This implements the new string_view constructor proposed by P1989R2.
This hasn't been voted into the C++23 draft yet, but it's been reviewed
by LWG and is expected to be approved at the next WG21 meeting.
libstdc++-v3/ChangeLog:
* include/std/string_view (basic_string_view(Range&&)): Define new
constructor and deduction guide.
* testsuite/21_strings/basic_string_view/cons/char/range_c++20.cc: New test.
* testsuite/21_strings/basic_string_view/cons/wchar_t/range_c++20.cc: New test.
This implements the proposed changes for LWG 3537 (which we're allowed
to do as an extension whatever the outcome of the issue). I noticed we
didn't implement LWG 2280 completely, as the std::begin and std::end
overloads for arrays were not noexcept.
libstdc++-v3/ChangeLog:
* include/bits/range_access.h (begin(T (&)[N]), end(T (&)[N])):
Add missing 'noexcept' as per LWG 2280.
(rbegin(T (&)[N]), rend(T (&)[N]), rbegin(initializer_list<T>))
(rend(initializer_list<T>)): Add 'noexcept' as per LWG 3537.
* testsuite/24_iterators/range_access/range_access.cc: Check for
expected noexcept specifiers. Check result types of generic
std::begin and std::end overloads.
* testsuite/24_iterators/range_access/range_access_cpp14.cc:
Check for expected noexcept specifiers.
* testsuite/24_iterators/range_access/range_access_cpp17.cc:
Likewise.
Implement this C++23 feature, as proposed by P1048R1.
This implementation assumes that a C++23 compiler supports concepts
already. I don't see any point in using preprocessor hacks to detect
compilers which define __cplusplus to a post-C++20 value but don't
support concepts yet.
libstdc++-v3/ChangeLog:
* include/std/type_traits (is_scoped_enum): Define.
* include/std/version (__cpp_lib_is_scoped_enum): Define.
* testsuite/20_util/is_scoped_enum/value.cc: New test.
* testsuite/20_util/is_scoped_enum/version.cc: New test.
This removes the new symbols added for the new futex-based
std::call_once implementation. These symbols were new on trunk, so not
in any released version. However, they are already present in some
beta distro releases (Fedora Linux 34) and in Fedora Linux rawhide. This
change can be locally reverted by distros that need to keep the symbols
present until affected packages have been rebuilt.
libstdc++-v3/ChangeLog:
PR libstdc++/99341
* config/abi/post/aarch64-linux-gnu/baseline_symbols.txt: Remove
std::once_flag symbols.
* config/abi/post/ia64-linux-gnu/baseline_symbols.txt: Likewise.
* config/abi/post/m68k-linux-gnu/baseline_symbols.txt: Likewise.
* config/abi/post/riscv64-linux-gnu/baseline_symbols.txt:
Likewise.
* config/abi/pre/gnu.ver: Likewise.
* src/c++11/mutex.cc [_GLIBCXX_HAVE_LINUX_FUTEX]
(struct __once_flag_compat): Remove.
(_ZNSt9once_flag11_M_activateEv): Remove.
(_ZNSt9once_flag9_M_finishEb): Remove.
The new std::call_once implementation is not backwards compatible,
contrary to my intention. Because std::once_flag::_M_active() doesn't
write glibc's "fork generation" into the pthread_once_t object, it's
possible for glibc and libstdc++ to run two active executions
concurrently. This violates the primary invariant of the feature!
This patch reverts std::once_flag and std::call_once to the old
implementation that uses pthread_once. This means PR 66146 is a problem
again, but glibc has been changed to solve that. A new API similar to
pthread_once but supporting failure and resetting the pthread_once_t
will be proposed for inclusion in glibc and other C libraries.
