Giving C a superpower: custom header file (safe_c.h)

Post by crosser » Tue, Nov 18, 2025, 2:37 PM UTC

cassepipe wrote: post #53

fuhsnn wrote: post #23

> C23 gave us [[cleanup]] attributes C23 didn't introduce it, it's still a GCC extension that needs to be spelled as [[gnu::cleanup()]] https://godbolt.org/z/Gsz9hs7TE

It is surprisingly hard to find information about it, do you have any ? From what I can guess it's a new syntax but it's the feature itself is still an extension ?

Post by 1718627440 » Tue, Nov 18, 2025, 3:24 PM UTC

Borg3 wrote: post #251

1718627440 wrote: post #209

Earlier quoted context omitted.

It also has different behaviour in a single thread. This can be what you want though, but I would prefer it to pass that context as a parameter instead of having it in a hidden static variable.

What different behaviour you mean? static in function means that this is just preallocated somewhere in data, not on stack nor heap. Thats it. Yes, its not thread safe so should never be used in libraries for any buffering. But in program, its not bad. If I ever need multiple calls to it in same thread: static char buf[8][32]; static int z; char *p=buf[z]; z=(z+1)&7; Works pretty well ;)

Post by 1718627440 » Tue, Nov 18, 2025, 5:44 PM UTC

uecker wrote: post #255

1718627440 wrote: post #210

Earlier quoted context omitted.

C does have the concept of lifetimes. There is just no syntax to specify it, so it is generally described along all the other semantic details of the API. And no it is not the same as for Rust, which causes clashes with the Rust people.

What clashes?

Post by uecker » Tue, Nov 18, 2025, 8:07 PM UTC

1718627440 wrote: post #256

uecker wrote: post #255

Earlier quoted context omitted.

What clashes?

I think there was a discussion in the Linux kernel between a kernel maintainer and the Rust people, which started by the Rust people demanding formal semantics, so that they could encode it in Rust, and the subsystem maintainer unwilling to do that.

Post by 1718627440 » Tue, Nov 18, 2025, 9:20 PM UTC

Borg3 wrote: post #257

1718627440 wrote: post #254

Earlier quoted context omitted.

> What different behaviour you mean? Static foremost means that the value is preserved from the last function invocation. This is very different behaviour, than an automatically allocated variable. So calling a function with a static variable isn't idempotent, even when all global variables are the same. > If I ever need multiple calls to it in same thread: What is this code supposed to do???? It hands out a differen…

If you want to return some precalculated stuff w/o using malloc() free(). So you just have 8 preallocated buffers and you rotate them between calls. Of course you need to be aware that results have short lifetime.