Panzerschrek3 hours ago
I don't understand people reinventing macro-based hacks in C to achieve what was achieved in other languages many years ago. Why not using C++, for example? It's available almost everywhere, introducing its usage in an existing C codebase is pretty simple. Sure, C++ has its own downsides, but is it better to create mess with macros in C rather then using exiting language facilities and standard library containers provided by C++?
psyclobean hour ago
Its rather hard to introduce c++ into legacy c projects. You basically have to decide on a subset of features to use, and then you'll have to explain to the teams why the same looking code now takes 10x more compute to build.
Usually the way we do it here is we honor some interface then rewrite the subsystem in c++.
And then there's the real hurdle and that is getting the c++ idiom correct as it is very easy to just open the floodgates and let everyone write code that looks vastly different.
uecker2 hours ago
Having used C++ a lot in the past, I think the mess in C++ is way worse. I also contribute to projects that introduce C++ into a C code base, and I really wish they hadn't done this.
Although there are C features I like that I would need to remove before introducing C++ to a codebase, so this may not always be so simple.
Panzerschrekan hour ago
> the mess in C++ is way worse
What is mess in C++? Yes, it has some shady parts and is more complex than C, but this complexity provides expressiveness and type safety. And you can always use only features from C++ you find useful.
> also contribute to projects that introduce C++ into a C code base, and I really wish they hadn't done this.
What is problematic in these projects other than unfamiliarity of C++ for developers previously used only C?
_gabe_an hour ago
> What is mess in C++?
Just a couple examples:
How do you make a shallow copy of an object in C++, how do you do the same thing in C? Knowing I can just memcpy _any_ struct in C and have a valid shallow copy is pretty huge.
How do you create a stable ABI in C++? How do you make one in C? In C, knowing that all my exported functions will mostly just work and be stable as long as I don’t change the interface is also huge and allows you to create cross language bindings pretty trivially.
Panzerschrek7 minutes ago
> How do you make a shallow copy of an object in C++
Shallow copies aren't generally possible for classes storing something indirectly, since it violates ownership semantics. That's not how things are done in C++.. Operator = is usually used for making copies, which is optimized to memcpy for POD structures, but for something more complex may perform extra work for doing an actual deep copy.
> How do you create a stable ABI in C++
It's a complex topic. Basic ABI for calling functions is identical to C. But one need to keep in mind, that type layouts and internal implementations of library types (like containers) may differ from implementation to implementation and from version to version.
> knowing that all my exported functions will mostly just work and be stable as long as I don’t change the interface
Nothing prevents you doing this in C++. You can have C-style external interface and use all goods of C++ internally.
lelanthran37 minutes ago
> And you can always use only features from C++ you find useful.
Ah, the old "programmers just need to be more disciplined when using C++".
Yeah, C programmers have never seen that argument before...
uecker14 minutes ago
My macro-vector types are type safe. In fact this is the point.
I do not think C++ is more expressive or type safe.
tliltocatl5 minutes ago
Not sure why author does it, but I use C over C++ for one reason: I'd rather not have random hidden malloc() scattered in my code. And no, it's not about latency or performance. Once my code takes an yet unexplored part and runs out of 200kB RAM, the will be no way for me to learn about it - running out of memory will bring down both the logger and the radio link, which is the only way to get the logs from a sensor installed twenty meters above ground in a hazardous environment facility. C may be unsafe, but most errors short of "writing to a random memory area" are either well-contained or at least reproducible. Dynamic memory allocation means that anything may crash everything. Manageable if you have a MMU and can contain crashes within isolated heap, but if not - I'd rather not bother. And yea, you can write zero-allocation C++ code, but why bother if most of STL is now unusable? And you get some new and exciting UB modes (seriously, no union aliasing, what the heck?)
Also, template metaprogramming is way more arcane than C macros. And I need compile-time metaprogramming in leu of dynamic allocation. So C macros it is for now (Zig is promising but still not there yet).
Joker_vD3 hours ago
For one reason, it is because C++ runtime (and its standard library) is a whole own can of worms which most people would rather not touch if they can afford to. Which they mostly can.
> Sure, C++ has its own downsides
"Sure, getting your eyes gouged out has its downsides, but is it better to read that awful mess of macros in C instead?" The answer most people would give to this question may surprise you.
kccqzy3 hours ago
Here we go again. Yes there are bad parts in the C++ standard library and there are good parts. But if you are just trying to do type safe generic data structures you are unlikely to touch the bad parts. Many codebases forbids parts of the standard library, e.g. LLVM forbids including <iostream>. You can forbid using parts of the standard library too.
