This also happens to fix composition of these closure objects.
PR libstdc++/112802
PR libstdc++/113068
libstdc++-v3/ChangeLog:
* include/std/ranges (__detail::_To::operator()): Add constraints.
(__detail::_To2::operator()): Likewise.
* testsuite/std/ranges/conv/1.cc (test_sfinae): New test.
(test_composition): New test.
On AIX fileno is a function-like macro, so enclose the name in
parentheses to ensure we use the real function.
libstdc++-v3/ChangeLog:
* src/c++23/print.cc (__open_terminal(FILE*)): Avoid fileno
macro.
This patch optimizes the compilation performance of std::remove_pointer
by dispatching to the new remove_pointer built-in trait.
libstdc++-v3/ChangeLog:
* include/std/type_traits (remove_pointer): Use __remove_pointer
built-in trait.
Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
This patch optimizes the compilation performance of std::is_object
by dispatching to the new __is_object built-in trait.
libstdc++-v3/ChangeLog:
* include/std/type_traits (is_object): Use __is_object built-in
trait.
(is_object_v): Likewise.
Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
This patch optimizes the compilation performance of std::is_function
by dispatching to the new __is_function built-in trait.
libstdc++-v3/ChangeLog:
* include/std/type_traits (is_function): Use __is_function
built-in trait.
(is_function_v): Likewise. Optimize its implementation. Move
this under is_const_v as this depends on is_const_v.
Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
This patch optimizes the compilation performance of std::is_reference
by dispatching to the new __is_reference built-in trait.
libstdc++-v3/ChangeLog:
* include/std/type_traits (is_reference): Use __is_reference
built-in trait.
(is_reference_v): Likewise.
Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
This patch optimizes the compilation performance of
std::is_member_object_pointer by dispatching to the new
__is_member_object_pointer built-in trait.
libstdc++-v3/ChangeLog:
* include/std/type_traits (is_member_object_pointer): Use
__is_member_object_pointer built-in trait.
(is_member_object_pointer_v): Likewise.
Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
This patch optimizes the compilation performance of
std::is_member_function_pointer by dispatching to the new
__is_member_function_pointer built-in trait.
libstdc++-v3/ChangeLog:
* include/std/type_traits (is_member_function_pointer): Use
__is_member_function_pointer built-in trait.
(is_member_function_pointer_v): Likewise.
Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
This patch optimizes the compilation performance of std::is_member_pointer
by dispatching to the new __is_member_pointer built-in trait.
libstdc++-v3/ChangeLog:
* include/std/type_traits (is_member_pointer): Use
__is_member_pointer built-in trait.
(is_member_pointer_v): Likewise.
Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
This patch optimizes the compilation performance of std::is_scoped_enum
by dispatching to the new __is_scoped_enum built-in trait.
libstdc++-v3/ChangeLog:
* include/std/type_traits (is_scoped_enum): Use
__is_scoped_enum built-in trait.
(is_scoped_enum_v): Likewise.
Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
This patch optimizes the compilation performance of std::is_bounded_array
by dispatching to the new __is_bounded_array built-in trait.
libstdc++-v3/ChangeLog:
* include/std/type_traits (is_bounded_array_v): Use
__is_bounded_array built-in trait.
Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
This patch optimizes the compilation performance of std::is_array
by dispatching to the new __is_array built-in trait.
libstdc++-v3/ChangeLog:
* include/std/type_traits (is_array): Use __is_array built-in
trait.
(is_array_v): Likewise.
Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:
* src/c++23/print.cc (__write_to_terminal) [_WIN32]: If handle
does not refer to the console then just write to it using normal
file I/O.
* testsuite/27_io/print/2.cc (as_printed_to_terminal): Print
error message on failure.
(test_utf16_transcoding): Adjust for as_printed_to_terminal
modifying its argument.
Since we don't need to do anything special to print Unicode on
non-Windows targets, we might as well just use std::vprint_nonunicode to
implement std::vprint_unicode. Removing the duplicated code should
reduce code size in cases where those calls aren't inlined.
