The std::thread::id formatter uses std::basic_ostringstream without
including <sstream>, which went unnoticed because the test for it uses
a stringstream to check the output is correct.
The fix implemented here is to stop using basic_ostringstream for
formatting thread::id and just use std::format instead.
As a drive-by fix, the formatter specialization is constrained to
require that the thread::id::native_handle_type can be formatted, to
avoid making the formatter ill-formed if the pthread_t type is not a
pointer or integer. Since non-void pointers can't be formatted, ensure
that we convert pointers to const void* for formatting. Make a similar
change to the existing operator<< overload so that in the unlikely case
that pthread_t is a typedef for char* we don't treat it as a
null-terminated string when inserting into a stream.
libstdc++-v3/ChangeLog:
PR libstdc++/115099
* include/bits/std_thread.h: Declare formatter as friend of
thread::id.
* include/std/thread (operator<<): Convert non-void pointers to
void pointers for output.
(formatter): Add constraint that thread::native_handle_type is a
pointer or integer.
(formatter::format): Reimplement without basic_ostringstream.
* testsuite/30_threads/thread/id/output.cc: Check output
compiles before <sstream> has been included.
Like pthread_create, pthread_join may fail to be statically linked in
absent strong uses, so add to user code strong references to both when
std::thread objects are created.
for libstdc++-v3/ChangeLog
PR libstdc++/104852
PR libstdc++/95989
PR libstdc++/52590
* include/bits/std_thread.h (thread::_M_thread_deps): New
static implicitly-inline member function.
(std::thread template ctor): Pass it to _M_start_thread.
* src/c++11/thread.cc (thread::_M_start_thread): Name depend
parameter, force it live on entry.
When I changed std::thread and std::async to avoid unnecessary move
construction of temporaries, I introduced a regression where types with
an explicit copy constructor could not be passed to std::thread or
std::async. The fix is to add a constructor instead of using aggregate
initialization of an unnamed temporary.
libstdc++-v3/ChangeLog:
PR libstdc++/106695
* include/bits/std_thread.h (thread::_State_impl): Forward
individual arguments to _Invoker constructor.
(thread::_Invoker): Add constructor. Delete copies.
* include/std/future (__future_base::_Deferred_state): Forward
individual arguments to _Invoker constructor.
(__future_base::_Async_state_impl): Likewise.
* testsuite/30_threads/async/106695.cc: New test.
* testsuite/30_threads/thread/106695.cc: New test.
This adds an inline wrapper for std::terminate that doesn't add the
declaration of std::terminate to namespace std. This allows the
library to terminate without including all of <exception>.
libstdc++-v3/ChangeLog:
* include/bits/atomic_timed_wait.h: Remove unused header.
* include/bits/c++config (std:__terminate): Define.
* include/bits/semaphore_base.h: Remove <exception> and use
__terminate instead of terminate.
* include/bits/std_thread.h: Likewise.
* libsupc++/eh_terminate.cc (std::terminate): Use qualified-id
to call __cxxabiv1::__terminate.
The new inline definition of std::thread::hardware_concurrency() for
non-gthreads targets is missing the noexcept-specifier that is on the
declaration.
libstdc++-v3/ChangeLog:
PR libstdc++/100298
* include/bits/std_thread.h (thread::hardware_concurrency): Add
missing noexcept to inline definition for non-gthreads targets.
This makes the hash function available without including the whole of
<thread>, which is needed for <barrier>.
libstdc++-v3/ChangeLog:
* include/bits/std_thread.h (hash<thread::id>): Move here,
from ...
* include/std/thread (hash<thread::id>): ... here.
Since glibc 2.27 the pthread_self symbol has been defined in libc rather
than libpthread. Because we only call pthread_self through a weak alias
it's possible for statically linked executables to end up without a
definition of pthread_self. This crashes when trying to call an
undefined weak symbol.
We can use the __GLIBC_PREREQ version check to detect the version of
glibc where pthread_self is no longer in libpthread, and call it
directly rather than through the weak reference.