Joker_vD2 hours ago
> Yes there are bad parts in the C++ standard library and there are good parts.
Okay, other than <vector>, what are the good parts? Because as the sibling comments rightfully point out, migrating your codebase from C to C++ just to be able to use <vector> is not worth it.
The <map> is a sad joke played upon the C++ programmers by the standard committee.
pjmlp2 hours ago
Strings, something that C still doesn't do properly, not even having something like SDS into the standard library.
<map> does the work just fine, not everyone has winning microbenchmarks as part of their daily work.
accelbred2 hours ago
Many of the big C++ projects I've worked with have custom string types since the standard one was defficient for some reason or another.
jstimpflean hour ago
Exactly, and a simple usable string type is just a struct MyString { char *buf; size_t len; }; away. Actual magic is in how you use it, where you allocate it, how you integrate allocation and formatting and logging and I/O... i.e. all the things that aren't solved by crufty complex std::string either.
Joker_vD2 hours ago
> <map> does the work just fine
It has a rather weird interface, at least until C++ 17 when some of the deficiencies were patched somewhat.
jstimpfle2 hours ago
It's a slow generic data structure with an unintuitive API. You can use it for leetcode or for CRUD. For anything more demanding it's horrifically bloated and bad. std::string too. Whenever you see STL datatypes like even string and map, you have to deal with RAII, implicit allocations, weird operator syntax, unexpected mutation (invalidation) and so on.
(Spporting or even encouraging destructive mutation, and by this I mean not incrementing counters or anything harmless but allowing iterator invalidations and crashes, are also why std::vector is bad in my opinion, these are idiomatic APIs for 90s and 2000s programming, which we should know better to avoid in 2026).
Panzerschrekan hour ago
> For anything more demanding it's horrifically bloated and bad
C++ containers are designed for average demands. If you need something more specific, you can always use an alternative implementation. And it's better than messing with macros in pure C.
> you have to deal with RAII
What's problematic with it?
> implicit allocations
Allocations aren't implicit. It's usually clear from the documentation where allocation takes place (like in concatenating strings or copying strings).
> unexpected mutation (invalidation)
It's not the case with standard library containers. Mutating methods aren't const-qualified, so that it's clear where mutation can take place. And in C++ it's strictly recommended to mark as const everything in regular user code which shouldn't be mutated.
jstimpflean hour ago
> C++ containers are designed for average demands. If you need something more specific, you can always use an alternative implementation.
As someone who has been programming exclusively in C/C++ for a long time -- the biggest selling point for these languages in 2026 is exactly being suited to doing something specific, not generic.
> Allocations aren't implicit
std::map<int,int> m;
m[1] = 42; // implicit alloc
auto m2 = m; // implicit too
Theory and practice. Making everything const correct is too painful in practice, often impossible. It's a trap for bean counters that can't focus on getting some actual useful work done. I'm being harsh to my own past self here. Counter question: why include allocation mechanics with some existing data that never gets changed? Why should we have to add much more boilerplate to get the simpler thing?
pifan hour ago
> you have to deal with RAII
If you find that RAII is a problem, I pity how poor a programmer you must be...
jstimpfle32 minutes ago
You must be very experienced to be so judgemental! But maybe ask the many billions of voxels that get tested per second on my multithreaded and SIMD'ed cutting simulation.
kccqzyan hour ago
So what? You like <vector>, and make it the only allowed include. Write all other type safe generic data structures by hand using C++ syntax. Problem solved.
accelbred2 hours ago
You cant touch C++ without bringing the object lifetime stuff in. And unlike strict aliasing, theres no flag to turn it off.
jeffbeean hour ago
Object lifetime is the entire point of C++ and it solves ~100% of the emergent flaws in C programs.
accelbredan hour ago
I was just dealing with this: https://bugs.gentoo.org/show_bug.cgi?id=974323.
Also std::start_lifetime_at is a hack and ive seen nobody using it in all the placed where it aught to be used.
