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

[John McCall via Phabricator via cfe-commits]

rjmccall added a comment.

In what sense is the bit-pattern of a null pointer indeterminate?  It's implementation-specified, but the compiler is certainly required to be able to produce that value during the constant initialization phase.  If the language committee wants to make this non-constant out of some sort of portability concern, that's its business, but it's certainly implementable even if the target has non-zero null pointers or even different null pointer patterns for different types (though of course `nullptr_t` uses `void*`'s pattern).


Repository:
  rC Clang

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  https://reviews.llvm.org/D62825/new/

https://reviews.llvm.org/D62825