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> Someone in the audience also pointed out that a tool like this could be used to compile rust programs, not just C programs, in which case it's odd to hear Fil

> Someone in the audience also pointed out that a tool like this could be used to compile rust programs, not just C programs, in which case it's odd to hear Fil-C repeatedly framed as a language in opposition to rust rather than as a tool which might complement it. You can combine both approaches for sure, but that doesn't change that they are indeed separate approaches. One (Rust) intends to characterize and prevent undefined behavior at compile time, and another (Fil-C) intends to make undefined behavior impossible at runtime, as evidenced by decisions like (for example) making unsafe usage of setjmp/longjmp safe. You could sort of achieve "safety-in-depth" by combining both approaches, but Rust prefers to prevent all undefined behavior statically, and Fil-C prefers to focus on dynamic approaches. They have real differences, so that's probably what comes off as "oppositional"

raggi 3mo ago
This presentation wasn’t too bad in terms of us vs theming, but in general throughout the lifetime of the project there’s been a strong us vs them rhetoric. I think it’s working as a marketing tactic to some extent but there are better, albeit harder ways to market the thing.
- LoganDark 3mo ago
  Rust generally invites us vs them everywhere because it's just so ambitious and attractive (to some). Fil-C probably receives questions all the time about why they don't just do X or Y that Rust does. Maybe they end up supporting their position against that type of pressure and it looks like they're opposing Rust when all they're doing is justifying themselves.
  - pjmlp 3mo ago
    Because by making Cyclone's ideas mainstream, which AT&T started alongside Cornell University, the C and C++ devs that so far felt safe from all those RC/GC languages, now had an actually problem as companies started paying attention and embracing the language's ideas, even extending the type system of existing RC/GC languages. Thus anyone that identifies themselves with the programming language they work with, gets dragged into a us vs them discussion.
n42 3mo ago
The combination of static safety gracefully degrading to runtime safety where not provable is interesting to me
- LoganDark 3mo ago
  This is sort of already possible in Rust when you use safe primitives (e.g., RefCell), but it doesn't cover unsafe code invoking Undefined Behavior. Placing something like Fil-C around unsafe code could prove to be interesting, especially since current approaches rely on interpretation (Miri, Soteria Rust) rather than translation.
uecker 3mo ago
Arguably the most important memory safety property, i.e. bounds checking for dynamic arrays, is also not statically checked in Rust.
- LoganDark 3mo ago
  It's possible to do this (WUFFS does it) but it's so invasive that, well, you basically end up with WUFFS. You end up having to track every set of possible and impossible values at every location, etc. (during each program location too.) WUFFS certainly has its place and I've kind of been itching to try it out myself, but I think getting to the point where dynamic arrays can be statically bounds-checked would have highly disabled Rust.
- woodruffw 3mo ago
  How would Rust perform static checks on dynamic bounds? That seems like an impossible order, i.e. not a reasonable evaluation criteria for any (general-purpose) language. (I'm separately skeptical that it's the most important memory safety property; I suspect that a review of Chrome and Firefox 0days would show that UAFs and type confusion are, at least to attackers, equally if not more important.)
  - LoganDark 3mo ago
    Presumably, they're talking about the possibility of explicitly replacing dynamic bounds checks in cases where it's statically provable that the access will not overrun. That doesn't necessarily mean you lose cases where you genuinely can't prove such a thing, but rather that it would be possible to opt into compiler assistance with proving it, rather than hoping LLVM will have your back. At least, that's how I'd envision such a thing for Rust. This would be similar to how you can already choose whether to invite more of the borrow checker by using references directly, or to do the checks at runtime with Rc/RefCell, etc.
    - woodruffw 3mo ago
      Yeah, that seems like a nice thing that Rust could offer. It strikes me as a weird thing to get hung up on, though, given that the norm in compiled languages - including C - is to express your bounds such that an optimizing compiler can (but won't necessarily) eliminate them. (You mentioned WUFFS below, which is why I qualified with general-purpose! One thing that WUFFS does that I think Rust could add pretty easily is provable indexing, e.g. allow me to use a `u8` to index a `[u8; 256]` without having to widen to a `usize` first and hope that LLVM optimizes it back out.)

raggi 3mo ago

This presentation wasn’t too bad in terms of us vs theming, but in general throughout the lifetime of the project there’s been a strong us vs them rhetoric. I think it’s working as a marketing tactic to some extent but there are better, albeit harder ways to market the thing.

LoganDark 3mo ago
Rust generally invites us vs them everywhere because it's just so ambitious and attractive (to some). Fil-C probably receives questions all the time about why they don't just do X or Y that Rust does. Maybe they end up supporting their position against that type of pressure and it looks like they're opposing Rust when all they're doing is justifying themselves.
- pjmlp 3mo ago
  Because by making Cyclone's ideas mainstream, which AT&T started alongside Cornell University, the C and C++ devs that so far felt safe from all those RC/GC languages, now had an actually problem as companies started paying attention and embracing the language's ideas, even extending the type system of existing RC/GC languages. Thus anyone that identifies themselves with the programming language they work with, gets dragged into a us vs them discussion.

n42 3mo ago

The combination of static safety gracefully degrading to runtime safety where not provable is interesting to me

LoganDark 3mo ago
This is sort of already possible in Rust when you use safe primitives (e.g., RefCell), but it doesn't cover unsafe code invoking Undefined Behavior. Placing something like Fil-C around unsafe code could prove to be interesting, especially since current approaches rely on interpretation (Miri, Soteria Rust) rather than translation.

uecker 3mo ago

Arguably the most important memory safety property, i.e. bounds checking for dynamic arrays, is also not statically checked in Rust.

LoganDark 3mo ago
It's possible to do this (WUFFS does it) but it's so invasive that, well, you basically end up with WUFFS. You end up having to track every set of possible and impossible values at every location, etc. (during each program location too.) WUFFS certainly has its place and I've kind of been itching to try it out myself, but I think getting to the point where dynamic arrays can be statically bounds-checked would have highly disabled Rust.
woodruffw 3mo ago
How would Rust perform static checks on dynamic bounds? That seems like an impossible order, i.e. not a reasonable evaluation criteria for any (general-purpose) language. (I'm separately skeptical that it's the most important memory safety property; I suspect that a review of Chrome and Firefox 0days would show that UAFs and type confusion are, at least to attackers, equally if not more important.)
- LoganDark 3mo ago
  Presumably, they're talking about the possibility of explicitly replacing dynamic bounds checks in cases where it's statically provable that the access will not overrun. That doesn't necessarily mean you lose cases where you genuinely can't prove such a thing, but rather that it would be possible to opt into compiler assistance with proving it, rather than hoping LLVM will have your back. At least, that's how I'd envision such a thing for Rust. This would be similar to how you can already choose whether to invite more of the borrow checker by using references directly, or to do the checks at runtime with Rc/RefCell, etc.
  - woodruffw 3mo ago
    Yeah, that seems like a nice thing that Rust could offer. It strikes me as a weird thing to get hung up on, though, given that the norm in compiled languages - including C - is to express your bounds such that an optimizing compiler can (but won't necessarily) eliminate them. (You mentioned WUFFS below, which is why I qualified with general-purpose! One thing that WUFFS does that I think Rust could add pretty easily is provable indexing, e.g. allow me to use a `u8` to index a `[u8; 256]` without having to widen to a `usize` first and hope that LLVM optimizes it back out.)