On Tue, Jul 8, 2025 at 9:57 AM Yongwei Wu via Std-Discussion <
std-discussion_at_[hidden]> wrote:

> Assume I am working on a little-endian machine only. Is the following
> code undefined behaviour?
>
> uint32_t data = 0x40400000;
> auto f = *std::start_lifetime_as<float>(&data);
>

It's fine as long as `sizeof(float) <= sizeof(uint32_t)`. See
https://eel.is/c++draft/obj.lifetime#2


>
> If it is not, is the data variable still accessible now?
>

No. The `data` object's lifetime has ended because its storage has been
reused. https://eel.is/c++draft/basic.life#2.5


>
> Best regards,
>
> Yongwei
>
> --
> Yongwei Wu
> URL: http://wyw.dcweb.cn/
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-- 
*Brian Bi*