Created on 2024-04-05.00:00:00 last changed 1 month ago
Proposed resolution:
This wording is relative to N4971.
Modify [cstring.syn] as indicated:
-3- The functions memcpy and memmove are signal-safe ([support.signal]). Both functions implicitly create objects ([intro.object]) in the destination region of storage immediately prior to copying the sequence of characters to the destination. Both functions return a pointer to a suitable created object.
int x = 0; alignas(int) std::byte y[sizeof(int)]; int z = *static_cast<int*>(std::memcpy(y, &x, sizeof(int)));
This example should be well-defined, even without the use of std::launder. std::memcpy implicitly creates an int inside y, and https://www.iso-9899.info/n3047.html#7.26.2.1p3 states that
The memcpy function returns the value of [the destination operand].
In conjunction with [cstring.syn] p3, this presumably means that std::memcpy returns a pointer to the (first) implicitly-created object, and no use of std::launder is necessary.
The wording should be clarified to clearly support this interpretation or reject it.History | |||
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Date | User | Action | Args |
2024-04-05 12:16:18 | admin | set | messages: + msg14053 |
2024-04-05 00:00:00 | admin | create |