> theoretically RAII is about general resource management, not just about memory. But at least in my experience, it’s always about memory management
only if you ignore things like iostreams, thread locks, etc.
only if you ignore things like iostreams, thread locks, etc.
I can grab a mutex with std::unique_lock and not have to worry about releasing it manually, which means simpler code and fewer bugs.
RAII can improve "scripting" speed when putting a lot of automatic variables on the stack. However, a lot of those variables need to be moved to the heap when proofing out the code, and that consolidation isn't going well because RAII doesn't work with generic code (void-pointers, memcpy etc). You need to go all-in with RAII containers. Which causes a lot of boilerplate and increases compilation times.
For RAII on heap objects, you have std::unique_ptr, and no boilerplate. Anyone failing to lean into RAII to manage resources is just choosing to write unreliable code. Or C, but I repeat myself.
Interestingly, it seems Rust programmers do the same too, because otherwise programming in Rust is too hard.
I wouldn't approve. Make shared (i.e. ref-counted) pointers when actually needed. Writing C is best when not mimicking bigger languages (i.e. with GC), but when figuring out how a system can work optimally.
In any case, in my experience this bad practice comes from Java devs who’ve moved to C++.
But most shared pointer ownership in C is wholly ad hoc, without even reference counting.
Even if I generously assume you're thinking of C++ "shared pointers", and so you've concluded that Rust's Rc<T> (a reference counted T) is basically the same thing, I don't see where you'd come to the conclusion that Rust programmers do this for "all their variables" as this seems wildly unlikely.
It's essentially a cop out to not have to think about ownership and lifetime, and not have to worry about the borrow checker.
The fact that this is so pervasive throughout Rust code is for me a sign that Rust failed to deliver on its initial promise. The borrow checker was meant to be its main value added. But heh, people still find value added to Rust otherwise.
So I did go look at Cargo itself, but unlike you although I do see some use of Rc and fewer of Arc it was scarcely "all over the place" when I looked and in the cases I spent any time actually thinking about it's a shared value, so, yeah, that makes sense.
I randomly looked at cargo/core/profiles.rs and cargo/core/registry.rs and cargo/core/compiler/compilation.rs without finding either Rc or Arc used in those files at all. Searching across the whole repository I found some places which do use Rc, and fewer using Arc (implying this data is shared between threads) -- but this doesn't really support your original claim does it?
Not a cop out. Something very much like Rc<> is needed whenever an object's lifecycle might be independently extended by multiple referencing "owners", none of which is subsumed by the others. That's a matter of broad high-level design that can't generally be avoided, least of all in a multi-threaded context (as shown by the use of Arc<>).
Since you're already schooling me on the meaning of terms, you probably have enough experience to have realized that the typical code begins life in a stubbed out form that is barely functional enough to deliver first results. It is then iteratively enhanced and made more widely applicable, more robust, more refined, better specified, more performant, and so on. In the process, the code is undergoing many revisions, and moving data structures from automatic storage (stack) to the heap is very typical.
Another word I'm thinking of for this process is "consolidation", which I have also used. My apologies if I don't speak in your terms / in the most precise terms.
This proofing process is another example of what makes coding C more costly and buggy than coding C++. I did it for years, and miss it not at all.
There's no clear scope anymore, ownership has to be moved from function scopes to RAII managed container structures. Things are quickly getting more complicated and expensive (software complexity/bloat, compile times, binary size...) when you have to nest your structures in templated containers that don't know what you're nesting in them...
This is where all the complexity with 17 constructor types and 99 move semantics with const, non-const, r-valued references and abstract virtual base classes came from, and there might be less than a dozen persons left on the planet who really understand it all...
It has been many years since I found a use for an abstract virtual base class.
Literally millions of people understand it all, and use it every day with no difficulty. You don't need to invent difficulties, or waste days "proofing" code that may be written exactly once and never touched again.
