diff --git a/cppwinrt/cppwinrt.vcxproj b/cppwinrt/cppwinrt.vcxproj
index b8beed890..3efa7a64c 100644
--- a/cppwinrt/cppwinrt.vcxproj
+++ b/cppwinrt/cppwinrt.vcxproj
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Project DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
-  <Import Project="..\packages\Microsoft.Windows.WinMD.1.0.210629.2\build\native\Microsoft.Windows.WinMD.props" Condition="Exists('..\packages\Microsoft.Windows.WinMD.1.0.210629.2\build\native\Microsoft.Windows.WinMD.props')" />
+  <Import Project="..\packages\Microsoft.Windows.WinMD.1.0.260529.3\build\native\Microsoft.Windows.WinMD.props" Condition="Exists('..\packages\Microsoft.Windows.WinMD.1.0.260529.3\build\native\Microsoft.Windows.WinMD.props')" />
   <ItemGroup Label="ProjectConfigurations">
     <ProjectConfiguration Include="Debug|ARM64">
       <Configuration>Debug</Configuration>
@@ -309,6 +309,6 @@
     <PropertyGroup>
       <ErrorText>This project references NuGet package(s) that are missing on this computer. Use NuGet Package Restore to download them.  For more information, see http://go.microsoft.com/fwlink/?LinkID=322105. The missing file is {0}.</ErrorText>
     </PropertyGroup>
-    <Error Condition="!Exists('..\packages\Microsoft.Windows.WinMD.1.0.210629.2\build\native\Microsoft.Windows.WinMD.props')" Text="$([System.String]::Format('$(ErrorText)', '..\packages\Microsoft.Windows.WinMD.1.0.210629.2\build\native\Microsoft.Windows.WinMD.props'))" />
+    <Error Condition="!Exists('..\packages\Microsoft.Windows.WinMD.1.0.260529.3\build\native\Microsoft.Windows.WinMD.props')" Text="$([System.String]::Format('$(ErrorText)', '..\packages\Microsoft.Windows.WinMD.1.0.260529.3\build\native\Microsoft.Windows.WinMD.props'))" />
   </Target>
 </Project>
\ No newline at end of file
diff --git a/cppwinrt/cppwinrt.vcxproj.filters b/cppwinrt/cppwinrt.vcxproj.filters
index 96129ab20..935ef8c20 100644
--- a/cppwinrt/cppwinrt.vcxproj.filters
+++ b/cppwinrt/cppwinrt.vcxproj.filters
@@ -197,9 +197,9 @@
     </Filter>
   </ItemGroup>
   <ItemGroup>
-    <None Include="packages.config" />
+    <Manifest Include="app.manifest" />
   </ItemGroup>
   <ItemGroup>
-    <Manifest Include="app.manifest" />
+    <None Include="packages.config" />
   </ItemGroup>
 </Project>
\ No newline at end of file
diff --git a/cppwinrt/packages.config b/cppwinrt/packages.config
index 9b3264e46..7b2ee1f28 100644
--- a/cppwinrt/packages.config
+++ b/cppwinrt/packages.config
@@ -1,4 +1,4 @@
 <?xml version="1.0" encoding="utf-8"?>
 <packages>
-  <package id="Microsoft.Windows.WinMD" version="1.0.210629.2" targetFramework="native" />
+  <package id="Microsoft.Windows.WinMD" version="1.0.260529.3" targetFramework="native" />
 </packages>
\ No newline at end of file
diff --git a/strings/base_activation.h b/strings/base_activation.h
index c657c692d..a2442d774 100644
--- a/strings/base_activation.h
+++ b/strings/base_activation.h
@@ -133,6 +133,10 @@ WINRT_EXPORT namespace winrt::impl
         std::int32_t const result = *target;
         _ReadWriteBarrier();
         return result;
+#elif defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
+        std::int32_t const result = *target;
+        std::atomic_signal_fence(std::memory_order_acq_rel);
+        return result;
 #elif defined _M_ARM64
 #if defined(__GNUC__)
         std::int32_t const result = *target;
@@ -146,13 +150,17 @@ WINRT_EXPORT namespace winrt::impl
 #endif
     }
 
