In the following code I loop through a map and test if an element needs to be erased. Is it safe to erase the element and keep iterating or do I need to collect the keys in another container and do a second loop to call the erase()?
map<string, SerialdMsg::SerialFunction_t>::iterator pm_it;
for (pm_it = port_map.begin(); pm_it != port_map.end(); pm_it++)
{
if (pm_it->second == delete_this_id) {
port_map.erase(pm_it->first);
}
}
UPDATE: Of course, I then read this question which I didn't think would be related but answers my question.
This has been fixed in C++11 (or erase has been improved/made consistent across all container types).
The erase method now returns the next iterator.
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;
}
}
Erasing elements in a map does not invalidate any iterators.
(apart from iterators on the element that was deleted)
Actually inserting or deleting does not invalidate any of the iterators:
Also see this answer:
Mark Ransom Technique
But you do need to update your code:
In your code you increment pm_it after calling erase. At this point it is too late and is already invalidated.
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
}
}