undefined | Better HN

0 pointscharleslmunger1mo ago0 comments

Is that really a meaningful distinction?

Once you are addressing arbitrary values you are firmly in the realm of "anything happening" in practice, but you've now given up optimization opportunities. As has been repeatedly demonstrated over the years, once memory safety breaks it is practically impossible to make any guarantees about program behavior.

0 comments

3 comments · 1 top-level

marcosdumay1mo ago· 2 in thread

Yes, it's a meaningful distinction. No you are not into "anything happening" in practice.

Your compiler emitting a load operation and it failing isn't "anything". The failure being handled by code that the compiler authors can't predict doesn't make it "anything".

And if you lose optimization opportunities because of this it's because your optimization is broken. By the way, if you lose optimization opportunities because of this, that means both codes are meaningfully different and you knew it all the time.

saagarjha1mo ago

Compilers elide loads all the time this is one of the more basic optimizations a compiler can do. We just mostly think those are "good" optimizations.

charleslmungerOP1mo ago

I mean... You can turn a one byte out of bounds write into code execution.

https://daniel.haxx.se/blog/2016/10/14/a-single-byte-write-o...

And if you get code execution, then you by definition have "anything".

j / k navigate · click thread line to collapse