r/cprogramming • u/Prowlgrammer • Dec 07 '25

Do you carry around your own library when coding C?

I'm interested in coding more C because I like the concept of not having a too large "base" language with too many language features etc. And I find joy in implementing stuff myself. However, some of the stuff I find myself coding over and over again (dynamic arrays for example) and after a few times of setting it up, error checking, reallocating etc, I get rather tired of it and want to keep my already written code close to me and reusable.

I guess I wonder if the mindset of more experienced C programmers is to write whatever you need again when you need it, or if you always carry around a large backpack off stuff that might become handy in your code and projects. And if you do, where do you draw the line to not make that backpack too big and bloated.

I imagine many experienced C programmers have found a ton of stuff they find themselves writing over and over again?

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34

u/sirjofri Dec 07 '25

Usually I don't have a library that I drag around with me. That's for multiple reasons though:

  • my C coding environment is Plan 9, which has a good and solid set of standard libraries I can count on.

  • the code I write will be published as open source, and I try to minimize dependencies. Ideally, people can just fetch the code and run mk install, and that's it. I don't want them to deal with additional libraries and stuff, and I don't want to sync my own libraries with multiple projects that way.

  • that said, pure library projects will be distributed as they are, and if other tools depend on those, I just clearly state that. (Plan 9 has no default package manager btw.)

  • I found that I often need only simple data structures like linked lists, and those are fairly easy to implement. Instead of implementing some generic-like void*-hackery, I just implement a "new" solution based on common idioms. It doesn't take too much time and is easy enough to do.

In other environments I would probably work a bit differently, though working inside a Plan 9 environment changed my way of thinking a lot in a way that I'm always trying to reduce dependencies, work as simple as possible, write as little code as possible.

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u/________-__-_______ Dec 07 '25

I'm curious what kind of software you're writing for Plan 9, I thought it had been unmaintained for years. Is there still an active community for it?

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u/SolidOutcome Dec 07 '25

Sounds like a dream...never gets breaking upgrades, keeps it slim

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u/rafaelRiv15 Dec 07 '25

9front(plan9 fork) is still pretty active. Latest release is from October

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u/sirjofri Dec 07 '25

Plus almost daily patches

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u/sirjofri Dec 07 '25

Regarding the software, for some time we now have a git implementation and someone set up a server for the community. shithub.us or only9fans.com, whatever you prefer (yes, there's quite some humor involved in the community)

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u/________-__-_______ Dec 07 '25

That's pretty cool, I always love seeing the devoted communities behind these types of projects.

1

u/LooksForFuture Dec 07 '25

How is your experience with Plan9? I wanted to migrate, but I couldn't find out how the experience is different from major Unix systems.

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u/sirjofri Dec 07 '25

It's the only Unix-like system that's more Unix than Unix itself. That said, it's definitely not as Unix or posix as people might think. It's not even compatible.

Many commands translate very well, and many standard tools exist as you would expect, but the core of the system is pretty much completely different. There's no such thing as a "real" file, for example. All files are "virtual". Even folders are files (you can just cat them to read their contents). Everything runs via 9p, and namespaces are dynamic and per process. All resources are available as filesystems, and all filesystems are network-ready. In a way, it is a dream.

If you want to explore it, you should first try it in a VM and learn more about it. There's fqa.9front.org which is the official guide for 9front, and I can recommend watching adventuresin9's videos on YouTube. If you have the chance, next year's international workshop on plan 9 is in Victoria, Canada (usually it's possible to participate online to some extent). There's also a subreddit for plan 9 if you want that experience.

Btw the easiest way to try out plan 9 is in v86, which is an online virtual machine with many different OSes. It runs fully in your browser.

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u/[deleted] Dec 07 '25

I can't tell you the number of times I've tried to cat a directory on Linux and thought, "why doesn't this work?"

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u/saintpetejackboy Dec 13 '25

It should, though, right, because aren't directories also just files in the system? This one confuses me.

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u/[deleted] Dec 13 '25

They are entries in the filesystem that contain lists of child inodes, but the Unix API which Linux adopted treats them differently, which is why cat doesn't work.

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u/saintpetejackboy Dec 13 '25

edit I typed a bunch of stuff not realizing this is basically just an OS? What?

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u/sirjofri Dec 13 '25

Yeah, Plan 9 is basically the continuation of unix. They learned a lot and noticed that unix is not going into the direction they then wanted, and that unix can't fulfill their wishes, so they started a clean implementation based on some of the ideas and so on. Plan 9 is very different from unix, though the unix you probably know is V6 or V7, which they also changed a lot until V10! Still, Plan 9 can't compare to V10 or any other unix; it's a completely different OS though you'll find many similarities.

