The concept __integral_constant_like doesn't consider traits with a
boolean member `value` as an integer constant. This is done to reject
various completely unrelated traits like is_const, is_abstract, etc.
LWG4351 adjusts the check to strip references and cv qualifiers before
checking if `value` is bool. The immediate context is constant_wrapper
which defines:
template<...>
struct constant_wrapper
{
static constexpr const auto& value = ...;
};
Without LWG4351, std::cw<true> and std::cw<false> would both be
considered integer constants (by __integral_constant_like); but both
std::{true,false}_type are not considered integer constants. Hence,
LWG4351 removes inconsistent behaviour between std::integral_constant
and std::constant_wrapper.
libstdc++-v3/ChangeLog:
* include/std/span (__integral_constant_like): Use
remove_cvref_t before checking if _Tp::value is boolean.
* testsuite/23_containers/mdspan/extents/misc.cc: Update test.
* testsuite/23_containers/mdspan/mdspan.cc: Ditto.
* testsuite/23_containers/span/deduction.cc: Ditto.
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>
A usecase for P2781R9 is more ergonomic creation of span and mdspan with
mixed static and dynamic extents, e.g.:
span(ptr, cw<3>)
extents(cw<3>, 5, cw<7>)
mdspan(ptr, cw<3>, 5, cw<7>)
should be deduced as:
span<..., 3>
extents<..., 3, dyn, 7>
mdspan<..., extents<..., 3, dyn, 7>>
The change required is to strip cv-qualifiers and references from
`_Tp::value`, because of:
template<_CwFixedValue _X, typename>
struct constant_wrapper : _CwOperators
{
static constexpr const auto& value = _X._M_data;
libstdc++-v3/ChangeLog:
* include/std/span (__integral_constant_like): Allow the member
`value` of a constant wrapping type to be a const reference of
an integer.
* testsuite/23_containers/mdspan/extents/misc.cc: Add test for
cw and constant_wrapper.
* testsuite/23_containers/mdspan/mdspan.cc: Ditto.
* testsuite/23_containers/span/deduction.cc: Ditto.
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com>
Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>
As the bug report shows, for span<const bool> the return statements of
the form `return {data(), count};` will use the new C++26 constructor,
span(initializer_list<element_type>).
Although the conversions from data() to bool and count to bool are
narrowing and should be ill-formed, in system headers the narrowing
diagnostics are suppressed. In any case, even if the compiler diagnosed
them as ill-formed, we still don't want the initializer_list constructor
to be used. We want to use the span(element_type*, size_t) constructor
instead.
Replace the braced-init-list uses with S(data(), count) where S is the
correct return type. We need to make similar changes in the C++26
working draft, which will be taken care of via an LWG issue.
libstdc++-v3/ChangeLog:
PR libstdc++/120997
* include/std/span (span::first, span::last, span::subspan): Do
not use braced-init-list for return statements.
* testsuite/23_containers/span/120997.cc: New test.
This implements P3029R1. In P3029R1, the CTAD for span is refined to
permit deducing the extent of the span from an integral constant, e.g.
span((T*) ptr, integral_constant<size_t, 5>{});
is deduced as span<T, 5>. Similarly, in
auto exts = extents(integral_constant<int, 2>);
auto md = mdspan((T*) ptr, integral_constant<int, 2>);
exts and md have types extents<size_t, 2> and mdspan<double,
extents<size_t, 2>>, respectively.
PR libstdc++/120914
libstdc++-v3/ChangeLog:
* include/std/span (span): Update CTAD to enable
integral constants [P3029R1].
* include/std/mdspan (extents): ditto.
(mdspan): ditto.
* testsuite/23_containers/span/deduction.cc: Test deduction
guide.
* testsuite/23_containers/mdspan/extents/misc.cc: ditto.
* testsuite/23_containers/mdspan/mdspan.cc: ditto.
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com>
Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>
This destructor declaration serves no purpose, as pointed out by LWG
3903 which was approved at Varna, June 2023.
libstdc++-v3/ChangeLog:
* include/std/span (span::~span): Remove, as per LWG 3903.
