alt Hacker News> Anything that does that is broken and terrible anyway
which is why it is undefined behaviour. the optimizer writers have told me consistently that if they can assume you're not doing this thing that's stupid anyway, they can make my code faster. And since I'm not doing that stupid thing anyway, I want my code to be faster.
Unaligned memory access isn't really stupid though. Not in the general case. Not to the point where it should give the compiler free reign to crash things or introduce security holes. It should just introduce a performance regression instead, which is a tractable problem. Just measure it and fix it by making things aligned.
Compilers can add some custom attributes that encode whatever semantics the badly designed hardware requires. This lets it freely break incorrect code in the small sections that are actually handling those special variables, while allowing the rest of the language to make sense.