* * * * *

         A bit of background on compilers exploiting signed overflow

> Why do compilers even bother with exploiting undefinedness signed overflow?
> And what are those mysterious cases where it helps?
>
> A lot of people (myself included) are against transforms that aggressively
> exploit undefined behavior, but I think it's useful to know what compiler
> writers are accomplishing by this.
>
> TL;DR (Too Long; Didn't Read): C doesn't work very well if int!=register
> width, but (for backwards compat) int is 32-bit on all major 64-bit
> targets, and this causes quite hairy problems for code generation and
> optimization in some fairly common cases. The signed overflow UB (Undefined
> Behavior) exploitation is an attempt to work around this.
>

Via Comment on ”Bug in my code from compiler optimization [video] | Hacker
News” [1], “A bit of background on compilers exploiting signed overflow [2]”

A cautionary tale about compiler writers exploiting undefined behavior. I
don't have much to add here, other than to spread a bit of awareness of why
this happens.

[1] https://news.ycombinator.com/item?id=38662881
[2] https://gist.github.com/rygorous/e0f055bfb74e3d5f0af20690759de5a7

Email author at [email protected]

You are viewing proxied material from gopher.conman.org. The copyright of proxied material belongs to its original authors. Any comments or complaints in relation to proxied material should be directed to the original authors of the content concerned. Please see the disclaimer for more details.