[gcc r14-5262] libstdc++: [_Hashtable] Use RAII type to guard node while constructing value

[Francois Dumont]

https://gcc.gnu.org/g:04d8a47608dcae7f61805e3566e3a1571b574405

commit r14-5262-g04d8a47608dcae7f61805e3566e3a1571b574405
Author: François Dumont <fdumont@gcc.gnu.org>
Date:   Mon Oct 30 06:39:00 2023 +0100

    libstdc++: [_Hashtable] Use RAII type to guard node while constructing value
    
    libstdc++-v3/ChangeLog:
    
            * include/bits/hashtable_policy.h
            (struct _NodePtrGuard<_HashtableAlloc, _NodePtr>): New.
            (_ReuseAllocNode::operator()(_Args&&...)): Use latter to guard allocated node
            pointer while constructing in place the value_type instance.

Diff:
---
 libstdc++-v3/include/bits/hashtable_policy.h | 46 ++++++++++++++++------------
 1 file changed, 26 insertions(+), 20 deletions(-)

diff --git a/libstdc++-v3/include/bits/hashtable_policy.h b/libstdc++-v3/include/bits/hashtable_policy.h
index a2731b3f63f..46d05922532 100644
--- a/libstdc++-v3/include/bits/hashtable_policy.h
+++ b/libstdc++-v3/include/bits/hashtable_policy.h
@@ -173,6 +173,19 @@ namespace __detail
 	{ return __node_gen(std::forward<_Kt>(__k)); }
     };
 
+  template<typename _HashtableAlloc, typename _NodePtr>
+    struct _NodePtrGuard
+    {
+      _HashtableAlloc& _M_h;
+      _NodePtr _M_ptr;
+
+      ~_NodePtrGuard()
+      {
+	if (_M_ptr)
+	  _M_h._M_deallocate_node_ptr(_M_ptr);
+      }
+    };
+
   template<typename _NodeAlloc>
     struct _Hashtable_alloc;
 
@@ -201,26 +214,19 @@ namespace __detail
 	__node_ptr
 	operator()(_Args&&... __args) const
 	{
-	  if (_M_nodes)
-	    {
-	      __node_ptr __node = _M_nodes;
-	      _M_nodes = _M_nodes->_M_next();
-	      __node->_M_nxt = nullptr;
-	      auto& __a = _M_h._M_node_allocator();
-	      __node_alloc_traits::destroy(__a, __node->_M_valptr());
-	      __try
-		{
-		  __node_alloc_traits::construct(__a, __node->_M_valptr(),
-						 std::forward<_Args>(__args)...);
-		}
-	      __catch(...)
-		{
-		  _M_h._M_deallocate_node_ptr(__node);
-		  __throw_exception_again;
-		}
-	      return __node;
-	    }
-	  return _M_h._M_allocate_node(std::forward<_Args>(__args)...);
+	  if (!_M_nodes)
+	    return _M_h._M_allocate_node(std::forward<_Args>(__args)...);
+
+	  __node_ptr __node = _M_nodes;
+	  _M_nodes = _M_nodes->_M_next();
+	  __node->_M_nxt = nullptr;
+	  auto& __a = _M_h._M_node_allocator();
+	  __node_alloc_traits::destroy(__a, __node->_M_valptr());
+	  _NodePtrGuard<__hashtable_alloc, __node_ptr> __guard { _M_h, __node };
+	  __node_alloc_traits::construct(__a, __node->_M_valptr(),
+					 std::forward<_Args>(__args)...);
+	  __guard._M_ptr = nullptr;
+	  return __node;
 	}
 
     private: