I notice std::timespec and std::timespec_get are used in preprocessor
condition _GLIBCXX_HAVE_TIMESPEC_GET. So in module std, it should be
the same.

libstdc++-v3:

	* src/c++23/std-clib.cc.in (timespec): Move within preprocessor
	group guarded by _GLIBCXX_HAVE_TIMESPEC_GET.

The compiler emits code with init_priority(99) for -fvtable-verify=std
and that creates a section conflict with the uses of init_priority(99)
that I recently added to src/c++20/tzdb.cc.

Change tzdb.cc to use a different priority to avoid the conflict.

libstdc++-v3/ChangeLog:

	PR c++/118981
	* src/c++20/tzdb.cc: Use init_priority(98) instead of
	init_priority(99).

In r15-7647-g32457bc25fea80 I added a cast and also changed the type of
the variable, making the cast redundant. This removes the cast.

libstdc++-v3/ChangeLog:

	* src/c++17/floating_from_chars.cc (__floating_from_chars_hex):
	Remove redundant cast.

These should have been unsigned, but the static assertions are only in
the public std::bit_ceil and std::bit_width functions, not the internal
__bit_ceil and __bit_width ones.

libstdc++-v3/ChangeLog:

	* include/experimental/bits/simd.h (__find_next_valid_abi): Cast
	__bit_ceil argument to unsigned.
	* src/c++17/floating_from_chars.cc (__floating_from_chars_hex):
	Cast __bit_ceil argument to unsigned.
	* src/c++17/memory_resource.cc (big_block): Cast __bit_width
	argument to unsigned.

Since r15-7511-g4e7f74225116e7 we can disable the warnings for using a
reserved priority using a diagnostic pragma. That means we no longer
need to put globals using that attribute into separate files that get
included.

This replaces the two uses of such separate files by moving the variable
definition into the source file and adding the diagnostic pragma.

libstdc++-v3/ChangeLog:

	* src/c++17/memory_resource.cc (default_res): Define here
	instead of including default_resource.h.
	* src/c++98/globals_io.cc (__ioinit): Define here instead of
	including ios_base_init.h.
	* src/c++17/default_resource.h: Removed.
	* src/c++98/ios_base_init.h: Removed.

When linking statically to libstdc++.a (or to libstdc++_nonshared.a in
the RHEL devtoolset compiler) there's a static initialization order
problem where user code might be constructed before the
std::chrono::tzdb_list globals, and so might try to use them after
they've already been destroyed.

Use the init_priority attribute on those globals so that they are
initialized early. Since r15-7511-g4e7f74225116e7 we can disable the
warnings for using a reserved priority using a diagnostic pragma.

libstdc++-v3/ChangeLog:

	PR libstdc++/118811
	* src/c++20/tzdb.cc (tzdb_list::_Node): Use init_priority
	attribute on static data members.
	* testsuite/std/time/tzdb_list/pr118811.cc: New test.

Do not report an error for (is_other(s1) && is_other(s2)) as the
standard originally said, nor for (is_other(s1) || is_other(s2)) as
libstdc++ was doing. We can compare inode numbers for special files and
so give sensible answers.

libstdc++-v3/ChangeLog:

	PR libstdc++/118158
	* src/c++17/fs_ops.cc (fs::equivalent): Remove error reporting
	for is_other(s1) && is_other(s2) case, as per LWG 2937.
	* testsuite/27_io/filesystem/operations/pr118158.cc: New test.

std::to_underlying was missing from the std module introduced in
r15-5366-g7db55c0ba1baaf. This patch adds the missing export for this
utility.

libstdc++-v3/ChangeLog:

	PR libstdc++/106852
	* src/c++23/std.cc.in (to_underlying): Add.

Signed-off-by: Nicolas Werner <nicolas.werner@hotmail.de>

The std-clib.cc module definition file assumes that all names are
available unconditionally, but that's not true for all targets. Use the
same preprocessor conditions as are present in the <cxxx> headers.

A similar change is needed in std.cc.in for the <chrono> features that
depend on the SSO std::string, guarded with a __cpp_lib_chrono value
indicating full C++20 support.

