Strange behavior with QString - qt

Question

Here's my code:
#include <QCoreApplication>
#include <QTextStream>
#include <iostream>
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
QTextStream out(stdout);
QString filename = "F:/temp/йцук.tx";
out << filename << endl;
const wchar_t* fn_wch = filename.toStdWString().c_str();
std::wcout << filename.toStdWString().c_str() << std::endl; //1
std::wcout << fn_wch << std::endl; //2
return a.exec();
}
The problem is rows "1" and "2" outputs different strings. But aren't they should be the same? Because I assigned fn_wch to filename.toStdWString().c_str() before that.
UPD0:
I've changed the code to prevent accessing to data of the destroyed wstring:
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
QTextStream out(stdout);
QString filename = "F:/temp/йцук.tx";
out << filename << endl;
auto wstr = filename.toStdWString();
auto wchar = wstr.c_str();
std::wcout << wchar << std::endl; //1
std::wcout << wchar << std::endl; //2
std::wcout << wstr; //3
return a.exec();
}
But problem remains the same: row 1 outputs data, but 2 and 3 doesn't.

Answer 1

int main(int argc, char *argv[])
{
setlocale(LC_ALL, "russian");
QCoreApplication a(argc, argv);
QTextStream out(stdout);
QString filename = "F:/temp/йцук.tx";
out << filename << endl;
auto wstr = filename.toStdWString();
//auto wchar = wstr.c_str();
wchar_t wchar[wstr.size()];
wcscpy(wchar, wstr.c_str());
std::wcout << wchar << std::endl; //1
std::wcout << wchar << std::endl; //2
std::wcout << wstr; //3
return a.exec();
}
It works. Pointer in c_str() is destryed, so you need to copy data.