This change doesn't simply revert r11-4691 because I want to retain the
new implementation for non-ghtreads targets (which didn't previously
support std::call_once at all, so there's no backwards compatibility
concern). This also leaves the new std::call_once::_M_activate() and
std::call_once::_M_finish(bool) symbols present in libstdc++.so.6 so
that code already compiled against GCC 11 can still use them. Those
symbols will be removed in a subsequent commit (which distros can choose
to temporarily revert if needed).
libstdc++-v3/ChangeLog:
PR libstdc++/99341
* include/std/mutex [_GLIBCXX_HAVE_LINUX_FUTEX] (once_flag):
Revert to pthread_once_t implementation.
[_GLIBCXX_HAVE_LINUX_FUTEX] (call_once): Likewise.
* src/c++11/mutex.cc [_GLIBCXX_HAVE_LINUX_FUTEX]
(struct __once_flag_compat): New type matching the reverted
implementation of once_flag using futexes.
(once_flag::_M_activate): Remove, replace with ...
(_ZNSt9once_flag11_M_activateEv): ... alias symbol.
(once_flag::_M_finish): Remove, replace with ...
(_ZNSt9once_flag9_M_finishEb): ... alias symbol.
* testsuite/30_threads/call_once/66146.cc: Removed.
This fixes PR 99172
Currently when GCC is configured with --enable-vtable-verify, the
libstdc++-v3 Makefiles add "-fvtable-verify=std
-Wl,-u_vtable_map_vars_start,-u_vtable_map_vars_end" to libtool link
commands. The "-fvtable-verify=std" piece causes alternate versions of
libtool (such as slibtool) to fail, unable to find "-lvtv" (GNU
libtool just removes that piece).
This patch updates the libstdc++-v3 Makefiles to not pass
"-fvtable-verify=std" to the libtool link commands.
For all current Darwin SDKs inttypes.h has:
extern intmax_t imaxabs(intmax_t j);
So we need to exclude j from the defined test symbols.
libstdc++-v3/ChangeLog:
* testsuite/17_intro/names.cc: Exclude j from the list
of test symbols for Darwin.
We need to add the symbols for to_chars and from_chars for the
long double cases.
libstdc++-v3/ChangeLog:
* config/os/bsd/darwin/ppc-extra.ver: Add matching for
to_chars and from_chars for long double.
This implements operator++, operator-- and operator<=> for the
integer-class types defined in max_size_type.h, which I overlooked
when originally implementing the class.
libstdc++-v3/ChangeLog:
* include/bits/max_size_type.h (__max_size_type::operator _Tp):
Fix formatting.
(__max_size_type::operator++): Define.
(__max_size_type::operator--): Likewise.
(__max_size_type::operator<=>): Conditionally define (in place
of the other comparison operators).
(__max_diff_type::operator _Tp): Fix formatting.
(__max_diff_type::operator++): Define.
(__max_diff_type::operator--): Likewise.
(__max_diff_type::operator<=>): Conditionally define (in place
of the other comparison operators).
* testsuite/std/ranges/iota/max_size_type.cc (test01): Test
these operator overloads.
This implements a minimal integer class type that emulates 128-bit
unsigned arithmetic using a pair of 64-bit integers, which the
floating-point std::to_chars implementation then uses as a drop-in
replacement for unsigned __int128 on targets that lack the latter.
After this patch, we now fully support formatting of large long double
types on such targets.
Since Ryu performs 128-bit division/modulus only by 2, 5 and 10, this
integer class type supports only these divisors rather than general
division/modulus.
libstdc++-v3/ChangeLog:
* src/c++17/floating_to_chars.cc: Simplify the file as if
__SIZEOF_INT128__ is always defined.
[!defined __SIZEOF_INT128__]: Include "uint128_t.h". Define
a base-10 to_chars overload for the uint128_t class type.
* src/c++17/uint128_t.h: New file.
* testsuite/20_util/to_chars/long_double.cc: No longer expect an
execution FAIL on targets that have a large long double type
but lack __int128.
This makes Ryu consistently use the uint128_t alias that's defined in
floating_to_chars.cc.
libstdc++-v3/ChangeLog:
* src/c++17/ryu/LOCAL_PATCHES: Update.
* src/c++17/ryu/d2s_intrinsics.h: Don't define uint128_t.
