Is it legal to std::memmove() from one union member to another?

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This code is an attempt to reinterpret memory contents as a different type without violating strict aliasing rules. It was suggested as an answer to "Using std::memmove to work around strict aliasing?", and it may be worth reading the comments there before answering.
an answer to "Using std::memmove to work around strict aliasing?"
Using std::memmove to work around strict aliasing?
#include cstring
#include cstdint
#include iomanip
#include iostream

struct Parts {
std::uint16_t v[2u];
};

static_assert(sizeof (Parts) == sizeof (std::uint32_t));
static_assert(alignof(Parts) = alignof(std::uint32_t));

int main()
{
union {
std::uint32_t u;
Parts p;
};
u = 0xdeadbeef;
std::clog std::hex u " ~ ";

std::memmove(&p, &u, sizeof u);
std::clog p.v[0] ", " p.v[1] '\n';
}

#include cstring
#include cstdint
#include iomanip
#include iostream

struct Parts {
std::uint16_t v[2u];
};

static_assert(sizeof (Parts) == sizeof (std::uint32_t));
static_assert(alignof(Parts) = alignof(std::uint32_t));

int main()
{
union {
std::uint32_t u;
Parts p;
};
u = 0xdeadbeef;
std::clog std::hex u " ~ ";

std::memmove(&p, &u, sizeof u);
std::clog p.v[0] ", " p.v[1] '\n';
}

I don't believe that the std::memmove() call is legal because class.union.general.2 says that at most one of the non-static data members of an object of union type can be active at any time. But my belief doesn't seem to be shared.
std::memmove()
class.union.general.2
at most one of the non-static data members of an object of union type can be active at any time
Is this legal? Which parts of the standard permit/prohibit this?
Tags: c++,language-lawyer,unions,memmoveSource of the question:
https://stackoverflow.com/questions/79007001

Question and source license information:
https://meta.stackexchange.com/help/licensing
https://stackoverflow.com/

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