--- gcc/c-family/c.opt.jj	2023-12-20 11:31:07.897806698 +0100
+++ gcc/c-family/c.opt	2023-12-20 20:02:36.889910599 +0100
@@ -332,7 +332,7 @@ C ObjC C++ ObjC++ Var(warn_alloca) Warni
 Warn on any use of alloca.
 
 Walloc-size
-C ObjC Var(warn_alloc_size) Warning LangEnabledBy(C ObjC, Wextra)
+C ObjC C++ ObjC++ Var(warn_alloc_size) Warning LangEnabledBy(C ObjC C++ ObjC++, Wextra)
 Warn when allocating insufficient storage for the target type of the assigned pointer.
 
 Walloc-size-larger-than=
--- gcc/cp/cp-gimplify.cc.jj	2023-12-15 10:08:53.877236695 +0100
+++ gcc/cp/cp-gimplify.cc	2023-12-20 20:10:59.689914648 +0100
@@ -2048,6 +2048,25 @@ cp_genericize_r (tree *stmt_p, int *walk
 
     case NOP_EXPR:
       *stmt_p = predeclare_vla (*stmt_p);
+
+      /* Warn of new allocations that are not big enough for the target
+	 type.  */
+      if (warn_alloc_size
+	  && TREE_CODE (TREE_OPERAND (stmt, 0)) == CALL_EXPR
+	  && POINTER_TYPE_P (TREE_TYPE (stmt)))
+	{
+	  if (tree fndecl = get_callee_fndecl (TREE_OPERAND (stmt, 0)))
+	    if (DECL_IS_MALLOC (fndecl))
+	      {
+		tree attrs = TYPE_ATTRIBUTES (TREE_TYPE (fndecl));
+		tree alloc_size = lookup_attribute ("alloc_size", attrs);
+		if (alloc_size)
+		  warn_for_alloc_size (EXPR_LOCATION (stmt),
+				       TREE_TYPE (TREE_TYPE (stmt)),
+				       TREE_OPERAND (stmt, 0), alloc_size);
+	      }
+	}
+
       if (!wtd->no_sanitize_p
 	  && sanitize_flags_p (SANITIZE_NULL | SANITIZE_ALIGNMENT)
 	  && TYPE_REF_P (TREE_TYPE (stmt)))
--- gcc/cp/semantics.cc.jj	2023-12-14 07:49:53.150580801 +0100
+++ gcc/cp/semantics.cc	2023-12-20 20:13:33.773772759 +0100
@@ -2939,15 +2939,24 @@ finish_call_expr (tree fn, vec<tree, va_
 
       if (!result)
 	{
-	  if (warn_sizeof_pointer_memaccess
+	  tree alloc_size_attr = NULL_TREE;
+	  if (warn_calloc_transposed_args
+	      && TREE_CODE (fn) == FUNCTION_DECL
+	      && (alloc_size_attr
+		  = lookup_attribute ("alloc_size",
+				      TYPE_ATTRIBUTES (TREE_TYPE (fn)))))
+	    if (TREE_VALUE (alloc_size_attr) == NULL_TREE
+		|| TREE_CHAIN (TREE_VALUE (alloc_size_attr)) == NULL_TREE)
+	      alloc_size_attr = NULL_TREE;
+	  if ((warn_sizeof_pointer_memaccess || alloc_size_attr)
 	      && (complain & tf_warning)
 	      && !vec_safe_is_empty (*args)
 	      && !processing_template_decl)
 	    {
-	      location_t sizeof_arg_loc[3];
-	      tree sizeof_arg[3];
+	      location_t sizeof_arg_loc[6];
+	      tree sizeof_arg[6];
 	      unsigned int i;
-	      for (i = 0; i < 3; i++)
+	      for (i = 0; i < (alloc_size_attr ? 6 : 3); i++)
 		{
 		  tree t;
 