Reviewed-by: Patrick Palka <ppalka@redhat.com>
This commit implements P2447R6. The code is straightforward (just one
extra constructor, with constraints and conditional explicit).
I decided to suppress -Winit-list-lifetime because otherwise it would
give too many false positives. The new constructor is meant to be used
as a parameter-passing interface (this is a design choice, see
P2447R6/§2) and, as such, the initializer_list won't dangle despite
GCC's warnings.
The new constructor isn't 100% backwards compatible. A couple of
examples are included in Annex C, but I have also lifted some more
from R4. A new test checks for the old and the new behaviors.
libstdc++-v3/ChangeLog:
* include/bits/version.def: Add the new feature-testing macro.
* include/bits/version.h: Regenerate.
* include/std/span: Add constructor from initializer_list.
* testsuite/23_containers/span/init_list_cons.cc: New test.
* testsuite/23_containers/span/init_list_cons_neg.cc: New test.
Signed-off-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
Any std::span<T, N> constructor with a runtime length has a precondition
that the length is equal to N (except when N == std::dynamic_extent).
Currently every constructor with a runtime length does:
if constexpr (extent != dynamic_extent)
__glibcxx_assert(n == extent);
We can move those assertions into the __detail::__extent_storage<N>
constructor so they are only done in one place. To avoid checking the
assertions when we have a constant length we can add a second
constructor which is consteval and takes a integral_constant<size_t, N>
argument. The std::span constructors can pass a size_t for runtime
lengths and a std::integral_constant<size_t, N> for constant lengths
that don't need to be checked.
The __detail::__extent_storage<dynamic_extent> specialization only needs
one constructor, as a std::integral_constant<size_t, N> argument can
implicitly convert to size_t.
For the member functions that return a subspan with a constant extent we
return std::span<T,C>(ptr, C) which is redundant in two ways. Repeating
the constant length C when it's already a template argument is
redundant, and using the std::span(T*, size_t) constructor implies a
runtime length which will do a redundant assertion check. Even though
that assertion won't fail and should be optimized away, it's still
unnecessary code that doesn't need to be instantiated and then optimized
away again. We can avoid that by adding a new private constructor that
only takes a pointer (wrapped in a custom tag struct to avoid
accidentally using that constructor) and automatically sets _M_extent to
the correct value.
libstdc++-v3/ChangeLog:
* include/std/span (__detail::__extent_storage): Check
precondition in constructor. Add consteval constructor for valid
lengths and deleted constructor for invalid constant lengths.
Make member functions always_inline.
(__detail::__span_ptr): New class template.
(span): Adjust constructors to use a std::integral_constant
value for constant lengths. Declare all specializations of
std::span as friends.
(span::first<C>, span::last<C>, span::subspan<O,C>): Use new
private constructor.
(span(__span_ptr<T>)): New private constructor for constant
lengths.
As PR c++/117966 shows, the Debug Mode checks cause a compilation error
for a global constexpr std::span. Those debug checks are redundant when
constructing from an array or a range, because we already know we have a
valid range and we know its size. Instead of delegating to the
std::span(contiguous_iterator, contiguous_iterator) constructor, just
initialize the data members directly.
libstdc++-v3/ChangeLog:
PR libstdc++/117966
* include/std/span (span(T (&)[N])): Do not delegate to
constructor that performs redundant checks.
(span(array<T, N>&), span(const array<T, N>&)): Likewise.
(span(Range&&), span(const span<T, N>&)): Likewise.
* testsuite/23_containers/span/117966.cc: New test.
Because std::span<Incomplete> can be useful, it makes sense to define
std::span<Incomplete>::iterator such that Incomplete is not an
associated class, and so the compiler won't attempt to complete it when
doing ADL for span iterators (including during the definition of
std::span<Incomplete>::const_iterator which checks that iterator
satisfies std::input_or_output_iterator).
We can't make this change for std::vector<Incomplete> because it would
change the mangled name of std::vector<Incomplete>::iterator which would
affect the mangled names of templates and functions written by users.