* src/c++17/ryu/generic_128.h: Likewise.
* src/c++17/ryu/ryu_generic_128.h (struct floating_decimal_128):
Use uint128_t instead of __uint128_t.
(generic_binary_to_decimal): Likewise.
Since Ryu has the alias uint128_t for this same purpose, it seems best
for us to use this name as well, so as to minimize the amount of local
modifications we'd need to make to our copy of Ryu. (In a subsequent
patch, we're going to remove Ryu's aliases so that it uses this one
defined in floating_to_chars.cc.)
libstdc++-v3/ChangeLog:
* src/c++17/floating_to_chars.cc (uint128_t): New conditionally
defined alias of unsigned __int128.
(floating_type_traits_binary128::mantissa_t): Use uint128_t
instead of unsigned __int128.
(floating_type_traits<long double>::mantissa_t)
[LONG_DOUBLE_KIND == LDK_IBM128]: Likewise.
(get_ieee_repr): Likewise. Make casts from uint_t to mantissa_t
and uint32_t explicit. Simplify the extraction of mantissa,
exponent and sign bit.
The standard only specifies that barrier::arrival_token is a move
constructible and move assignable type. We originally used a scoped enum
type, but that means we do not diagnose non-portable code that makes
copies of arrival tokens (or compares them for equality, or uses them as
keys in map!) This wraps the enum in a move-only class type, so that
users are forced to pass it correctly.
The move constructor and move assignment operator of the new class do
not zero out the moved-from token, as that would add additional
instructions. That means that passing a moved-from token will work with
our implementation, despite being a bug in the user code. We could
consider doing that zeroing out in debug mode.
libstdc++-v3/ChangeLog:
* include/std/barrier (barrier::arrival_token): New move-only
class that encapsulates the underlying token value.
The find_type helper function sometimes results in "class X::name" and
lookup for that fails. For more details see "Problem 1" in
https://gcc.gnu.org/pipermail/libstdc++/2021-March/052132.html and the
example at https://sourceware.org/bugzilla/show_bug.cgi?id=27510#c2
This patch replaces typ.unqualified() with typ.tag, which is never
qualified, and will never include the 'class' or 'struct' keywords.
Using the .tag attribute should be safe here because we know we are
looking at a class type and we've already used strip_typedefs().
libstdc++-v3/ChangeLog:
* python/libstdcxx/v6/printers.py (find_type): Use tag attribute
instead of unqualified() method.
As Lewis Baker wrote in the PR:
> The 'fetch_sub()' operation in _M_release_ownership() should be using
> memory_order::acq_rel instead of memory_order::release. The use of
> 'release' only is insufficient as it does not synchronise with any
> corresponding 'acquire' operation.
> With the current implementation, it's possible that a prior write to
> one of the _M_value or _M_head data-members by a thread releasing the
> second-to-last reference might not be visible to another thread that
> releases the last reference and frees the memory, resulting in
> potential write to freed memory.
This simply changes the memory order to acq_rel as suggested.
libstdc++-v3/ChangeLog:
PR libstdc++/99537
* include/std/stop_token (_Stop_state_t::_M_release_ownership):
Use acq_rel memory ordering.
Contrary to what POSIX says, some directory operations on MacOS can fail
with EPERM instead of EACCES, so we need to handle both.
libstdc++-v3/ChangeLog:
PR libstdc++/99537
* src/c++17/fs_dir.cc (recursive_directory_iterator): Use new
helper function to check for permission denied errors.
* src/filesystem/dir.cc (recursive_directory_iterator):
Likewise.
* src/filesystem/dir-common.h (is_permission_denied_error): New
helper function.
This avoids a false positive -Wmaybe-uninitialized warning, by
initializing _M_saved on construction.
libstdc++-v3/ChangeLog:
PR libstdc++/99536
* include/bits/random.h (normal_distribution): Use
default-initializer for _M_saved and _M_saved_available.