It would be better to check for pthread_self in libc during configure
instead of hardcoding the __GLIBC_PREREQ check. That would be
complicated by the fact that prior to glibc 2.27 libc.a didn't have the
pthread_self symbol, but libc.so.6 did. The configure checks would need
to try to link both statically and dynamically, and the result would
depend on whether the static libc.a happens to be installed during
configure (which could vary between different systems using the same
version of glibc). Doing it properly is left for a future date, as that
will be needed anyway after glibc moves all pthread symbols from
libpthread to libc. When that happens we should revisit the whole
approach of using weak symbols for pthread symbols.
For the purposes of std::this_thread::get_id() we call
pthread_self() directly when using glibc 2.27 or later. Otherwise, if
__gthread_active_p() is true then we know the libpthread symbol is
available so we call that. Otherwise, we are single-threaded and just
use ((__gthread_t)1) as the thread ID.
An undesirable consequence of this change is that code compiled prior to
the change might inline the old definition of this_thread::get_id()
which always returns (__gthread_t)1 in a program that isn't linked to
libpthread. Code compiled after the change will use pthread_self() and
so get a real TID. That could result in the main thread having different
thread::id values in different translation units. This seems acceptable,
as there are not expected to be many uses of thread::id in programs
that aren't linked to libpthread.
An earlier version of this patch also changed __gthread_self() to use
__GLIBC_PREREQ(2, 27) and only use the weak symbol for older glibc. Tha
might still make sense to do, but isn't needed by libstdc++ now.
libstdc++-v3/ChangeLog:
PR libstdc++/95989
* config/os/gnu-linux/os_defines.h (_GLIBCXX_NATIVE_THREAD_ID):
Define new macro to get reliable thread ID.
* include/bits/std_thread.h: (this_thread::get_id): Use new
macro if it's defined.
* testsuite/30_threads/jthread/95989.cc: New test.
* testsuite/30_threads/this_thread/95989.cc: New test.
This makes it possible to use std::thread without including the whole of
<thread>. It also makes this_thread::get_id() and this_thread::yield()
available even when there is no gthreads support (e.g. when GCC is built
with --disable-threads or --enable-threads=single).
In order for the std::thread::id return type of this_thread::get_id() to
be defined, std:thread itself is defined unconditionally. However the
constructor that creates new threads is not defined for single-threaded
builds. The thread::join() and thread::detach() member functions are
defined inline for single-threaded builds and just throw an exception
(because we know the thread cannot be joinable if the constructor that
creates joinable threads doesn't exit).
The thread::hardware_concurrency() member function is also defined
inline and returns 0 (as suggested by the standard when the value "is
not computable or well-defined").
The main benefit for most targets is that other headers such as <future>
do not need to include the whole of <thread> just to be able to create a
std::thread. That avoids including <stop_token> and std::jthread where
not required. This is another partial fix for PR 92546.
This also means we can use this_thread::get_id() and this_thread::yield()
in <stop_token> instead of using the gthread functions directly. This
removes some preprocessor conditionals, simplifying the code.
libstdc++-v3/ChangeLog:
PR libstdc++/92546
* include/Makefile.am: Add new <bits/std_thread.h> header.
* include/Makefile.in: Regenerate.
* include/std/future: Include new header instead of <thread>.
* include/std/stop_token: Include new header instead of
<bits/gthr.h>.
(stop_token::_S_yield()): Use this_thread::yield().
(_Stop_state_t::_M_requester): Change type to std::thread::id.
(_Stop_state_t::_M_request_stop()): Use this_thread::get_id().
(_Stop_state_t::_M_remove_callback(_Stop_cb*)): Likewise.
Use __is_single_threaded() to decide whether to synchronize.
* include/std/thread (thread, operator==, this_thread::get_id)
(this_thread::yield): Move to new header.
(operator<=>, operator!=, operator<, operator<=, operator>)
(operator>=, hash<thread::id>, operator<<): Define even when
gthreads not available.
* src/c++11/thread.cc: Include <memory>.
* include/bits/std_thread.h: New file.
(thread, operator==, this_thread::get_id, this_thread::yield):
Define even when gthreads not available.
[!_GLIBCXX_HAS_GTHREADS] (thread::join, thread::detach)
(thread::hardware_concurrency): Define inline.
Jakub Jelinek