On 2020-10-01 14:54, Szabolcs Nagy wrote:
The 10/01/2020 12:14, Alejandro Colomar via Gcc wrote:
Here is the rendered intmax_t:
intmax_t
Include: <stdint.h>. Alternatively, <inttypes.h>.
A signed integer type capable of representing any value of any
signed integer type supported by the implementation. According
to the C language standard, it shall be capable of storing val-
ues in the range [INTMAX_MIN, INTMAX_MAX].
The macro INTMAX_C() expands its argument to an integer constant
of type intmax_t.
The length modifier for intmax_t for the printf(3) and the
scanf(3) families of functions is j; resulting commonly in %jd
or %ji for printing intmax_t values.
Bugs: intmax_t is not large enough to represent values of type
__int128 in implementations where __int128 is defined and long
long is less than 128 bits wide.
or __int128 is not an integer type.
integer types are either standard or extended.
and __int128 is neither because it can be
larger than intmax_t and stdint.h does not
provide the necessary macros for it.
Hi Szabolcs,
I know GCC decided to not call it an integer type, and call it instead a
scalar type, just to conform with the standards, at the same time
provide a 128 int, and at the same time, not have to change the ABI of
intmax_t.
But it looks like an integer type,
and in almost any possible way, it acts like an integer type.
I could call '__int128' a signed _scalar_ type in the description, but
that might confuse those who don't know these details. Do you think it
would be better to call it that way, or just keep the integer word?
(Jonathan, I'd also like to know your thoughts on this, BTW).
However, I would still have that bug documented, because in the end, the
information programmers need is exactly that, and they don't really care
if GCC calls it one way or the other just to avoid technical issues with
the standards, IMO.
Thanks,
Alex
BTW, the updated rendered version is like this right now:
[[
__int128
[signed] __int128
A signed integer type of a fixed width of exactly 128 bits.
// This could change to "signed scalar type", but...
When using GCC, it is supported only for targets where the com-
piler is able to generate efficient code for 128-bit arith-
metic".
Versions: GCC 4.6.0 and later.
Conforming to: This is a non-standard extension, present in GCC.
It is not standardized by the C language standard nor POSIX.
Notes: This type is available without including any header.
Bugs: It is not possible to express an integer constant of type
__int128 in implementations where long long is less than 128
bits wide.
See also the intmax_t, intN_t and unsigned __int128 types in
this page.
[...]
unsigned __int128
An unsigned integer type of a fixed width of exactly 128 bits.
// This could change to "signed scalar type", but...
According to GNU, it is supported only for targets where the
compiler is able to generate efficient code for 128-bit arith-
metic".
Versions: GCC 4.6.0 and later.
Conforming to: This is a non-standard extension, present in GCC.
It is not standardized by the C language standard nor POSIX.
Notes: This type is available without including any header.
Bugs: It is not possible to express an integer constant of type
unsigned __int128 in implementations where unsigned long long is
less than 128 bits wide.
See also the __int128, uintmax_t and uintN_t types in this page.
]]
