id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
5644	tellg returns different results for gnu libstd++ and others standard libraries for codecvt_null	Michael.Kv@…	Robert Ramey	"I believe the tellg funtion below shall return the stream position 2 after reading single wide character and it does so for non-gnu standard library. But it returs 1 instead for gnu libstd++ (mingw 4.5.2) though as you may see the wifstream::read call reads two bytes indeed. You may also see that subsequent read operations will be incorrect -- you will get 5bff instead of 005b.

You may also want to take http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49269 into consideration.

--

Michael Kochetkov
{{{
#include <fstream>
#include <iostream>
#include <stdexcept>
#include <boost/archive/codecvt_null.hpp>

int
main() {
	try {
		std::wifstream is;
		is.imbue(std::locale(std::locale::classic(), new boost::archive::codecvt_null<wchar_t>()));
		is.exceptions(std::ios::badbit);
		// Samples.txt shall look in hex like this:
		// FEFF 005B 0030 0020 ¦ 0020 0020 0031 005D | ?[0   1]
		is.open(""samples.txt"",std::ios::in | std::ios::binary);
		unsigned int bom = 0;
		is.read(reinterpret_cast<wchar_t*>(&bom),1);
		const unsigned short bomLE = 0xFEFF;
		if (bom != bomLE) {
			throw std::runtime_error(""Invalid BOM. Only LE is supported"");
		}
		std::cout << ""Current position: "" <<  is.tellg() << std::endl;
	}
	catch(const std::exception& e) {
		std::cout << e.what() << std::endl;
	}
}
}}}
"	Bugs	closed	To Be Determined	serialization	Boost 1.46.1	Problem	wontfix