`<condition_variable>`: Avoid squirrelly forward declaration of `_Cnd_internal_imp_t` (#4545)

stl/inc/__msvc_threads_core.hpp

@@ -33,50 +33,38 @@ struct _Stl_critical_section {
 };
 
 struct _Mtx_internal_imp_t {
-#if defined(_CRT_WINDOWS) || defined(UNDOCKED_WINDOWS_UCRT)
-#ifdef _WIN64
-    static constexpr size_t _Critical_section_size = 16;
-#else // ^^^ defined(_WIN64) / !defined(_WIN64) vvv
-    static constexpr size_t _Critical_section_size = 8;
-#endif // ^^^ !defined(_WIN64) ^^^
-#else // ^^^ Windows private STL / public STL vvv
-#ifdef _WIN64
+#if defined(_CRT_WINDOWS) || defined(UNDOCKED_WINDOWS_UCRT) // for Windows-internal code
+    static constexpr size_t _Critical_section_size = 2 * sizeof(void*);
+#elif defined(_WIN64) // ordinary 64-bit code
     static constexpr size_t _Critical_section_size = 64;
-#else // ^^^ defined(_WIN64) / !defined(_WIN64) vvv
+#else // vvv ordinary 32-bit code vvv
     static constexpr size_t _Critical_section_size = 36;
-#endif // ^^^ !defined(_WIN64) ^^^
-#endif // ^^^ public STL ^^^
-
-    static constexpr size_t _Critical_section_align = alignof(void*);
+#endif // ^^^ ordinary 32-bit code ^^^
 
     int _Type{};
     union {
         _Stl_critical_section _Critical_section{};
-        _STD _Aligned_storage_t<_Critical_section_size, _Critical_section_align> _Cs_storage;
+        _STD _Aligned_storage_t<_Critical_section_size, alignof(void*)> _Cs_storage;
     };
     long _Thread_id{};
     int _Count{};
 };
 
-// Size and alignment for _Cnd_internal_imp_t
-#if defined(_CRT_WINDOWS) // for Windows-internal code
-_INLINE_VAR constexpr size_t _Cnd_internal_imp_size = 2 * sizeof(void*);
-#elif defined(_WIN64) // ordinary 64-bit code
-_INLINE_VAR constexpr size_t _Cnd_internal_imp_size = 72;
-#else // vvv ordinary 32-bit code vvv
-_INLINE_VAR constexpr size_t _Cnd_internal_imp_size = 40;
-#endif // ^^^ ordinary 32-bit code ^^^
-
-_INLINE_VAR constexpr size_t _Cnd_internal_imp_alignment = alignof(void*);
-
 using _Mtx_t = _Mtx_internal_imp_t*;
 
-#ifdef _M_CEE // avoid warning LNK4248: unresolved typeref token for '_Cnd_internal_imp_t'; image may not run
-using _Cnd_t = void*;
-#else // ^^^ defined(_M_CEE) / !defined(_M_CEE) vvv
-struct _Cnd_internal_imp_t;
+struct _Cnd_internal_imp_t {
+#if defined(_CRT_WINDOWS) // for Windows-internal code
+    static constexpr size_t _Cnd_internal_imp_size = 2 * sizeof(void*);
+#elif defined(_WIN64) // ordinary 64-bit code
+    static constexpr size_t _Cnd_internal_imp_size = 72;
+#else // vvv ordinary 32-bit code vvv
+    static constexpr size_t _Cnd_internal_imp_size = 40;
+#endif // ^^^ ordinary 32-bit code ^^^
+
+    _STD _Aligned_storage_t<_Cnd_internal_imp_size, alignof(void*)> _Cv_storage;
+};
+
 using _Cnd_t = _Cnd_internal_imp_t*;
-#endif // ^^^ !defined(_M_CEE) ^^^
 } // extern "C"
 
 #pragma pop_macro("new")

stl/inc/condition_variable

@@ -220,10 +220,10 @@ public:
 private:
     shared_ptr<mutex> _Myptr;
 
-    _Aligned_storage_t<_Cnd_internal_imp_size, _Cnd_internal_imp_alignment> _Cnd_storage;
+    _Cnd_internal_imp_t _Cnd_storage;
 
-    _NODISCARD _Cnd_t _Mycnd() noexcept { // get pointer to _Cnd_internal_imp_t inside _Cnd_storage
-        return reinterpret_cast<_Cnd_t>(&_Cnd_storage);
+    _NODISCARD _Cnd_t _Mycnd() noexcept {
+        return &_Cnd_storage;
     }
 
     template <class _Lock>

stl/inc/mutex

@@ -637,10 +637,10 @@ public:
     }
 
 private:
-    _Aligned_storage_t<_Cnd_internal_imp_size, _Cnd_internal_imp_alignment> _Cnd_storage;
+    _Cnd_internal_imp_t _Cnd_storage;
 
