On Wed, 2024-03-27 at 12:07 -0700, Linus Torvalds wrote: > On Wed, 27 Mar 2024 at 11:51, Kent Overstreet > <kent.overstreet@xxxxxxxxx> wrote: > > > > On Wed, Mar 27, 2024 at 09:16:09AM -0700, comex wrote: > > > Meanwhile, Rust intentionally lacks strict aliasing. > > > > I wasn't aware of this. Given that unrestricted pointers are a real > > impediment to compiler optimization, I thought that with Rust we > > were > > finally starting to nail down a concrete enough memory model to > > tackle > > this safely. But I guess not? > > Strict aliasing is a *horrible* mistake. > > It's not even *remotely* "tackle this safely". It's the exact > opposite. It's completely broken. > > Anybody who thinks strict aliasing is a good idea either > > (a) doesn't understand what it means > > (b) has been brainwashed by incompetent compiler people. > > it's a horrendous crock that was introduced by people who thought it > was too complicated to write out "restrict" keywords, and that > thought > that "let's break old working programs and make it harder to write > new > programs" was a good idea. > > Nobody should ever do it. The fact that Rust doesn't do the C strict > aliasing is a good thing. Really. Btw, for the interested, that's a nice article on strict aliasing: https://blog.regehr.org/archives/1307 Dennis Ritchie, the Man Himself, back in the 1980s pushed back quite strongly on (different?) aliasing experiments: https://www.yodaiken.com/2021/03/19/dennis-ritchie-on-alias-analysis-in-the-c-programming-language-1988/ No idea why they can't just leave C alone... It's not without reason that new languages like Zig and Hare want to freeze the language (standard) once they are released. P. > > I suspect you have been fooled by the name. Because "strict aliasing" > sounds like a good thing. It sounds like "I know these strictly can't > alias". But despite that name, it's the complete opposite of that, > and > means "I will ignore actual real aliasing even if it exists, because > I > will make aliasing decisions on entirely made-up grounds". > > Just say no to strict aliasing. Thankfully, there's an actual > compiler > flag for that: -fno-strict-aliasing. It should absolutely have been > the default. > > Linus >
