This reverts the changes in r12-1778 which added a noexcept-specifier to
std::unique_ptr<T[]>::operator[], and the changes in r12-1844 which
tried to make it work with incomplete types (for PR 101236).
The noexcept-specifier is not required by the standard, and is causing
regressions, so just remove it.
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:
PR libstdc++/101271
* include/bits/unique_ptr.h (unique_ptr<T[],D>::operator[]):
Remove noexcept-specifier.
(unique_ptr<T[],D>::_S_nothrow_deref): Remove.
* testsuite/20_util/unique_ptr/lwg2762.cc: Remove checks for
operator[].
This attempst to improve the doxygen output to work around what seems to
be some bugs in doxygen (issues 8635 and 8638).
The @addtogroup command doesn't work for entities inside a nested
namespace (see 8635) so we need to close and reopen groups on entering
and elaving nested namespaces. This fixes the problem that
chrono::duration and chrono::time_point were not documented in the
"Time" documentation group. I am unable to make the path classes appear
as part of their relevant groups (File System and Filesystem TS), nor
the contents of <exception> or <system_error>. I have made some minor
improvements to the docs for those types, including starting to address
PR 97001 by adding @since to the doxygen comments.
This change also excludes the <experimental/bits/net.h> header from
Doxygen processing, so we don't get an unwanted "Networking-ts" group
in the documentation.
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:
* doc/doxygen/doxygroups.cc: Fix docs for std::literals.
* doc/doxygen/user.cfg.in: Exclude the Networking TS header.
Add some more predefined macros.
* include/bits/fs_fwd.h: Move @addtogroup commands inside
namespaces. Add better documentation.
* include/bits/fs_path.h: Likewise.
* include/experimental/bits/fs_fwd.h: Likewise.
* include/experimental/bits/fs_path.h: Likewise.
* include/ext/throw_allocator.h: Fix typo and improve docs.
* include/std/chrono: Move @addtogroup commands.
* include/std/system_error: Move @addtogroup commands.
* libsupc++/exception: Improve documentation.
* libsupc++/exception.h: Add @since documentation.
This defines some new Doxygen groups for C++17 variable templates and
for the contents of <experimental/type_traits>. By documenting the group
as a whole and adding each template to a group we don't need to document
them individually.
Also mark more internals with "@cond undocumented" so that Doxygen
ignores them by default. Also make Doxygen process <experimental/simd>.
For some reason, many of the class templates in <type_traits> do not
appear in the "Metaprogramming" group. For example, add_cv,
remove_extent, and all the is_xxx_constructible and is_xxx_assignable
traits. For some reason, Doxygen doesn't include them in the group,
despite doing it correctly for other traits in the same header.
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:
PR libstdc++/101258
* doc/doxygen/user.cfg.in (INPUT): Add <experimental/simd>.
(COLS_IN_ALPHA_INDEX): Remove obsolete tag.
(PREDEFINED): Add/fix some more macros that need to be expanded.
* include/bits/random.h: Stop Doxygen from documenting internal
implementation details.
* include/bits/random.tcc: Likewise.
* include/bits/this_thread_sleep.h: Fix @file name.
* include/experimental/bits/simd.h: Add to Doxygen group. Do not
document internal implementation details.
* include/experimental/bits/simd_detail.h: Do not document
internal implementation details.
* include/experimental/simd: Define Doxygen groups.
* include/experimental/type_traits: Improve documentation for
the header file. Define groups. Use @since commands.
* include/std/scoped_allocator (scoped_allocator_adaptor): Move
declaration before undocumented region.
* include/std/type_traits (true_type, false_type): Use using
declaration instead of typedef.
(is_invocable_v, is_nothrow_invocable_v, is_invocable_r_v)
(is_nothrow_invocable_r_v): Move definitions next to other C++17
variable templates.
Do not document internal implementation details. Move misplaced
group-end command. Define group for variable templates.
* include/std/variant: Do not document internal implementation
details.
* testsuite/26_numerics/random/pr60037-neg.cc: Adjust dg-error
line number.
Since C++17 the static members of the random number engines are
implicitly inline, so don't need definitions.
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:
* include/bits/random.tcc [__cpp_inline_variables]: Remove
redundant definitions of static constexpr member variables.
* testsuite/26_numerics/random/pr60037-neg.cc: Adjust dg-error
line number.
