Type Safe Generic Data Structures in C

Type Safe Generic Data Structures in C(danielchasehooper.com)

79 points by AlexeyBrin 2 days ago | 19 comments

Panzerschrek 36 minutes 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++?

uecker 4 minutes 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.

rwbt 11 minutes 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++.

Joker_vD 29 minutes 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.

kccqzy 14 minutes 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. LLVM forbids including <iostream>. You can forbid using parts of the standard library too.

lor_louis 2 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.

veexx103 1 hour ago |

Is it feasible to create a new language by adding features to C

just as was done with C++?

pjmlp 1 hour ago | |

And Objective-C, yet somehow people reinvent them badly in C.

nikbackm 1 hour ago | |

There are already plenty of such languages, Zig among others.

peesem 57 minutes ago | | |

zig doesn't "extend" C in the way that C++ does.

tniemi 1 hour 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...

JdeBP 42 minutes 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):...) .

Xirdus 1 hour ago | |

Expressions that compile but never evaluate are bread and butter in C++ template metaprogramming.

rramadass 2 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.

podocarp 2 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

nice_byte 1 hour 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.

carlos256 1 hour 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.

pjmlp 1 hour ago | |

The extent some will go to avoid touching C++.