@@ -2964,9 +2973,15 @@ finish_call_expr (tree fn, vec<tree, va_
 		    sizeof_arg[i] = TREE_OPERAND (t, 0);
 		  sizeof_arg_loc[i] = EXPR_LOCATION (t);
 		}
-	      sizeof_pointer_memaccess_warning
-		(sizeof_arg_loc, fn, *args,
-		 sizeof_arg, same_type_ignoring_top_level_qualifiers_p);
+	      if (warn_sizeof_pointer_memaccess)
+		{
+		  auto same_p = same_type_ignoring_top_level_qualifiers_p;
+		  sizeof_pointer_memaccess_warning (sizeof_arg_loc, fn, *args,
+						    sizeof_arg, same_p);
+		}
+	      if (alloc_size_attr)
+		warn_for_calloc (sizeof_arg_loc, fn, *args, sizeof_arg,
+				 alloc_size_attr);
 	    }
 
 	  if ((complain & tf_warning)
--- gcc/testsuite/g++.dg/warn/Wcalloc-transposed-args-1.C.jj	2023-12-20 19:52:10.303641708 +0100
+++ gcc/testsuite/g++.dg/warn/Wcalloc-transposed-args-1.C	2023-12-20 20:16:09.239611657 +0100
@@ -0,0 +1,54 @@
+// { dg-do compile }
+// { dg-options "-Wcalloc-transposed-args" }
+
+typedef __SIZE_TYPE__ size_t;
+extern "C" void free (void *);
+extern "C" void *calloc (size_t, size_t);
+void *myfree (void *, int, int);
+void *mycalloc (int, int, size_t, size_t) __attribute__((malloc, malloc (myfree), alloc_size (3, 4)));
+
+void
+foo (int n)
+{
+  void *p;
+  p = __builtin_calloc (1, sizeof (int));
+  __builtin_free (p);
+  p = __builtin_calloc (n, sizeof (int));
+  __builtin_free (p);
+  p = __builtin_calloc (sizeof (int), 1);		// { dg-warning "'\[^']*__builtin_calloc\[^']*' sizes specified with 'sizeof' in the earlier argument and not in the later argument" }
+  __builtin_free (p);					// { dg-message "earlier argument should specify number of elements, later size of each element" "" { target *-*-* } .-1 }
+  p = __builtin_calloc (sizeof (int), n);		// { dg-warning "'\[^']*__builtin_calloc\[^']*' sizes specified with 'sizeof' in the earlier argument and not in the later argument" }
+  __builtin_free (p);					// { dg-message "earlier argument should specify number of elements, later size of each element" "" { target *-*-* } .-1 }
+  p = __builtin_calloc ((sizeof (int)), 1);		// { dg-warning "'\[^']*__builtin_calloc\[^']*' sizes specified with 'sizeof' in the earlier argument and not in the later argument" }
+  __builtin_free (p);					// { dg-message "earlier argument should specify number of elements, later size of each element" "" { target *-*-* } .-1 }
+  p = __builtin_calloc (sizeof (int) + 0, 1);
+  __builtin_free (p);
+  p = __builtin_calloc (sizeof (int), sizeof (char));
+  __builtin_free (p);
+  p = __builtin_calloc (1 * sizeof (int), 1);
+  __builtin_free (p);
+  p = calloc (1, sizeof (int));
+  free (p);
+  p = calloc (n, sizeof (int));
+  free (p);
+  p = calloc (sizeof (int), 1);				// { dg-warning "'\[^']*calloc\[^']*' sizes specified with 'sizeof' in the earlier argument and not in the later argument" }
+  free (p);						// { dg-message "earlier argument should specify number of elements, later size of each element" "" { target *-*-* } .-1 }
+  p = calloc (sizeof (int), n);				// { dg-warning "'\[^']*calloc\[^']*' sizes specified with 'sizeof' in the earlier argument and not in the later argument" }
+  free (p);						// { dg-message "earlier argument should specify number of elements, later size of each element" "" { target *-*-* } .-1 }
+  p = calloc (sizeof (int), sizeof (char));
+  free (p);
