C seems ok no?
I would almost never write C++ (in the context of low level and performance-relevant code; I write a lot of things for a lot of stuff) if the type system was a touch more rigorous (why can't I specify, and have the compiler yell at me if I don't properly handle, "this pointer may never be null"? TypeScript can do this kind of type narrowing in its sleep!) and if error handling/lifecycle cleanup wasn't hazardous (I'm not even saying exceptions and try-catch, just make it easier to guarantee that a cleanup clause gets called when leaving scope, like Ruby's def-ensure-end).
As it is, whenever I finally hit the breaking point with C++ (which I write mostly from inertia because I know it pretty well) it's probably Rust for me.
I am a fan of Rust, but I am not 100% sold on it. The safety features and ADT's are nice, but I find it quite clunky in practice, and it is just such a huge language full of so many features. It almost feels more like a test language to try the concept of static memory management than a properly designed language in some ways.
I feel it's missing the quality from C/C++ that they are a very thin abstraction over assembly.
Read [0] for a comparison among Zig, D, Rust, and C++, and read [1] for a deeper look at the language's goals. I personally really love Zig's type system [2], with a system for generics that is very simple and consistent.
[0]: https://ziglang.org/learn/why_zig_rust_d_cpp/
[1]: https://ziglang.org/learn/overview/
[2]: https://nathancraddock.com/blog/consistency-in-zigs-type-sys...
We knew about many of these features then, when C was created - but it wasn't until the 2000's really where computing horsepower caught up to be able to use them in a universal way.
I think this statement implies that it’s clear and obvious what assembly will be generated from a snippet of C/C++ code. But few people can understand everything that optimising compilers and modern processors do to normal looking code. An example of this lack of knowledge is seeing people disagree on if a snippet contains UB or not.
If C is so simple, why do people struggle to write it?
Well when I'm talking about an abstraction over assembly I'm not talking about optimizing compilers. That's another topic entirely. What I mean is, if you look at a block of C code, it's very easy to understand what the machine is doing.
> If C is so simple, why do people struggle to write it?
Do they? I think people struggle to write correct, bug-free code in C, but that's because it doesn't save you from yourself, and it's happy to let you do whatever the hardware will do. That's a much larger programmable space than the set of all safe correct programs.
But I don't think people in general have difficulty looking at a snippet of C code and understanding it.
So they simultaneously understand what the machine is doing but don’t know what assembly will be generated? Both can’t be true.
If everyone understood what the machine was doing, everyone would be able to look at a snippet and agree - “that’s UB, let’s not do that”. But they can’t agree. Because few people understand what the compiler and the processor will do.
The “thin layer of assembly” was true for the first generation of C compilers. But it hasn’t been true for a long time. It’s a complete black box now. Anyone who thinks that it’s straightforward isn’t being upfront with themselves.
I mean I can understand a reasonable mapping to what the un-optimized assembly would be. Compiler optimization is very complex, and is going to obscure the results in every language.
> If everyone understood what the machine was doing, everyone would be able to look at a snippet and agree - “that’s UB, let’s not do that”. But they can’t agree. Because few people understand what the compiler and the processor will do.
What? I think everyone can agree that UB is much harder to detect in assembly than in higher level languages than assembly, and assembly gives the most clear view of what the machine is doing. It's a very complex topic to create a system which detects and disallows UB automatically in the compiler - this requires a lot more complexity than a simple mapping of high level instructions to machine instructions.
> The “thin layer of assembly” was true for the first generation of C compilers. But it hasn’t been true for a long time. It’s a complete black box now. Anyone who thinks that it’s straightforward isn’t being upfront with themselves.
I don't know, seems pretty straightforward to me: https://godbolt.org
Can you look at a non trivial C code base and make such an assertion? You can’t. Even simple looking C code could be translated into problematic assembly because such a transformation is technically valid. And it’s beyond the ability of anyone but an expert to guard against that.
C is a very useful language. Very important. Very fast. A great tool in the right hands. The world wouldn’t run without it. And it will remain useful and important and fast for decades to come, certainly. But it’s not simple and hasn’t been for a long time. Let’s acknowledge that.
Do you agree that this statement implies 2 things
1. The compiler isn’t doing anything unusual or unexpected. It applies only basic, easily understandable transformations from C to assembly
2. An intermediate C programmer would be able to guess correctly most of the time what the generated assembly would look like. And thanks to this, such a programmer would be able to avoid most footguns.
But the compiler does unusual/unexpected things, and it’s hard to guess what assembly will be generated or what that assembly does, it’s not a “thin abstraction”. Would you agree?
I think a better metric is: an average CS grad with a little bit of background in compilers and assembly could reasonably be expected to be able to write a naive C compiler which covers say 80% of the footprint of the core language on their own in a matter of weeks.
What do you think is the size of the cohort of people who could write a naive Rust compiler, with borrow checking, ADT's, traits and non-lexical lifetimes? Even without some of the fancy bits like async you're already talking about grad level CS topics at the very least.
I don't find the idea of a new non-memory-safe C replacement in 2022 very exciting. We should be moving away as an industry from non-memory-safe languages, for the obvious security and productivity reasons.
And if you index into an array in C, that's basically like saying `root memory location + stride * index`. In Rust it's calling a trait function which could be doing arbitrary work.
Rust and C++ are on similar levels of abstraction, but C is much, much simpler.
And it's certainly true that Rust has overloading and C doesn't, but that wasn't what I was getting at. The point is that C is defined in terms of the C virtual machine, not the underlying hardware. The C virtual machine is quite far from the actual CPU instructions.
Rust is clearly not at a higher level of abstraction than C++, yet in your own argument you've put C and C++ on the same ground…
> I feel it's missing the quality from C/C++ that they are a very thin abstraction over assembly.
> Rust and C++ are on similar levels of abstraction, but C is much, much simpler.
We can argue the thinkness (or the thinness) of the abstraction until cows come home, but
while (*dst++ = *src++) ;
L1:
movb @(r0)+, @(r1)+
tstb (r0)
bne L1
*ptr &= 1;
and #1, (r0)
C++ is much less of a hardware abstraction, specifically when it comes to the higher level language features.
Or 8 bit CPUs like 6502 and Z80 that aren't even able to fully support C.
Yes – historically – C has never been a perfect fit for 8-bit architectures as it had been conceived for a 16-bit architecture. So what? There are C compilers for 68HC08 68HC11 MCU's as well.
Yet, C has outlived «many languages offering the same "low level" capabilities of C».
You can do so easily. A reference is a pointer that is never null.
>I would almost never write C++ …
Edit: nevermind, I missed the point! GP is saying he wouldn’t write C++ if C supported these features.
This isn't even theoretically true:
void blah(int &x) { x++; }
int main() {
int *x = NULL;
blah(*x);
}
So it will crash, whether that's undefined behaviour or not. The thing at issue here is that other languages have reference types that are more strictly statically guaranteed to be non-null. My point is that references are not a substitute for those, because holding them wrong is not only easy, it's extremely likely to happen in code of any reasonable complixity that mixes pointers and references (ie. almost all production C++ code).
C23 is about to
- add keywords that was valid identifiers before
- remove K&R parameter syntax
- change semantics of the most popular function argument list declaration
- forbid representations other than 2's complement