-#if defined _WIN64
+#if defined(_WIN64) || defined(WINRT_IMPL_64)
     inline std::int64_t interlocked_read_64(std::int64_t const volatile* target) noexcept
     {
 #if defined _M_X64
         std::int64_t const result = *target;
         _ReadWriteBarrier();
         return result;
+#elif defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
+        std::int64_t const result = *target;
+        std::atomic_signal_fence(std::memory_order_acq_rel);
+        return result;
 #elif defined _M_ARM64
 #if defined(__GNUC__)
         std::int64_t const result = *target;
@@ -176,14 +184,14 @@ WINRT_EXPORT namespace winrt::impl
     template <typename T>
     T* interlocked_read_pointer(T* const volatile* target) noexcept
     {
-#ifdef _WIN64
+#if defined(_WIN64) || defined(WINRT_IMPL_64)
         return (T*)interlocked_read_64((std::int64_t*)target);
 #else
         return (T*)interlocked_read_32((std::int32_t*)target);
 #endif
     }
 
-#ifdef _WIN64
+#if defined(_WIN64) || defined(WINRT_IMPL_64)
     inline constexpr std::uint32_t memory_allocation_alignment{ 16 };
 #ifdef _MSC_VER
 #pragma warning(push)
@@ -237,7 +245,7 @@ WINRT_EXPORT namespace winrt::impl
         explicit factory_count_guard(std::size_t& count) noexcept : m_count(count)
         {
 #ifndef WINRT_NO_MODULE_LOCK
-#ifdef _WIN64
+#if defined(_WIN64) || defined(WINRT_IMPL_64)
             _InterlockedIncrement64((std::int64_t*)&m_count);
 #else
             _InterlockedIncrement((long*)&m_count);
@@ -248,7 +256,7 @@ WINRT_EXPORT namespace winrt::impl
         ~factory_count_guard() noexcept
         {
 #ifndef WINRT_NO_MODULE_LOCK
-#ifdef _WIN64
+#if defined(_WIN64) || defined(WINRT_IMPL_64)
             _InterlockedDecrement64((std::int64_t*)&m_count);
 #else
             _InterlockedDecrement((long*)&m_count);
@@ -282,7 +290,7 @@ WINRT_EXPORT namespace winrt::impl
 
             object_and_count current_value{ pointer_value, 0 };
 
-#if defined _WIN64
+#if defined(_WIN64) || defined(WINRT_IMPL_64)
 #if defined(__GNUC__)
             bool exchanged = __sync_bool_compare_and_swap((__int128*)this, *(__int128*)&current_value, (__int128)0);
 #else
@@ -305,7 +313,7 @@ WINRT_EXPORT namespace winrt::impl
 
     static_assert(std::is_standard_layout_v<factory_cache_entry_base>);
 
-#if !defined _M_IX86 && !defined _M_X64 && !defined _M_ARM64
+#if !defined _M_IX86 && !defined _M_X64 && !defined _M_ARM64 && !(defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__) || defined(__aarch64__)))
 #error Unsupported architecture: verify that zero-initialization of SLIST_HEADER is still safe
 #endif
 
diff --git a/strings/base_extern.h b/strings/base_extern.h
index a17908ac4..4ef71ca4a 100644
--- a/strings/base_extern.h
+++ b/strings/base_extern.h
@@ -2,10 +2,10 @@
 // These global function pointers must use WINRT_EXPORT (which expands to
 // 'export extern "C++"' in module builds) so that module and non-module TUs
 // in the same binary share the same instances.
-WINRT_EXPORT __declspec(selectany) std::int32_t(__stdcall* winrt_to_hresult_handler)(void* address) noexcept {};
-WINRT_EXPORT __declspec(selectany) winrt::hstring(__stdcall* winrt_to_message_handler)(void* address) {};
-WINRT_EXPORT __declspec(selectany) void(__stdcall* winrt_throw_hresult_handler)(std::uint32_t lineNumber, char const* fileName, char const* functionName, void* returnAddress, winrt::hresult const result) noexcept {};
-WINRT_EXPORT __declspec(selectany) std::int32_t(__stdcall* winrt_activation_handler)(void* classId, winrt::guid const& iid, void** factory) noexcept {};
+WINRT_EXPORT WINRT_IMPL_SELECTANY std::int32_t(__stdcall* winrt_to_hresult_handler)(void* address) noexcept {};
+WINRT_EXPORT WINRT_IMPL_SELECTANY winrt::hstring(__stdcall* winrt_to_message_handler)(void* address) {};
+WINRT_EXPORT WINRT_IMPL_SELECTANY void(__stdcall* winrt_throw_hresult_handler)(std::uint32_t lineNumber, char const* fileName, char const* functionName, void* returnAddress, winrt::hresult const result) noexcept {};
+WINRT_EXPORT WINRT_IMPL_SELECTANY std::int32_t(__stdcall* winrt_activation_handler)(void* classId, winrt::guid const& iid, void** factory) noexcept {};
 
