this post was submitted on 04 Aug 2024
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DARPA suggests turning legacy C code automatically into Rust • The Register (www.theregister.com)
submitted 3 months ago by sabreW4K3@lazysoci.al to c/tech@programming.dev
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[–] uservoid1@lemmy.world 21 points 3 months ago (4 children)

How are they going to tackle heavy use of the C preprocessor?

What about pointer arithmetic without decorating everything with "unsafe"? As the whole point is making the code safer.

[–] Diplomjodler3@lemmy.world 20 points 3 months ago

Can't have code vulnerabilities if the code doesn't run. *taps forehead*

[–] killingspark@feddit.org 7 points 3 months ago

What about pointer arithmetic without decorating everything with "unsafe"? As the whole point is making the code safer.

The point is to reduce the amount of work by doing the boring work automatically. Manually copying struct definitions, functions, etc etc would be very boring but error prone work which is kind of the worst combination.

If that's done you can start improving the codebase module by module.

[–] pelya@lemmy.world 4 points 3 months ago (1 children)

I guess it will translate the majority of the code which does not contain unsafe parts, and leave the pointer manipulation for manual rewrite.

[–] FlorianSimon@sh.itjust.works 2 points 3 months ago (1 children)

Or maybe it'll write the unsafe parts in unsafe blocks?

[–] pelya@lemmy.world 2 points 3 months ago (1 children)

Then there's no point. Converting the code to Rust as-is will also transfer all the bugs.

[–] FlorianSimon@sh.itjust.works 4 points 3 months ago

There is. It's a starting point to start converting the code to safe Rust. Some obstacles are removed.

[–] sukhmel@programming.dev 4 points 3 months ago (1 children)

~~you can just wrap a whole C code into a macro~~

yeah, preprocessor is going to blow everything, I forgot how good it is. Maybe there's a way by preprocessing and then leaving it as the code, but that wouldn't be as useful and configurable

[–] killingspark@feddit.org 1 points 3 months ago (1 children)

Rust also has powerful macros, are you sure that those can't mimic at least most uses of the preprocessor?

[–] sukhmel@programming.dev 2 points 3 months ago (1 children)

You're right, but:

  • Rust goes out of the way to make macro safer and less error-prone, which means it will not be able to cover exactly the same especially in some fringe hacky cases
  • I was commenting along the lines of automatically converting one into another, I find it will either be very difficult or outright impossible without human rewriting the macro from ground up (that is, if we know what problem it solved in the very beginning, otherwise it quickly would become guessing game)
[–] killingspark@feddit.org 1 points 3 months ago (1 children)

There is the project c2rust which is being used to transpile c projects to rust. I didn't find any mentions on restrictions in this regard but I obviously agree it's a complicated issue.

, which means it will not be able to cover exactly the same especially in some fringe hacky cases

I'm just not sure this is true. Maybe you and I just don't see that there is always an equivalent solution in rust macros even if it's going to be unconventional/unidiomatic use of rust macros?

[–] sukhmel@programming.dev 2 points 3 months ago

Maybe you and I just don't see that there is always an equivalent solution in rust macros even if it's going to be unconventional/unidiomatic use

Maybe so, but large part of where it will be impossible is reproducing bugs introduced by unsanitized macros in C /half joking