We can do the same thing for std::basic_stacktrace<Alloc> just so that
Alloc is not an associated class. This is probably less beneficial, as
Alloc can't be incomplete, and using SomeAllocator<Incomplete> as the
allocator parameter doesn't seem useful. But simply making the
stacktrace iterator not use Alloc for ADL lookup seems worthwhile. This
is doable because std::stacktrace is part of C++23 so its ABI isn't
considered stable yet.
libstdc++-v3/ChangeLog:
* include/std/span (span::__iter_tag): Declare nested type.
(span::iterator): Use __iter_tag as second template argument.
* include/std/stacktrace (basic_stacktrace::iterator): Use _Impl
as second template argument.
In r14-5689-g1fa85dcf656e2f I added std::span::at and made the correct
changes to the __cpp_lib_span macro (with tests for the correct value in
C++20/23/26). But I didn't make the declaration of std::span::at
actually depend on the macro, so it was defined for C++20 and C++23, not
only for C++26. This fixes that oversight.
libstdc++-v3/ChangeLog:
PR libstdc++/115335
* include/std/span (span::at): Guard with feature test macro.
Also define the new feature test macros from P2833R2, indicating that
std::span and std::expected are supported for freestanding mode.
libstdc++-v3/ChangeLog:
* include/bits/version.def (freestanding_expected): New macro.
(span): Add C++26 value.
* include/bits/version.h: Regenerate.
* include/std/expected (__glibcxx_want_freestanding_expected):
Define.
* include/std/span (span::at): New member function.
* testsuite/20_util/expected/version.cc: Add checks for
__cpp_lib_freestanding_expected.
* testsuite/23_containers/span/2.cc: Moved to...
* testsuite/23_containers/span/version.cc: ...here. Add checks
for __cpp_lib_span in <span> as well as in <version>.
* testsuite/23_containers/span/1.cc: Removed.
* testsuite/23_containers/span/at.cc: New test.
All std::span member functions are pure functions that have no side
effects. They are only useful for their return value, so they should all
warn if that value is not used.
libstdc++-v3/ChangeLog:
* include/std/span (span, as_bytes, as_writable_bytes): Add
[[nodiscard]] attribute on all non-void functions.
* testsuite/23_containers/span/back_assert_neg.cc: Suppress
nodiscard warning.
* testsuite/23_containers/span/back_neg.cc: Likewise.
* testsuite/23_containers/span/first_2_assert_neg.cc: Likewise.
* testsuite/23_containers/span/first_assert_neg.cc: Likewise.
* testsuite/23_containers/span/first_neg.cc: Likewise.
* testsuite/23_containers/span/front_assert_neg.cc: Likewise.
* testsuite/23_containers/span/front_neg.cc: Likewise.
* testsuite/23_containers/span/index_op_assert_neg.cc: Likewise.
* testsuite/23_containers/span/index_op_neg.cc: Likewise.
* testsuite/23_containers/span/last_2_assert_neg.cc: Likewise.
* testsuite/23_containers/span/last_assert_neg.cc: Likewise.
* testsuite/23_containers/span/last_neg.cc: Likewise.
* testsuite/23_containers/span/subspan_2_assert_neg.cc:
Likewise.
* testsuite/23_containers/span/subspan_3_assert_neg.cc:
Likewise.
* testsuite/23_containers/span/subspan_4_assert_neg.cc:
Likewise.
* testsuite/23_containers/span/subspan_5_assert_neg.cc:
Likewise.
* testsuite/23_containers/span/subspan_6_assert_neg.cc:
Likewise.
* testsuite/23_containers/span/subspan_assert_neg.cc: Likewise.
* testsuite/23_containers/span/subspan_neg.cc: Likewise.
* testsuite/23_containers/span/nodiscard.cc: New test.
The default constructor has a constraint that is always false if
arithmetic on size_t values promotes to int. Rewrite the constraint
exactly as written in the standard, which works correctly.
libstdc++-v3/ChangeLog:
PR libstdc++/108221
* include/std/span (span::span()): Un-simplify constraint to
work for size_t of lesser rank than int.
