Are there any things in Linux that need to be started over from scratch?

sepulcher@lemmy.ca to Linux@lemmy.ml – 162 points –

I'm curious how software can be created and evolve over time. I'm afraid that at some point, we'll realize there are issues with the software we're using that can only be remedied by massive changes or a complete rewrite.

Are there any instances of this happening? Where something is designed with a flaw that doesn't get realized until much later, necessitating scrapping the whole thing and starting from scratch?

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There is some Rust code that needs to be rewritten in C.

Strange. I’m not exactly keeping track. But isn’t the current going in just the opposite direction? Seems like tons of utilities are being rewritten in Rust to avoid memory safety bugs

You got it right, the person you replied to made a joke.

The more the code is used, the faster it ought to be. A function for an OS kernel shouldn't be written in Python, but a calculator doesn't need to be written in assembly, that kind of thing.

I can't really speak for Rust myself but to explain the comment, the performance gains of a language closer to assembly can be worth the headache of dealing with unsafe and harder to debug languages.

Linux, for instance, uses some assembly for the parts of it that need to be blazing fast. Confirming assembly code as bug-free, no leaks, all that, is just worth the performance sometimes.

But yeah I dunno in what cases rust is faster than C/C++.

C/C++ isn’t really faster than Rust. That’s the attraction of Rust; safety AND speed.

Of course it also depends on the job.

https://benchmarksgame-team.pages.debian.net/benchmarksgame/box-plot-summary-charts.html

C/C++ isn’t

You're talking about two languages, one is C, the other is C++. C++ is not a superset of C.

Yes thank you. But my statement remains true nevertheless.

But yeah I dunno in what cases rust is faster than C/C++.

First of all C and C++ are very different, C is faster than C++. Rust is not intrinsically faster than C in the same way that C is faster than C++, however there's a huge difference, safety.

Imagine the following C function:

void do_something(Person* person);

Are you sure that you can pass NULL? Or that it won't delete your object? Or delete later? Or anything, you need to know what the function does to be sure and/or perform lots of tests, e.g. the proper use of that function might be something like:

if( person ) {
  person_uses++;
  do_something(person);
}

...

if( --person_uses == 0 )
  free( person )

That's a lot more calls than just calling the function, but it's also a lot more secure.

In C++ this is somewhat solved by using smart pointers, e.g.

void do_something(std::unique_ptr person);
void something_else(std::shared_ptr person);

That's a lot more secure and readable, but also a lot slower. Rust achieves the C++ level of security and readability using only the equivalent of a single C call by performing pre-compile analysis and making the assembly both fast and secure.

Can the same thing be done on C? Absolutely, you could use macros instead of ifs and counters and have a very fast and safe code but not easy to read at all. The thing is Rust makes it easy to write fast and safe code, C is faster but safe C is slower, and since you always want safe code Rust ends up being faster for most applications.

Rust is faster than C. Iterators and mutable noalias can be optimized better. There's still FORTRAN code in use because it's noalias and therefore faster

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