Investigate 32-bit integer overflow on length

[fereidani]

I'm not sure about if it is valid or not, But just not to forget it I open this issue.

I'm worried on 32-bit systems overflowing the length results in UB for small u8 sized structures with drop.
I'll investigate it myself, but if anyone is interested feel free to audit it.

[fereidani]

Please assign this to me.