These function templates are explicitly specialized for char and wchar_t
streambufs, so the explicit instantiations do nothing. Remove them, to
avoid confusion.
libstdc++-v3/ChangeLog:
* include/bits/streambuf.tcc (__copy_streambufs_eof): Remove
explicit instantiation declarations.
* src/c++11/streambuf-inst.cc (__copy_streambufs_eof): Remove
explicit instantiation definitions.
I meant to undef the names that clash with newlib headers for newlib,
but I only undef'd them for non-newlib targets. This means they still
cause errors for newlib, and aren't tested for other targets.
This fixes the test to check those names for non-newlib targets, and to
undef them to avoid errors for newlib.
libstdc++-v3/ChangeLog:
PR libstdc++/97088
* testsuite/17_intro/names.cc: Fix #if condition for names used
by newlib headers.
PR libstdc++/101236 shows that LLVM depends on being able to use
unique_ptr<T[]>::operator[] when T is incomplete. This is undefined, but
previously worked with libstdc++. When I added the conditional noexcept
to that operator we started to diagnose the incomplete type.
This change restores support for that case, by making the noexcept
condition check that the type is complete before checking whether
indexing on the pointer can throw. A workaround for PR c++/101239 is
needed to avoid a bogus error where G++ fails to do SFINAE on the
ill-formed p[n] expression and gets an ICE. Instead of checking that the
p[n] expression is valid in the trailing-return-type, we only check that
the element_type is complete.
libstdc++-v3/ChangeLog:
PR libstdc++/101236
* include/bits/unique_ptr.h (unique_ptr<T[], D>::operator[]):
Fail gracefully if element_type is incomplete.
* testsuite/20_util/unique_ptr/cons/incomplete.cc: Clarify that
the standard doesn't require this test to work for array types.
* testsuite/20_util/unique_ptr/lwg2762.cc: Check that incomplete
types can be used with array specialization.
* testsuite/20_util/unique_ptr/101236.cc: New test.
For C++11 std::ws changed to be an unformatted input function, meaning
it constructs a sentry and sets badbit on exceptions.
libstdc++-v3/ChangeLog:
* doc/xml/manual/intro.xml: Document LWG 415 change.
* doc/html/manual/bugs.html: Regenerate.
* include/bits/istream.tcc (ws): Create sentry and catch
exceptions.
* testsuite/27_io/basic_istream/ws/char/lwg415.cc: New test.
* testsuite/27_io/basic_istream/ws/wchar_t/lwg415.cc: New test.
Currently if ostream::write fails and sets badbit and that causes an
exception, we will catch the exception, set badbit again, and rethrow
the exception.
This change delays setting badbit until after the try-catch block, so
that if it causes an exception we don't need to catch and rethrow it.
This removes the last remaining use of _M_write, so it can be made
private (or removed entirely for versioned namespace builds, where ABI
compatibility is not required). All other uses of _M_write were replaced
by calls to __ostream_insert, so make _M_write use that too.
libstdc++-v3/ChangeLog:
* include/bits/ostream.tcc (basic_ostream::write): Call sputn
directly instead of using _M_write. Do setstate(__err) all
outside the try-catch block.
* include/std/ostream (basic_ostream::_M_write): Declare
private. Use __ostream_insert. Do not define for the versioned
namespace.
N3168 added the requirement that the [ostream.seeks] functions create a
sentry object. Nothing in the requirements of those functions says
anything about catching exceptions and setting badbit.
As well as not catching exceptions, this change results in another
observable behaviour change. Previously seeking on a stream with eofbit
set would work (as long as badbit and failbit weren't set). The
construction of a sentry causes failbit to be set when eofbit is set,
which causes the seek to fail. It is necessary to clear the eofbit
before seeking now.
libstdc++-v3/ChangeLog:
* include/bits/ostream.tcc (sentry): Only set failbit if badbit
is set, not if eofbit is set.
(tellp, seekp, seekp): Create sentry object. Do not set badbit
on exceptions.
* testsuite/27_io/basic_ostream/seekp/char/exceptions_badbit_throw.cc:
Adjust expected behaviour.
* testsuite/27_io/basic_ostream/seekp/wchar_t/exceptions_badbit_throw.cc:
Likewise.
* testsuite/27_io/basic_ostream/tellp/char/exceptions_badbit_throw.cc:
Likewise.
* testsuite/27_io/basic_ostream/tellp/wchar_t/exceptions_badbit_throw.cc:
Likewise.
* testsuite/27_io/basic_ostream/seekp/char/n3168.cc: New test.
* testsuite/27_io/basic_ostream/seekp/wchar_t/n3168.cc: New test.
