Casting from any T* to void* back to T* is always safe. That is one of the few safe things you can do with a void*, and kinda the whole point. :-) I think ca

Casting from any T* to void* back to T* is always safe. That is one of the few safe things you can do with a void*, and kinda the whole point. :-) I think casting from void* back to double* is the better option here. memcpy() is overkill here since that idiom is mainly for reinterpreting data with a different type without triggering undefined behavior: https://stackoverflow.com/questions/98650/what-is-the-strict-aliasing-rule https://stackoverflow.com/questions/98650/what-is-the-strict.... We're not changing the type, so why confused people with an overly powerful idiom? That said, the memcpy() idiom is common and useful enough that C++ added a specific API for it: https://en.cppreference.com/w/cpp/numeric/bit_cast https://en.cppreference.com/w/cpp/numeric/bit_cast. Casting and the memcpy() idiom compile down to the same code https://godbolt.org/z/xY6W9ja69 https://godbolt.org/z/xY6W9ja69*