Also use an RAII type for the unused case where a non-Windows target
calls __open_terminal(streambuf*) and needs to fclose the result. This
makes the code futureproof in case we ever start using the
__write_terminal function for non-Windows targets.
libstdc++-v3/ChangeLog:
* include/std/ostream (vprint_unicode) [_WIN32]: Use RAII guard.
(vprint_unicode) [!_WIN32]: Just call vprint_nonunicode.
* include/std/print (vprint_unicode) [!_WIN32]: Likewise.
Tim Song pointed out that although std::print behaves as a formatted
output function, it does "determine padding" using the stream's flags.
libstdc++-v3/ChangeLog:
* include/std/ostream (vprint_nonunicode, vprint_unicode): Do
not insert padding.
* testsuite/27_io/basic_ostream/print/1.cc: Adjust expected
behaviour.
This adds the C++23 std::print functions, which use std::format to write
to a FILE stream or std::ostream (defaulting to stdout).
The new extern symbols are in the libstdc++exp.a archive, so we aren't
committing to stable symbols in the DSO yet. There's a UTF-8 validating
and transcoding function added by this change. That can certainly be
optimized, but it's internal to libstdc++exp.a so can be tweaked later
at leisure.
Currently the external symbols work for all targets, but are only
actually used for Windows, where it's necessary to transcode to UTF-16
to write to the console. The standard seems to encourage us to also
diagnose invalid UTF-8 for non-Windows targets when writing to a
terminal (and only when writing to a terminal), but I'm reliably
informed that that wasn't the intent of the wording. Checking for
invalid UTF-8 sequences only needs to happen for Windows, which is good
as checking for a terminal requires a call to isatty, and on Linux that
uses an ioctl syscall, which would make std::print ten times slower!
Testing the std::print behaviour is difficult if it depends on whether
the output stream is connected to a Windows console or not, as we can't
(as far as I know) do that non-interactively in DejaGNU. One of the new
tests uses the internal __write_to_terminal function directly. That
allows us to verify its UTF-8 error handling on POSIX targets, even
though that's not actually used by std::print. For Windows, that
__write_to_terminal function transcodes to UTF-16 but then uses
WriteConsoleW which fails unless it really is writing to the console.
That means the 27_io/print/2.cc test FAILs on Windows. The UTF-16
transcoding has been manually tested using mingw-w64 and Wine, and
appears to work.
libstdc++-v3/ChangeLog:
PR libstdc++/107760
* include/Makefile.am: Add new header.
* include/Makefile.in: Regenerate.
* include/bits/version.def (__cpp_lib_print): Define.
* include/bits/version.h: Regenerate.
* include/std/format (__literal_encoding_is_utf8): New function.
(_Seq_sink::view()): New member function.
* include/std/ostream (vprintf_nonunicode, vprintf_unicode)
(print, println): New functions.
* include/std/print: New file.
* src/c++23/Makefile.am: Add new source file.
* src/c++23/Makefile.in: Regenerate.
* src/c++23/print.cc: New file.
* testsuite/27_io/basic_ostream/print/1.cc: New test.
* testsuite/27_io/print/1.cc: New test.
* testsuite/27_io/print/2.cc: New test.
Fix an incorrect call to _Sink::_M_reserve() which should have passed
the __n parameter. This was not actually a problem because it was in an
discarded statement, because only the _Seq_sink<basic_string<C>>
specialization was used.
Also add some branch prediction hints, explanatory comments, and debug
mode assertions to _Seq_sink.
libstdc++-v3/ChangeLog:
* include/std/format (_Seq_sink): Fix missing argument in
discarded statement. Add comments, likely/unlikely attributes
and debug assertions as sanity checks.
These tests are expected to run interactively, with the output checked
by eye. Nobody ever does that, but we can at least use dg-output to
check that the output is as expected.
libstdc++-v3/ChangeLog:
* testsuite/27_io/objects/char/2.cc: Use dg-output.
* testsuite/27_io/objects/wchar_t/2.cc: Use dg-output.