The conditions for <cmath> are omitted from this change, as there are a
large number of them. That probably needs to be fixed.

libstdc++-v3/ChangeLog:

	PR libstdc++/118177
	* src/c++23/std-clib.cc.in: Use preprocessor conditions for
	names which are not always defined.
	* src/c++23/std.cc.in: Likewise.

The current check for negative times (i.e. before the epoch) only checks
for a negative number of seconds. For a time 1ms before the epoch the
seconds part will be zero, but the futex syscall will still fail with an
EINVAL error. Extend the check to handle this case.

This change adds a redundant check in the headers too, so that we avoid
even calling into the library for negative times. Both checks can be
marked [[unlikely]]. The check in the headers avoids the cost of
splitting the time into seconds and nanoseconds and then making a PLT
call. The check inside the library matches where we were checking
already, and fixes existing binaries that were compiled against older
headers but use a newer libstdc++.so.6 at runtime.

libstdc++-v3/ChangeLog:

	PR libstdc++/118093
	* include/bits/atomic_futex.h (_M_load_and_test_until_impl):
	Return false for times before the epoch.
	* src/c++11/futex.cc (_M_futex_wait_until): Extend check for
	negative times to check for subsecond times. Add unlikely
	attribute.
	(_M_futex_wait_until_steady): Likewise.
	* testsuite/30_threads/future/members/118093.cc: New test.

This implements the C++23 container adaptors std::flat_set and
std::flat_multiset from P1222R4.  The implementation is essentially
an simpler and pared down version of std::flat_map.

libstdc++-v3/ChangeLog:

	* include/Makefile.am: Add new header <flat_set>.
	* include/Makefile.in: Regenerate.
	* include/bits/version.def (__cpp_flat_set): Define.
	* include/bits/version.h: Regenerate
	* include/precompiled/stdc++.h: Include <flat_set>.
	* include/std/flat_set: New file.
	* src/c++23/std.cc.in: Export <flat_set>.
	* testsuite/23_containers/flat_multiset/1.cc: New test.
	* testsuite/23_containers/flat_set/1.cc: New test.

Co-authored-by: Jonathan Wakely <jwakely@redhat.com>
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>

This implements the C++23 container adaptors std::flat_map and
std::flat_multimap from P0429R9.  The implementation is shared
as much as possible between the two adaptors via a common base
class that's parameterized according to key uniqueness.

libstdc++-v3/ChangeLog:

	* include/Makefile.am: Add new header <flat_map>.
	* include/Makefile.in: Regenerate.
	* include/bits/alloc_traits.h (__not_allocator_like): New concept.
	* include/bits/stl_function.h (__transparent_comparator): Likewise.
	* include/bits/stl_iterator_base_types.h (__has_input_iter_cat):
	Likewise.
	* include/bits/uses_allocator.h (__allocator_for): Likewise.
	* include/bits/utility.h (sorted_unique_t): Define for C++23.
	(sorted_unique): Likewise.
	(sorted_equivalent_t): Likewise.
	(sorted_equivalent): Likewise.
	* include/bits/version.def (flat_map): Define.
	* include/bits/version.h: Regenerate.
	* include/precompiled/stdc++.h: Include <flat_map>.
	* include/std/flat_map: New file.
	* src/c++23/std.cc.in: Export <flat_map>.
	* testsuite/23_containers/flat_map/1.cc: New test.
	* testsuite/23_containers/flat_multimap/1.cc: New test.

Co-authored-by: Jonathan Wakely <jwakely@redhat.com>
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>

libstdc++-v3/ChangeLog:

	* src/c++17/fs_dir.cc: Fix typo in comment.

This avoids some warnings when building the std module.

libstdc++-v3/ChangeLog:

	* src/c++23/std.cc.in: Disable deprecated warnings when
	exporting std::rel_ops members.

This declares the range adaptor pipe operators a friend of the
_RangeAdaptorClosure base class so that the std module doesn't need to
export them for ADL to find them.

Note that we deliberately don't define these pipe operators as hidden
friends, see r14-3293-g4a6f3676e7dd9e.

libstdc++-v3/ChangeLog:

	* include/std/ranges (views::__adaptor::_RangeAdaptorClosure):
	Befriend both operator| overloads.
	* src/c++23/std.cc.in: Don't export views::__adaptor::operator|.

