From: Jonathan Wakely <jwakely@redhat.com>
Date: Tue, 18 Jan 2022 21:15:05 +0000 (+0000)
Subject: libstdc++: Fix std::atomic<std::shared_ptr<T>> for AIX [PR104101]
X-Git-Tag: basepoints/gcc-13~1605
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=c3861f79859d96777f86a24261fe639538fd2e1c;p=thirdparty%2Fgcc.git

libstdc++: Fix std::atomic<std::shared_ptr<T>> for AIX [PR104101]

This fixes an on AIX.

The lock function currently just spins, which should be changed to use
back-off, and maybe then _M_val.wait(__current) when supported.

libstdc++-v3/ChangeLog:

	PR libstdc++/104101
	* include/bits/shared_ptr_atomic.h (_Sp_atomic::_Atomic_count::lock):
	Only use __thread_relax if __cpp_lib_atomic_wait is defined.
---

diff --git a/libstdc++-v3/include/bits/shared_ptr_atomic.h b/libstdc++-v3/include/bits/shared_ptr_atomic.h
index 50aa46370cab..35f781dc9a09 100644
--- a/libstdc++-v3/include/bits/shared_ptr_atomic.h
+++ b/libstdc++-v3/include/bits/shared_ptr_atomic.h
@@ -392,7 +392,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  auto __current = _M_val.load(memory_order_relaxed);
 	  while (__current & _S_lock_bit)
 	    {
+#if __cpp_lib_atomic_wait
 	      __detail::__thread_relax();
+#endif
 	      __current = _M_val.load(memory_order_relaxed);
 	    }
 
@@ -401,7 +403,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 						 __o,
 						 memory_order_relaxed))
 	    {
+#if __cpp_lib_atomic_wait
 	      __detail::__thread_relax();
+#endif
 	      __current = __current & ~_S_lock_bit;
 	    }
 	  return reinterpret_cast<pointer>(__current);