I got the order of arguments to std::format_to wrong. It was in a
discarded statement, for a case which wasn't being tested.
libstdc++-v3/ChangeLog:
* include/bits/chrono_io.h (__formatter_chrono::_M_S): Fix order
of arguments to std::format_to.
* testsuite/20_util/duration/io.cc: Test subsecond duration with
floating-point rep.
This makes constexpr std::vector (mostly) work in Debug Mode. All safe
iterator instrumentation and checking is disabled during constant
evaluation, because it requires mutex locks and calls to non-inline
functions defined in libstdc++.so. It should be OK to disable the safety
checks, because most UB should be detected during constant evaluation
anyway.
We could try to enable the full checking in constexpr, but it would mean
wrapping all the non-inline functions like _M_attach with an inline
_M_constexpr_attach that does the iterator housekeeping inline without
mutex locks when called for constant evaluation, and calls the
non-inline function at runtime. That could be done in future if we find
that we've lost safety or useful checking by disabling the safe
iterators.
There are a few test failures in C++20 mode, which I'm unable to
explain. The _Safe_iterator::operator++() member gives errors for using
non-constexpr functions during constant evaluation, even though those
functions are guarded by std::is_constant_evaluated() checks. The same
code works fine for C++23 and up.
libstdc++-v3/ChangeLog:
PR libstdc++/109536
* include/bits/c++config (__glibcxx_constexpr_assert): Remove
macro.
* include/bits/stl_algobase.h (__niter_base, __copy_move_a)
(__copy_move_backward_a, __fill_a, __fill_n_a, __equal_aux)
(__lexicographical_compare_aux): Add constexpr to overloads for
debug mode iterators.
* include/debug/helper_functions.h (__unsafe): Add constexpr.
* include/debug/macros.h (_GLIBCXX_DEBUG_VERIFY_COND_AT): Remove
macro, folding it into ...
(_GLIBCXX_DEBUG_VERIFY_AT_F): ... here. Do not use
__glibcxx_constexpr_assert.
* include/debug/safe_base.h (_Safe_iterator_base): Add constexpr
to some member functions. Omit attaching, detaching and checking
operations during constant evaluation.
* include/debug/safe_container.h (_Safe_container): Likewise.
* include/debug/safe_iterator.h (_Safe_iterator): Likewise.
* include/debug/safe_iterator.tcc (__niter_base, __copy_move_a)
(__copy_move_backward_a, __fill_a, __fill_n_a, __equal_aux)
(__lexicographical_compare_aux): Add constexpr.
* include/debug/vector (_Safe_vector, vector): Add constexpr.
Omit safe iterator operations during constant evaluation.
* testsuite/23_containers/vector/bool/capacity/constexpr.cc:
Remove dg-xfail-if for debug mode.
* testsuite/23_containers/vector/bool/cmp_c++20.cc: Likewise.
* testsuite/23_containers/vector/bool/cons/constexpr.cc:
Likewise.
* testsuite/23_containers/vector/bool/element_access/1.cc:
Likewise.
* testsuite/23_containers/vector/bool/element_access/constexpr.cc:
Likewise.
* testsuite/23_containers/vector/bool/modifiers/assign/constexpr.cc:
Likewise.
* testsuite/23_containers/vector/bool/modifiers/constexpr.cc:
Likewise.
* testsuite/23_containers/vector/bool/modifiers/swap/constexpr.cc:
Likewise.
* testsuite/23_containers/vector/capacity/constexpr.cc:
Likewise.
* testsuite/23_containers/vector/cmp_c++20.cc: Likewise.
* testsuite/23_containers/vector/cons/constexpr.cc: Likewise.
* testsuite/23_containers/vector/data_access/constexpr.cc:
Likewise.
* testsuite/23_containers/vector/element_access/constexpr.cc:
Likewise.
* testsuite/23_containers/vector/modifiers/assign/constexpr.cc:
Likewise.
* testsuite/23_containers/vector/modifiers/constexpr.cc:
Likewise.
* testsuite/23_containers/vector/modifiers/swap/constexpr.cc:
Likewise.
