Re: [akpm-mm:mm-new 36/102] error[E0425]: cannot find value `VM_READ` in crate `bindings`

[Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>]

On Fri, Oct 10, 2025 at 8:59 AM Miguel Ojeda
<miguel.ojeda.sandonis@gmail.com> wrote:
>
> The best would be to use C23-like `enum : unsigned long { ... }`, but
> sadly we don't have a recent enough GCC as a minimum in the kernel
> (GCC 13).

The `mode` attribute also influences the `enum` constants -- doing
something like:

    enum { ... } __mode(pointer);

will make `VM_MERGEABLE` either `long` or `unsigned long` depending on
the compiler and version.

So with:

    #ifdef __clang__
        #define __unsigned_long_enum : unsigned long
    #else
        #define __unsigned_long_enum __mode(pointer)
    #endif

And then using it like:

    enum __unsigned_long_enum { ... };

I can get quite close: old GCC will use `int` for smaller constants
and `unsigned long` for the bigger ones, and everything else (new GCC
and all Clangs) will use `unsigned long` for everything.

Perhaps this may be useful on its own for C in some cases.

Cheers,
Miguel