Stupid Smart Pointers in C

#1

Post by seansh » Mon, Mar 17, 2025, 11:29 AM UTC

Stupid Smart Pointers in C
blog.kevinalbs.com

Re: Stupid Smart Pointers in C

#2

Post by adrianN » Mon, Mar 17, 2025, 12:04 PM UTC

I wonder how that affects compiler optimization

Re: Stupid Smart Pointers in C

#3

Post by pjdesno » Mon, Mar 17, 2025, 12:10 PM UTC

Note that this will probably cause branch prediction misses, just like thread switching does - modern CPUs have a return address predictor which is just a simple stack. I don’t think you can avoid this without compiler support.

Re: Stupid Smart Pointers in C

#4

Post by dhsysusbsjsi » Mon, Mar 17, 2025, 12:14 PM UTC

adrianN wrote: post #2

I wonder how that affects compiler optimization

and stack protection cookies

Re: Stupid Smart Pointers in C

#5

Post by rwmj » Mon, Mar 17, 2025, 12:14 PM UTC

Really, don't do this, it's a portability and safety nightmare (aside from C not being memory safe already).

C programmers are better off with either of these two techniques:

* Use __attribute__((cleanup)). It's available in GCC and Clang, and we hope will be added to the C spec one day. This is widely used by open source software, eg. in systemd.

* Use a pool allocator like Samba's talloc (https://talloc.samba.org/talloc/doc/html/libtalloc__tutorial...) or Apache's APR.

(I didn't include using reference counting, since although that is also widely used, I've seen it cause so many bugs, plus it interacts badly with how modern CPUs work.)

Re: Stupid Smart Pointers in C

#6

Post by bsenftner » Mon, Mar 17, 2025, 12:39 PM UTC

[flagged]

Re: Stupid Smart Pointers in C

#7

Post by scoopr » Mon, Mar 17, 2025, 12:41 PM UTC

Oh well, maybe we'll soon have `defer`? [0]

[0] https://thephd.dev/c2y-the-defer-technical-specification-its...

Re: Stupid Smart Pointers in C

#8

Post by abcd_f » Mon, Mar 17, 2025, 12:41 PM UTC

Hacky and not really fit for production for more reasons than one, but clever and nice nonetheless. Good stuff.

Re: Stupid Smart Pointers in C

#9

Post by MrBuddyCasino » Mon, Mar 17, 2025, 12:47 PM UTC

rwmj wrote: post #5

Really, don't do this, it's a portability and safety nightmare (aside from C not being memory safe already). C programmers are better off with either of these two techniques: * Use __attribute__((cleanup)). It's available in GCC and Clang, and we hope will be added to the C spec one day. This is widely used by open source software, eg. in systemd. * Use a pool allocator like Samba's talloc ( https://talloc.samba.org/…

> __attribute__((cleanup))

Interesting. I'm not very proficient in C, this looks like some sort of finalizers for local variables?

Re: Stupid Smart Pointers in C

#10

Post by feverzsj » Mon, Mar 17, 2025, 12:49 PM UTC

Just C programmer's daily struggle to mimic a fraction of C++.