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libstdc++: Do not define lock-free atomic aliases if not fully lock-free [PR114103]

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The whole point of these typedefs is to guarantee lock-freedom, so if
the target has no such types, we shouldn't defined the typedefs at all.

libstdc++-v3/ChangeLog:

	PR libstdc++/114103
	* include/bits/version.def (atomic_lock_free_type_aliases): Add
	extra_cond to check for at least one always-lock-free type.
	* include/bits/version.h: Regenerate.
	* include/std/atomic (atomic_signed_lock_free)
	(atomic_unsigned_lock_free): Only use always-lock-free types.
	* src/c++20/tzdb.cc (time_zone::_Impl::RulesCounter): Don't use
	atomic counter if lock-free aliases aren't available.
	* testsuite/29_atomics/atomic/lock_free_aliases.cc: XFAIL for
	targets without lock-free word-size compare_exchange.
This commit is contained in:
Jonathan Wakely 2024-02-26 13:17:32 +00:00
parent ddd347fca0
commit e162b2ff52
5 changed files with 12 additions and 5 deletions
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1
libstdc++-v3/include/bits/version.def
View file

@ -739,6 +739,7 @@ ftms = {
values = {
v = 201907;
cxxmin = 20;
extra_cond = "(__GCC_ATOMIC_INT_LOCK_FREE | __GCC_ATOMIC_LONG_LOCK_FREE | __GCC_ATOMIC_CHAR_LOCK_FREE) & 2";
};
};

2
libstdc++-v3/include/bits/version.h
View file

@ -819,7 +819,7 @@
#undef __glibcxx_want_atomic_float
#if !defined(__cpp_lib_atomic_lock_free_type_aliases)
# if (__cplusplus >= 202002L)
# if (__cplusplus >= 202002L) && ((__GCC_ATOMIC_INT_LOCK_FREE | __GCC_ATOMIC_LONG_LOCK_FREE | __GCC_ATOMIC_CHAR_LOCK_FREE) & 2)
# define __glibcxx_atomic_lock_free_type_aliases 201907L
# if defined(__glibcxx_want_all) || defined(__glibcxx_want_atomic_lock_free_type_aliases)
# define __cpp_lib_atomic_lock_free_type_aliases 201907L

6
libstdc++-v3/include/std/atomic
View file

@ -1774,13 +1774,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
= atomic<make_signed_t<__detail::__platform_wait_t>>;
using atomic_unsigned_lock_free
= atomic<make_unsigned_t<__detail::__platform_wait_t>>;
# elif ATOMIC_INT_LOCK_FREE || !(ATOMIC_LONG_LOCK_FREE || ATOMIC_CHAR_LOCK_FREE)
# elif ATOMIC_INT_LOCK_FREE == 2
using atomic_signed_lock_free = atomic<signed int>;
using atomic_unsigned_lock_free = atomic<unsigned int>;
# elif ATOMIC_LONG_LOCK_FREE
# elif ATOMIC_LONG_LOCK_FREE == 2
using atomic_signed_lock_free = atomic<signed long>;
using atomic_unsigned_lock_free = atomic<unsigned long>;
# elif ATOMIC_CHAR_LOCK_FREE
# elif ATOMIC_CHAR_LOCK_FREE == 2
using atomic_signed_lock_free = atomic<signed char>;
using atomic_unsigned_lock_free = atomic<unsigned char>;
# else

7
libstdc++-v3/src/c++20/tzdb.cc
View file

@ -651,7 +651,7 @@ namespace std::chrono
template<typename _Tp> requires _Tp::is_always_lock_free
struct RulesCounter<_Tp>
{
atomic_signed_lock_free counter{0};
_Tp counter{0};
void
increment()
@ -703,7 +703,12 @@ namespace std::chrono
};
#endif // __GTHREADS && __cpp_lib_atomic_wait
#if __cpp_lib_atomic_lock_free_type_aliases
RulesCounter<atomic_signed_lock_free> rules_counter;
#else
RulesCounter<void> rules_counter;
#endif
#else // TZDB_DISABLED
_Impl(weak_ptr<tzdb_list::_Node>) { }
struct {

1
libstdc++-v3/testsuite/29_atomics/atomic/lock_free_aliases.cc
View file

@ -1,5 +1,6 @@
// { dg-do compile { target c++20 } }
// { dg-add-options no_pch }
// { dg-require-atomic-cmpxchg-word "PR libstdc++/114103" }
#include <atomic>