* testsuite/23_containers/vector/cons/destructible_debug_neg.cc:
Adjust dg-error line number.
The change in r14-6468-ga01462ae8bafa8 was only supposed to apply to %C
formats, not %Y.
libstdc++-v3/ChangeLog:
* include/bits/chrono_io.h (__formatter_chrono::_M_C_y_Y): Do
not round century down for %Y formats.
When I added a fast path for std::format("{}", x) in
r14-5587-g41a5ea4cab2c59 I forgot to handle char separately from other
integral types. That caused std::format("{}", 'c') to return "99"
instead of "c".
libstdc++-v3/ChangeLog:
* include/std/format (__do_vformat_to): Handle char separately
from other integral types.
* testsuite/std/format/functions/format.cc: Check for expected
output for char and bool arguments.
* testsuite/std/format/string.cc: Check that 0 filling is
rejected for character and string formats.
During discussion of LWG 4022 I noticed that we do not correctly
implement floored division for the century. We were just truncating
towards zero, rather than applying the floor function. For negative
values that rounds the wrong way.
libstdc++-v3/ChangeLog:
* include/bits/chrono_io.h (__formatter_chrono::_M_C_y_Y): Fix
rounding for negative centuries.
* testsuite/std/time/year/io.cc: Check %C for negative years.
In r14-4060-gc4baeaecbbf7d0 I moved some files from src/c++98 to
src/c++11 but I didn't remove the redundant -std=gnu++11 flags for those
files. The flags aren't needed now, because AM_CXXFLAGS for that
directory already uses -std=gnu++11. This removes them.
libstdc++-v3/ChangeLog:
* src/c++11/Makefile.am: Remove redundant -std=gnu++11 flags.
* src/c++11/Makefile.in: Regenerate.
As noted in the PR, we support both features required for the 202110L
value, so we should define it with that value.
libstdc++-v3/ChangeLog:
PR libstdc++/111826
* include/bits/version.def (format): Update value.
* include/bits/version.h: Regenerate.
* testsuite/std/format/functions/format.cc:
What I implemented in r14-6199-g45630fbcf7875b does not match what I
proposed for LWG 4016, and it imposes additional, unwanted requirements
on the emplace and insert member functions of the container being
populated.
libstdc++-v3/ChangeLog:
PR libstdc++/112876
* include/std/ranges (ranges::to): Do not try to use an iterator
returned by the container's emplace or insert member functions.
* testsuite/std/ranges/conv/1.cc (Cont4::emplace, Cont4::insert):
Use the iterator parameter. Do not return an iterator.
We can use the existing _Partial range adaptor closure object for
ranges::to instead of essentially reimplementing it.
libstdc++-v3/ChangeLog:
* include/std/ranges (__detail::_ToClosure): Replace with ...
(__detail::_To): ... this.
(__detail::_ToClosure2): Replace with ...
(__detail::To2): ... this.
(to): Simplify using the existing _Partial range adaptor
closure object.
This local typedef for uintptr_t was accidentally named uint64_t,
probably from a careless code completion shortcut. We don't need the
typedef at all since it's only used once. Just use __UINTPTR_TYPE__
directly instead.
libstdc++-v3/ChangeLog:
* include/std/format (_Iter_sink<charT, contiguous_iterator>):
Remove uint64_t local type.
In r14-5922-g6c8f2d3a08bc01 I added <stdint.h> to <bits/atomic_wait.h>,
so that uintptr_t is declared if that header is compiled as a header
unit. I used <stdint.h> because that's what <atomic> already includes,
so it seemed simpler to be consistent. However, this means that name
lookup for uintptr_t in <bits/atomic_wait.h> depends on whether
<cstdint> has been included by another header first. Whether name lookup
finds std::uintptr_t or ::uintptr_t will depend on include order. This
causes problems when compiling modules with Clang:
bits/atomic_wait.h:251:7: error: 'std::__detail::__waiter_pool_base' has different definitions in different modules; first difference is defined here found method '_S_for' with body
_S_for(const void* __addr) noexcept
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
bits/atomic_wait.h:251:7: note: but in 'tm.<global>' found method '_S_for' with different body
_S_for(const void* __addr) noexcept
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
By including <cstdint> we would ensure that name lookup always finds the
name in namespace std. Alternatively, we can stop including <stdint.h>
for those types, so that we don't declare the entire contents of
<stdint.h> when we only need a couple of types from it. This patch does
the former, which is appropriate for backporting.
libstdc++-v3/ChangeLog:
* include/bits/atomic_wait.h: Include <cstdint> instead of
<stdint.h>.
