True but I think the real cause of this is surely that C makes it too hard to use a sorting library that someone competent has written. I would not be surprised if the author was fully aware of the N^2 complexity but opted for a simpler implementation anyway.
(More realistically, below people are discussing that in the kernel environment the set of standard or third party library available may be unavoidably limited)
There is a quirk (almost a bug?) in FreeBSD's qsort where it will switch to insertsort for the whole array under certain conditions, which we hit in production given how our data was arranged.
I like how someone felt the need to write out insertion sort in some 4 line code golf challenge in the midst of qsort. This right here is why no one wants to deal with C anymore.
Did a bit of digging and found that there used to be a comment for why it was done, but it got removed [0] when they switched to the implementation from Bentley & McIlroy's "engineering a sort function" [1] around 1992.
qsort() is pretty slow if you're sorting something like long[]. In that case, radix sort goes 5x faster and vectorized quicksort goes 10x faster. If you're sorting int[] then vectorized quicksort goes 25x faster than qsort(). Nothing goes faster. The issue is it's a big ugly c++ monstrosity that's a huge pain to compile.
That's fair if the constant factor is relevant, but if bubble sort is terminating in any reasonable timescale then the difference between qsort, C++ std::sort, and a custom implementation is really not a factor.
A lot of languages now have common tooling (cargo for rust, pip for python, etc) which makes it easier to find and incorporate the libraries you want. Apparently there are tools like https://conan.io/ but they're not as widely-adopted.
C's build system is similarly non-uniform. Many packages use Makefiles, others use different build mechanisms.
C has no universally-agreed error handling mechanism or convention. Whether exceptions or golang's error interface, you can generally assume that a random package in most languages will handle errors the way you expect. In C it's a lot more varied.
Similarly memory allocation - sometimes in a larger application you want to customize how malloc and friends work. How and whether you can do that for a C package is non-uniform.
Mind you the C standard library has a sort() function which will have sensible big-O behavior on pretty much any platform. I suspect this specific problem is more to do with this being kernel-mode code which has a lot of special conditions.
I am always amazed by arguments that say that not having a language package manager like cargo or pip makes it hard.
Really? Is it really considered hard to link a library without them? Am I so old that somehow I grew up in a world where linking a library was not considered black magic?
The first issue is actually downloading the dependencies, doing this manually quickly becomes infeasible for any non-trivial project.
The second issue is keeping everything updated, and making sure that all packages are compatible with all other packages. Doing this manually is also not easy.
With C specifically, you need to wrangle different build systems, and once you have them built and "installed", you need to figure out which linker and compiler flags are needed to consume the libraries.
If you are working on a small project with maybe a few dependencies you can do this by hand, but when you get to say, 15 dependencies, it quickly becomes very difficult.
You can use the system package manager on some systems to install libraries I guess (assuming it has the packages and versions that you need), in this case manually managing things could be a lot easier, but you still should be using pkg-config for portability purposes.
But none of that supports the assertion that C makes it hard to use good libraries. You can even use libraries not written in C if you want.
If the argument is really "it's impossible to make a good library in C", that's different. I'd very much disagree with that, but it would be to the point.
I'm saying "it is harder to consume good libraries in C, because it is harder to find them & harder to build them; and once you have done both, you find that good library A and good library B work in very different ways, so you have to do more work to adapt".
And I haven't mentioned the lack of a strong universal string type, the way many libraries typedef their own family of different kinds of integer, the way one library will require you to free() a returned structure and another will require you to call my_library_free()...
It all adds up to additional friction.
You don't have to agree! Maybe I am out of date, I haven't really dealt with this since the mid 2000's. I'd be thrilled to hear this isn't an issue any more.
It's not really a matter of whether or not I agree. I was just trying to understand what the assertion was!
I was baffled by the notion because I couldn't think of anything inherent in the language that made it hard to use good libraries. Now I understand that's not really what the assertion was.
The original assertion was about difficulty of using C libraries in the kernel or bootloader. In the bootloader you're the OS. There's no file system, no dynamic linker, and no processes. There's no guarantee some third party library will work in that environment. It might but it's work to make sure it does or adapt it if it doesn't.
Let's say you want to develop a CLI tool in C for crawling a website's sitemap.xml as advertised by the website's robots.txt.
How would you approach this development in C?
With e.g. Java, Javascript, PHP, and Python it's clear to me.
There's no standard build system. Think about how you add a dependency in Rust, Go, JavaScript, even Python.
Now do it in C/C++. Absolute nightmare.
