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layer8 | on: The C23 edition of Modern C
> no array bounds checking is possible.

This isn’t strictly true, a C implementation is allowed to associate memory-range (or more generally, pointer provenance) metadata with a pointer.

The DeathStation 9000 features a conforming C implementation which is known to catch all array bounds violations. ;)

trealira | parent | next
> The DeathStation 9000 features a conforming C implementation which is known to catch all array bounds violations. ;)

That actually really does exist already with CHERI CPUs, whose pointers are tagged with "capabilities," which catch buffer overruns at runtime.

https://tratt.net/laurie/blog/2023/two_stories_for_what_is_c...

https://msrc.microsoft.com/blog/2022/01/an_armful_of_cheris/

uecker | parent | next
Right. Also it might it sound like array-to-pointer decay is forced onto the programmer. Instead, you can take the address of an array just fine without letting it decay. The type then preserves the length.
WalterBright | root | parent | next
C: int foo(int a[]) { return a[5]; }

    int main() {
        int a[3];
        return foo(a);
    }

    > gcc test.c
    > ./a.out
Oops.

D: int foo(int[] a) { return a[5]; }

    int main() {
        int[3] a;
        return foo(a);
    }

    > ./cc array.d
    > ./array
    core.exception.ArrayIndexError@array.d(1): index [5] is out of bounds for array of length 3
Ah, Nirvana!

How to fix it for C:

https://www.digitalmars.com/articles/C-biggest-mistake.html

uecker | root | parent
You need to take the address of the array instead of letting it decay and then size is encoded in the type:

  int foo(int (*a)[6]) { return a[5]; }
  int main() {
  int a[3];
    return foo(&a);
  }
Or for run-time length:

  int foo(int n, int (*a)[n]) { return (\*a)[5]; }
  int main() {
    int a[3];
    return foo(ARRAY_SIZE(a), &a);
  }
  /app/example.c:4:38: runtime error: index 5 out of bounds for 
 type 'int[n]'
https://godbolt.org/z/dxx7TsKbK\*
codr7 | root | parent
Nice, when you know the length at compile time, which is rarely from my experience.

The holy grail is runtime access to the length, which means an array would have to be backed by something more elaborate.

uecker | root | parent
Oh, it also work for runtime length:

https://godbolt.org/z/PnaWWcK9o

pjmlp | root | parent
Now try that on a compiler without -fsanitize=bounds, yet full ISO C compliant.
TZubiri | parent
"The DeathStation 9000"

The what now?

bsder | root | parent | next
Nasal daemons for those of us of a slightly older vintage ...
layer8 | root | parent
Google it.
TZubiri | root | parent
Yeah, why have any type of human interaction in a forum when you can just refer your fellow brethren to the automaton.
layer8 | root | parent
I’m saying this because any explanation I could offer would provide less insight than the Google results.
TZubiri | root | parent
Less insight, perhaps, but of higher quality, which is subjective.

I personally find that googling stuff provides not much connection to the subject of study, very impersonal and try to avoid it.

For example I did google the concept, and found this https://github.com/cousteaulecommandant/ds9k.

Which is not trivial to parse, bing posited the answer as authoritative, and if you look at the code it is really nothing, it seems to be a folklore concept, and as such, it is much more aptly transmitted by speaking to a human and getting a live version than by googling an authoratitative static answer.