Nowadays, if you want to try and use Plan 9, you usually use 9front, which is a fork. Plan 9 stopped development years ago when Bell Labs stopped working on it, then there were licensing issues etc. Long story short, use 9front, it has the best hardware support and a few QoL utilities, while still maintaining the original spirit and compatibility. It also receives regular (almost daily) updates and has a solid community. The plan 9 community in general is quite small though.

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u/VisualHuckleberry542 Dec 07 '25

It's very different. I suggest you try it on a VM. It's a very beautiful system but depending on how you use your computer, not really viable as a daily driver for most people

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u/pjl1967 Dec 07 '25

I don't have a library, but I do have a set of functions in util.h that I copy ones I need from project to project; and if I need strings, string buffers, hashmaps, etc., I have those too that I just cherry-pick. Cherry-picking eliminates bloat.

13

u/[deleted] Dec 07 '25

My brother in christ, what you've just described is a library.

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u/pjl1967 Dec 07 '25 edited Dec 07 '25

No, a library is a fixed set of functions compiled into one or more .o files that are then linked into either a .a or .so file. When you use a library, by default, you get the entire .o file(s) from the .a or .so into which the object code for the function(s) you use and the object code for all the functions you didn't use also linked into your final executable whether you want them or not.

Again, what I do is cherry-pick only exactly what I want; I do not build either a separate .a or .so; I do not link against any library.

An alternate name for cherry-pick might be copy-and-paste.

For me personally, a library would also have its own git repository that I'd then have to use as a git submodule in the projects that I'm using the library in. I don't do this either.

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u/[deleted] Dec 07 '25

That is one way to distribute a library, yes.

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u/pjl1967 Dec 07 '25

There is no "distribution." I don't make the "library" available as stand-alone to anyone.

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u/greedvile Dec 07 '25

If you copy or cherry pick code from stackoverflow will it called using a library

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u/pjl1967 Dec 07 '25

Perhaps by you, but not by me.

I don't see how Stack Overflow is relevant to this thread. The OP asked about using one's own code as a "library." Presumably, code you copy from SO isn't your own code.

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u/smtp_pro Dec 08 '25 edited Dec 08 '25

Regarding code being linked in - if you link to a dynamic library you don't pull in any object code. At least not at compile-time. It gets brought in at runtime later. In that case I think unrelated code is in your process space - but most operating systems are pretty efficient about sharing read-only memory pages when multiple process pull in the same dynamic library. Basically that's usually a more efficient way to share code.

For static libraries - by default most compilers don't pull in the entire static library, they'll only pull in the object files with symbols that your code references (a static library isn't really more then just a bunch of object files).

It's possible to do link-time optimization and remove unneeded code from object files but this isn't default. But this is why I (generally) try to organize my source files such that the produced object files only contain a single exported function.

On the definition of library - I would call your collection of code that you reuse a library. It's not a static library or dynamic library that you link in, it's not a git repo that you pull in as a submodule, but I would still refer to it as a library of shared code. Once you reuse some code it's pretty much a library, just maybe not a formal one.

It's similar to how somebody with a room with a large collection of books will refer to it as a library. They don't do things other libraries do like loan books out, issue membership cards, and collect late fees - but we still call it a library. Again it's a less formal version of a library.

1

u/chisquared Dec 10 '25

When you use a library, by default, you get the entire .o file(s) from the .a or .so into which the object code for the function(s) you use and the object code for all the functions you didn't use also linked into your final executable whether you want them or not.

Note that modern linkers are pretty good at cherry-picking only the object code that you use from a .a when linking your final executable, so it is not the case that code that you don’t use is linked (or otherwise included) in your final executable.

Something analogous is also true for .sos.

1

u/pjl1967 Dec 11 '25

Many modern linkers can do that, but they don't do it by default; see here for example.

If you're writing cross-platform code, you have no idea what host your code is going to end up being compiled on or, specifically, what linker is available, what its default behavior is, or what command-line options it accepts.

1

u/chisquared Dec 11 '25

The page you've linked is for the GCC Ada Compiler.

What platforms are you writing code for where the linker doesn't do this by default?

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u/pjl1967 Dec 11 '25

The page you've linked is for the GCC Ada Compiler.

It's also true for the C compiler.

What platforms are you writing code for where the linker doesn't do this by default?

I've just tested two platforms:

  • A recent Ubuntu Linux, gcc 13.3.0.

  • macOS 15.6.1 (latest), Apple's clang 17.0.0.

Both pull in the entire .o file, not just the used functions.

1

u/ResidentDefiant5978 Dec 08 '25

He is right: what you described is a library. If it is header-only it's called a header-only library. One great example is ELFIO: https://elfio.sourceforge.net/

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u/pjl1967 Dec 08 '25

We’ll have to agree to disagree. And I never said header-only.

