What are the Implications of Removing Map Elements While Iterating in C ?

Consequences of Erasing a Map Element During Iteration in C

In C , iterating through a map and erasing elements can raise concerns regarding iterator validity. The behavior varies based on the C version used.

C 11 and Later

In C 11, the erase() method has been enhanced to return the iterator to the subsequent element. This simplifies the process:

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;
    }
}

C 03

In C 03, erasing elements from a map does not automatically invalidate iterators. However, the iterator pointing to the deleted element becomes invalid. To maintain iterator validity, the code must be updated:

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
    } else {
        ++pm_it;
    }
}

Here, the post-increment operator ( ) is used in the erase() call to ensure that the returned iterator points to the correct element.

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