If optimizing based on object lifetimes could be turned off, itd be turned off everywhere for hardening like strict aliasing is.
jeffbeean hour ago
In my personal opinion, the fix[1] for that issue clearly implicates C-style habits polluting a C++ code base. No right-thinking knower of C++ initializes objects with memset! Also I believe that -Wall would have flagged that, and I know for certain that cppcoreguidelines-init-variables + cppcoreguidelines-pro-type-member-init would have flagged it.
1: https://github.com/llvm/llvm-project/commit/905a88b923433eb8...
rwbt3 hours ago
I'd rather not migrate my C codebase to C++ just to use an array container. Very hard to consistently limit the codebase to a strict subset of C++.
pjmlp2 hours ago
It is called a linter, more devs should learn to use a tool that was originally created for C in 1979.
accelbred2 hours ago
The only decent linters I know of for C++ are clang-tidy and coverity and they are not good enough.
0xbadcafebee2 hours ago
If you want better tires on your car, why not just get a different car?
lor_louis5 hours ago
I wrote a summarizing article on type safe container types a while back, but with some C23 specific changes and a few tweaks to work better for complex types.
https://louissven.xyz/article/how_I_do_container_types_in_C....
Feel free to flag/delete if this isn't the place.
rramadass34 minutes ago
Thanks for sharing.
It is really nice that you studied both Martin Uecker and Daniel Hooper's techniques and tweaked them to suit your ideas/taste.
mkehrt19 minutes ago
I absolutely cannot remember the details, but we did typesafe, macro based generic data structures in C in an undergrad class I took ~20 years ago (CMU Operating Systems). The idea has definitely been around, though I don't know if the implantation was the same.
tniemi4 hours ago
That `(1 ? (item) : (list)->payload)` was a neat trick. It gets optimized away, but the type comparison happens before that.
Still feels a bit like a party trick, but if it works...
JdeBP3 hours ago
It's somewhat of a forced trick nowadays, I think.
I actually thought from the title before I read the article that it was going to use _Generic, as in something like _Generic((item),__typeof__((list)->payload):...) .
Xirdus4 hours ago
Expressions that compile but never evaluate are bread and butter in C++ template metaprogramming.
veexx1034 hours ago
Is it feasible to create a new language by adding features to C
just as was done with C++?
pornel2 hours ago
It's not worth it. The value of C is in compatibility, availability of compilers, and familiarity.
As soon as you change anything in a breaking way, start requiring your own compiler/transpiler, or introduce new idioms, you end up losing the things that keep C alive.
Users of C either like it exactly the way it is, or have to use a specific C version due to a vendor dependency or compliance.
An upgraded C not approved by the standards body gives you yet another niche language that is not C, but is still burdened with its old flaws.
rramadassan hour ago
Well said.
I really don't understand why people bring up other languages when one is discussing implementation of some "advanced/tricky/hackish/new" features in C. It is not as if the implementer does not know about the ease of availability in other languages but there is always some set of criteria which prevents switching to a new language.
On a related note, there is a dearth of written/learning material (books etc.) cataloging and explaining advanced architecture/design/implementation patterns in C though we know they exist in the tons of industrial-strength codebases out there.
There is also the fact that when you see an implementation in C of some feature from another language you better understand language design pragmatics eg. implementing inheritance and virtual functions in C gives you insight into how they work in C++/Java/C#/etc.
actionfromafaran hour ago
It would be nice to have something like C which was very much like C and Pascal (not the syntax) but which was basically C except no naked pointers by default etc, fewer footguns, but which would generate C.
pjmlp4 hours ago
And Objective-C, yet somehow people reinvent them badly in C.
accelbred2 hours ago
I am working on a language that was C with extensions, transpiled to plain C, but the C syntax is kinda not great to work with (stuff like needing type tables and unbounded lookahead). At the point you clean up the syntax, you're not really C with extensions anymore.
FullGarden_S2 hours ago
C3 might be it because C3 has full C ABI compatibility so unlike most modern C-like alternatives, it checks out.
nikbackm4 hours ago
There are already plenty of such languages, Zig among others.
