* [Bug c/84764] Wrong warning "so large that it is unsigned" for __int128 constant
[not found] <bug-84764-4@http.gcc.gnu.org/bugzilla/>
@ 2023-01-25 9:45 ` daniel.lundin.mail at gmail dot com
2023-01-25 10:36 ` redi at gcc dot gnu.org
` (2 subsequent siblings)
3 siblings, 0 replies; 4+ messages in thread
From: daniel.lundin.mail at gmail dot com @ 2023-01-25 9:45 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84764
Daniel Lundin <daniel.lundin.mail at gmail dot com> changed:
What |Removed |Added
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CC| |daniel.lundin.mail at gmail dot co
| |m
--- Comment #3 from Daniel Lundin <daniel.lundin.mail at gmail dot com> ---
This is a bug as in the wrong text is displayed in the diagnostic message. gcc
picks `__int128` and it is not an unsigned type.
Decimal integer constants use the the quoted list in 6.4.4.1: `int` then `long`
then `long long`. Therefore this normative text (from C99 to C23) applies: "If
all of the types in the list for the constant are signed, the extended integer
type shall be signed."
gcc behaves just like required too, since `__int128` ought to be one of the
extended integer types and it is signed.
I would guess this message is some remain from C90 where extended integer types
didn't exist. Compiling with -std=c90 adds an additional warning "warning: this
decimal constant is unsigned only in ISO C90". It would appear that this is the
correct warning that should always be displayed. Seems to be a minor bug that
occurred during the switch (gcc 5.0.0) from gnu90 to gnu11 as default option.
^ permalink raw reply [flat|nested] 4+ messages in thread* [Bug c/84764] Wrong warning "so large that it is unsigned" for __int128 constant
[not found] <bug-84764-4@http.gcc.gnu.org/bugzilla/>
2023-01-25 9:45 ` [Bug c/84764] Wrong warning "so large that it is unsigned" for __int128 constant daniel.lundin.mail at gmail dot com
@ 2023-01-25 10:36 ` redi at gcc dot gnu.org
2023-01-26 1:26 ` joseph at codesourcery dot com
2023-01-26 7:53 ` daniel.lundin.mail at gmail dot com
3 siblings, 0 replies; 4+ messages in thread
From: redi at gcc dot gnu.org @ 2023-01-25 10:36 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84764
--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Daniel Lundin from comment #3)
> gcc behaves just like required too, since `__int128` ought to be one of the
> extended integer types and it is signed.
But it's not an extended integer type, see comment 2.
I think that will change for C23, which allows intmax_t to be be defined to
long long even if there are larger extended integer types. But in GCC today,
there are no extended integer types.
^ permalink raw reply [flat|nested] 4+ messages in thread* [Bug c/84764] Wrong warning "so large that it is unsigned" for __int128 constant
[not found] <bug-84764-4@http.gcc.gnu.org/bugzilla/>
2023-01-25 9:45 ` [Bug c/84764] Wrong warning "so large that it is unsigned" for __int128 constant daniel.lundin.mail at gmail dot com
2023-01-25 10:36 ` redi at gcc dot gnu.org
@ 2023-01-26 1:26 ` joseph at codesourcery dot com
2023-01-26 7:53 ` daniel.lundin.mail at gmail dot com
3 siblings, 0 replies; 4+ messages in thread
From: joseph at codesourcery dot com @ 2023-01-26 1:26 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84764
--- Comment #5 from joseph at codesourcery dot com <joseph at codesourcery dot com> ---
Also, for it to become an extended integer type, it would be necessary to
define integer constant suffixes and implement printf / scanf support in
the library, because <stdint.h> is now required to provide intN_t /
uintN_t when there is a matching standard or extended integer type, so
would be required to provide int128_t / uint128_t, which in turn would
require the corresponding <stdint.h> and <inttypes.h> macros, so requiring
constant suffixes and printf / scanf support.
^ permalink raw reply [flat|nested] 4+ messages in thread* [Bug c/84764] Wrong warning "so large that it is unsigned" for __int128 constant
[not found] <bug-84764-4@http.gcc.gnu.org/bugzilla/>
` (2 preceding siblings ...)
2023-01-26 1:26 ` joseph at codesourcery dot com
@ 2023-01-26 7:53 ` daniel.lundin.mail at gmail dot com
3 siblings, 0 replies; 4+ messages in thread
From: daniel.lundin.mail at gmail dot com @ 2023-01-26 7:53 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84764
--- Comment #6 from Daniel Lundin <daniel.lundin.mail at gmail dot com> ---
Call it what you will, either way there is nothing here that's "so large that
it is unsigned". The main point is that the diagnostic message is wrong.
typeof(18446744073709551615) x = -1;
Gives a 128 bit integer type with the value -1. If it was "so large that it is
unsigned" then this would have resulted in an unsigned type with an unsigned
value. The diagnostic message is plain wrong and misleading.
^ permalink raw reply [flat|nested] 4+ messages in thread