In PR libstdc++/103013 Tim Song pointed out that we could reorder the
constraints of this constructor. That's worth doing just to reduce the
work the compiler has to do during overload resolution, even if it isn't
needed to make the code in the PR work.
libstdc++-v3/ChangeLog:
* include/std/span (span(Range&&)): Reorder constraints.
This implements P1739R4 along with the resolution for LWG 3407 which
corrects the paper's wording.
libstdc++-v3/ChangeLog:
* include/bits/ranges_util.h (views::_Drop): Forward declare.
(subrange): Befriend views::_Drop.
(subrange::_S_store_size): Declare constexpr instead of just
const, remove obsolete comment.
* include/std/ranges (views::__detail::__is_empty_view): Define.
(views::__detail::__is_basic_string_view): Likewise.
(views::__detail::__is_subrange): Likewise.
(views::__detail::__is_iota_view): Likewise.
(views::__detail::__can_take_view): Rename template parm _Tp to _Dp.
(views::_Take): Rename template parm _Tp to _Dp, make it non-deducible
and fix it to range_difference_t<_Range>. Implement P1739R4 and
LWG 3407 changes.
(views::__detail::__can_drop_view): Rename template parm _Tp to _Dp.
(views::_Drop): As with views::_Take.
(views::_Counted): Implement P1739R4 changes.
* include/std/span (__detail::__is_std_span): Rename to ...
(__detail::__is_span): ... this and turn it into a variable
template.
(__detail::__is_std_array): Turn it into a variable template.
(span::span): Adjust uses of __is_std_span and __is_std_array
accordingly.
* testsuite/std/ranges/adaptors/p1739.cc: New test.
The std::as_writable_bytes function should be constrained to only accept
writable spans. Currently it can be called but then gives an error in
the function body.
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:
PR libstdc++/101411
* include/std/span (as_writable_bytes): Add requires-clause.
* testsuite/23_containers/span/101411.cc: New test.
This implements the wording changes of P2325R3 "Views should not be
required to be default constructible". Changes are relatively
straightforward, besides perhaps those to __box (which now stands
for copyable-box instead of semiregular-box) and __non_propagating_cache.
For __box, this patch implements the recommended practice to also avoid
std::optional when the boxed type is nothrow_move/copy_constructible.
For __non_propagating_cache, now that it's used by split_view::_M_current,
we need to add assignment from a value of the underlying type to the
subset of the std::optional API implemented for the cache (needed by
split_view::begin()). Hence the new __non_propagating_cache::operator=
overload.
In passing, this fixes the undesirable list-init in the constructors of
the partial specialization of __box as reported in PR100475 comment #7.
libstdc++-v3/ChangeLog:
* include/bits/iterator_concepts.h (weakly_incrementable): Remove
default_initializable requirement.
* include/bits/ranges_base.h (ranges::view): Likewise.
* include/bits/ranges_util.h (subrange): Constrain the default
ctor.
* include/bits/stl_iterator.h (back_insert_iterator): Remove the
default ctor.
(front_insert_iterator): Likewise.
(insert_iterator): Likewise. Remove NSDMIs.
(common_iterator): Constrain the default ctor.
(counted_iterator): Likewise.
* include/bits/stream_iterator.h (ostream_iterator): Remove the
default ctor.
* include/std/ranges (__detail::__box::operator=): Handle
self-assignment in the primary template.
(__detail::__box): In the partial specialization: adjust
constraints as per P2325. Add specialized operator= for the
case when the wrapped type is not copyable. Constrain the
default ctor. Avoid list-initialization.
(single_view): Constraint the default ctor.
(iota_view): Relax semiregular constraint to copyable.
Constrain the default ctor.
(iota_view::_Iterator): Constraint the default ctor.
(basic_istream_view): Remove the default ctor. Remove NSDMIs.
Remove redundant checks for empty _M_stream.
(basic_istream_view::_Iterator): Likewise.