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peesem3 hours ago
zig doesn't "extend" C in the way that C++ does.
krior2 hours ago
But C++ does not extend C as well.
christophilus3 hours ago
C3?
pjmlp2 hours ago
Nope, they went their own way now, see recent blog posts.
randomNumber72 hours ago
As far as I know many C programmers think the addition of variable length arrays in C99 was a mistake. What would be the downside of this approach?
pjmlp2 hours ago
So much so, that it was made optional annex in C11, while Google paid to remove all their use from the Linux kernel.
uecker2 hours ago
I do not get the connection with a VLA in this context, but if you need a VLA, by all means use it. It is basically always better than the alternative.
randomNumber72 hours ago
> I do not get the connection with a VLA in this context
The article uses a struct with a VLA as the last element.
uecker2 hours ago
I see. This array of unknown length at the end of a struct is called a flexible array member and not a variable length array (although it also refers to an array of variable length it is a different language feature).
lukasgelbmann2 hours ago
Yes, and variable length arrays were made an optional part of the standard in C11. Whereas flexible array members remain a standard required feature.
Flexible array members don’t allocate a dynamic amount of memory on the stack.
uecker2 hours ago
VLAs are supported by basically all modern C compilers though, and I do not think adding them was a mistake (I certainly use them a lot!). They got a bad reputation due to stack clash attacks, but in the past some compilers did not implement stack probing (clang was very late). But this was fixed a decade ago.
[deleted]an hour agocollapsed
randomNumber7an hour ago
What happens when I put a variable of a struct type that contains a flexible array member on the stack?
uecker7 minutes ago
The array has size 0. In GNU C, you can initialize it and then it has a fixed size corresponding to the initializer.
rramadass5 hours ago
Also see Templates in C by David Priver - https://www.davidpriver.com/ctemplates.html
He also has other interesting C techniques, namely;
Adding reflection to C - https://news.ycombinator.com/item?id=49964525
_Generic for Type Reification in C - https://www.davidpriver.com/creification.html
See also his C2y interpreter with REPL named "DrC" for the upcoming C29 standard (https://en.wikipedia.org/wiki/C29_(C_standard_revision)) - https://github.com/drpriver/drc
PS: I really like his style of writing and presentation; concise and precise without unnecessary fluff and page beautifying.
david2ndaccount2 hours ago
Hey that’s me! Cool to see people like my stuff.
rramadass2 hours ago
You should write more ;-)
I also posted your "Adding Reflection to C" at https://news.ycombinator.com/item?id=49964525 and hope HN picks up on it and has a decent discussion.
You definitely should add a detailed post on your "DrC" compiler/interpreter; usecase, scope, techniques used etc. Since this is looking forward to C2y/C29 with some more extensions, i think people will enjoy playing with it in the REPL format.
david2ndaccount14 minutes ago
I agree. Alas I have a day job and my other hobby is going for long hikes. But when the days get shorter and the weather is worse I’ll write some more!
warmwaffles2 hours ago
I do wish to see comptime stuff in C some day. Or at a minimum your `defblock` implemented. I am so tired of having to escape new lines.
uecker2 hours ago
There is a proposal for #def / #enddef:
podocarp4 hours ago
Lol at some point just implement a small compiler in C… reflection is kinda a hilarious thing to have like I understand the use case for generics, since it's not that that that hard to do with macros and quite commonly wished for
carlos2564 hours ago
Jesus, I hate those macro hacks so much. Most of the time you only need a single container, so writing an ad-hoc implementation is cleaner than that.
pjmlp4 hours ago
The extent some will go to avoid touching C++.
uecker2 hours ago
Indeed. After having suffered from C++ a lot, I am also really avoid touching it if I can.
But if you compare some C++ template container to a C macro solution, I also do not find the macro solution to be more complex.
pjmlp2 hours ago
I would not expect any other kind of answer.
We will keep on agreeing to disagree.
uecker2 hours ago
The difference between me and you is that I do not usually post under C++ articles something negative about C++. Instead I respect that people interested in C++ may have their own reasons. For some reason you find it appropriate to post something negative under each C article.
I could tolerate it if it were at least some interesting criticism,.
nice_byte4 hours ago
I've tried doing this for a few years and it just sucks ass. Just use c++ and templates if you need proper generic data structures. C is a defective language.
uecker2 hours ago
I start to like my experimental macro containers: https://codeberg.org/uecker/noplate/
Examples: https://godbolt.org/z/hecqs78xs https://godbolt.org/z/YnrcjKrEn
Not perfect, but also not really inferior to C++ in my opinion.
loeg2 hours ago
Or, in 2026, Rust (or Zig, I don't care).
0xbadcafebee2 hours ago
Can't be all that defective if it underpins most of the technology in the world
sophacles44 minutes ago
It absolutely can. See for example: lead.
esafakan hour ago
When has that ever stopped a shit language? Just let it die already.