This adds missing includes to internal library headers which get
included from more than one other header, so that they can be compiled
as a stand-alone header unit.
For existing use cases these includes are no-ops because they're already
done by the header that includes these files. For compiling them as a
header unit, this ensures that they include what they use.
libstdc++-v3/ChangeLog:
PR libstdc++/99413
* include/bits/align.h: Include debug/assertions.h.
* include/bits/codecvt.h: Include bits/c++config.h.
* include/bits/enable_special_members.h: Likewise.
* include/bits/erase_if.h: Likewise.
* include/bits/functional_hash.h: Include <type_traits>.
* include/bits/invoke.h: Include bits/move.h.
* include/bits/ostream_insert.h: Include bits/exception_defines.h.
* include/bits/parse_numbers.h: Include <type_traits>.
* include/bits/predefined_ops.h: Include bits/c++config.h.
* include/bits/range_access.h: Include bits/stl_iterator.h.
* include/bits/stl_bvector.h: Do not include bits/stl_vector.h.
* include/bits/stl_iterator.h: Include bits/stl_iterator_base_types.h.
* include/bits/stl_uninitialized.h: Include bits/stl_algobase.h.
* include/bits/uniform_int_dist.h: Include bits/concept_check.h.
* include/bits/unique_lock.h: Include bits/std_mutex.h.
* include/debug/assertions.h: Include bits/c++config.h.
The proposed resolution for this library issue simplifies the
constraints for compare_three_way, ranges::equal_to, ranges::less etc.
so that they do not work with types which are convertible to pointers
but which fail to meet the usual syntactic requirements for the
comparisons.
This affects the example in PR libstdc++/93628 but doesn't fix the
problem described in that report.
libstdc++-v3/ChangeLog:
* include/bits/ranges_cmp.h (__eq_builtin_ptr_cmp): Remove.
(ranges::equal_to, ranges::not_equal_to): Do not constrain
with __eq_builtin_ptr_cmp.
(ranges::less, ranges::greater, ranges::less_equal)
(ranges::greater_equal): Do not constrain with
__less_builtin_ptr_cmp.
* libsupc++/compare (compare_three_way): Do not constrain with
__3way_builtin_ptr_cmp.
* testsuite/18_support/comparisons/object/builtin-ptr-three-way.cc: Moved to...
* testsuite/18_support/comparisons/object/lwg3530.cc: ...here.
* testsuite/20_util/function_objects/range.cmp/lwg3530.cc: New test.
As can be seen on:
unsigned char f1 (unsigned char x, int y) { return std::rotl (x, y); }
unsigned char f2 (unsigned char x, int y) { return std::rotr (x, y); }
unsigned short f3 (unsigned short x, int y) { return std::rotl (x, y); }
unsigned short f4 (unsigned short x, int y) { return std::rotr (x, y); }
unsigned int f5 (unsigned int x, int y) { return std::rotl (x, y); }
unsigned int f6 (unsigned int x, int y) { return std::rotr (x, y); }
unsigned long int f7 (unsigned long int x, int y) { return std::rotl (x, y); }
unsigned long int f8 (unsigned long int x, int y) { return std::rotr (x, y); }
unsigned long long int f9 (unsigned long long int x, int y) { return std::rotl (x, y); }
unsigned long long int f10 (unsigned long long int x, int y) { return std::rotr (x, y); }
//unsigned __int128 f11 (unsigned __int128 x, int y) { return std::rotl (x, y); }
//unsigned __int128 f12 (unsigned __int128 x, int y) { return std::rotr (x, y); }
constexpr auto a = std::rotl (1234U, 0);
constexpr auto b = std::rotl (1234U, 5);
constexpr auto c = std::rotl (1234U, -5);
constexpr auto d = std::rotl (1234U, -__INT_MAX__ - 1);
the current <bit> definitions of std::__rot[lr] aren't pattern recognized
as rotates, they are too long/complex for that, starting with signed modulo,
special case for 0 and different cases for positive and negative.