(ref_view): Remove the default ctor. Remove NSDMIs.
(ref_view::_Iterator): Constrain the default ctor.
(__detail::__non_propagating_cache::operator=): Define overload
for assigning from a value of the underlying type.
(filter_view): Likewise.
(filter_view::_Iterator): Likewise.
(transform_view): Likewise.
(transform_view::_Iterator): Likewise.
(take_view): Likewise.
(take_view::_Iterator): Likewise.
(take_while_view): Likewise.
(take_while_view::_Iterator): Likewise.
(drop_while_view): Likewise.
(drop_while_view::_Iterator): Likewise.
(join_view): Likewise.
(split_view::_OuterIter::__current): Adjust after changing the
type of _M_current.
(split_view::_M_current): Wrap it in a __non_propagating_cache.
(split_view::split_view): Constrain the default ctor.
(common_view): Constrain the default ctor.
(reverse_view): Likewise.
(elements_view): Likewise.
* include/std/span (enable_view<span<_ElementType, _Extent>>):
Define this partial specialization to true unconditionally.
* include/std/version (__cpp_lib_ranges): Adjust value.
* testsuite/24_iterators/back_insert_iterator/constexpr.cc:
Don't attempt to default construct a back_insert_iterator.
* testsuite/24_iterators/front_insert_iterator/constexpr.cc:
Don't attempt to default construct a front_insert_iterator.
* testsuite/24_iterators/insert_iterator/constexpr.cc:
Don't attempt to default construct an insert_iterator.
* testsuite/24_iterators/ostream_iterator/requirements/constexpr.cc:
Remove this test for default constructibility of ostream_iterator.
* testsuite/std/ranges/97600.cc: Don't attempt to default
construct a basic_istream_view.
* testsuite/std/ranges/adaptors/detail/semiregular_box.cc:
Rename to ...
* testsuite/std/ranges/adaptors/detail/copyable_box.cc: ... this.
(test02): Adjust now that __box is copyable-box not
semiregular-box.
(test03): New test.
* testsuite/std/ranges/p2325.cc: New test.
* testsuite/std/ranges/single_view.cc (test06): New test.
* testsuite/std/ranges/view.cc: Adjust now that view doesn't
require default_initializable.
This change reorders the data members of std::span so that span<byte> is
layout-compatible with common implementations of struct iovec. This will
allow span<byte> to be used directly in places that use a struct iovec
to do scatter-gather I/O.
It's important to note that POSIX doesn't specify the order of members
in iovec. Also the equivalent type on Windows has members in the other
order, and uses type ULONG (which is always 32-bit whereas size_t is
64-bit for Win64). So this change will only help for certain targets and
an indirection between std::span and I/O system calls will still be
needed for the general case.
libstdc++-v3/ChangeLog:
PR libstdc++/95609
* include/std/span (span): Reorder data members to match common
implementations of struct iovec.
* testsuite/23_containers/span/layout_compat.cc: New test.
This introduces two new headers:
<bits/ranges_base.h> defines the minimal components needed
for using C++20 ranges (customization point objects such as
std::ranges::begin, concepts such as std::ranges::range, etc.)
<bits/ranges_util.h> includes <bits/ranges_base.h> and additionally
defines subrange, which is needed by <bits/ranges_algo.h>.
Most of the content of <bits/ranges_base.h> was previously defined in
<bits/range_access.h>, but a few pieces were only defined in <ranges>.
This meant the entire <ranges> header was needed in <algorithm> and
<memory>, even though they don't use all the range adaptors.
By moving the ranges components out of <bits/range_access.h> that file
is left defining just the contents of [iterator.range] i.e. std::begin,
std::end, std::size etc. and not C++20 ranges components.
For consistency with other C++20 ranges headers, <bits/range_cmp.h> is
renamed to <bits/ranges_cmp.h>.
libstdc++-v3/ChangeLog:
* include/Makefile.am: Add new headers and adjust for renamed
header.
* include/Makefile.in: Regenerate.
* include/bits/iterator_concepts.h: Adjust for renamed header.
