
 A Windows Runtime class (runtime class) is really an abstraction. This abstraction defines a binary interface (the Application Binary Interface, or ABI) that allows various programming languages to interact with an object. Regardless of programming language, client code interaction with a Windows Runtime object happens at the lowest level, with client language constructs translated into calls into the object's ABI.
 
@@ -149,11 +152,11 @@ For the lowest-level conversions, which only copy addresses, you can use the [**
     // Lowest-level conversions that only copy addresses
 
     // Convert to a non-owning ABI object with get_abi.
-    abi::IStringable* non_owning{ static_cast<abi::IStringable*>(winrt::get_abi(uriAsIStringable)) };
+    abi::IStringable* non_owning{ reinterpret_cast<abi::IStringable*>(winrt::get_abi(uriAsIStringable)) };
     WINRT_ASSERT(non_owning);
 
     // Avoid interlocks this way.
-    owning = static_cast<abi::IStringable*>(winrt::detach_abi(uriAsIStringable));
+    owning = reinterpret_cast<abi::IStringable*>(winrt::detach_abi(uriAsIStringable));
     WINRT_ASSERT(!uriAsIStringable);
     winrt::attach_abi(uriAsIStringable, owning);
     WINRT_ASSERT(uriAsIStringable);
@@ -350,7 +353,7 @@ void GetString(_Out_ HSTRING* value);
 
 | Operation | How to do it | Notes |
 |-|-|-|
-| Extract **HSTRING** from **hstring** | `h = static_cast<HSTRING>(get_abi(s));` | *s* still owns the string. |
+| Extract **HSTRING** from **hstring** | `h = reinterpret_cast<HSTRING>(get_abi(s));` | *s* still owns the string. |
 | Detach **HSTRING** from **hstring** | `h = reinterpret_cast<HSTRING>(detach_abi(s));` | *s* no longer owns the string. |
 | Set **HSTRING** into **hstring** | `*put_abi(s) = h;` | *s* takes ownership of string. Any string previously owned by *s* is leaked (will assert in debug). |
 | Receive **HSTRING** into **hstring** | `GetString(reinterpret_cast<HSTRING*>(put_abi(s)));` | *s* takes ownership of string. Any string previously owned by *s* is leaked (will assert in debug). |