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From: Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: _BitInt(N)
Date: Mon, 01 Dec 2025 18:21:00 -0800
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antispam@fricas.org (Waldek Hebisch) writes:
[...]
> I see nothing in the standard that prevents '_BitInt(64)' and 'long'
> to be the same type.  And AFICS promotion rules are the only thing
> which prevents 'uint8_t' and '_BitInt(8)' to be the same type.
> Maybe I missed something, but I have read posts that appeared here
> and I saw nothing indicating otherwise.

My initial reaction is that *obviously* _BitInt(64) and long are
distinct types.  But what's obvious isn't always true.

Nevertheless ...

Looking through N3220 6.2.5 (Types), it specifies several groups of
types: standard signed integer types, bit-precise signed integer
type, extended signed integer types, and their corresponding
unsigned types.  It's "obvious" that these sets are meant to be
disjoint, but it doesn't actually say so.

But section 6.3.1.1 defines the concept of *integer conversion rank*.
In particular :

    The rank of any standard integer type shall be greater than
    the rank of any extended integer type with the same width or
    bit-precise integer type with the same width.

So even if long has a width of 64 bits and exactly the same
representation as _BitInt(64), it has a greater integer conversion
rank, so it can't be the same type.

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
void Void(void) { Void(); } /* The recursive call of the void */