Very true. It is easy. Not difficult. That doesn't seem to stop enormous amounts of C++ code being created in which this is simply got wrong. Just because it's easy doesn't mean that huge numbers of programmers won't still get it wrong. They do. Regularly. If they adopt RAII conventions, they screw it up far less frequently. Those are the facts.
"don't hide complexity in small, single-purpose, composable containers, instead hide complexity in hulking behemoths which can consume months of refactorings & iterations" ?
That's not simplifying your code to be generic. That's adopting a particular framework & coding style. Which yes, you have to do in C, but you're doing that because of language issues. You're not saving yourself from "language cleverness"
(That was sarcasm, FYI. Obviously it's 2023 and nobody wants to do manual function calling boilerplate as if you're programming 1960's assembly.)
void err() { printf("oops, we failed"); }
...
if (errno) return err();
Why C doesn't officially have nested functions is, well, that's C!
It starts with one goto, then one more, then another.
The first goto is usually clever but then someone else arrives and hacks another one because they don't want to change the code too much.
Maybe some day it will. It should anyway
But GCC and Clang already support it, and while I can't find if MSVC does, it probably does
edit: also, now I see that the goto in if (errno) goto err is really just an (inlined) tail call!
In general, any random C compiler is likely to not support that feature, because the way it interacts with function pointers makes it unnecessarily complicated.
Pascal could do it in the 1970s, and even Tiny Pascal could do it, see the listing for the compiler in BYTE.
https://archive.org/details/byte-magazine-1978-09
As for function pointers, a simple solution is to not allow them unless the function is declared `static`. `static` functions don't have a hidden static link.
The problem is doing it in an ABI-compatible way when you already have an ABI. The gcc implementation of nested functions does that - they are compatible with regular function pointers - but at the cost of requiring executable stack on at least some platforms.
And for C compilers that aren't gcc, the question becomes: why partially implement a non-standard gcc feature?
if err != nil {
return nil, err
}It is hard to tell what the point is of this article is. Yes, the C-ish subset of C++ differs from ISO C, in trivial details. That is irrelevant to C++ users, who may consult ISO C++ to discover the actual subset. They interact with any C only when they #include a header for a 3rd party C library, and then the relevant subset is what, exactly, appears in that header.
There is really no legitimate reason to code C anymore: A C++ compiler is available for any modern development target. Confining yourself to any C subset (with or without ISO C marginalia) amounts to crawling when you can fly.
To be more specific: nothing that can be done using C is unavailable to the C++ coder, but enormous power is available to the C++ coder and wholly unavailable in C.
There is hardly a need for more (to do what I do -- systems in the broadest sense) and there's a lot of time saved by not thinking about 21 "safe" and "ergonomic" ways to write everything in C++ (that very often end up being not that safe, and unintelligible).
Yes, there is the "subset" argument, only use what you need. But I don't buy that, I'm not like that, it doesn't work for me. Constraining myself makes things easier.
I started in C, and am still in it for systems/OS development at work.
In UI development, we had older C toolkits, but are replacing them with newer toolkits that are C++. I started off trying to just do C business logic with some C++ glue code for the UI. Sticking to what's familiar. In the end, it was just easier to do everything properly. All C in areas that are C. All C++ in areas that are C++. Same with C#. Trying to mix them is just more work than necessary.
At least I get to add C++ to my resume. There is a little joke at work, w.r.t. our existing codebases and code choices. They are career-driven choices, not technical choices. The result is a mess of a codebase, but I'm fully embracing that now.
If I want to just get stuff done, C++ is great for that. Don’t underestimate how much you gain by having string, vector, and map when you just want to crank out code.
Nobody is forcing you to overdesign stuff. You can always just crank out the code you want.
The main reason I still sometimes use C is compiler support for microcontrollers where everything tends to have a C compiler but not everything has a C++ one (or if it does, not necessarily an up to date one).
