libstdc++: Extend __is_standard_integer to cover extended integer types

We have __is_signed_integer and __is_unsigned_integer traits which
should have been updated by r16-2190-g4faa42ac0dee2c when making
__int128 an extended integer type (for PR libstdc++/96710). Currently
they check whether the type is a signed integer type or an unsigned
integer type, or a cv-qualified version of one of those. This doesn't
match the standard's definition, which does not include cv-qualified
types. This change ensures that signed __int128 and unsigned __int128
are included in those traits in strict -std modes, and it removes the
use of remove_cv_t so that they are not true for cv-qualified types.
This makes the traits match the meaning of "signed integer type" and
"unsigned integer type" in the standard ([basic.fundamental]).

We also have an __is_standard_integer trait, which is true if either
__is_signed_integer or __is_unsigned_integer is true, but that's also
not a match for the definition in the standard. The definitions of
"signed integer type" and "unsigned integer type" include both standard
and extended integer types, so only saying "standard" in the trait name
is misleading (even before this change, because in non-strict -std modes
the __GLIBCXX_TYPE_INT_N_0 .. __GLIBCXX_TYPE_INT_N_3 types were always
included in the trait, and they aren't standard integer types).

This change renames __is_standard_integer to the more accurate
__is_signed_or_unsigned_integer. Because the set of signed and
unsigned integer types is the same as the set of standard and extended
integer types, the trait could instead have been renamed to
__is_standard_or_extended_integer. I think it's clearer and more
self-explanatory to avoid "standard and extended" and name it for the
signed and unsigned integer types.

N.B. we don't want to call it just __is_integer_type because the integer
types includes cv-qualified types and also bool and the character types
char, wchar_t, char16_t etc.

The consequences of redefining and renaming these traits are small, and
only positive.

Apart from the uses in the __is_standard_integer trait, the only other
uses of __is_signed_integer and __is_unsigned_integer are in <format>
and those uses are unaffected by this change to add 128-bit integers to
the traits. In both uses the type argument is already cv-unqualified,
and there is already explicit handling for 128-bit integers where that
is required.

The existing uses of __is_standard_integer can simply be changed to use
the new name. This does change the behaviour of those uses of the trait,
because the __is_signed_or_unsigned_integer trait now includes
128-bit integers in strict modes. However, that is a desirable change
that fixes some bugs. Specifically, the [utility.intcmp] functions such
as std::cmp_less and the [numeric.sat.arith] functions such as
std::add_sat did not support 128-bit integers in strict modes. Since the
standard says they should be enabled for all signed and unsigned integer
types (or equivalently, for all standard and extended integer types),
those functions should all support __int128 and unsigned __int128. That
is fixed by this change.  Additionally, the same changes in <charconv>,
<mdspan>, and <stdckdint.h> enable the use of 128-bit integers for those
APIs in strict modes.

Finally, this also make a drive-by fix to the enable_if constraints for
the integer overloads of std::from_chars. That used remove_cv_t and so
enabled the overload for lvalue arguments of type const char, which
won't work and should not be enabled.

libstdc++-v3/ChangeLog:

	* include/bits/intcmp.h: Replace all uses of
	__is_standard_integer with __is_signed_or_unsigned_integer.
	* include/bits/max_size_type.h: Fix outdated comment.
	* include/bits/sat_arith.h: Replace all uses of
	__is_standard_integer with __is_signed_or_unsigned_integer.
	* include/c_compatibility/stdckdint.h: Replace all uses of the
	__cv_unqual_signed_or_unsigned_integer_type concept with
	__is_signed_or_unsigned_integer.
	(__cv_unqual_signed_or_unsigned_integer_type): Remove.
	* include/ext/numeric_traits.h: Fix outdated comment.
	* include/std/charconv (from_chars): Replace use of
	__is_standard_integer with __is_signed_or_unsigned_integer.
	Do not enable for cv-qualified char.
	* include/std/mdspan: Likewise.
	* include/std/type_traits (__is_unsigned_integer): Include
	unsigned __int128 in type list.
	(__is_signed_integer): Include signed __int128 in type list.
	(__is_standard_integer): Rename to ...
	(__is_signed_or_unsigned_integer): ... this.
	* testsuite/23_containers/mdspan/extents/ctor_ints.cc: Test
	with 128-bit integers.
	* testsuite/23_containers/mdspan/submdspan/strided_slice.cc:
	Likewise.
	* testsuite/20_util/integer_comparisons/extended.cc: New test.
	* testsuite/26_numerics/saturation/extended.cc: New test.
	* testsuite/26_numerics/stdckdint/extended.cc: New test.

Reviewed-by: Patrick Palka <ppalka@redhat.com>

0 files changed, 0 insertions, 0 deletions