From: Jonathan Wakely <jwakely@redhat.com>
Date: Mon, 25 Apr 2022 17:25:07 +0000 (+0100)
Subject: libstdc++: Add std::atomic<shared_ptr>(nullptr_t) constructor (LWG 3661)
X-Git-Tag: basepoints/gcc-13~46
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=41ccd683f0002d7b5127aafc00dcd59e7837f0ab;p=thirdparty%2Fgcc.git

libstdc++: Add std::atomic<shared_ptr>(nullptr_t) constructor (LWG 3661)

This DR was approved at the February 2022 plenary.

libstdc++-v3/ChangeLog:

	* include/bits/shared_ptr_atomic.h (atomic<shared_ptr>): Add
	constructor for constant initialization from nullptr_t.
	* testsuite/20_util/shared_ptr/atomic/atomic_shared_ptr.cc:
	Check for new constructor.
---

diff --git a/libstdc++-v3/include/bits/shared_ptr_atomic.h b/libstdc++-v3/include/bits/shared_ptr_atomic.h
index 9e4df7da7f8b..ff86432f0b40 100644
--- a/libstdc++-v3/include/bits/shared_ptr_atomic.h
+++ b/libstdc++-v3/include/bits/shared_ptr_atomic.h
@@ -573,6 +573,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
       constexpr atomic() noexcept = default;
 
+      // _GLIBCXX_RESOLVE_LIB_DEFECTS
+      // 3661. constinit atomic<shared_ptr<T>> a(nullptr); should work
+      constexpr atomic(nullptr_t) noexcept : atomic() { }
+
       atomic(shared_ptr<_Tp> __r) noexcept
       : _M_impl(std::move(__r))
       { }
diff --git a/libstdc++-v3/testsuite/20_util/shared_ptr/atomic/atomic_shared_ptr.cc b/libstdc++-v3/testsuite/20_util/shared_ptr/atomic/atomic_shared_ptr.cc
index 1f97224bf6aa..a1902745a3ef 100644
--- a/libstdc++-v3/testsuite/20_util/shared_ptr/atomic/atomic_shared_ptr.cc
+++ b/libstdc++-v3/testsuite/20_util/shared_ptr/atomic/atomic_shared_ptr.cc
@@ -18,6 +18,8 @@
 
 // Check constexpr constructor.
 constinit std::atomic<std::shared_ptr<int>> a;
+// LWG 3661. constinit atomic<shared_ptr<T>> a(nullptr); should work
+constinit std::atomic<std::shared_ptr<int>> a2 = nullptr;
 
 void
 test_is_lock_free()