Seriously please can all of you other programmers stop pointlessly abbreviating things that are already quite short?! "read_path" is perfectly fine.
I think, the main point is to make it as easy as possible to use.
The core issue is that userspace programs and libraries can be compiled using structs with the old size (in theory the libc can abstract this using symbol versioning but then the same issue lies within the libc) causing out-of-bounds memory accesses when the kernel tries to access the struct fields. There's also forwards-compatibility issues but bad memory accesses are marginally worse.
I (obviously) prefer the extensible struct solution but there are downsides (and other solutions weren't an option for Linux anyway).
>This mechanism works by marshaling parameters to a system call into a single C structure; a pointer to that structure and the size of the structure are passed as the parameters to the system call. That size parameter acts as a sort of version number.
Oh hey, that’s exactly how every WIN32 call works. I see an article from 2003 talking about why Windows is strict about the struct size parameter: https://devblogs.microsoft.com/oldnewthing/20031212-00/?p=41...
> You can't trivially extend structs in a kernel ABI
IMO the article you linked is evidence that this is trivial. Especially for syscalls that will only be called a few times in a process’s lifetime. I dunno why there’s so much bike shedding about this on the mailing list.
Edit: Ahh I didn’t realize you were the Aleksa mentioned in the article. I wish you good luck.
But yes, it is relatively trivial -- my point was more that you can't just use a struct in the way the first comment suggested, you need to come up with some scheme (even if it seems trivial in retrospect).
As for the bike-shedding, that's LKML for you (though in fairness it is a bit of a tall order to try to come up with some enforceable API design rules in Linux -- syscalls with half-baked designs being added is less rare than one would hope, so clearly there's not an overarching design principle being applied already, though thankfully it's becoming pretty rare to see a completely borked syscall that clearly has no users being merged).
> Although using strings subverts C’s already weak type checking, that’s probably not a major concern. One can screw up bit masks by using || in place of |. Or, as above, one can incorrectly pack the magic array. It’s usually much easier to visually audit a string than the C code used to plaster a dozen option together.
It's pretty easy to design an interface that is way way less error-prone than strings (especially ones full of single-letter differences!) and the visual auditing argument falls apart as soon as you have to `snprintf()` some string together from parts.
This code is way more readable, way less error prone, more discoverable, faster and more easily extendable than strings:
auto config = make_pledge_config();
config.read_path = true;
config.stdio = true;
pledge(&config);