The changes in r14-6198-g5e8a30d8b8f4d7 were broken, as I used
_GLIBCXX17_CONSTEXPR for the 'if _GLIBCXX17_CONSTEXPR (true)' condition,
forgetting that it would also be used for the is_constant_evaluated()
check. Using 'if constexpr (std::is_constant_evaluated())' is a bug.
Additionally, relying on __glibcxx_assert_fail to give a "not a constant
expression" error is a problem because at -O0 an undefined reference to
__glibcxx_assert_fail is present in the compiled code. This means you
can't use libstdc++ headers without also linking to libstdc++ for the
symbol definition.
This fix rewrites the __glibcxx_assert macro again. This still avoids
doing the duplicate checks, once for constexpr and once at runtime (if
_GLIBCXX_ASSERTIONS is defined). When _GLIBCXX_ASSERTIONS is defined we
still rely on __glibcxx_assert_fail to give a "not a constant
expression" error during constant evaluation (because when assertions
are defined it's not a problem to emit a reference to the symbol). But
when that macro is not defined, we use a new inline (but not constexpr)
overload of __glibcxx_assert_fail to cause compilation to fail. That
inline function doesn't cause an undefined reference to a symbol in the
library (and will be optimized away anyway).
We can also add always_inline to the __is_constant_evaluated function,
although this doesn't actually matter for -O0 and it's always inlined
with any optimization enabled.
libstdc++-v3/ChangeLog:
PR libstdc++/112882
* include/bits/c++config (__is_constant_evaluated): Add
always_inline attribute.
(_GLIBCXX_DO_ASSERT): Remove macro.
(__glibcxx_assert): Define separately for assertions-enabled and
constexpr-only cases.
g++.dg/tls/thread_local-order2.C fails when the toolchain is built for
a platform that lacks __cxa_thread_atexit_impl, even if the program is
built and run using that toolchain on a (later) platform that offers
__cxa_thread_atexit_impl.
This patch adds runtime testing for __cxa_thread_atexit_impl on select
platforms (GNU variants, for starters) that support weak symbols.
for libstdc++-v3/ChangeLog
PR libstdc++/112858
* config/os/gnu-linux/os_defines.h
(_GLIBCXX_MAY_HAVE___CXA_THREAD_ATEXIT_IMPL): Define.
* libsupc++/atexit_thread.cc [__GXX_WEAK__ &&
_GLIBCXX_MAY_HAVE___CXA_THREAD_ATEXIT_IMPL]
(__cxa_thread_atexit): Add dynamic detection of
__cxa_thread_atexit_impl.
Looks like we implemented option 1 (skip the object parameter) for CWG532
before the issue was resolved, and never updated to the final resolution of
option 2 (model it as a reference). More recently CWG2445 extended this
handling to static member functions; I think that's wrong, and have
opened CWG2834 to address that and how explicit object member functions
interact with it.
The FIXME comments are to guide how the explicit object member function
support should change the uses of DECL_NONSTATIC_MEMBER_FUNCTION_P.
The library testsuite changes are to make partial ordering work again
between the generic operator- in the testcase and
_Pointer_adapter::operator-.
DR 532
PR c++/53499
gcc/cp/ChangeLog:
* pt.cc (more_specialized_fn): Fix object parameter handling.
gcc/testsuite/ChangeLog:
* g++.dg/template/partial-order4.C: New test.