* testsuite/27_io/basic_ostream/tellp/char/n3168.cc: New test.
* testsuite/27_io/basic_ostream/tellp/wchar_t/n3168.cc: New test.
The proposed resolution for the inconsistent noexcept-specifiers in the
spec is to remove it from bto hthe assignment operator and swap.
libstdc++-v3/ChangeLog:
* include/std/syncstream (basic_syncbuf::swap()): Remove
noexcept, as per LWG 3498.
Conditionally #undef some more names that are used in system headers.
libstdc++-v3/ChangeLog:
PR libstdc++/97088
* testsuite/17_intro/names.cc: Undef more names for newlib and
also for arm-none-linux-gnueabi.
* testsuite/experimental/names.cc: Disable PCH.
The __bit_cast function was a hack to achieve what __builtin_bit_cast
can do, therefore use __builtin_bit_cast if possible. However,
__builtin_bit_cast cannot be used to cast from/to fixed_size_simd, since
it isn't trivially copyable (in the language sense — in principle it
is). Therefore add __proposed::simd_bit_cast to enable the use case
required in the test framework.
Signed-off-by: Matthias Kretz <m.kretz@gsi.de>
libstdc++-v3/ChangeLog:
* include/experimental/bits/simd.h (__bit_cast): Implement via
__builtin_bit_cast #if available.
(__proposed::simd_bit_cast): Add overloads for simd and
simd_mask, which use __builtin_bit_cast (or __bit_cast #if not
available), which return an object of the requested type with
the same bits as the argument.
* include/experimental/bits/simd_math.h: Use simd_bit_cast
instead of __bit_cast to allow casts to fixed_size_simd.
(copysign): Remove branch that was only required if __bit_cast
cannot be constexpr.
* testsuite/experimental/simd/tests/bits/test_values.h: Switch
from __bit_cast to __proposed::simd_bit_cast since the former
will not cast fixed_size objects anymore.
Signed-off-by: Matthias Kretz <m.kretz@gsi.de>
libstdc++-v3/ChangeLog:
* include/experimental/bits/simd_x86.h (_S_trunc, _S_floor)
(_S_ceil): Set bit 8 (_MM_FROUND_NO_EXC) on AVX and SSE4.1
roundp[sd] calls.
This improves codegen of ldexp if AVX512VL is available.
Signed-off-by: Matthias Kretz <m.kretz@gsi.de>
libstdc++-v3/ChangeLog:
* include/experimental/bits/simd_x86.h (_S_ldexp): The AVX512F
implementation doesn't require a _VecBltnBtmsk ABI tag, it
requires either a 64-Byte input (in which case AVX512F must be
available) or AVX512VL.
Signed-off-by: Matthias Kretz <m.kretz@gsi.de>
libstdc++-v3/ChangeLog:
* include/experimental/bits/simd_math.h: Undefine internal
macros after use.
(frexp): Move #if to a more sensible position and reformat
preceding code.
(logb): Call _SimdImpl::_S_logb for fixed_size instead of
duplicating the code here.
(modf): Simplify condition.
fabs(int) returns double, this one didn't. This overload is not
specified in the Parallelism TS 2. Also remove the comment about labs
and llabs: it doesn't belong here.
Signed-off-by: Matthias Kretz <m.kretz@gsi.de>
libstdc++-v3/ChangeLog:
* include/experimental/bits/simd_math.h (fabs): Remove
fabs(simd<integral>) overload.
Sometimes fixed_size objects will get unnecessarily copied on the stack.
The simd implementation should never pass _SimdTuple by value to avoid
requiring the optimizer to see through these copies.
Signed-off-by: Matthias Kretz <m.kretz@gsi.de>
libstdc++-v3/ChangeLog:
* include/experimental/bits/simd_converter.h
(_SimdConverter::operator()): Pass _SimdTuple by const-ref.
* include/experimental/bits/simd_fixed_size.h
(_GLIBCXX_SIMD_FIXED_OP): Pass binary operator _SimdTuple
arguments by const-ref.
(_S_masked_unary): Pass _SimdTuple by const-ref.
This helper type became unused at some point.
Signed-off-by: Matthias Kretz <m.kretz@gsi.de>
libstdc++-v3/ChangeLog:
* include/experimental/bits/simd_fixed_size.h
(_AbisInSimdTuple): Removed.
This also resolves a test failure on aarch64 with -ffast-math and
fixed_size<N> with large N.
