Is it safe to index a little bit out of bounds

[David Feuer]

What do you gain from this?

On Mar 8, 2018 9:19 AM, "Andrew Martin" <andrew.thaddeus at gmail.com> wrote:

> Let's say I have a gc-managed byte array of length 19. GHC promises that
> byte arrays are machine-word-aligned on the front end. That is, on a 64-bit
> machine, this array starts on a memory address that divide 8 evenly.
> However, the back end will certainly be unaligned. So, these two calls will
> be fine:
>
> - indexWordArray# myArr# 0#
> - indexWordArray# myArr# 1#
>
> But this one is non-deterministic:
>
> - indexWordArray# myArr# 2#
>
> Some of the bytes in the word will have garbage in them. However, this
> could always be masked out with a bit mask (you have to know the platform
> endianness for this to work right). Is this safe? I doubt think this could
> ever cause a segfault but I wanted to check.
>
> --
> -Andrew Thaddeus Martin
>
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