I don’t use either in my day to day really but I do have sone personal projects. Ultimately I foresee doing these in Rust where I can, but for stuff like hobbyist game development, I’m currently too bought into some of the C++ libraries, primarily EnTT, but even there I think I’ll eventually just end up using Rust with Bevy. For now though, I actually quite enjoy using C++17 (and maybe 20 soon if I find the free time).
Which, in any case, have companies like Mikroe selling Basic and Pascal compilers.
As a counterargument, sometimes constraints can be valuable in their own right rather than just being requirements for some larger goal. The most prominent example of this in programming design is type checking; enforcing type checking at compile time strictly reduces the number of programs you can express, so dynamic languages can do everything that static languages and more, and yet it turns out that it's still pretty useful specifically because we sometimes want to avoid the programs that a dynamic language would allow but a static language would reject. At the risk of getting too philosophical, imagine framing programming as an exercise in trying to write rules to specify one program out of the set of all possible programs, where each bug you write that changes the semantics moves one step further from your goal. The compiler can act as a "filter" on the set of programs you can potentially select by refusing to process your rules if they would specify one of the forbidden programs, which reduces the chance selecting the wrong program by mistake. In this scenario, the theoretically ideal compiler would be the one that rejects all programs other than the exact one you want! This obviously isn't possible in the general case, but the point here is that as long as compilers don't reject the exact program you want, a compiler that rejects more programs is _more_ useful.
I'm not making any claim about whether it is in fact worth it to code C anymore, but I disagree with the logic that C++ letting you do anything C can do and more is proof that C++ should always be used over C. Maybe C is crawling compared to C++'s flying, but if my goal is to get a pen that falls under my desk, it's a lot more useful for me to not use an airplane to do it.
We generally don't know, when we set out, how much support we will be able to benefit from, down the road.
That's an interesting statement. Reminds me of statements indicating any new code base should be started in rust over c++.
"Using a language other than C is like using a non-standard feature: it will cause trouble for users. Even if GCC supports the other language, users may find it inconvenient to have to install the compiler for that other language in order to build your program. So please write in C."
GNU Coding Standard in 1994, http://web.mit.edu/gnu/doc/html/standards_7.html#SEC12
"When you want to use a language that gets compiled and runs at high speed, the best language to use is C. Using another language is like using a non-standard feature: it will cause trouble for users. Even if GCC supports the other language, users may find it inconvenient to have to install the compiler for that other language in order to build your program. For example, if you write your program in C++, people will have to install the GNU C++ compiler in order to compile your program.
C has one other advantage over C++ and other compiled languages: more people know C, so more people will find it easy to read and modify the program if it is written in C.
So in general it is much better to use C, rather than the comparable alternatives."
http://gnu.ist.utl.pt/prep/standards/html_node/Source-Langua...
As project lead, his opinions always mattered for what goes into GNU.
What the rustaceans are doing nowadays I lived as C++ fanboy, so I am pretty aware how things went.
Remember that besides the license issue, another big reason why GNOME came to be was because KDE uses C++, hence the whole GObject stuff in C.
But I will note that GNU Gcc and Gdb are both C++ projects now. Gold, the current GNU linker, started out C++. Are there any other still-relevant GNU projects?
The latest version of the GNU coding standard is much more permissive.
C++ did add stronger modularity with its public and private member specifiers, namespacing etc. but that was mostly useful on larger projects.
It is still far from clear whether anybody will be learning Rust, in ten years, instead of whatever is the new hotness then. Hiring a domain expert who also knows Rust is generally impossible today, and will be for, at least, a long time. So, starting a new project in Rust is OK for a project you know won't matter, but absurdly risky for one that will.
C++ is mature. None of the above is a concern, for C++.
Given the money already invested into internal tooling and infrastructure specifically for Rust, I just don't see those large companies suddenly dropping it. Regardless of how good the language itself is, the sunk cost alone makes it hard to turn ship. And the language is good, so it'll use that time to entrench itself further.
