Question

People tend to say pass by (const) reference if you want speed, to be honest I rarely use const reference on methods I create just because of speed, I only make a reference when I need it, for example to give a value to a variable, as in this SSCE

void Do( int& iref )
{
    a = 2;
}

{
    int a = 0;
    Do( a );
}

The question actually is, if the object was created on the function call, if will it also be passed as a reference, how does that works?

void Add( CString& strPath )
{
    g_Path.push_back( strPath );
}

for( std::string line; getline( input, line ); )
{
    Add( CString( line.c_str() ) ); //object created on function call
}

Answer 1

How does that work? It doesn’t. The code doesn’t compile, since temporary objects cannot bind to non-const lvalue references.

(Temporary objects can bind to const references, or to rvalue references, though.)