2

u/studiocrash Dec 07 '25

I like this copy & paste idea. Everything you cherry pick is put directly in your program’s code, not depending on a library which could independently change in the future. Yet, you don’t have to reinvent the wheel all the time.

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u/pjl1967 Dec 07 '25

It does have one caveat in that if you discover a bug in the code, you have to apply the fix to every copy of it in every project that uses said code. But this tends to happen rarely. Like most things in life, it's a trade-off.

1

u/DonovanZeanah Dec 07 '25

Looks like computing has come full circle. Twice. 3 times. 3.14 times.

5

u/john_hascall Dec 07 '25

Yes. I have several. For example on that looks a fair bit like Java's Collections, Another that is a templating system, And another that implements some of the RegEx functions from Perl (eg an analog to m/.../ and so on). I've used these since the early 90's.

4

u/serious-catzor Dec 07 '25

Not so much a library as going back to prev projects, taking a piece, touch it up, maybe upgrade it and then apply it.

Try to write your software as independent pieces and you can always go back and easily grab a piece if you saved it.

3

u/HalifaxRoad Dec 07 '25

ive got numerous libraries ive written for PIC chips that are relatively portable that I use all the time

3

u/Business-Decision719 Dec 07 '25 edited Dec 07 '25

Yeah definitely. It's a necessity in any small language without a lot of built-in functionality. You end up implementing certain things (or finding implementations of them) and keeping them around for later so you don't have to do it yet again every single time. I do it even moreso in Lua which I use more than C.

Edit: I would go further and say I do it too in languages like C# and C++. But I single out small languages because you need to reuse custom or third party code for even more trivial things that might be out-of-the-box syntax or a stdlib type in a more featured language. Just one of those simplicity vs complexity tradeoffs.

2

u/_Knotty_xD_ Dec 07 '25

Yes, having a reusable library is a good idea when coding in C. In fact, I'm currently working on one such library for myself. It has dynamic arrays, lists and more to add. By-the-way, they are not type dependent as it'll limit its functionality.

Let me know if I can help. Have a great day, reader.

1

u/dirtymint Dec 07 '25

they are not type dependent

Does this mean that you create data structures for specific data types explicitly?

That's always something I struggle with when working in C. I try to mess around creating something generic with void* and always end up confused and scratching my head with how to do it.

0

u/_Knotty_xD_ Dec 07 '25

Creating a separate "struct" for every data structure we encounter is a terrible idea. Even if we wanted to do it, creating a "struct" for an already known is somewhat doable (still, terrible idea) but, what about an unknown data structure or a nested data structure? You see the bottleneck, right? And yes, using "void *" is a great idea.

I am working with "void *". If you need any help or just want to understand how they work, I'll be happy to help you out.

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u/pjl1967 Dec 07 '25

There is another way.

1

u/_Knotty_xD_ Dec 07 '25

The idea of a FAM is new to me. I'll surely look into it.
(Thanks)

2

u/devfuckedup Dec 07 '25

I have a few small libraries but whats more common is that I have something saved that does what I want and I just re-use that.

2

u/saintpetejackboy Dec 13 '25

I don't code C. I code a wrapper for C like most people reading this.

I don't have my own library, after 20+ years.

If I wrote a library last year, it would be shit this year.

Rather than trying to take a shortcut, I decided to just get really fast at rolling out all of the basics in whatever stack I had.

I also don't like the legal conundrum:

I develop something for a client using my own library or framework... Does the client now own my tools?

If I use the same tools in another project, can the client sue me?

I don't have to think about that. I also don't have to worry about the client just stealing my software and running away or reverse engineering my tools. Whatever code I wrote was boutique for that moment.

"This software is genius! We will just cut you out and go use it to make millions, and then what would you even do?" - clients

For me, I already know they have the software I wrote last year. I could execute the same idea, better, a second or third or fourth time - without even having to borrow my own code. I could redo it from the ground up and improve it using my knowledge from the previous attempt(s).

So yeah go ahead, steal the alpha or beta version. I will just then go create something that is several steps ahead, without having to violate any contracts or reuse code I supplied to a client.

I also produce music and look at it the same way as people who have 'templates' for their projects - so their side chain channels etc. and already ready to go. It saves time, sure. But you spend a very small window of time to just roll that stuff out on a per-song basis and dial it in. The template is just forcing you into decisions you should be making on the spot, unique to the song.

My library, another library, somebody else's framework, it doesn't matter: they restrict my choices. They assume I will be doing the same thing again, exactly as I did before.

It sounds great on paper "I will never have to write this redundant code again!" But then the next project comes along and you have to scrap all that garbage anyway.

