will pointer to a variable in the map be invalidated?

Question

I have something in my codes:

class Foo {
// something
};

std::unordered_map<int, Foo> foo_map;
// some insertion on the map

auto iter = foo_map.find(1);
auto foo = &iter->second;  //assume iter!=foo_map.end()
// a lot of operation on the map, may need the rehashing....

So my question is whether the pointer foo is still invalid or not after all this operations?

Answer 1

Mostly, iterators in unordered_map remain valid after insertion/deletion. The only exception being when the growth of the container forces a rehash.

References/pointers to elements remain valid in all cases, even after a rehash.

Answer 2

Have a look at the reference for unordered_map :

References and pointers to either key or data stored in the container are only invalidated by erasing that element, even when the corresponding iterator is invalidated.