* include/bits/range_access.h (ranges::*): Move to new
<bits/ranges_base.h> header.
* include/bits/ranges_algobase.h: Include new <bits/ranges_base.h>
header instead of <ranges>.
* include/bits/ranges_algo.h: Include new <bits/ranges_util.h>
header.
* include/bits/range_cmp.h: Moved to...
* include/bits/ranges_cmp.h: ...here.
* include/bits/ranges_base.h: New header.
* include/bits/ranges_util.h: New header.
* include/experimental/string_view: Include new
<bits/ranges_base.h> header.
* include/std/functional: Adjust for renamed header.
* include/std/ranges (ranges::view_base, ranges::enable_view)
(ranges::dangling, ranges::borrowed_iterator_t): Move to new
<bits/ranges_base.h> header.
(ranges::view_interface, ranges::subrange)
(ranges::borrowed_subrange_t): Move to new <bits/ranges_util.h>
header.
* include/std/span: Include new <bits/ranges_base.h> header.
* include/std/string_view: Likewise.
* testsuite/24_iterators/back_insert_iterator/pr93884.cc: Add
missing <ranges> header.
* testsuite/24_iterators/front_insert_iterator/pr93884.cc:
Likewise.
For a span with statically empty extent, we currently model the
preconditions of front(), back(), and operator[] as if they are
mandates, by using a static_assert to verify that extent != 0. This
causes us to reject valid programs that would instantiate these member
functions and at runtime never call them.
Since they are already followed by more general runtime asserts, this
patch just removes these static_asserts altogether,
libstdc++-v3/ChangeLog:
* include/std/span (span::front): Remove static_assert.
(span::back): Likewise.
(span::operator[]): Likewise.
* testsuite/23_containers/span/back_neg.cc: Rewrite to verify
that we check the preconditions of back() only when it's called.
* testsuite/23_containers/span/front_neg.cc: Likewise for
front().
* testsuite/23_containers/span/index_op_neg.cc: Likewise for
operator[].
The 23_containers/span/deduction.cc test was already passing, but only
because I had previously implemented the original proposed resolution of
3255. As pointed out in 3255 that original P/R was incorrect because it
broke construction from array xvalues. This reverts the incorrect part
of 3255 (and adds tests for the case it broke), and implements the
resolution of 3369 instead.
* include/std/span (span(T (&)[N])): Use non-deduced context to
prevent first parameter from interfering with class template argument
deduction (LWG 3369).
* testsuite/23_containers/span/deduction.cc: Add missing 'const'.
* testsuite/23_containers/span/lwg3255.cc: Check for construction from
rvalues.
This includes fixes for first, last, as_bytes and as_writable_bytes
which were missing from the paper.
* include/std/span (__cpp_lib_span): Update value.
(span(It, size_type), span(It, End)): Make conditionally explicit. Add
assertion.
(span(R&&), span(const span<OType, OExtent>&)): Likewise and relax
constraints.
(span::first<Count>(), span::last<Count>()): Use explicit type in
return statement.
(as_bytes, as_writable_bytes): Likewise.
* include/std/version (__cpp_lib_span): Update value.
* testsuite/23_containers/span/1.cc: Check new value.
* testsuite/23_containers/span/2.cc: Check new value.
* testsuite/23_containers/span/explicit.cc: New test.
This makes the constraints consistent with the pre-Prague working paper.
* include/std/span (span::__is_compatible_array): Simplify alias
template by using requires-clause.
(span::__is_compatible_ref): New alias template for constraining
constructors.
(span::__is_compatible_iterator, span::__is_compatible_range): Remove.
(span(It, size_type), span(It, End)): Use __is_compatible_ref.
(span(T(&)[N], span(array<T, N>&), span(const array<T, N>&)): Remove
redundant parentheses.
(span(R&&)): Add missing constraints.
I find it easier to work with this class when the declarations match the
order in the C++2a working paper.
There's no need to use long, descriptive template parameter names like
_ContiguousIterator when the parameter is already constrained by the
std::contiguous_iterator concept. This is also consistent with the
naming conventions in the working paper.
