[PATCH] c++: Mark replaceable global operator new/delete with const std::nothrow_t& argument as DECL_IS_REPLACEABLE_OPERATOR [PR117370]

[Jakub Jelinek]

Hi!

cxx_init_decl_processing predeclares 12 out of the 20 replaceable global
new/delete operators and sets DECL_IS_REPLACEABLE_OPERATOR on those.
But it doesn't handle the remaining 8, in particular
void* operator new(std::size_t, const std::nothrow_t&) noexcept;
void* operator new[](std::size_t, const std::nothrow_t&) noexcept;
void operator delete(void*, const std::nothrow_t&) noexcept;
void operator delete[](void*, const std::nothrow_t&) noexcept;
void* operator new(std::size_t, std::align_val_t, const std::nothrow_t&) 
noexcept;
void* operator new[](std::size_t, std::align_val_t, const std::nothrow_t&) 
noexcept;
void operator delete(void*, std::align_val_t, const std::nothrow_t&) noexcept;
void operator delete[](void*, std::align_val_t, const std::nothrow_t&) noexcept;

The following patch sets that flag during grok_op_properties for those, so
that they don't need to be predeclared.
The patch doesn't fix the whole PR, as some work is needed on the CDDCE side
too, unlike the throwing operator new case the if (ptr) conditional around
operator delete isn't removed by VRP and so we need to handle conditional
delete for unconditional new.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2024-10-31  Jakub Jelinek  <ja...@redhat.com>

        PR c++/117370
        * decl.cc (grok_op_properties): Mark global replaceable
        operator new/delete operators with const std::nothrow_t & last
        argument with DECL_IS_REPLACEABLE_OPERATOR.

--- gcc/cp/decl.cc.jj   2024-10-25 10:00:29.413768644 +0200
+++ gcc/cp/decl.cc      2024-10-30 17:50:48.165446364 +0100
@@ -16191,6 +16191,52 @@ grok_op_properties (tree decl, bool comp
            }
        }
 
+      /* Check for replaceable global new/delete operators with
+        const std::nothrow_t & last argument, other replaceable global
+        new/delete operators are marked in cxx_init_decl_processing.  */
+      if (CP_DECL_CONTEXT (decl) == global_namespace)
+       {
+         tree args = argtypes;
+         if (args
+             && args != void_list_node
+             && same_type_p (TREE_VALUE (args),
+                             (op_flags & OVL_OP_FLAG_DELETE)
+                             ? ptr_type_node : size_type_node))
+           {
+             args = TREE_CHAIN (args);
+             if (aligned_new_threshold
+                 && args
+                 && args != void_list_node)
+               {
+                 tree t = TREE_VALUE (args);
+                 if (TREE_CODE (t) == ENUMERAL_TYPE
+                     && DECL_NAMESPACE_STD_P (CP_TYPE_CONTEXT (t))
+                     && TYPE_NAME (t)
+                     && TREE_CODE (TYPE_NAME (t)) == TYPE_DECL
+                     && DECL_NAME (TYPE_NAME (t))
+                     && id_equal (DECL_NAME (TYPE_NAME (t)), "align_val_t"))
+                   args = TREE_CHAIN (args);
+               }
+             if (args
+                 && args != void_list_node
+                 && TREE_CHAIN (args) == void_list_node)
+               {
+                 tree t = TREE_VALUE (args);
+                 if (TYPE_REF_P (t)
+                     && !TYPE_REF_IS_RVALUE (t)
+                     && (t = TREE_TYPE (t))
+                     && TYPE_QUALS (t) == TYPE_QUAL_CONST
+                     && TREE_CODE (t) == RECORD_TYPE
+                     && DECL_NAMESPACE_STD_P (CP_TYPE_CONTEXT (t))
+                     && TYPE_NAME (t)
+                     && TREE_CODE (TYPE_NAME (t)) == TYPE_DECL
+                     && DECL_NAME (TYPE_NAME (t))
+                     && id_equal (DECL_NAME (TYPE_NAME (t)), "nothrow_t"))
+                   DECL_IS_REPLACEABLE_OPERATOR (decl) = 1;
+               }
+           }
+       }
+
       if (op_flags & OVL_OP_FLAG_DELETE)
        {
          DECL_SET_IS_OPERATOR_DELETE (decl, true);

        Jakub