Item — HN Reader

I plan to bring such a proposal forward for the next version. Note that C already has everything to do this without much overhead, e.g. in C23 you can write:

  int N = 10;
  char buf[N] = { };
  auto x = &buf;

and 'x' has a slice type that automatically remebers the size. This works today with GCC / clang (with extensions or C2X language mode: https://godbolt.org/z/cMbM57r46 ).

We simply can not name it without referring to N and we can also not use it in structs (ouch).

1 comments

You know what i think about auto :-)

How is this not a quality of implementation issue? Any implementation is free to track all sizes as much as they want with the current standard.

Either a implementation is forced to issue an error at run time if there is an out of bounds read/write and in that case its a very different language than C, or its feature as-if lets any implementation ignore.

Tracking sizes for purposes of bounds checking is QoI and I think this is perfectly fine. But here we can also recover the size with sizeof, so it is also required for compliance:

https://godbolt.org/z/qh7P93Tcd

And I agree that this is a misuse of auto. I only used it here to show that the type we miss already exists inside the C compiler, we simply can name it only by constructing it again:

char (buf)[N] = ...

but we could simply allow

char (buf)[:] =

and be done (as suggested by Dennis Richtie: https://www.bell-labs.com/usr/dmr/www/vararray.pdf)