C で反復中にマップ要素を消去するとどうなりますか?

auto pm_it = port_map.begin();
while (pm_it != port_map.end()) {
    if (pm_it->second == delete_this_id) {
        pm_it = port_map.erase(pm_it);
    } else {
        ++pm_it;
    }
}

map<string, SerialdMsg::SerialFunction_t>::iterator pm_it = port_map.begin();
while (pm_it != port_map.end()) {
    if (pm_it->second == delete_this_id) {
        port_map.erase(pm_it++); // Use iterator.
        // Note the post increment.
        // Increments the iterator but returns the
        // original value for use by erase
    } else {
        ++pm_it; // Can use pre-increment in this case
        // To make sure you have the efficient version
    }
}