Other, newer languages will come up continually, siphoning off the most mobile who have begun to find Rust familiar and pedestrian.
I work on embedded systems. There are roughly 3 choices for languages[1]. C, Ada, and C++. Except the version of C++ is sometimes often vendor specific and may lack features that are "standard C++", and never have a "full" STL. In addition, if you're not super careful with C++, what you thought was a copy or declaration can execute additional constructor or assignment logic. It might just interfere with your estimate of how long something can take (which is super important in interrupt handlers), or worst case, smash your stack (which can be as small as 1-2k). With C, you pretty much know what's going to happen and what's getting called. The fact that C doesn't require a runtime (nor does Ada), means you can use it to write kernels. You can't do the same with a 'full' version of C++, so you're back to a cut down C++.
I also spend time debugging compiled, optimized code by tracing instructions. This is hard enough in C, where I don't magically jump to a constructor function or an assignment function. I can visualize in my head how the C code could look like, given the instructions the optimizer produced. So it may not look like my code, but it is a version of the code that I can at least logically infer.
Ada is nice, but outside of some super-safety critical realms, it hasn't had the uptake. Private industry prefers not having to make the investment and the government let everyone waive out of it.
1. I know people are going to to say 'what about Rust, Go, or embedded something or other?' They are not as mature in their development lifecycle. So there's no validated RTOS for Rust (there are some experimental ones). Go is even further behind. Basically, you need a vendor supported RTOS that's validated for the safety and operational requirements of your use case, before you can be a serious choice for a lot of embedded work.
What does a vendor compiler do or do better than a compatible generic one?
With a vendor supplied compiler you can say, "We're using version 11.2". A year or two later an issue is discovered, the vendor will backport a fix to 11.2 giving you 11.2.1 which is much less effort for recertification. You aren't depending on the kindness of strangers (a terrible strategy) because you're actually paying someone to do the work.
Do the vendor compilers have a very focused feature set as a result? To reduce both test surface area and chance of expensive mistakes?
But even if you do use GCC or Clang, it doesn't change the mechanics of C++ as a poor language for embedded or operating system work. It just means you have the same choices (e.g. limited support for containers and strings, no exceptions, limited smart pointers, etc.) and you're making that choice based on GCC or Clang's limits.
And on a validated RTOS - it might be in C++ under the covers. The examples that come to my mind aren't. But the world is a big and magical place, so I can't say for certain on every RTOS. The F35 uses C++ and a set of very restrictive internal coding standards built on https://en.wikipedia.org/wiki/MISRA_C.
And no one will die if their copy of Serenity OS crashes.
Regarding language guides, C doesn't stop being C, even when castrated via MISRA-C.
Most OS code is written in C++ or Object-C, not C. Between Android, MacOS/iOS, and Windows there's not a lot of C code. The kernels are most of it. The NT kernel has C++, but hard to get a source on how much is still C or not. But the kernel is far from being most of the OS regardless.
> The fact that C doesn't require a runtime (nor does Ada), means you can use it to write kernels. You can't do the same with a 'full' version of C++, so you're back to a cut down C++.
For a huge number of users, "full" C++ is C++ with -fno-exceptions and -fno-rtti anyway, at which point the 'runtime' is like 2 functions and it's absolutely perfectly fine to use in a kernel. But regardless neither of those features are inherently incompatible with being in a kernel. You just have to implement a runtime to do that, just like kernels written in C have to implement a libc replacement.
Unless you're talking about the standard library (even though nearly all of it is completely kernel-compatible out of the box), but then you'd have to include libc & friends in the "C runtime" category and then it's equally impossible to use in a kernel.
And C in the kernel isn’t really a libc replacement. They often have different behaviors because they need to run without allocating memory, or be interrupt safe. For example, in some situations I use a function call instruction that specifically does not creat a new stack frame.
And of course asm {} works the same regardless.