[Fix] (TLS): drop the context reference before clearing the slot at thread exit

MobileGL/MG_State/GLState/Core.cpp

@@ -1658,12 +1658,15 @@ namespace MobileGL::MG_State {
     constinit thread_local CurrentGLContextSlot pGLContext;
 
     // The reference that keeps the calling thread's pGLContext alive (Core.h). Registered for
-    // destruction on the thread's first assignment; at thread exit it clears the slot first, so
-    // whatever the context's destructor reaches sees no current context rather than one that is
-    // being destroyed.
+    // destruction on the thread's first assignment. At thread exit it drops the reference first,
+    // with the slot still naming the context - what destroying the SharedPtr this used to be did
+    // - and then clears the slot, so no pointer outlives the context.
     struct CurrentGLContextOwner {
         SharedPtr<GLState::GLContext> context;
-        ~CurrentGLContextOwner() { pGLContext.m_context = nullptr; }
+        ~CurrentGLContextOwner() {
+            context.reset();
+            pGLContext.m_context = nullptr;
+        }
     };
     namespace {
         thread_local CurrentGLContextOwner tCurrentGLContextOwner;

MobileGL/MG_State/GLState/Core.h

@@ -790,9 +790,9 @@ namespace MobileGL {
         // every API level. This object is trivially destructible and constant-initialized, so a
         // read is one TLS address computation and a load. The SharedPtr that keeps the context
         // alive lives in a separate thread_local in Core.cpp, written only by the assignments
-        // below (eglMakeCurrent and the release edge, MG_State::Init(), tests); its destructor
-        // clears this pointer before it drops the reference, so a thread's exit leaves no
-        // dangling pointer behind.
+        // below (eglMakeCurrent and the release edge, MG_State::Init(), tests); at thread exit its
+        // destructor drops the reference and then clears this pointer, so no dangling pointer is
+        // left behind.
         //
         // Assignment, reset() and the SharedPtr conversions touch the owner and belong to the
         // CALLING THREAD only: never assign through a reference to another thread's slot.

MobileGL/MG_Test/SanityTest.cpp

@@ -234,7 +234,7 @@ namespace {
     // restores the process-wide state even when a gtest assertion unwinds the test body.
     struct ScopedDirectGLESTextureBindings {
         ScopedDirectGLESTextureBindings():
-            previousContext(MobileGL::Move(MobileGL::MG_State::pGLContext)),
+            previousContext(MobileGL::MG_State::pGLContext.Take()),
             previousFunctions(MobileGL::MG_Backend::DirectGLES::g_GLESFuncs),
             previousActiveUnit(MobileGL::MG_Backend::DirectGLES::TextureImpl::g_activeTextureUnit),
             previousCache(MobileGL::MG_Backend::DirectGLES::TextureImpl::g_boundTexturesCache),