Look at how many header-only C++ libraries there are out there. They're making compilation time drastically worse purely to avoid the need to faff with a shitty build system. It's a good trade-off too. I use header-only libraries where possible. They're convenient and popular.
Actually vcpkg seems to be going some way to fixing that but I have yet to convince my co-workers to use it.
> to avoid the need to faff with a shitty build system.
Then maybe don't use a shitty build system?
It's true, C is not trying to be a programming environment or tech stack. It's a language, that's it. Whether or not that's desirable depends on what you're trying to do, it's not something that is good or bad in some absolute sense.
You have your choice of build systems, so pick one that meets your needs.
Vcpkg isn't for me, either, because it doesn't solve any problem I have. If it does for you, awesome!
Then build them. I'm not seeing the issue here, to be honest, so I'm not sure what I should be addressing.
If the issue is that you don't like how the dependency has arranged to build (I'm not sure why you'd actually care, but just in case...), then port the makefile (or whatever) to your preferred system.
Or, another guess, is the issue that you want to build all your dependencies as if they were an integral part of your own project? If that's the case, I would argue that you're doing it wrong and another tech stack would make you happier.
With what? The whole point of this line of discussion is that building stuff in C is suboptimal, often requiring the end user to juggle n different build systems by hand to get all the dependencies installed.
Since we're talking FreeBSD here, thirty years ago we had Modula-3 whose build system is lightyears ahead of anything make based.
And now we're back at: this is why C is more difficult, for no good reason, than the alternatives. For small projects that you're only building locally, your approach may work. Once you expect any sort of cross-platform compatibility and/or start distributing your project to others, this approach falls apart and fast. Instead of focusing on development you'll be focusing on playing whack-a-mole with incompatibilities between the different shells (or versions of make, etc.) offered on different operating systems.
Again the problem is that no package/dependency management for C/C++ means that C is balkanized and more difficult to deal with compared to other languages. Using third party libraries in C is far more difficult and error prone than it ought to be.
Pretty much every language that provides more comprehensive dependency management also provides easy enough access to allow you to NIH/DIY it if you need/want to. For instance contrast this with something like rust where cargo is standard across all supported platforms and provides proper dependency management. You can still call the rust compiler (rustc) and whatever linker yourself if you so desire.
Honestly if you lack the vision to see why that sucks I really suggest you try a language with good package management - e.g. Go or Rust. Maybe it will make it easier to see all the problems with the traditional C approach if you can see how it should work.
C and C++ dependency installation is "sub-optimal" but it is certainly well understood. The fact that there are many cross platform, open source projects written in C and C++ proves this. If you can't deal with makefiles and scripts, maybe stick to Go and Rust?
C and C++ dependency installation is "sub-optimal" but it is certainly well
understood. The fact that there are many cross platform, open source projects
written in C and C++ proves this.
Nope. It proves that people have found work arounds up to and including cargo culting things. Any large enough project is going to rely on something else to generate the makefiles, and if you depend on anything large enough you're gonna get stuck having to build and/or install whatever other makefile generators are required. Simply put it's an archaic mess.
If you can't deal with makefiles and scripts, maybe stick to Go and Rust?
To be clear it's not that I can't deal with makefiles it's that I don't find it a good use of my time*. Take, for instance, the FreeBSD ports tree. make(1) is its achilles heal and the main reason it's obscenely slow to deal with (even compared to something like portage). Besides, doing anything by hand is inherently error prone be it bounds checking array access or cobbling together dependency management.
* And, sure, in years past I wrote a drop-in replacement for automake/autoconf in perl whose big (speed) advantage was that it didn't spawn a new shell for each check. It was a neat hack, but that's all anything papering over the make(1) interface is.
C can’t be used to implement a good library for many problems due to being inexpressive. For example, you can’t write an efficient, generic vector data structure, but sort functions are also only fast due to the compiler’s smartness — passing a function pointer would be strictly slower.
Though this has not much relevance here as it is about assembly.
C arrays suck on the best of days and qsort requires that you understand function pointers and types which are some of the hairiest C syntax in common use. The C Clockwise Spiral rule is truly special.
It's easy to lose sight of the climb once you're at the top.
This actually made me laugh out loud. Yes, if your problem with C is that it doesn't need a package management mechanism like some other languages, then C is clearly not for you. But C is very far from the only language like this.
It's a bit like criticizing a fish for having no legs.
I sense that we have some sort of real miscommunication going on here, because the only response I can think of to
> I have no idea why you would think that it doesn't need one.
Is that I have no idea why anyone would think that it does need one.