Reviewed-by: Jonathan Wakely <jwakely@redhat.com>

Some tests were failing due to the exported using declaration of iter_move
conflicting with friend declarations; the exported using needs to be in the
inline namespace, like the customization point itself, rather than
std::ranges.

Also add a few missing exports.

Some tests failed to find some operators defined in implementation-detail
namespaces; this exports them as well, but as previously discussed it's
probably preferable to make those operators friends so ADL can find them
that way.

libstdc++-v3/ChangeLog:

	* src/c++23/std.cc.in: Fix iter_move/swap.  Add fold_left_first, to,
	concat, and some operators.

As described in PR 117630 the cow-stdexcept.cc file pulls in symbols
from system_error.cc, which are not actually needed there. Moving the
definition of error_category::_M_message to a separate file should solve
it.

libstdc++-v3/ChangeLog:

	PR libstdc++/117630
	* src/c++11/Makefile.am: Add new file.
	* src/c++11/Makefile.in: Regnerate.
	* src/c++11/cow-stdexcept.cc (error_category::_M_message): Move
	member function definition to ...
	* src/c++11/cow-system_error.cc: New file.

Standard JSON doesn't have comments, and it seems this file needs to be
conforming, not the common JSON-with-comments dialect.

libstdc++-v3/ChangeLog:

	* src/c++23/libstdc++.modules.json.in: Remove C++ comment.

This patch introduces an installed source form of module std and std.compat.
To help a build system find them, we install a libstdc++.modules.json file
alongside libstdc++.so, which tells the build system where the files are and
any special flags it should use when compiling them (none, in this case).
The format is from a proposal in SG15.  The build system can find this file
with 'gcc -print-file-name=libstdc++.modules.json'.

It seems preferable to use a relative path from this file to the sources so
that moving the installation doesn't break the reference, but I didn't see
any obvious way to compute that without relying on coreutils, perl, or
python, so I wrote a POSIX shell script for it.  The .. canonicalization
bits aren't necessary since I discovered $(abspath), but I guess I might as
well leave them in.

Currently this installs the sources under $(gxx_include_dir)/bits/,
i.e. /usr/include/c++/15/bits.  So with my -fsearch-include-path change,
std.cc can be compiled with g++ -fsearch-include-path bits/std.cc.  Note
that if someone actually tries to #include <bits/std.cc> it will fail with
"error: module control-line cannot be in included file".

Any ideas about a more user-friendly way to express "compile module std" are
welcome.

The sources currently have the extension .cc, like other source files.

std.cc started with m.cencora's implementation in PR114600.  I've made some
adjustments, but more is probably desirable, e.g. of the <algorithm>
handling of namespace ranges, and to remove exports of templates that are
only specialized in a particular header.  I've filled in a bunch of missing
exports, and added some FIXMEs where I noticed bits that are not implemented
yet.

Since bits/stdc++.h also intends to include the whole standard library, I
include it rather than duplicate it.  But stdc++.h comments out <execution>,
due to TBB issues; I include it separately and suppress TBB usage, so module
std won't currently provide parallel execution.

It seemed most convenient for the two files to be monolithic so we don't
need to worry about include paths.  So the C library names that module
std.compat exports in both namespace std and :: are a block of code that is
appended to both files, adjusted based on whether the macro STD_COMPAT is
defined before the block.

In this implementation std.compat imports std; it would also be valid for it
to duplicate everything in std.  I see the libc++ std.compat also imports
std.

As discussed in the PR, module std is supported in C++20 mode even though it
was added in C++23.

Changes to test module std will follow in a separate patch.  In my testing
I've noticed a few compiler bugs that break various testcases, so I don't
expect to enable module std testing by default at first.

	PR libstdc++/106852

libstdc++-v3/ChangeLog:

	* include/bits/version.def: Add __cpp_lib_modules.
	* include/bits/version.h: Regenerate.
	* src/c++23/Makefile.am: Add modules std and std.compat.
	* src/c++23/Makefile.in: Regenerate.
	* src/c++23/std-clib.cc.in: New file.
	* src/c++23/std.cc.in: New file.
	* src/c++23/std.compat.cc.in: New file.
	* src/c++23/libstdc++.modules.json.in: New file.

contrib/ChangeLog:

	* relpath.sh: New file.