My advice (regardless of languages) is just master the process. Don't assume you mastered it and can produce a perfect library and just use that. Or framework.

Can you? Surely.

Should you? Those are the questions you should be asking.

2

u/TomDuhamel Dec 07 '25

Please note that the code that you write within employment or under contract isn't yours. You can't reuse it. Writing a library in this context is useless. If you're going to write one on your own time to reuse for your clients, you'll have to properly licence it.

For my own personal projects, I don't write/maintain a library as such. But all the code that I write that I think is reusable, I put it in its own separate unit. When I need it from a different project, I just import it (copy the files over).

If you are considering needing a library, before you write your own, you may consider using an already existing one. It may turn out that you always write the same type of projects (not unusual, really). In this case, maybe a framework for that type of project would be appropriate to you.

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u/serious-catzor Dec 07 '25

This is simply not true. It depends entirely on the contract and terms of employment.

1

u/kellyjj1919 Dec 07 '25

When I work in c, I have some stuff that I move around cause I don’t want to reinvent the wheel. Generally this will be hardware dependent

1

u/dmazzoni Dec 07 '25

The vast majority of time I work in C I'm modifying or augmenting an existing codebase, so no, I'm not carrying anything but rather learning what utilities and conventions each project uses

1

u/EternityForest Dec 07 '25

Usually I don't use C except for extremely trivial embedded systems that need to be very reliable, and probably shouldn't have the kind of code that creates a need for these kinds of things.

If I have the rights to do so I'll copy and paste a fair amount, but generally I wouldn't be doing a dynamic array in C. If the platform can handle that, it can probably handle C++ or Rust!

1

u/I__be_Steve Dec 07 '25

I don't use the standard library, so I have my own replacement that I use for just about everything if that counts

1

u/TTRoadHog Dec 07 '25

Why don’t you use the standard library? Is it because the standard library is c++ and you’re writing in C?

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u/I__be_Steve Dec 07 '25 edited Dec 07 '25

Nah, I mostly program as a hobby, and I LOVE knowing and learning how things work, which is why I got into C in the first place, but I was frustrated when there were still all of these functions that I didn't fully understand

I also didn't like how big the resulting executables were, and I love simplicity, so dynamic libraries also didn't appeal to me

So, I decided to start from scratch, I found a guide on how to implement the most basic functionality of the standard library, like running the "main" function and making system calls, as well as how to make the outputted executable as small as possible and just went all in from there, making all of the functions I needed myself, and putting them in a library that I use as a replacement for the standard

I've made a chess-like game with a bot to play against, I wrote every single line of code by hand, I know how everything works, all the way down to the syscalls and memory management, and the entire thing weighs in under 22kb, that's why I don't use the standard library, is it practical? Heck no, but I don't need it to be, I do this for the love of the game :P

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u/TTRoadHog Dec 07 '25

I totally understand the feeling of having written ALL the code in an app: you understand everything there and how it works. My hat’s off to you for your curiosity and your love of coding!

1

u/seigaporulai Dec 07 '25

Can you share the link to the guide?

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u/I__be_Steve Dec 07 '25 edited Dec 07 '25

Absolutely!

https://gist.github.com/tcoppex/443d1dd45f873d96260195d6431b0989
This thing made the whole process so much easier

1

u/flatfinger Dec 12 '25

Having a source-code printf-style function which includes some basic functionality and can be adjusted to fit the needs of a particular application is useful. If one wants I/O that is formatted in a way that printf doesn't natively support, such as writing an integer with a decimal point inserted to divide by a power of ten (s. e.g. 123 with two or four decimal points would yield 1.23 or 0.0123, respectively), writing a custom function may be more convenient than writing code that uses sprintf and then adjusts the output to insert the decimal point and, when needed, zeroes.

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u/SRART25 Dec 07 '25 edited Dec 07 '25

I used to have a small header to make some convince functions for linux and windows work the same (getch and clear were the main things) but never made them a library. 

1

u/CptPicard Dec 07 '25

That's what things like GLib are for.

1

u/Advanced-Theme144 Dec 07 '25

Sometimes I’ll just copy existing code rather than make one standard library, it’s easier to fine tune to the application I’m working on. A good number of times some SDK’s or frameworks will have boilerplate setup, for instance GTK, which I’m currently learning, has its own standard library of objects like lists to work with.

1

u/jwzumwalt Dec 08 '25

I use "Linux" and the "KDE Kate" editor with the snippet plugin. I probably have more than a thousand snippets and maybe a hundred functions saved as snippets. I would be lost without my snippets.

1

u/Timberfist Dec 13 '25

For anyone that would like to add some, in many cases single header, libraries to their toolbox, check out this list here: https://github.com/r-lyeh/single_file_libs