Signed-off-by: Matthias Kretz <m.kretz@gsi.de>
libstdc++-v3/ChangeLog:
* include/experimental/bits/simd.h: Add missing operator~
overload for simd<floating-point> to __float_bitwise_operators.
* include/experimental/bits/simd_builtin.h
(_SimdImplBuiltin::_S_complement): Bitcast to int (and back) to
implement complement for floating-point vectors.
* include/experimental/bits/simd_fixed_size.h
(_SimdImplFixedSize::_S_copysign): New function, forwarding to
copysign implementation of _SimdTuple members.
* include/experimental/bits/simd_math.h (copysign): Call
_SimdImpl::_S_copysign for fixed_size arguments. Simplify
generic copysign implementation using the new ~ operator.
The LWG issue proposes to add a conditional noexcept-specifier to
std::unique_ptr's dereference operator. The issue is currently in
Tentatively Ready status, but even if it isn't voted into the draft, we
can do it as a conforming extensions. This commit also adds a similar
noexcept-specifier to operator[] for the unique_ptr<T[], D> partial
specialization.
Also ensure that all dereference operators for shared_ptr are noexcept,
and adds tests for the std::optional accessors modified by the issue,
which were already noexcept in our implementation.
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:
* include/bits/shared_ptr_base.h (__shared_ptr_access::operator[]):
Add noexcept.
* include/bits/unique_ptr.h (unique_ptr::operator*): Add
conditional noexcept as per LWG 2762.
* testsuite/20_util/shared_ptr/observers/array.cc: Check that
dereferencing cannot throw.
* testsuite/20_util/shared_ptr/observers/get.cc: Likewise.
* testsuite/20_util/optional/observers/lwg2762.cc: New test.
* testsuite/20_util/unique_ptr/lwg2762.cc: New test.
We set DECL_CONTEXT on implicitly generated deduction guides so that
their access is consistent with that of the constructor. But this
apparently leads to excessive instantiation in some cases, ultimately
because instantiation of a deduction guide should be independent of
instantiation of the resulting class specialization, but setting the
DECL_CONTEXT of the former to the latter breaks this independence.
To fix this, this patch makes push_access_scope handle artificial
deduction guides specifically rather than setting their DECL_CONTEXT
in build_deduction_guide. We could alternatively make the class
befriend the guide via DECL_BEFRIENDING_CLASSES, but that wouldn't
be a complete fix and would break class-deduction-access3.C below
since friendship isn't transitive.
PR c++/101174
gcc/cp/ChangeLog:
* pt.c (push_access_scope): For artificial deduction guides,
set the access scope to that of the constructor.
(pop_access_scope): Likewise.
(build_deduction_guide): Don't set DECL_CONTEXT on the guide.
libstdc++-v3/ChangeLog:
* testsuite/23_containers/multiset/cons/deduction.cc:
Uncomment CTAD example that was rejected by this bug.
* testsuite/23_containers/set/cons/deduction.cc: Likewise.
gcc/testsuite/ChangeLog:
* g++.dg/cpp1z/class-deduction-access3.C: New test.
* g++.dg/cpp1z/class-deduction91.C: New test.
For most uses --quiet was too quiet while the default was too noisy. Now
the default output, if stdout is a tty, shows the last successful test
on the same line. With --percentage it adds a percentage at the start of
the line. --percentage is not default because it requires more resources
and might not be 100% compatible to all environments.
If stdout is not a tty the default is quiet output like for dejagnu.
Additionally, argument parsing now recognizes contracted short options
which is easier to use with e.g. DRIVEROPTS=-pxk.
Signed-off-by: Matthias Kretz <m.kretz@gsi.de>
libstdc++-v3/ChangeLog:
* testsuite/experimental/simd/driver.sh: Rewrite output
verbosity logic. Add -p/--percentage option. Allow -v/--verbose
to be used twice. Add -x and -o short options. Parse long
options with = instead of separating space generically. Parce
contracted short options. Make unrecognized options an error.
If same-line output is active, trap on EXIT to increment the
progress (only with --percentage), erase the line and print the
current status.
* testsuite/experimental/simd/generate_makefile.sh: Initialize
helper files for progress account keeping. Update help target
for changes to DRIVEROPTS.
Simple change to std::chrono::year::is_leap. If a year is multiple of 100,
then it's divisible by 400 if and only if it's divisible by 16. The latter
allows for better code generation.
The expression is then either y%16 or y%4 which are both powers of two
and so it can be rearranged to use simple bitmask operations.
