Work around a thread_local bug in MinGW with the WIN32 threading model

src/common/String.cpp

@@ -296,15 +296,19 @@ String numberString(numberChars);
 
 static thread_local struct LocaleImpl
 {
-	std::basic_stringstream<char> stream;
-	std::basic_stringstream<wchar_t> wstream;
+	std::basic_stringstream<char> &stream;
+	std::basic_stringstream<wchar_t> &wstream;
 
-	LocaleImpl()
+	LocaleImpl():
+		stream(*new std::basic_stringstream<char>()),
+		wstream(*new std::basic_stringstream<wchar_t>())
 	{
 		stream.imbue(std::locale::classic());
 		wstream.imbue(std::locale::classic());
 	}
 
+	~LocaleImpl();
+
 	inline void PrepareStream(ByteStringBuilder &b)
 	{
 		stream.flags(b.flags);
@@ -373,6 +377,20 @@ static thread_local struct LocaleImpl
 }
 LocaleImpl;
 
+// This specific implementation of destruction seems to help against the
+// currently broken WIN32 threading model on MinGW. The real destructor is
+// called by the runtime as cdecl but the compiled code expects thiscall.
+static destroyLocaleImpl()
+{
+	delete &LocaleImpl.stream;
+	delete &LocaleImpl.wstream;
+}
+
+LocaleImpl::~LocaleImpl()
+{
+	destroyLocaleImpl();
+}
+
 ByteString ByteStringBuilder::Build() const
 {
 	return ByteString(buffer.begin(), buffer.end());