c++ - Alternative for fflush(stdin)?

Question

Is fflush(stdin) is really required in C++ and is it good to do it this way to flush the newline in the buffer?

Answer 1

The call to fflush(stdin) is undefined behavior in C (and, consequetly, in C++).

The C language standard, ISO 9899:1999 states in 7.19.5.2/2

If stream points to an output stream or an update stream in which the most recent operation was not input, the fflush function causes any unwritten data for that stream to be delivered to the host environment to be written to the file; otherwise, the behavior is undefined

To discard the entire input up to the next end of line, in C++, the most robust approach is

std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '
');

As for the program "flashing and going away", are you perhaps executing a console application on a Windows platform? Such applications are best executed from a console window (Start->run->cmd.exe)