Here's a code snippet:

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

using namespace std; 

int main(void) 
{ 
    stringstream ss("bla  a bla"); 
    string s; 
    
    while (getline(ss, s, ' ')) 
    { 
        if(!s.empty())  //unable to resolve identifier "empty"
        {
            cout << s << endl; 
        }
    } 
    
    cin.ignore(2);   //unable to resolve identifier "ignore"
    return 0; 
}

The code compiles just fine. It also happens with ifstream stuff such as open, is_open and close.