Co-authored-by: Jonathan Wakely <jwakely@redhat.com>
Co-authored-by: Ulrich Drepper <drepper@redhat.com>
libstdc++-v3/ChangeLog:
* include/std/chrono (chrono::year::is_leap()): Optimize.
During CTAD, we select the best viable deduction guide using
build_new_function_call, which performs overload resolution on the set
of candidate guides and then forms a call to the guide. As the PR
points out, this latter step is unnecessary and occasionally incorrect
since a call to the selected guide may be ill-formed, or forming the
call may have side effects such as prematurely deducing the type of a {}.
So this patch introduces a specialized subroutine based on
build_new_function_call that stops short of building a call to the
selected function, and makes do_class_deduction use this subroutine
instead. And since a call is no longer built, do_class_deduction
doesn't need to set tf_decltype or cp_unevaluated_operand anymore.
This change causes us to reject some container CTAD examples in the
libstdc++ testsuite due to deduction failure for {}, which AFAICT is the
correct behavior. Previously in e.g. the first removed example
std::map{{std::pair{1, 2.0}, {2, 3.0}, {3, 4.0}}, {}},
the type of the {} would get deduced to less<int> as a side effect of
forming a call to the chosen guide
template<typename _Key, typename _Tp, typename _Compare = less<_Key>,
typename _Allocator = allocator<pair<const _Key, _Tp>>>
map(initializer_list<pair<_Key, _Tp>>,
_Compare = _Compare(), _Allocator = _Allocator())
-> map<_Key, _Tp, _Compare, _Allocator>;
which made later overload resolution for the constructor call
unambiguous. Now, the type of the {} remains undeduced until
constructor overload resolution, and we complain about ambiguity
for the two equally good constructor candidates
map(initializer_list<value_type>,
const _Compare& = _Compare(),
const allocator_type& = allocator_type())
map(initializer_list<value_type>, const allocator_type&).
This patch fixes these problematic container CTAD examples by giving
the {} an appropriate concrete type. Two of these adjusted CTAD
examples (one for std::set and one for std::multiset) end up triggering
an unrelated CTAD bug on trunk, PR101174, so these two adjusted examples
are commented out for now.
PR c++/86439
gcc/cp/ChangeLog:
* call.c (print_error_for_call_failure): Constify 'args' parameter.
(perform_dguide_overload_resolution): Define.
* cp-tree.h: (perform_dguide_overload_resolution): Declare.
* pt.c (do_class_deduction): Use perform_dguide_overload_resolution
instead of build_new_function_call. Don't use tf_decltype or
set cp_unevaluated_operand. Remove unnecessary NULL_TREE tests.
libstdc++-v3/ChangeLog:
* testsuite/23_containers/map/cons/deduction.cc: Replace ambiguous
CTAD examples.
* testsuite/23_containers/multimap/cons/deduction.cc: Likewise.
* testsuite/23_containers/multiset/cons/deduction.cc: Likewise.
Mention one of the replaced examples is broken due to PR101174.
* testsuite/23_containers/set/cons/deduction.cc: Likewise.
* testsuite/23_containers/unordered_map/cons/deduction.cc: Replace
ambiguous CTAD examples.
* testsuite/23_containers/unordered_multimap/cons/deduction.cc:
Likewise.
* testsuite/23_containers/unordered_multiset/cons/deduction.cc:
Likewise.
* testsuite/23_containers/unordered_set/cons/deduction.cc: Likewise.
gcc/testsuite/ChangeLog:
* g++.dg/cpp1z/class-deduction88.C: New test.
* g++.dg/cpp1z/class-deduction89.C: New test.
* g++.dg/cpp1z/class-deduction90.C: New test.
The std::try_lock and std::lock algorithms can use iteration instead of
recursion when all lockables have the same type and can be held by an
array of unique_lock<L> objects.
By making this change to __detail::__try_lock_impl it also benefits
__detail::__lock_impl, which uses it. For std::lock we can just put the
iterative version directly in std::lock, to avoid making any call to
__detail::__lock_impl.
Signed-off-by: Matthias Kretz <m.kretz@gsi.de>
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
Co-authored-by: Matthias Kretz <m.kretz@gsi.de>
libstdc++-v3/ChangeLog:
* include/std/mutex (lock): Replace recursion with iteration
when lockables all have the same type.
(__detail::__try_lock_impl): Likewise. Pass lockables as
parameters, instead of a tuple. Always lock the first one, and
recurse for the rest.
