Various cleanups

[YexuanXiao]

• Replace unsafe C-style casts with reinterpret_cast and merge some into abi_cast and abi_t_abi_cast.
• Use __builtin_bit_cast to avoid strict aliasing violations and eliminate GCC warnings (supported by GCC, Clang, and MSVC post-2020 as underlying intrinsic of C++20 std::bit_cast). Fixes Bug: GCC warns about breaking strict-aliasing rules for 32-bit builds #1568.
• Simplify interlocked_read_pointer.

If C++/WinRT decide to discontinue support for C++17, it can use std::bit_cast instead of __builtin_bit_cast, and use std::atomic_ref instead of interlocked_read_pointer and other raw synchronization intrinsics.

[Copilot]

Pull request overview

This PR performs a set of internal header cleanups in the C++/WinRT projection, primarily refactoring ABI access patterns (replacing C-style casts), addressing strict-aliasing warnings (notably on GCC x86), and simplifying some low-level interlocked helpers. It also updates the code generator to emit the new ABI-cast helpers.

Changes:

• Introduces shared ABI cast helpers (impl::abi_cast, impl::abi_t_abi_cast) and updates many get_abi/shim call sites to use them.
• Reworks factory_cache_entry_base::clear() to use __builtin_bit_cast when performing 64/128-bit CAS to avoid strict-aliasing warnings.
• Simplifies interlocked_read_pointer and updates code generation templates to match the new ABI-cast helpers.

Reviewed changes

Copilot reviewed 19 out of 20 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
strings/base_windows.h	Adds impl::abi_cast and refactors ABI shims/calls to use new helpers.
strings/base_string.h	Switches hstring ABI helpers to impl::abi_cast.
strings/base_string_input.h	Updates param::hstring ABI access to impl::abi_cast.
strings/base_reference_produce.h	Replaces C-style cast in unbox_value_or default path with reinterpret_cast.
strings/base_natvis.h	Replaces C-style casts with reinterpret_cast for natvis inspection helpers.
strings/base_meta.h	Adds impl::abi_t_abi_cast helper for ABI-vtable access.
strings/base_macros.h	Updates WINRT_IMPL_SHIM macro to use impl::abi_t_abi_cast.
strings/base_implements.h	Replaces C-style casts with reinterpret_cast in producer conversion helpers.
strings/base_events.h	Updates event revoker teardown to use impl::abi_t_abi_cast.
strings/base_delegate.h	Replaces C-style cast with reinterpret_cast in delegate invocation.
strings/base_coroutine_foundation.h	Updates when_any completion handler ABI access and interlocked exchange usage.
strings/base_collections_input_vector.h	Updates collection param ABI extraction to impl::abi_cast.
strings/base_collections_input_vector_view.h	Updates collection param ABI extraction to impl::abi_cast.
strings/base_collections_input_map.h	Updates collection param ABI extraction to impl::abi_cast.
strings/base_collections_input_map_view.h	Updates collection param ABI extraction to impl::abi_cast.
strings/base_collections_input_iterable.h	Updates collection param ABI extraction to impl::abi_cast.
strings/base_array.h	Refactors array_view ABI extraction and inspectable helper calls to use impl::abi_cast.
strings/base_agile_ref.h	Minor preprocessor formatting cleanup for defined(...).
strings/base_activation.h	Simplifies interlocked_read_pointer, adds __builtin_bit_cast for CAS, updates activation factory ABI calls.
cppwinrt/code_writers.h	Updates generated code templates to emit impl::abi_cast / impl::abi_t_abi_cast.

[Copilot]

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