@cr1901 @RichFelker It removes the ability for the compiler to assume that signed overflow doesn't happen, causing missed optimizations.
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Replying to @CopperheadOS
@CopperheadSec@RichFelker Oh hmmm, I thought the predictability of signed overflow would've led to some new optimizations...2 replies 0 retweets 0 likes -
Replying to @cr1901
@cr1901@RichFelker Having it undefined gives the compiler the freedom to assume whatever it wants about it on a case-by-case basis.1 reply 0 retweets 0 likes -
Replying to @CopperheadOS
@cr1901@RichFelker Undefined doesn't just mean unspecified. It means it's guaranteed to never happen.1 reply 0 retweets 0 likes -
Replying to @CopperheadOS
@cr1901@RichFelker The compiler can interpret x + INT_MAX as a guarantee that x <= 0. And that's starting to be what actually happens.1 reply 2 retweets 1 like -
Replying to @CopperheadOS
@cr1901@RichFelker Compilers are really bad at integer range analysis right now... but as they get better, lots of code is going to break.1 reply 1 retweet 0 likes -
Replying to @CopperheadOS
@CopperheadSec@RichFelker The C-Pocalypse. I mean, the C-hate is already pretty bad if Twitter is any indication.2 replies 0 retweets 0 likes -
Replying to @cr1901
@cr1901@RichFelker Yeah, they already make the assumptions that are going to break incorrect code. They just aren't yet optimizing enough.1 reply 0 retweets 0 likes -
Replying to @CopperheadOS
@cr1901@RichFelker The adoption of link-time optimization will uncover a lot of these issues too. Not just compiler improvements.2 replies 0 retweets 0 likes -
Replying to @CopperheadOS
@CopperheadSec@cr1901 Indeed, most UB is undetectable by the compiler without explicit runtime checks since extern acts as compiler barrier2 replies 0 retweets 0 likes
@CopperheadSec @cr1901 LTO is completely game-changing here. I'm proactively trying to find anything in @musllibc assuming extern-as-barrier
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