(__detail::__lock_impl): Adjust call to __try_lock_impl.
(__detail::__try_to_lock): Remove.
* testsuite/30_threads/lock/3.cc: Check that mutexes are locked.
* testsuite/30_threads/lock/4.cc: Also test non-heterogeneous
arguments.
* testsuite/30_threads/unique_lock/cons/60497.cc: Also check
std::try_lock.
* testsuite/30_threads/try_lock/5.cc: New test.
This removes the non-functional garbage colection support from <memory>,
as proposed for C++23 by P2186R2.
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:
* include/std/memory (declare_reachable, undeclare_reachable)
(declare_no_pointers, undeclare_no_pointers, get_pointer_safety)
(pointer_safety): Only define for C++11 to C++20 inclusive.
* testsuite/20_util/pointer_safety/1.cc: Do not run for C++23.
This ensures that the std::seed_seq initializer-list constructor will
not be used for list-initialization unless the initializers in the list
are integers. This allows list-initialization syntax to be used with a
pair of pointers and for that to use the appropriate constructor.
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:
* include/bits/random.h (seed_seq): Constrain initializer-list
constructor.
* include/bits/random.tcc (seed_seq): Add template parameter.
* testsuite/26_numerics/random/seed_seq/cons/default.cc: Check
for noexcept.
* testsuite/26_numerics/random/seed_seq/cons/initlist.cc: Check
constraints.
libstdc++-v3/ChangeLog:
PR libstdc++/100806
* include/bits/semaphore_base.h (__atomic_semaphore::_M_release):
Force _M_release() to wake all waiting threads.
* testsuite/30_threads/semaphore/100806.cc: New test.
The current std::lock algorithm is the one called "persistent" in Howard
Hinnant's https://howardhinnant.github.io/dining_philosophers.html post.
While it tends to perform acceptably fast, it wastes a lot of CPU cycles
by continuously locking and unlocking the uncontended mutexes.
Effectively, it's a spin lock with no back-off.
This replaces it with the one Howard calls "smart and polite". It's
smart, because when a Mi.try_lock() call fails because mutex Mi is
contended, the algorithm reorders the mutexes until Mi is first, then
calls Mi.lock(), to block until Mi is no longer contended. It's
polite because it uses std::this_thread::yield() between the failed
Mi.try_lock() call and the Mi.lock() call. (In reality it uses
__gthread_yield() directly, because using this_thread::yield() would
require shuffling code around to avoid a circular dependency.)
This version of the algorithm is inspired by some hints from Howard, so
that it has strictly bounded stack usage. As the comment in the code
says:
// This function can recurse up to N levels deep, for N = 1+sizeof...(L1).
// On each recursion the lockables are rotated left one position,
// e.g. depth 0: l0, l1, l2; depth 1: l1, l2, l0; depth 2: l2, l0, l1.
// When a call to l_i.try_lock() fails it recurses/returns to depth=i
// so that l_i is the first argument, and then blocks until l_i is locked.
The 'i' parameter is the desired permuation of the lockables, and the
'depth' parameter is the depth in the call stack of the current
instantiation of the function template. If i == depth then the function
calls l0.lock() and then l1.try_lock()... for each lockable in the
parameter pack l1. If i > depth then the function rotates the lockables
to the left one place, and calls itself again to go one level deeper.
Finally, if i < depth then the function returns to a shallower depth,
equivalent to a right rotate of the lockables. When a call to
try_lock() fails, i is set to the index of the contended lockable, so
that the next call to l0.lock() will use the contended lockable as l0.
This commit also replaces the std::try_lock implementation details. The
new code is identical in behaviour, but uses a pair of constrained
function templates. This avoids instantiating a class template, and is a
litle simpler to call where used in std::__detail::__lock_impl and
std::try_lock.
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:
* include/std/mutex (__try_to_lock): Move to __detail namespace.
(struct __try_lock_impl): Replace with ...
(__detail::__try_lock_impl<Idx>(tuple<Lockables...>&)): New
function templates to implement std::try_lock.
(try_lock): Use new __try_lock_impl.
(__detail::__lock_impl(int, int&, L0&, L1&...)): New function
template to implement std::lock.
(lock): Use __lock_impl.
r12-1606 bumped the value of __cpp_lib_ranges defined in <version>,
but this macro is also defined in <bits/range_cmp.h>, so it needs to
be updated there as well.
libstdc++-v3/ChangeLog:
* include/bits/ranges_cmp.h (__cpp_lib_ranges): Adjust value.
