[PATCH] D62825: [C++2a] Add __builtin_bit_cast, used to implement std::bit_cast

[Richard Smith - zygoloid via Phabricator via cfe-commits]

rsmith added a comment.

In D62825#1542247 <https://reviews.llvm.org/D62825#1542247>, @rjmccall wrote:

> In what sense is the bit-pattern of a null pointer indeterminate?


The problem is not null pointers, it's `nullptr_t`, which is required to have the same size and alignment as `void*` but which comprises only padding bits. (Loads of `nullptr_t` are not even permitted to touch memory...).


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