So how is the 10000th element stored here?
The element isn’t stored in the vector. It’s ‘stored’ in a piece of memory that is unrelated to the vector.
Isn’t the expected behavior here a “Segmentation fault”?
No. The behaviour is undefined, so there is no behaviour to expect.
But the above runs successfully.
That’s a possible behaviour when the behaviour is undefined.
solved How does vector’s growth function work? [closed]