Re: Unaligned memory access

You can also look at std::align or how sol2 manages this: https://github.com/ThePhD/sol2/blob/develop/include/sol/stack_core.hpp#L129
On Feb 14, 2026 at 21:31 +0300, Andre Leiradella <[email protected]>, wrote:
> Em sábado, 14 de fevereiro de 2026 às 14:00:40 UTC, Sainan escreveu:
> > lua_newuserdata does not provide alignment guarantees, but practically, you will see that it is only 8-byte aligned (on 64-bit). Of course, your workaround of using 'new' works, but you can also simply allocate 15 more bytes so you can safely offset the pointer:
> >
> > char *data = reinterpret_cast<char*>(lua_newuserdata(L, data_len + 15));
> > if (reinterpret_cast<uintptr_t>(data) % 16) { /* data is not 16-byte aligned? */
> > data = reinterpret_cast<char*>(reinterpret_cast<uintptr_t>(data) + (16 - (reinterpret_cast<uintptr_t>(data) % 16))); /* align data to 16-byte boundary */
> > }
> >
> > -- Sainan
>
> Good idea, I ended up using it instead of the additional pointer indirection:
>
> ud = (ud + 15) & ~(uintptr_t)15;
>
> Andre
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