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libstdc++: Only include <condition_variable> in <shared_mutex> if needed

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The <condition_variable> header is not small, so <shared_mutex> should
not include it unless it actually needs std::condition_variable, which
is only the case when we don't have pthread_rwlock_t and the POSIX
Timers option.

The <shared_mutex> header would be even smaller if we had a header for
std::condition_variable (separate from std::condition_variable_any).
That's already planned for a future change.

And <memory_resource> would be even smaller if it was possible to get
std::shared_mutex without std::shared_timed_mutex (which depends on
<chrono>). For that to be effective, the synchronized_pool_resource
would have to create its own simpler version of std::shared_lock without
the timed waiting functions. I have no plans to do that.

libstdc++-v3/ChangeLog:

	* include/std/shared_mutex: Only include <condition_variable>
	when pthread_rwlock_t and POSIX timers are not available.
	(__cpp_lib_shared_mutex, __cpp_lib_shared_timed_mutex): Change
	value to be type 'long'.
	* include/std/version (__cpp_lib_shared_mutex)
	(__cpp_lib_shared_timed_mutex): Likewise.
This commit is contained in:
Jonathan Wakely 2020-10-22 18:42:03 +01:00
parent b1e7c6fce1
commit f5d9bc8ae8
2 changed files with 13 additions and 8 deletions
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17
libstdc++-v3/include/std/shared_mutex
View file

@ -33,9 +33,14 @@
#if __cplusplus >= 201402L
#include <bits/c++config.h>
#include <condition_variable>
#include <chrono>
#include <bits/functexcept.h>
#include <bits/move.h> // move, __exchange
#include <bits/std_mutex.h> // defer_lock_t
#if ! (_GLIBCXX_USE_PTHREAD_RWLOCK_T && _GTHREAD_USE_MUTEX_TIMEDLOCK)
# include <condition_variable>
#endif
namespace std _GLIBCXX_VISIBILITY(default)
{
@ -49,11 +54,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
#ifdef _GLIBCXX_HAS_GTHREADS
#if __cplusplus >= 201703L
#define __cpp_lib_shared_mutex 201505
#define __cpp_lib_shared_mutex 201505L
class shared_mutex;
#endif
#define __cpp_lib_shared_timed_mutex 201402
#define __cpp_lib_shared_timed_mutex 201402L
class shared_timed_mutex;
/// @cond undocumented
@ -399,7 +404,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
#endif
/// @endcond
#if __cplusplus > 201402L
#if __cplusplus >= 201703L
/// The standard shared mutex type.
class shared_mutex
{
@ -814,7 +819,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
release() noexcept
{
_M_owns = false;
return std::exchange(_M_pm, nullptr);
return std::__exchange(_M_pm, nullptr);
}
// Getters

4
libstdc++-v3/include/std/version
View file

@ -89,7 +89,7 @@
# define __cpp_lib_quoted_string_io 201304
# define __cpp_lib_robust_nonmodifying_seq_ops 201304
# ifdef _GLIBCXX_HAS_GTHREADS
# define __cpp_lib_shared_timed_mutex 201402
# define __cpp_lib_shared_timed_mutex 201402L
# endif
# define __cpp_lib_string_udls 201304
# define __cpp_lib_transparent_operators 201510
@ -157,7 +157,7 @@
#define __cpp_lib_sample 201603
#ifdef _GLIBCXX_HAS_GTHREADS
# define __cpp_lib_scoped_lock 201703
# define __cpp_lib_shared_mutex 201505
# define __cpp_lib_shared_mutex 201505L
#endif
#define __cpp_lib_shared_ptr_weak_type 201606
#define __cpp_lib_string_view 201803L