Perhaps the disconnect is that you are wishing C addresses different use cases than it addresses? That you wish it were a different language? If so, that's fine. Use a more appropriate language for your task. I just find it odd if the criticism of C is that it isn't a different kind of language.
That's suboptimal for many reasons. Package names are not consistent. Installing multiple versions is usually impossible. Huge pain for library authors. Doesn't integrate with build systems usually (even basic pkg-config support is iffy). The command is OS-specific. You can't usually choose the linking method. Difficult to bundle dependencies. Usually out of date. Etc. etc.
A lot of these comments are like "C is hard if you don't know C and it scares you".
Not to mention kernel mode doesn't want a gigantic library package manager to pull in leftpad() from the internet. As mentioned, the kernel libraries on FreeBSD have a qsort, but they didn't in the original commit from 3 decades ago or whatever.
Annoyance #1: External symbols are expected to be unique within 31 characters according to the standard, so you're limited to a few namespace "levels", at most.
curl_easy_option_by_name() is already up to 24 characters and there's only two "levels" in curl_easy_*.
Annoyance #2: There's no formal registrar for LIBNAME. This isn't a big deal for popular libraries, but it's a pain having to keep a locally-modified copy of a less popular dependency just because it shares its name with another less popular dependency.
Annoyance #3: LIBNAME_actual_function_name() is a pain to read and using either the preprocessor or static inlines to locally alias function names for the sake of readability is silly.
@1: The limits are considered obsolete since C89 and implementations are encouraged to avoid them whenever possible. I think the same way we disregard non ASCII character sets, non two's complement encodings and similar, we are safe in assuming sane implementation being able to handle longer names. And being honest, if given implementation isn't capable of more than 31 significant characters, then it would have problems with namespaces too.
@2: Agree, although I don't recall this ever happening to me.
@3: Is it? How is libname::actual_function_name() much better?
I actually like to use libname__actual_function_name(), as it further separates "namespace" from function name (unless we need compatibility with C++, as IIRC it reserves all double underscores, not only at the beginning).
> @1: The limits are considered obsolete since C89 and implementations are encouraged to avoid them whenever possible.
This is still the case in C11, Section 5.2.4.1. Did this change in the most recent standard?
> @2: Agree, although I don't recall this ever happening to me.
It happened to me once. I ran across a library from 1994 and another from the 2010s which shared a simple name like "libamc". I'll comb through my records later to figure out the actual name.
> @3: Is it? How is libname::actual_function_name() much better?
It's not, but I wasn't thinking of C++ specifically. (I don't know C++. I've somehow managed to avoid it in many years of writing C.)
I was thinking more like the file-local namespace clobbering offered by Python e.g., from LIBNAME import actual_function_name.
> This is still the case in C11, Section 5.2.4.1. Did this change in the most recent standard?
Well, no, it's still marked "just" obsolete. For it to be deprecated or removed there would need to be anybody caring about it enough to put some work. But since it doesn't affect vendors at all (they can just ignore) and users don't complain, it's just a forgotten "law" - still law, but a dead one.
> I was thinking more like the file-local namespace clobbering offered by Python e.g., from LIBNAME import actual_function_name.
Oh, that's... way more than just namespaces. Way more. That would require more fundamental changes and additions. C++ just added modules in C++20 (not sure how well those will catch on), but I don't think something like that is to be expected in C for feasible future.
They used "_Generic" as a keyword but it doesn't really do that.
Suppose I need to define a copy assignment operator for the library's sort function to use. Is there a good way to overload it? Can the library know what the size of each element is based on its type without having to pass it in as a parameter?
You can pass function pointers to the library, but that quickly becomes awful.
Or, you get one function that takes all of the arguments and have to define and pass in a bunch of function pointers and type size parameters that are each an opportunity for bugs or UB in order to sort a simple array of integers.
If my type needs a custom assignment operator, I need each library I use to take that as an argument. One expects the function pointer to take the arguments in the order (src, dst), another as (dst, src), a third specifies the return value as int instead of void, a fourth takes the source argument as "void *" instead of "const void *" in case you want to implement move semantics and a fifth doesn't support custom assignment operators at all.
It's no surprise that people prefer to avoid this.
having said that this specific sort is somewhere deep in kernel boot land. and kernel code can't really use the standard library. I am not sure if there is a standard kernel sort.
> C makes it too hard to use a sorting library that someone competent has written.
rust makes it easy to create generic data structures via generics. It would be trivial to swap between different underlying sorting algos as long as it was given a type compatible function for how to compare the contained items.