* include/std/span (span): Reorder members and rename template
parameters to match declarations in the C++2a working paper.
Following this change it's no longer possible to use std::span with
structured bindings or with the tuple-like API. It will probably come
back for C++23 though.
P2116R0 Remove tuple-like protocol support from fixed-extent span
* include/std/span (get, tuple_size, tuple_element): Remove.
* testsuite/23_containers/span/everything.cc: Remove checks for
tuple-like API.
* testsuite/23_containers/span/get_neg.cc: Remove.
* testsuite/23_containers/span/tuple_element_dynamic_neg.cc: Remove.
* testsuite/23_containers/span/tuple_element_oob_neg.cc: Remove.
* testsuite/23_containers/span/tuple_size_neg.cc: Remove.
The deduction guide from an iterator and sentinel used the wrong alias
template and so didn't work.
PR libstdc++/93426
* include/std/span (span): Fix deduction guide.
* testsuite/23_containers/span/deduction.cc: New test.
As discussed at https://github.com/cplusplus/draft/issues/3534 two
std::span constructors specify incorrect conditions for throwing
exceptions. This patch makes those constructors have correct
noexcept-specifiers that accurately reflect what can actually throw.
(span(ContiguousIterator, Sentinel)): Add conditional noexcept.
* include/std/span (span(ContiguousIterator, size_type)): Change
noexcept to be unconditionally true.
* testsuite/23_containers/span/nothrow_cons.cc: New test.
From-SVN: r279206
This change replaces the __forwarding_range implementation detail with
the ranges::safe_range concept and adds the ranges::enable_safe_range
variable template for opt-in in to the concept.
It also adjusts the begin/end/rbegin/rend customization point objects to
match the new rules for accessing rvalue ranges only when safe to do so.
* include/bits/range_access.h (ranges::enable_safe_range): Define.
(ranges::begin, ranges::end, ranges::rbegin, ranges::rend): Constrain
to only accept types satisfying safe_range and treat argument as an
lvalue when calling a member of performing ADL.
(ranges::__detail::__range_impl, ranges::__detail::__forwarding_range):
Remove.
(ranges::range): Adjust definition.
(ranges::safe_range): Define.
(ranges::iterator_t, ranges::range_difference_t): Reorder definitions
to match the synopsis in the working draft.
(ranges::disable_sized_range): Remove duplicate definition.
* include/experimental/string_view (ranges::enable_safe_range): Add
partial specialization for std::experimental::basic_string_view.
* include/std/ranges (ranges::viewable_range, ranges::subrange)
(ranges::empty_view, ranges::iota_view): Use safe_range. Specialize
enable_safe_range.
(ranges::safe_iterator_t, ranges::safe_subrange_t): Define.
* include/std/span (ranges::enable_safe_range): Add partial
specialization for std::span.
* include/std/string_view (ranges::enable_safe_range): Likewise for
std::basic_string_view.
* testsuite/std/ranges/access/begin.cc: Adjust expected results.
* testsuite/std/ranges/access/cbegin.cc: Likewise.
* testsuite/std/ranges/access/cdata.cc: Likewise.
* testsuite/std/ranges/access/cend.cc: Likewise.
* testsuite/std/ranges/access/crbegin.cc: Likewise.
* testsuite/std/ranges/access/crend.cc: Likewise.
* testsuite/std/ranges/access/data.cc: Likewise.
* testsuite/std/ranges/access/end.cc: Likewise.
* testsuite/std/ranges/access/rbegin.cc: Likewise.
* testsuite/std/ranges/access/rend.cc: Likewise.
* testsuite/std/ranges/empty_view.cc: Test ranges::begin and
ranges::end instead of unqualified calls to begin and end.
* testsuite/std/ranges/safe_range.cc: New test.
* testsuite/std/ranges/safe_range_types.cc: New test.
* testsuite/util/testsuite_iterators.h: Add comment about safe_range.
