[PATCH] D80414: [lld-macho] Ensure reads from nlist_64 structs are aligned when necessary

[Shoaib Meenai via Phabricator via llvm-commits]

smeenai added a comment.

In D80414#2055477 <https://reviews.llvm.org/D80414#2055477>, @efriedma wrote:

> Alternatively, we have some integer wrappers in llvm/Support/Endian.h that deal with both endianness and alignment.  For example, you could define nlist_64 like this:
>
>   struct nlist_64 {
>     support::ulittle32_t n_strx;
>     uint8_t n_type;
>     uint8_t n_sect;
>     support::ulittle16_t n_desc;
>     support::ulittle64_t n_value;
>   };
>


Ah, those look really neat! Thanks for the pointer.

I don't know if it'd be wise to change BinaryFormat's `nlist_64` definition at this point (the pervasive pattern with Mach-O is to use various `swapStruct` overloads to handle endianness), but we can look into that for LLD. Under the hood, those seem to use `memcpy` as well, but with some `__builtin_assume_aligned` trickery that might help with the elision?


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