Several member functions of filesystem::directory_iterator and
filesystem::recursive_directory_iterator currently dereference their
shared_ptr data member without checking for non-null. Because they use
operator-> and that function only uses _GLIBCXX_DEBUG_PEDASSERT rather
than __glibcxx_assert there is no assertion even when the library is
built with _GLIBCXX_ASSERTIONS defined. This means that dereferencing
invalid directory iterators gives an unhelpful segfault.

By using (*p). instead of p-> we get an assertion when the library is
built with _GLIBCXX_ASSERTIONS, with a "_M_get() != nullptr" message.

libstdc++-v3/ChangeLog:

	* src/c++17/fs_dir.cc (fs::directory_iterator::operator*): Use
	shared_ptr::operator* instead of shared_ptr::operator->.
	(fs::recursive_directory_iterator::options): Likewise.
	(fs::recursive_directory_iterator::depth): Likewise.
	(fs::recursive_directory_iterator::recursion_pending): Likewise.
	(fs::recursive_directory_iterator::operator*): Likewise.
	(fs::recursive_directory_iterator::disable_recursion_pending):
	Likewise.

libstdc++-v3/ChangeLog:

	* src/c++11/cxx11-ios_failure.cc (__iosfail_type_info): Unhide
	the three-arg overload of __do_upcast.

The undefined std::ios_base_library_init() symbol that is referenced by
<iostream> is only supposed to be used for targets where symbol
versioning is supported.

The mingw-w64 target defaults to --enable-symvers=gnu due to using GNU
ld but doesn't actually support symbol versioning. This means it tries
to emit references to the std::ios_base_library_init() symbol, which
isn't really defined in the library. This causes problems when using lld
to link user binaries.

Disable the undefined symbol reference for non-ELF targets.

libstdc++-v3/ChangeLog:

	PR libstdc++/116159
	* include/std/iostream (ios_base_library_init): Only define for
	ELF targets.
	* src/c++98/ios_init.cc (ios_base_library_init): Likewise.

The recent change to use auto_win_file_handle for
std::filesystem::hard_link_count caused a regression. The
std::error_code argument should be cleared if no error occurs, but this
no longer happens. Add a call to ec.clear() in fs::hard_link_count to
fix this.

Also change the auto_win_file_handle class to take a reference to the
std::error_code and set it if an error occurs, to slightly simplify the
control flow in the fs::equiv_files function.

libstdc++-v3/ChangeLog:

	* src/c++17/fs_ops.cc (auto_win_file_handle): Add error_code&
	member and set it if CreateFileW or GetFileInformationByHandle
	fails.
	(fs::equiv_files) [_GLIBCXX_FILESYSTEM_IS_WINDOWS]: Simplify
	control flow.
	(fs::hard_link_count) [_GLIBCXX_FILESYSTEM_IS_WINDOWS]: Clear ec
	on success.
	* testsuite/27_io/filesystem/operations/hard_link_count.cc:
	Check error handling.

libstdc++-v3/ChangeLog:

	* src/c++11/debug.cc: Replace throw() with noexcept.

This is LWG 4084 which I filed recently. LWG seems to support making the
change, so that std::num_put can use the %F format for floating-point
numbers.

libstdc++-v3/ChangeLog:

	PR libstdc++/114862
	* src/c++98/locale_facets.cc (__num_base::_S_format_float):
	Check uppercase flag for fixed format.
	* testsuite/22_locale/num_put/put/char/lwg4084.cc: New test.

libstdc++-v3/ChangeLog:

	* src/c++20/format.cc [!_GLIBCXX_HAS_GTHREADS] (mutex): Define
	dummy mutex type.
	* testsuite/std/time/format_localized.cc: Use loop variable
	instead of creating the same locale on every iteration.

The linux man page for strerror says that some systems return NULL for
an unknown error number. That violates the C and POSIX standards, but we
can esily handle it to avoid a segfault.

libstdc++-v3/ChangeLog:

	* src/c++11/system_error.cc (strerror_string): Handle
	non-conforming NULL return from strerror.

This implements the C++23 paper P2419R2 (Clarify handling of encodings
in localized formatting of chrono types). The requirement is that when
the literal encoding is "a Unicode encoding form" and the formatting
locale uses a different encoding, any locale-specific strings such as
"août" for std::chrono::August should be converted to the literal
encoding.

