From e162b2ff52c5e20f6624ff6b66845fe573cef183 Mon Sep 17 00:00:00 2001
From: Jonathan Wakely <jwakely@redhat.com>
Date: Mon, 26 Feb 2024 13:17:32 +0000
Subject: [PATCH] libstdc++: Do not define lock-free atomic aliases if not
fully lock-free [PR114103]
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.
---
libstdc++-v3/include/bits/version.def | 1 +
libstdc++-v3/include/bits/version.h | 2 +-
libstdc++-v3/include/std/atomic | 6 +++---
libstdc++-v3/src/c++20/tzdb.cc | 7 ++++++-
.../testsuite/29_atomics/atomic/lock_free_aliases.cc | 1 +
5 files changed, 12 insertions(+), 5 deletions(-)
diff --git a/libstdc++-v3/include/bits/version.def b/libstdc++-v3/include/bits/version.def
index 502961eb2699..d298420121b8 100644
--- a/libstdc++-v3/include/bits/version.def
+++ b/libstdc++-v3/include/bits/version.def
@@ -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";
};
};
diff --git a/libstdc++-v3/include/bits/version.h b/libstdc++-v3/include/bits/version.h
index 7a6fbd35e2ef..9107b45a4841 100644
--- a/libstdc++-v3/include/bits/version.h
+++ b/libstdc++-v3/include/bits/version.h
@@ -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
diff --git a/libstdc++-v3/include/std/atomic b/libstdc++-v3/include/std/atomic
index 559f8370459e..1462cf5ec23f 100644
--- a/libstdc++-v3/include/std/atomic
+++ b/libstdc++-v3/include/std/atomic
@@ -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
diff --git a/libstdc++-v3/src/c++20/tzdb.cc b/libstdc++-v3/src/c++20/tzdb.cc
index e03f4a5c32ac..890a4c53e2d4 100644
--- a/libstdc++-v3/src/c++20/tzdb.cc
+++ b/libstdc++-v3/src/c++20/tzdb.cc
@@ -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 {
diff --git a/libstdc++-v3/testsuite/29_atomics/atomic/lock_free_aliases.cc b/libstdc++-v3/testsuite/29_atomics/atomic/lock_free_aliases.cc
index 372a63129ff7..489d181d136f 100644
--- a/libstdc++-v3/testsuite/29_atomics/atomic/lock_free_aliases.cc
+++ b/libstdc++-v3/testsuite/29_atomics/atomic/lock_free_aliases.cc
@@ -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>
--
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