 #if defined(_MSC_VER)
 #ifdef _M_HYBRID
diff --git a/strings/base_includes.h b/strings/base_includes.h
index 287a09709..65c0bceeb 100644
--- a/strings/base_includes.h
+++ b/strings/base_includes.h
@@ -1,5 +1,7 @@
 
+#if defined(_WIN32)
 #include <intrin.h>
+#endif
 #include <algorithm>
 #include <array>
 #include <atomic>
diff --git a/strings/base_macros.h b/strings/base_macros.h
index 91b0121d9..1e236fddc 100644
--- a/strings/base_macros.h
+++ b/strings/base_macros.h
@@ -73,6 +73,37 @@
 #define WINRT_IMPL_NOVTABLE
 #endif
 
+// Non-Windows (ELF) platform shims. On Linux/macOS GCC/Clang there is a single
+// calling convention, so __stdcall is meaningless and undefined as a token;
+// map it away. __declspec(selectany) has no ELF equivalent keyword — the COMDAT
+// "pick any" semantics map to a weak symbol.
+#if !defined(_WIN32)
+#ifndef __stdcall
+#define __stdcall
+#endif
+#define WINRT_IMPL_SELECTANY __attribute__((weak))
+#else
+#define WINRT_IMPL_SELECTANY __declspec(selectany)
+#endif
+
+// On 64-bit ELF (LP64) select the 64-bit interlocked/slist code paths that are
+// otherwise gated on _WIN64, and supply the MSVC interlocked intrinsics the
+// activation/factory-cache machinery references, implemented with GCC/Clang
+// atomic builtins. (The Add slice constructs via winrt::make and never hits the
+// factory cache at runtime, but the projected constructor is still instantiated,
+// so these must compile and link.)
+#if !defined(_WIN32)
+#if defined(__LP64__) || (defined(__SIZEOF_POINTER__) && __SIZEOF_POINTER__ == 8)
+#define WINRT_IMPL_64 1
+#endif
+inline long _InterlockedIncrement(long volatile* operand) noexcept { return __atomic_add_fetch(operand, 1, __ATOMIC_SEQ_CST); }
+inline long _InterlockedDecrement(long volatile* operand) noexcept { return __atomic_sub_fetch(operand, 1, __ATOMIC_SEQ_CST); }
+inline __INT64_TYPE__ _InterlockedIncrement64(__INT64_TYPE__ volatile* operand) noexcept { return __atomic_add_fetch(operand, 1, __ATOMIC_SEQ_CST); }
+inline __INT64_TYPE__ _InterlockedDecrement64(__INT64_TYPE__ volatile* operand) noexcept { return __atomic_sub_fetch(operand, 1, __ATOMIC_SEQ_CST); }
+inline __INT64_TYPE__ _InterlockedCompareExchange64(__INT64_TYPE__ volatile* dest, __INT64_TYPE__ exchange, __INT64_TYPE__ comparand) noexcept { __atomic_compare_exchange_n(dest, &comparand, exchange, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST); return comparand; }
+inline void* _InterlockedCompareExchangePointer(void* volatile* dest, void* exchange, void* comparand) noexcept { __atomic_compare_exchange_n(dest, &comparand, exchange, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST); return comparand; }
+#endif
+
 #if defined(__clang__) && defined(__has_attribute)
 #if __has_attribute(__lto_visibility_public__)
 #define WINRT_IMPL_PUBLIC __attribute__((lto_visibility_public))
diff --git a/strings/base_natvis.h b/strings/base_natvis.h
index 9e78563cb..71fbc57f6 100644
--- a/strings/base_natvis.h
+++ b/strings/base_natvis.h
@@ -85,11 +85,11 @@ WINRT_EXPORT namespace winrt::impl
 }
 
 extern "C"
-__declspec(selectany)
+WINRT_IMPL_SELECTANY
 decltype(winrt::impl::natvis::abi_val) & WINRT_abi_val = winrt::impl::natvis::abi_val;
 
 extern "C"
-__declspec(selectany)
+WINRT_IMPL_SELECTANY
 decltype(winrt::impl::natvis::get_val) & WINRT_get_val = winrt::impl::natvis::get_val;
 
 #ifdef _M_IX86
diff --git a/strings/base_version.h b/strings/base_version.h
index 13d21fb2a..27ce4fcfb 100644
--- a/strings/base_version.h
+++ b/strings/base_version.h
@@ -1,7 +1,7 @@
 
 // WINRT_version is used by Microsoft to analyze C++/WinRT library adoption and inform future product decisions.
 extern "C"
-__declspec(selectany)
+WINRT_IMPL_SELECTANY
 char const * const WINRT_version = "C++/WinRT version:" CPPWINRT_VERSION;
 
 #if defined(_MSC_VER)