Using the recently-added std::locale::encoding() function we can check
the locale's encoding and then use iconv if a conversion is needed.
Because nl_langinfo_l and iconv_open both allocate memory, a naive
implementation would perform multiple allocations and deallocations for
every snippet of locale-specific text that needs to be converted to
UTF-8. To avoid that, a new internal locale::facet is defined to store
the text_encoding and an iconv_t descriptor, which are then cached in
the formatting locale. This requires access to the internals of a
std::locale object in src/c++20/format.cc, so that new file needs to be
compiled with -fno-access-control, as well as -std=gnu++26 in order to
use std::text_encoding.

Because the new std::text_encoding and std::locale::encoding() symbols
are only in the libstdc++exp.a archive, we need to include
src/c++26/text_encoding.cc in the main library, but not export its
symbols yet. This means they can be used by the two new functions which
are exported from the main library.

The encoding conversions are done for C++20, treating it as a DR that
resolves LWG 3656.

With this change we can increase the value of the __cpp_lib_format macro
for C++23. The value should be 202207 for P2419R2, but we already
implement P2510R3 (Formatting pointers) so can use the value 202304.

libstdc++-v3/ChangeLog:

	PR libstdc++/109162
	* acinclude.m4 (libtool_VERSION): Update to 6:34:0.
	* config/abi/pre/gnu.ver: Disambiguate old patters. Add new
	GLIBCXX_3.4.34 symbol version and new exports.
	* configure: Regenerate.
	* include/bits/chrono_io.h (_ChronoSpec::_M_locale_specific):
	Add new accessor functions to use a reserved bit in _Spec.
	(__formatter_chrono::_M_parse): Use _M_locale_specific(true)
	when chrono-specs contains locale-dependent conversion
	specifiers.
	(__formatter_chrono::_M_format): Open iconv descriptor if
	conversion to UTF-8 will be needed.
	(__formatter_chrono::_M_write): New function to write a
	localized string with possible character conversion.
	(__formatter_chrono::_M_a_A, __formatter_chrono::_M_b_B)
	(__formatter_chrono::_M_p, __formatter_chrono::_M_r)
	(__formatter_chrono::_M_x, __formatter_chrono::_M_X)
	(__formatter_chrono::_M_locale_fmt): Use _M_write.
	* include/bits/version.def (format): Update value.
	* include/bits/version.h: Regenerate.
	* include/std/format (_GLIBCXX_P2518R3): Check feature test
	macro instead of __cplusplus.
	(basic_format_context): Declare __formatter_chrono as friend.
	* src/c++20/Makefile.am: Add new file.
	* src/c++20/Makefile.in: Regenerate.
	* src/c++20/format.cc: New file.
	* testsuite/std/time/format_localized.cc: New test.
	* testsuite/util/testsuite_abi.cc: Add new symbol version.

libstdc++-v3/ChangeLog:

	* src/c++17/fs_ops.cc: Fix file name in comment.

There are no inode numbers on Windows filesystems, so stat_type::st_ino
is always zero and the check for equivalent files in do_copy_file was
incorrectly identifying distinct files as equivalent. This caused
copy_file to incorrectly report errors when trying to overwrite existing
files.

The fs::equivalent function already does the right thing on Windows, so
factor that logic out into a new function that can be reused by
fs::copy_file.

The tests for fs::copy_file were quite inadequate, so this also adds
checks for that function's error conditions.

libstdc++-v3/ChangeLog:

	* src/c++17/fs_ops.cc (auto_win_file_handle): Change constructor
	parameter from const path& to const wchar_t*.
	(fs::equiv_files): New function.
	(fs::equivalent): Use equiv_files.
	* src/filesystem/ops-common.h (fs::equiv_files): Declare.
	(do_copy_file): Use equiv_files.
	* src/filesystem/ops.cc (fs::equiv_files): Define.
	(fs::copy, fs::equivalent): Use equiv_files.
	* testsuite/27_io/filesystem/operations/copy.cc: Test
	overwriting directory contents recursively.
	* testsuite/27_io/filesystem/operations/copy_file.cc: Test
	overwriting existing files.

std::filesystem::hard_link_count() always returns 1 on
mingw-w64ucrt-11.0.1-r3 on Windows 10 19045

hard_link_count() queries _wstat64() on MinGW-w64
The MSFT documentation claims _wstat64() will always return 1 *non*-NTFS volumes
https://learn.microsoft.com/en-us/previous-versions/visualstudio/visual-studio-2013/14h5k7ff(v=vs.120)



My tests suggest that is not always true -
hard_link_count()/_wstat64() still returns 1 on NTFS.
GetFileInformationByHandle does return the correct result of 2.
Please see the PR for a minimal repro.