For types with power of two bits the following patch adds definitions that
the compiler can pattern recognize and turn e.g. on x86_64 into ro[lr][bwlq]
instructions. For weirdo types like unsigned __int20 etc. it keeps the
current definitions.
2021-03-06 Jakub Jelinek <jakub@redhat.com>
PR libstdc++/99396
* include/std/bit (__rotl, __rotr): Add optimized variants for power of
two _Nd which the compiler can pattern match the rotates.
This seems to be a typo/thinko in the definition of the arrays used as
storage.
libstdc++-v3/ChangeLog:
PR libstdc++/99382
* testsuite/20_util/specialized_algorithms/uninitialized_default_n/sizes.cc:
Make storage larger than required. Verify no write to the last
element.
* testsuite/20_util/specialized_algorithms/uninitialized_value_construct_n/sizes.cc:
Likewise.
The following patch updates the Solaris baselines for GCC 11.1. There's
only one caveat: comparing the Solaris 11.3 and 11.4 baselines, I find
+FUNC:_ZSt10from_charsPKcS0_RdSt12chars_format@@GLIBCXX_3.4.29
+FUNC:_ZSt10from_charsPKcS0_ReSt12chars_format@@GLIBCXX_3.4.29
+FUNC:_ZSt10from_charsPKcS0_RfSt12chars_format@@GLIBCXX_3.4.29
i.e.
std::from_chars(char const*, char const*, double&, std::chars_format)
and similarly for long double, float. Those are from from
src/c++17/floating_from_chars.cc and only defined if
_GLIBCXX_HAVE_USELOCALE, i.e. depend on the XPG7 addition. Given that
only Solaris 11.4 supports XPG7, I've taken the 11.3 baselines to avoid
having separate ones for 11.3 and 11.4.
Tested on i386-pc-solaris2.11 and sparc-sun-solaris2.11 (sparc and x86,
32 and 64-bit, 11.3 and 11.4).
2021-02-10 Rainer Orth <ro@CeBiTec.Uni-Bielefeld.DE>
libstdc++-v3:
* config/abi/post/i386-solaris/baseline_symbols.txt: Regenerate.
* config/abi/post/i386-solaris/amd64/baseline_symbols.txt:
Likewise.
* config/abi/post/sparc-solaris/baseline_symbols.txt: Likewise.
* config/abi/post/sparc-solaris/sparcv9/baseline_symbols.txt:
Likewise.
Two simd tests FAIL on Solaris, both SPARC and x86:
FAIL: experimental/simd/standard_abi_usable.cc -msse2 -O2 -Wno-psabi (test for excess errors)
FAIL: experimental/simd/standard_abi_usable_2.cc -msse2 -O2 -Wno-psabi (test for excess errors)
This happens because the simd headers use identifiers documented in the
libstdc++ manual as reserved by system headers.
Fixed as follows, tested on i386-pc-solaris2.11, sparc-sun-solaris2.11,
and x86_64-pc-linux-gnu.
2021-02-01 Rainer Orth <ro@CeBiTec.Uni-Bielefeld.DE>
libstdc++-v3:
* include/experimental/bits/simd.h: Replace reserved _X, _B by
_Xp, _Bp.
* include/experimental/bits/simd_builtin.h: Likewise.
* include/experimental/bits/simd_x86.h: Likewise.
The conversions to integer types are explicit, so need to use the
correct type. Converting to uint32_t only works if that is the same type
as unsigned.
libstdc++-v3/ChangeLog:
PR libstdc++/99301
* include/std/chrono (year_month_day::_M_days_since_epoch()):
Convert chrono::month and chrono::day to unsigned before
converting to uint32_t.
Implement P1682R2 as just approved for C++23.
libstdc++-v3/ChangeLog:
* include/std/utility (to_underlying): Define.
* include/std/version (__cpp_lib_to_underlying): Define.
* testsuite/20_util/to_underlying/1.cc: New test.
* testsuite/20_util/to_underlying/version.cc: New test.
