How does dynamic array memory reallocating work?

Question

Let's say I have a dynamic array of some length and I want to push a new element, but memory after last elem is already used.

What would happen in such case? Compiler would find a new 'chunk' of memory that can hold an array and copy it there or something else? And if yes, how this new address would be calculated?

Also, as I know, dynamic arrays in solidity works like mappings in some way, I mean each item of the array is laid out sequentially from address that is calculated with hash of array variable address:

keccak256(bytes32(variable_address))

And if memory was reallocated, how would solidity find this variable's new location? We don't store any pointers, just calculating hash.

Answer 1

Solidity never reallocates storage arrays (memory arrays can't even be resized). Solidity relies on the fact that all storage array locations are based on a KECCAK256 hash, and that KECCAK256 is believed to be collision-resistant, so the odds of two storage arrays ever colliding are infinitesimally small.