+  p = calloc (1 * sizeof (int), 1);
+  free (p);
+  p = mycalloc (42, 42, 1, sizeof (int));
+  myfree (p, 42, 42);
+  p = mycalloc (42, 42, n, sizeof (int));
+  myfree (p, 42, 42);
+  p = mycalloc (42, 42, sizeof (int), 1);		// { dg-warning "'\[^']*mycalloc\[^']*' sizes specified with 'sizeof' in the earlier argument and not in the later argument" }
+  myfree (p, 42, 42);					// { dg-message "earlier argument should specify number of elements, later size of each element" "" { target *-*-* } .-1 }
+  p = mycalloc (42, 42, sizeof (int), n);		// { dg-warning "'\[^']*mycalloc\[^']*' sizes specified with 'sizeof' in the earlier argument and not in the later argument" }
+  myfree (p, 42, 42);					// { dg-message "earlier argument should specify number of elements, later size of each element" "" { target *-*-* } .-1 }
+  p = mycalloc (42, 42, sizeof (int), sizeof (char));
+  myfree (p, 42, 42);
+  p = mycalloc (42, 42, 1 * sizeof (int), 1);
+  myfree (p, 42, 42);
+}
--- gcc/testsuite/g++.dg/warn/Walloc-size-1.C.jj	2023-12-20 19:51:45.828982748 +0100
+++ gcc/testsuite/g++.dg/warn/Walloc-size-1.C	2023-12-20 20:01:40.385697949 +0100
@@ -0,0 +1,52 @@
+// Tests the warnings for insufficient allocation size.
+// { dg-do compile }
+// { dg-options "-Walloc-size -Wno-calloc-transposed-args" }
+
+struct S { int x[10]; };
+void bar (S *);
+typedef __SIZE_TYPE__ size_t;
+void *myfree (void *, int, int);
+void *mymalloc (int, int, size_t) __attribute__((malloc, malloc (myfree), alloc_size (3)));
+void *mycalloc (int, int, size_t, size_t) __attribute__((malloc, malloc (myfree), alloc_size (3, 4)));
+
+void
+foo (void)
+{
+  S *p = (S *) __builtin_malloc (sizeof *p);
+  __builtin_free (p);
+  p = (S *) __builtin_malloc (sizeof p);	// { dg-warning "allocation of insufficient size" }
+  __builtin_free (p);
+  p = (S *) __builtin_alloca (sizeof p);	// { dg-warning "allocation of insufficient size" }
+  bar (p);
+  p = (S *) __builtin_calloc (1, sizeof p);	// { dg-warning "allocation of insufficient size" }
+  __builtin_free (p);
+  bar ((S *) __builtin_malloc (4));		// { dg-warning "allocation of insufficient size" }
+  __builtin_free (p);
+  p = (S *) __builtin_calloc (sizeof *p, 1);
+  __builtin_free (p);
+}
+
+void
+baz (void)
+{
+  S *p = (S *) mymalloc (42, 42, sizeof *p);
+  myfree (p, 42, 42);
+  p = (S *) mymalloc (42, 42, sizeof p);	// { dg-warning "allocation of insufficient size" }
+  myfree (p, 42, 42);
+  p = (S *) mycalloc (42, 42, 1, sizeof p);	// { dg-warning "allocation of insufficient size" }
+  myfree (p, 42, 42);
+  bar ((S *) mymalloc (42, 42, 4));		// { dg-warning "allocation of insufficient size" }
+  myfree (p, 42, 42);
+  p = (S *) mycalloc (42, 42, sizeof *p, 1);
+  myfree (p, 42, 42);
+  p = static_cast <S *> (mycalloc (42, 42, sizeof *p, 1));
+  myfree (p, 42, 42);
+  p = static_cast <S *> (mymalloc (42, 42, sizeof *p));
+  myfree (p, 42, 42);
+  p = static_cast <S *> (mymalloc (42, 42, sizeof p));		// { dg-warning "allocation of insufficient size" }
+  myfree (p, 42, 42);
+  p = static_cast <S *> (mycalloc (42, 42, 1, sizeof p));	// { dg-warning "allocation of insufficient size" }
+  myfree (p, 42, 42);
+  bar (static_cast <S *> (mymalloc (42, 42, 4)));		// { dg-warning "allocation of insufficient size" }
+  myfree (p, 42, 42);
+}