The code path in __floating_to_chars_precision for handling long double
by going through printf now also handles __float128, so the condition
that guards this code path needs to get updated accordingly.
libstdc++-v3/ChangeLog:
* src/c++17/floating_to_chars.cc (__floating_to_chars_precision):
Relax the condition that guards the printf code path to accept
F128_type as well as long double.
This patch reimplements std::chrono::year_month_day_last:day() which yields the
last day of a particular month. The current implementation uses a look-up table
implemented as an unsigned[12] array. The new implementation instead
is based on
the fact that a month m in [1, 12], except for m == 2 (February), is
either 31 or
30 days long and m's length depends on two things: m's parity and whether m >= 8
or not. These two conditions are determined by the 0th and 3th bit of m and,
therefore, cheap and straightforward bit-twiddling can provide the right result.
Measurements in x86_64 [1] suggest a 10% performance boost. Although this does
not seem to be huge, notice that measurements are done in hot L1 cache
conditions which might not be very representative of production runs. Also
freeing L1 cache from holding the look-up table might allow performance
improvements elsewhere.
References:
[1] https://github.com/cassioneri/calendar
libstdc++-v3/ChangeLog:
* include/std/chrono (year_month_day_last:day): New
implementation.
This patch reimplements std::chrono::year::is_leap(). Leap year check is
ubiquitously implemented (including here) as:
y % 4 == 0 && (y % 100 != 0 || y % 400 == 0).
The rationale being that testing divisibility by 4 first implies an earlier
return for 75% of the cases, therefore, avoiding the needless calculations of
y % 100 and y % 400. Although this fact is true, it does not take into account
the cost of branching. This patch, instead, tests divisibility by 100 first:
(y % 100 != 0 || y % 400 == 0) && y % 4 == 0.
It is certainly counterintuitive that this could be more efficient since among
the three divisibility tests (4, 100 and 400) the one by 100 is the only one
that can never provide a definitive answer and a second divisibility test (by 4
or 400) is always required. However, measurements [1] in x86_64 suggest this is
3x more efficient! A possible explanation is that checking divisibility by 100
first implies a split in the execution path with probabilities of (1%, 99%)
rather than (25%, 75%) when divisibility by 4 is checked first. This decreases
the entropy of the branching distribution which seems to help prediction.
Given that y belongs to [-32767, 32767] [time.cal.year.members], a more
efficient algorithm [2] to check divisibility by 100 is used (instead of
y % 100 != 0). Measurements suggest that this optimization improves performance
by 20%.
The patch adds a test that exhaustively compares the result of this
implementation with the ubiquitous one for all y in [-32767, 32767]. Although
its completeness, the test completes in a matter of seconds.
References:
[1] https://stackoverflow.com/a/60646967/1137388
[2] https://accu.org/journals/overload/28/155/overload155.pdf#page=16
libstdc++-v3/ChangeLog:
* include/std/chrono (year::is_leap): New implementation.
* testsuite/std/time/year/2.cc: New test.
This patch reimplements std::chrono::year_month_day::_M_days_since_epoch()
which calculates the number of elapsed days since 1970/01/01. The new
implementation is based on Proposition 6.2 of Neri and Schneider, "Euclidean
Affine Functions and Applications to Calendar Algorithms" available at
https://arxiv.org/abs/2102.06959.
The aforementioned paper benchmarks the implementation against several
counterparts, including libc++'s (which is identical to the current
implementation). The results, shown in Figure 3, indicate the new algorithm is
1.7 times faster than the current one.
The patch adds a test which loops through all dates in [-32767/01/01,
32767/12/31], and for each of them, gets the number of days and compares the
result against its expected value. The latter is calculated using a much
simpler and easy to understand algorithm but which is also much slower.
The dates used in the test covers the full range of possible values
[time.cal.year.members]. Despite its completeness the test runs in matter of
seconds.
libstdc++-v3/ChangeLog:
* include/std/chrono (year_month_day::_M_days_since_epoch):
New implementation.
* testsuite/std/time/year_month_day/4.cc: New test.