-    _Cnd_t _Mycnd() noexcept { // get pointer to _Cnd_internal_imp_t inside _Cnd_storage
-        return reinterpret_cast<_Cnd_t>(&_Cnd_storage);
+    _Cnd_t _Mycnd() noexcept {
+        return &_Cnd_storage;
     }
 };
 

stl/src/cond.cpp

@@ -14,7 +14,7 @@ extern "C" {
 
 
 _CRTIMP2_PURE void __cdecl _Cnd_init_in_situ(const _Cnd_t cond) noexcept { // initialize condition variable in situ
-    new (cond->_get_cv()) Concurrency::details::stl_condition_variable_win7;
+    new (Concurrency::details::_Get_cond_var(cond)) Concurrency::details::stl_condition_variable_win7;
 }
 
 _CRTIMP2_PURE void __cdecl _Cnd_destroy_in_situ(_Cnd_t) noexcept {} // destroy condition variable in situ
@@ -54,7 +54,7 @@ _CRTIMP2_PURE void __cdecl _Mtx_reset_owner(_Mtx_t mtx) noexcept { // set owner
 _CRTIMP2_PURE _Thrd_result __cdecl _Cnd_wait(const _Cnd_t cond, const _Mtx_t mtx) noexcept { // wait until signaled
     const auto cs = &mtx->_Critical_section;
     _Mtx_clear_owner(mtx);
-    cond->_get_cv()->wait(cs);
+    Concurrency::details::_Get_cond_var(cond)->wait(cs);
     _Mtx_reset_owner(mtx);
     return _Thrd_result::_Success; // TRANSITION, ABI: Always succeeds
 }
@@ -66,13 +66,14 @@ _CRTIMP2_PURE _Thrd_result __cdecl _Cnd_timedwait(
     const auto cs    = &mtx->_Critical_section;
     if (target == nullptr) { // no target time specified, wait on mutex
         _Mtx_clear_owner(mtx);
-        cond->_get_cv()->wait(cs);
+        Concurrency::details::_Get_cond_var(cond)->wait(cs);
         _Mtx_reset_owner(mtx);
     } else { // target time specified, wait for it
         _timespec64 now;
         _Timespec64_get_sys(&now);
         _Mtx_clear_owner(mtx);
-        if (!cond->_get_cv()->wait_for(cs, _Xtime_diff_to_millis2(target, &now))) { // report timeout
+        if (!Concurrency::details::_Get_cond_var(cond)->wait_for(
+                cs, _Xtime_diff_to_millis2(target, &now))) { // report timeout
             _Timespec64_get_sys(&now);
             if (_Xtime_diff_to_millis2(target, &now) == 0) {
                 res = _Thrd_result::_Timedout;
@@ -84,12 +85,12 @@ _CRTIMP2_PURE _Thrd_result __cdecl _Cnd_timedwait(
 }
 
 _CRTIMP2_PURE _Thrd_result __cdecl _Cnd_signal(const _Cnd_t cond) noexcept { // release one waiting thread
-    cond->_get_cv()->notify_one();
+    Concurrency::details::_Get_cond_var(cond)->notify_one();
     return _Thrd_result::_Success; // TRANSITION, ABI: Always succeeds
 }
 
 _CRTIMP2_PURE _Thrd_result __cdecl _Cnd_broadcast(const _Cnd_t cond) noexcept { // release all waiting threads
-    cond->_get_cv()->notify_all();
+    Concurrency::details::_Get_cond_var(cond)->notify_all();
     return _Thrd_result::_Success; // TRANSITION, ABI: Always succeeds
 }
 

stl/src/primitives.hpp

@@ -3,6 +3,7 @@
 
 #pragma once
 
+#include <__msvc_threads_core.hpp>
 #include <cstdlib>
 #include <type_traits>
 
@@ -43,18 +44,8 @@ namespace Concurrency {
             CONDITION_VARIABLE m_condition_variable = CONDITION_VARIABLE_INIT;
         };
 
+        [[nodiscard]] inline stl_condition_variable_win7* _Get_cond_var(::_Cnd_internal_imp_t* _Cond) noexcept {
+            return reinterpret_cast<stl_condition_variable_win7*>(&_Cond->_Cv_storage);
+        }
     } // namespace details
 } // namespace Concurrency
-
-extern "C" {
-
-struct _Cnd_internal_imp_t {
-    std::_Aligned_storage_t<_Cnd_internal_imp_size, _Cnd_internal_imp_alignment> cv;
-
-    [[nodiscard]] Concurrency::details::stl_condition_variable_win7* _get_cv() noexcept {
-        // get pointer to implementation
-        return reinterpret_cast<Concurrency::details::stl_condition_variable_win7*>(&cv);
-    }
-};
-
-} // extern "C"

stl/src/sharedmutex.cpp

@@ -50,7 +50,7 @@ _Thrd_result __stdcall _Cnd_timedwait_for(const _Cnd_t cond, const _Mtx_t mtx, c
     mtx->_Thread_id = -1;
     --mtx->_Count;
 
-    if (!cond->_get_cv()->wait_for(cs, target_ms)) { // report timeout
+    if (!Concurrency::details::_Get_cond_var(cond)->wait_for(cs, target_ms)) { // report timeout
         const auto end_ms = GetTickCount64();
         if (end_ms - start_ms >= target_ms) {
             res = _Thrd_result::_Timedout;