From-SVN: r279135
This also fixes a bug in the implementation of LWG 3255, which causes:
FAIL: 23_containers/span/lwg3255.cc (test for excess errors)
That's because the test was wrong and verified the buggy behaviour. That
will be fixed in the following commit.
2019-12-05 JeanHeyd "ThePhD" Meneide <phdofthehouse@gmail.com>
Implement P1872R0 and P1394R0 for std::span
* include/bits/range_access.h (__adl_begin, __adl_end): Remove.
(sentinel_t, range_value_t, range_reference_t)
(range_rvalue_reference_t, __forwarding_range, disable_sized_range)
(output_range, input_range, forward_range, bidirectional_range)
(random_access_range, contiguous_range, common_range): Move here from
<ranges>, to make this the "ranges lite" internal header.
* include/std/ranges: Move basic aliases and concepts to
<bits/range_access.h>.
* include/std/span: Use concepts and ranges:: calls instead of
enable_if and friends.
* include/std/type_traits: Add __is_array_convertible trait.
From-SVN: r279000
Also fix the constraints on span(Container&) and span(const Container&)
constructors so that they aren't used for const spans or const arrays.
* include/std/span (span(element_type(&)[N]))
(span(array<value_type, N>&), span(const array<value_type, N>&)):
Deduce array element type to allow safe const conversions (LWG 3255).
[!_GLIBCXX_P1394] (span(Container&), span(const Container&)): Use
remove_cv_t on arguments to __is_std_span and __is_std_array.
* testsuite/23_containers/span/lwg3255.cc: New test.
From-SVN: r276298
This patch simplifies the constraints on the constructors from arrays by
removing the redundant checks that element_type and value_type are
convertible to element_type. The incorrect uses of __adl_data in those
constructors are removed as well (they should use std::data not
std::ranges::data, and the former doesn't use ADL).
The range/container constructors are now constrained to exclude all
specializations of std::span, not just the current instantiation. The
range constructor now also checks s subset of the contiguous_range
requirements.
All relevant constructor constraints now use the _Require helper in
order to short circuit and avoid unnecessary instantiations after the
first failed constraint.
A new constructor supports initialization from different specializations
of std::span<OtherType, OtherExtent>, as specified in the C++20 draft.
* include/bits/range_access.h (__adl_to_address): Remove.
* include/std/span (__is_base_derived_safe_convertible_v): Replace
with span::__is_compatible.
(__is_std_array_v): Replace with __is_std_array class template and
partial specializations.
(__is_std_array, __is_std_span): New class templates and partial
specializations.
(span::__is_compatible): New alias template for SFINAE constraints.
(span::span(element_type (&)[N])): Remove redundant constraints. Do
not use __adl_data to obtain a pointer.
(span::span(array<value_type, N>&)): Likewise.
(span::span(const array<value_type, N>&)): Likewise.
[_GLIBCXX_P1394] (span::iter_reference_t, span::iterator_t)
(span::iter_value_t, span::derived_from): New alias templates for
SFINAE constraints, until the equivalents are supported in <concepts>
and <iterator>.
[_GLIBCXX_P1394] (span::__is_compatible_iterator): New alias template
for SFINAE constraints.
[_GLIBCXX_P1394] (span::is_compatible_range): New class template for
SFINAE constraints.
[_GLIBCXX_P1394] (span::span(Range&&)): Improve constraints.
[_GLIBCXX_P1394] (span::span(ContiguousIterator, Sentinel)): Likewise.
Use std::to_address instead of __adl_to_address.
[_GLIBCXX_P1394] (span::span(ContiguousIterator, size_type)): Likewise.
[!_GLIBCXX_P1394] (span::__is_compatible_container): New alias
template for SFINAE constraints.
[!_GLIBCXX_P1394] (span::span(Container&))
(span::span(const Container&)): Improve constraints.
[!_GLIBCXX_P1394] (span::span(pointer, size_type))
(span::span(pointer, pointer)): Remove redundant cast of pointer.
(span(const span<OType, OExtent>&)): New constructor.
From-SVN: r275513