This patch changes the Windows implementation to always call
GetFileInformationByHandle.

	PR libstdc++/113663

libstdc++-v3/ChangeLog:

	* src/c++17/fs_ops.cc (fs::equivalent): Moved helper class
	auto_handle to anonymous namespace as auto_win_file_handle.
	(fs::hard_link_count): Changed Windows implementation to use
	information provided by GetFileInformationByHandle which is more
	reliable.
	* testsuite/27_io/filesystem/operations/hard_link_count.cc: New
	test.

Signed-off-by: "Lennox" Shou Hao Ho <lennoxhoe@gmail.com>
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>

This avoids some warnings when the preprocessor conditions are not met.

libstdc++-v3/ChangeLog:

	* src/c++23/print.cc (__open_terminal): Use [[maybe_unused]] on
	parameter.

avrlibc has an incomplete unistd.h that doesn't have isatty.
So building libstdc++ fails when compiling c++23/print.cc.
As a workaround I added a check for AVR.

libstdc++-v3/ChangeLog:

	PR libstdc++/115482
	* src/c++23/print.cc (__open_terminal) [__AVR__]: Do not use
	isatty.

For the C locale we know the encoding is ASCII, so we can avoid using
newlocale and nl_langinfo_l. Similarly, for an unnamed locale, we aren't
going to get a useful answer, so we can just use a default-constrcuted
std::text_encoding representing an unknown encoding.

libstdc++-v3/ChangeLog:

	* src/c++26/text_encoding.cc (__locale_encoding): Add to unnamed
	namespace.
	(std::locale::encoding): Optimize for "C" and "*" names.

When the library is configured with --disable-libstdcxx-verbose the
assertions just abort instead of calling __glibcxx_assert_fail, and so I
didn't export that function for the non-verbose build. However, that
option is documented to not change the library ABI, so we still need to
export the symbol from the library. It could be needed by programs
compiled against the headers from a verbose build.

The non-verbose definition can just call abort so that it doesn't pull
in I/O symbols, which are unwanted in a non-verbose build.

libstdc++-v3/ChangeLog:

	PR libstdc++/115585
	* src/c++11/assert_fail.cc (__glibcxx_assert_fail): Add
	definition for non-verbose builds.

I found some issues in the std::chrono::tzdb parser by testing the
tzdata "vanguard" format, which uses new features that aren't enabled in
the "main" and "rearguard" data formats.

Since 2024a the keyword "minimum" is no longer valid for the FROM and TO
fields in a Rule line, which means that "m" is now a valid abbreviation
for "maximum". Previously we expected either "mi" or "ma". For backwards
compatibility, a FROM field beginning with "mi" is still supported and
is treated as 1900. The "maximum" keyword is only allowed in TO now,
because it makes no sense in FROM. To support these changes the
minmax_year and minmax_year2 classes for parsing FROM and TO are
replaced with a single years_from_to class that reads both fields.

The vanguard format makes use of %z in Zone FORMAT fields, which caused
an exception to be thrown from ZoneInfo::set_abbrev because no % or /
characters were expected when a Zone doesn't use a named Rule. The
ZoneInfo::to(sys_info&) function now uses format_abbrev_str to replace
any %z with the current offset. Although format_abbrev_str also checks
for %s and STD/DST formats, those only make sense when a named Rule is
in effect, so won't occur when ZoneInfo::to(sys_info&) is used.

