[Runtime] Prevent double delete when engine shutdown.

[VariantUtils] Fix `write_json` bug that returns positive integers when reading negative integers.
[Runtime] Remove `String::operator=(value_type ch)`, since it is not used at all and may cause ambiguity.

Modules/Luna/Runtime/Impl/String.inl

@@ -274,16 +274,6 @@ namespace Luna
         return *this;
     }
     template <typename _Char, typename _Alloc>
-    inline BasicString<_Char, _Alloc>& BasicString<_Char, _Alloc>::operator=(value_type ch)
-    {
-        clear();
-        reserve(1);
-        m_allocator_and_buffer.second()[0] = ch;
-        m_size = 1;
-        m_allocator_and_buffer.second()[m_size] = (value_type)0;
-        return *this;
-    }
-    template <typename _Char, typename _Alloc>
     inline BasicString<_Char, _Alloc>& BasicString<_Char, _Alloc>::operator=(InitializerList<value_type> ilist)
     {
         clear();

Modules/Luna/Runtime/Source/Runtime.cpp

@@ -67,8 +67,8 @@ namespace Luna
     {
         if (g_initialized) return true;
         OS::init();
-        stack_allocator_init();
         profiler_init();
+        stack_allocator_init();
         error_init();
         name_init();
         type_registry_init();
@@ -96,8 +96,8 @@ namespace Luna
         type_registry_close();
         name_close();
         error_close();
-        profiler_close();
         stack_allocator_close();
+        profiler_close();
         OS::close();
         g_initialized = false;
     }

Modules/Luna/Runtime/Source/StackAllocator.cpp

@@ -81,9 +81,12 @@ namespace Luna
     }
     void stack_allocator_close()
     {
+        {
+            LockGuard guard(g_stack_allocator_ctxs_lock);
+            g_stack_allocator_ctxs.clear();
+            g_stack_allocator_ctxs.shrink_to_fit();
+        }
         tls_free(g_stack_allocator_tls);
-        g_stack_allocator_ctxs.clear();
-        g_stack_allocator_ctxs.shrink_to_fit();
     }
     StackAllocatorTLSContext* get_stack_allocator_ctx()
     {

Modules/Luna/Runtime/String.hpp

@@ -154,11 +154,6 @@ namespace Luna
         //! @par Valid Usage
         //! * `s` must points to a valid null-terminated string.
         BasicString& operator=(const value_type* s);
-        //! Assigns the string with the specified character. This operation behaves the same as 
-        //! `assign(1, ch)`.
-        //! @param[in] ch The character to assign.
-        //! @return Returns `*this`.
-        BasicString& operator=(value_type ch);
         //! Assigns the string by coping characters from the initializer list.
         //! @param[in] ilist The initializer list to copy characters from.
         //! @return Returns `*this`.

Modules/Luna/VariantUtils/Source/JSON.cpp

@@ -408,7 +408,7 @@ namespace Luna
                     value *= 10;
                     value += i - '0';
                 }
-                return Variant(value);
+                return Variant(-value);
             }
         }
 

Tests/RuntimeTest/Source/StringTest.cpp

@@ -73,10 +73,6 @@ namespace Luna
             str8 = u8"Sample String";
             lutest(!strcmp(str8.c_str(), u8"Sample String"));
 
-            // operator=(value_type ch)
-            str8 = 'c';
-            lutest(!strcmp(str8.c_str(), u8"c"));
-
             // operator=(InitializerList<value_type> ilist)
             str8 = { 'e', 't', 'f' };
             lutest(!strcmp(str8.c_str(), u8"etf"));

Tests/VariantUtilsTest/Source/JSONTest.cpp

@@ -74,5 +74,14 @@ namespace Luna
             Variant& blob_var2 = blob_var2_r.get();
             luassert_always(blob_var == blob_var2);
         }
+
+        {
+            // Bugfix: reading negative number will result in positive number.
+            Variant var1((i64)-3);
+            String s = VariantUtils::write_json(var1);
+            R<Variant> var2 = VariantUtils::read_json(s.c_str());
+            luassert_always(succeeded(var2));
+            luassert_always(var1 == var2.get());
+        }
     }
 }