From 782dcd536a57fd5c6a215d1b9a3014ba4c25282f Mon Sep 17 00:00:00 2001
From: Casey Carter <cacarter@microsoft.com>
Date: Wed, 30 Aug 2023 10:19:43 -0700
Subject: [PATCH] Make the constexpr mutex constructor opt-in (#4000)

... via defining `_ENABLE_CONSTEXPR_MUTEX_CONSTRUCTOR`, instead of opt-out via `_DISABLE_CONSTEXPR_MUTEX_CONSTRUCTOR`. This avoids potential breakage until we can update the VCLibs UWP framework libraries.
---
 stl/inc/mutex                              | 12 ++++++------
 tests/std/tests/VSO_0226079_mutex/env.lst  |  2 +-
 tests/std/tests/VSO_0226079_mutex/test.cpp |  4 ++--
 3 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/stl/inc/mutex b/stl/inc/mutex
index b133a8c1ce..4954d7c338 100644
--- a/stl/inc/mutex
+++ b/stl/inc/mutex
@@ -32,18 +32,18 @@ _EXPORT_STD class condition_variable_any;
 
 class _Mutex_base { // base class for all mutex types
 public:
-#ifdef _DISABLE_CONSTEXPR_MUTEX_CONSTRUCTOR
-    _Mutex_base(int _Flags = 0) noexcept {
-        _Mtx_init_in_situ(_Mymtx(), _Flags | _Mtx_try);
-    }
-#else // ^^^ _DISABLE_CONSTEXPR_MUTEX_CONSTRUCTOR / !_DISABLE_CONSTEXPR_MUTEX_CONSTRUCTOR vvv
+#ifdef _ENABLE_CONSTEXPR_MUTEX_CONSTRUCTOR
     constexpr _Mutex_base(int _Flags = 0) noexcept {
         _Mtx_storage._Critical_section = {};
         _Mtx_storage._Thread_id        = -1;
         _Mtx_storage._Type             = _Flags | _Mtx_try;
         _Mtx_storage._Count            = 0;
     }
-#endif // !_DISABLE_CONSTEXPR_MUTEX_CONSTRUCTOR
+#else // ^^^ _ENABLE_CONSTEXPR_MUTEX_CONSTRUCTOR / !_ENABLE_CONSTEXPR_MUTEX_CONSTRUCTOR vvv
+    _Mutex_base(int _Flags = 0) noexcept {
+        _Mtx_init_in_situ(_Mymtx(), _Flags | _Mtx_try);
+    }
+#endif // !_ENABLE_CONSTEXPR_MUTEX_CONSTRUCTOR
 
     ~_Mutex_base() noexcept {
         _Mtx_destroy_in_situ(_Mymtx());
diff --git a/tests/std/tests/VSO_0226079_mutex/env.lst b/tests/std/tests/VSO_0226079_mutex/env.lst
index 371ea99eca..1fb3203d02 100644
--- a/tests/std/tests/VSO_0226079_mutex/env.lst
+++ b/tests/std/tests/VSO_0226079_mutex/env.lst
@@ -3,5 +3,5 @@
 
 RUNALL_INCLUDE ..\impure_matrix.lst
 RUNALL_CROSSLIST
-PM_CL="/D_DISABLE_CONSTEXPR_MUTEX_CONSTRUCTOR"
+PM_CL="/D_ENABLE_CONSTEXPR_MUTEX_CONSTRUCTOR"
 PM_CL=""
diff --git a/tests/std/tests/VSO_0226079_mutex/test.cpp b/tests/std/tests/VSO_0226079_mutex/test.cpp
index dd41244401..dd84dd39d9 100644
--- a/tests/std/tests/VSO_0226079_mutex/test.cpp
+++ b/tests/std/tests/VSO_0226079_mutex/test.cpp
@@ -468,7 +468,7 @@ void test_vso_1253916() {
     do_shared_locked_things(shared_lock<shared_mutex>{mtx});
 }
 
-#ifndef _DISABLE_CONSTEXPR_MUTEX_CONSTRUCTOR
+#ifdef _ENABLE_CONSTEXPR_MUTEX_CONSTRUCTOR
 struct test_constexpr_ctor {
     constexpr test_constexpr_ctor() {}
     mutex mtx;
@@ -478,7 +478,7 @@ test_constexpr_ctor obj;
 #if _HAS_CXX20 && !defined(_M_CEE)
 constinit test_constexpr_ctor obj2;
 #endif // _HAS_CXX20 && !defined(_M_CEE)
-#endif // !_DISABLE_CONSTEXPR_MUTEX_CONSTRUCTOR
+#endif // _ENABLE_CONSTEXPR_MUTEX_CONSTRUCTOR
 
 int main() {
     {