This change also implements a feature that has always been missing from
time_zone::_M_get_sys_info: finding the Rule that is active before the
specified time point, so that we can correctly handle %s in the FORMAT
for the first new sys_info that gets created. This requires implementing
a poorly documented feature of zic, to get the LETTERS field from a
later transition, as described at
https://mm.icann.org/pipermail/tz/2024-April/058891.html
In order for this to work we need to be able to distinguish an empty
letters field (as used by CE%sT where the variable part is either empty
or "S") from "the letters field is not known for this transition". The
tzdata file uses "-" for an empty letters field, which libstdc++ was
previously replacing with "" when the Rule was parsed. Instead, we now
preserve the "-" in the Rule object, so that "" can be used for the case
where we don't know the letters (and so need to decide it).

libstdc++-v3/ChangeLog:

	* src/c++20/tzdb.cc (minmax_year, minmax_year2): Remove.
	(years_from_to): New class replacing minmax_year and
	minmax_year2.
	(format_abbrev_str, select_std_or_dst_abbrev): Move earlier in
	the file. Handle "-" for letters.
	(ZoneInfo::to): Use format_abbrev_str to expand %z.
	(ZoneInfo::set_abbrev): Remove exception. Change parameter from
	reference to value.
	(operator>>(istream&, Rule&)): Do not clear letters when it
	contains "-".
	(time_zone::_M_get_sys_info): Add missing logic to find the Rule
	in effect before the time point.
	* testsuite/std/time/tzdb/1.cc: Adjust for vanguard format using
	"GMT" as the Zone name, not as a Link to "Etc/GMT".
	* testsuite/std/time/time_zone/sys_info_abbrev.cc: New test.

Several of the 19_diagnostics/stacktrace tests FAIL on Solaris/SPARC (32
and 64-bit), Solaris/x86 (32-bit only), and several other targets:

FAIL: 19_diagnostics/stacktrace/current.cc  -std=gnu++23 execution test
FAIL: 19_diagnostics/stacktrace/current.cc  -std=gnu++26 execution test
FAIL: 19_diagnostics/stacktrace/entry.cc  -std=gnu++23 execution test
FAIL: 19_diagnostics/stacktrace/entry.cc  -std=gnu++26 execution test
FAIL: 19_diagnostics/stacktrace/output.cc  -std=gnu++23 execution test
FAIL: 19_diagnostics/stacktrace/output.cc  -std=gnu++26 execution test
FAIL: 19_diagnostics/stacktrace/stacktrace.cc  -std=gnu++23 execution test
FAIL: 19_diagnostics/stacktrace/stacktrace.cc  -std=gnu++26 execution test

As it turns out, both the copy of libbacktrace in libstdc++ and the
testcases proper need to compiled with -funwind-tables, as is done for
libbacktrace itself.

This isn't an issue on Linux/x86_64 and Solaris/amd64 since 64-bit x86
always defaults to -funwind-tables.  32-bit x86 does, too, when
-fomit-frame-pointer is enabled as on Linux/i686, but unlike
Solaris/i386.

So this patch always enables the option both for the libbacktrace copy
and the testcases.

Tested on i386-pc-solaris2.11, sparc-sun-solaris2.11, and
x86_64-pc-linux-gnu.

2024-05-23  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>

	libstdc++-v3:
	PR libstdc++/111641
	* src/libbacktrace/Makefile.am (AM_CFLAGS): Add -funwind-tables.
	* src/libbacktrace/Makefile.in: Regenerate.

	* testsuite/19_diagnostics/stacktrace/current.cc (dg-options): Add
	-funwind-tables.
	* testsuite/19_diagnostics/stacktrace/entry.cc: Likewise.
	* testsuite/19_diagnostics/stacktrace/hash.cc: Likewise.
	* testsuite/19_diagnostics/stacktrace/output.cc: Likewise.
	* testsuite/19_diagnostics/stacktrace/stacktrace.cc: Likewise.

This fixes a bug in locale::combine where we fail to meet the standard's
requirement that the result is unnamed. It also implements two library
issues related to the names of combined locales (2295 and 3676).

libstdc++-v3/ChangeLog:

	PR libstdc++/108323
	* include/bits/locale_classes.tcc (locale(const locale&, Facet*)):
	Return a copy of the first argument when the facet pointer is
	null, as per LWG 2295.
	(locale::combine): Ensure the result is unnamed.
	* src/c++11/localename.cc (_M_replace_categories): Ignore
	whether the second locale has a name when cat == none, as per
	LWG 3676.
	* src/c++98/locale.cc (_M_install_facet): Use __builtin_expect
	to predict that the facet pointer is non-null.
	* testsuite/22_locale/locale/cons/names.cc: New test.