#include <iostream>
#include <string>
#include <sstream>

std::istream& get_line_strip_comments( std::istream& stm, std::string& str )
{
    if( std::getline( stm, str ) )
    {
        auto pos = str.find( "//" ) ;
        if( pos == 0 ) return get_line_strip_comments( stm, str ) ;
        else if( pos != std::string::npos ) str.erase(pos) ;
    }
    return stm ;
}


int main()
{
    std::istringstream stm( R"(
this is a line with no comments
// this is a comment line
some text // and then a comment
more text / / this is not a comment // but this is\n)" ) ;

    std::string str ;
    while( get_line_strip_comments( stm, str ) ) std::cout << str << '\n' ;
}