Re: Effect of CPP tags

Tim Rentsch <tr.17687@z991.linuxsc.com> writes:

Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:

[...]

(Aside: gcc has an extension adding __int128 as a keyword, supporting
types "__int128" and "unsigned __int128", but only on some target
systems.  These do not qualify as extended integer types.  I understand
that "__uint128_t" was a hypothetical example.)

>
On the systems I use the identifiers __int128_t and __uint128_t are
both predefined type names (and not keywords), under both gcc and
clang.  I see some support for __int128 as a keyword, but the
predefined type names seem to be more reliable (at least in my
environments).

That's odd.  The gcc documentation describes __int128 as an extension:
https://gcc.gnu.org/onlinedocs/gcc-13.2.0/gcc/_005f_005fint128.html

    As an extension the integer scalar type __int128 is supported for
    targets which have an integer mode wide enough to hold 128
    bits. Simply write __int128 for a signed 128-bit integer, or
    unsigned __int128 for an unsigned 128-bit integer. There is no
    support in GCC for expressing an integer constant of type __int128
    for targets with long long integer less than 128 bits wide.

It doesn't mention __int128_t or __uint128_t at all, though I see it
does recognize both, and as you say it doesn't treat them as keywords.
Likewise for clang, though I haven't checked the clang documentation.

(I might reply to other parts of your post later.)

--
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for Medtronic
void Void(void) { Void(); } /* The recursive call of the void */