* g++.dg/template/spec26.C: Adjust for CWG532.
libstdc++-v3/ChangeLog:
* testsuite/23_containers/vector/ext_pointer/types/1.cc
* testsuite/23_containers/vector/ext_pointer/types/2.cc
(N::operator-): Make less specialized.
libstdc++-v3/ChangeLog:
PR libstdc++/111948
* include/bits/ranges_util.h (subrange): Add constructor to
_Size to aoid setting member in constructor.
* testsuite/std/ranges/subrange/111948.cc: New test.
This implements the proposed resolution of LWG 4016, so that
std::ranges::to does not use std::back_inserter and std::inserter.
Instead it inserts at the back of the container directly, using
the first supported one of emplace_back, push_back, emplace, and insert.
Using emplace avoids creating a temporary that has to be moved into the
container, for cases where the source range and the destination
container do not have the same value type.
libstdc++-v3/ChangeLog:
* include/std/ranges (__detail::__container_insertable): Remove.
(__detail::__container_inserter): Remove.
(ranges::to): Use emplace_back or emplace, as per LWG 4016.
* testsuite/std/ranges/conv/1.cc (Cont4, test_2_1_4): Check for
use of emplace_back and emplace.
The changes in r14-5979 to support unknown references in constant
expressions caused some test regressions. The way that __glibcxx_assert
is defined for constant evaluation no longer works when
_GLIBCXX_ASSERTIONS is defined.
This change simplifies __glibcxx_assert so that there is only one check,
rather than a constexpr one and a conditionally-enabled runtime one. The
constexpr one does not need to use __builtin_unreachable to cause a
compilation failure, because __glibcxx_assert_fail is not usable in
constant expressions, so that will cause a failure too.
As well as fixing the regressions, this makes the code for the
assertions shorter and simpler, so should be quicker to compile, and
might inline better too.
libstdc++-v3/ChangeLog:
* include/bits/c++config (__glibcxx_assert_fail): Declare even
when assertions are not enabled.
(__glibcxx_constexpr_assert): Remove macro.
(__glibcxx_assert_impl): Remove macro.
(_GLIBCXX_ASSERT_FAIL): New macro.
(_GLIBCXX_DO_ASSERT): New macro.
(__glibcxx_assert): Simplify to a single definition that works
at runtime and during constant evaluation.
* testsuite/21_strings/basic_string_view/element_access/char/back_constexpr_neg.cc:
Adjust expected errors.
* testsuite/21_strings/basic_string_view/element_access/char/constexpr_neg.cc:
Likewise.
* testsuite/21_strings/basic_string_view/element_access/char/front_constexpr_neg.cc:
Likewise.
* testsuite/21_strings/basic_string_view/element_access/wchar_t/back_constexpr_neg.cc:
Likewise.
* testsuite/21_strings/basic_string_view/element_access/wchar_t/constexpr_neg.cc:
Likewise.
* testsuite/21_strings/basic_string_view/element_access/wchar_t/front_constexpr_neg.cc:
Likewise.
* testsuite/21_strings/basic_string_view/modifiers/remove_prefix/debug.cc:
Likewise.
* testsuite/21_strings/basic_string_view/modifiers/remove_suffix/debug.cc:
Likewise.
* testsuite/23_containers/span/back_neg.cc: Likewise.
* testsuite/23_containers/span/front_neg.cc: Likewise.
* testsuite/23_containers/span/index_op_neg.cc: Likewise.
* testsuite/26_numerics/lcm/105844.cc: Likewise.
All set_debug_format member functions should be guarded by the
__cpp_lib_formatting_ranges macro (which is not defined yet).
libstdc++-v3/ChangeLog:
PR libstdc++/112832
* include/std/format (formatter::set_debug_format): Ensure this
member is defined conditionally for all specializations.
* testsuite/std/format/formatter/112832.cc: New test.
Add a test to verify that the implementation of inout_ptr is not
vulnerable to LWG Issue 3897.
libstdc++-v3/ChangeLog:
* testsuite/20_util/smartptr.adapt/inout_ptr/2.cc: Add check
for LWG Issue 3897.
Co-authored-by: Jonathan Wakely <jwakely@redhat.com>
