#include <fstream>
#include <locale>

class Buf : public std::filebuf
{
protected:
	virtual int_type overflow(int_type c = traits_type::eof())
	{
		return traits_type::eq_int_type(c, traits_type::eof()) ?
			traits_type::eof() :
			std::filebuf::overflow(c);
	}
};

int main()
{
	using namespace std;

	Buf fb;
	fb.pubimbue(locale("en_US"));
	fb.open("tmp", ios_base::out);

	try
	{
		fb.sputc('a');
		fb.sputc('b');
		fb.pubimbue(locale::classic());
		fb.sputc('c');
		fb.pubsync();
		fb.close();
	}
	catch (exception&)
	{
	}
}