re PR c++/84076 (Warning about objects through POD mistakenly claims the object is a pointer)

	PR c++/84076
	* call.c (convert_arg_to_ellipsis): Instead of cp_build_addr_expr
	build ADDR_EXPR with REFERENCE_TYPE.
	(build_over_call): For purposes of check_function_arguments, if
	argarray[j] is ADDR_EXPR with REFERENCE_TYPE created above, use
	its operand rather than the argument itself.

	* g++.dg/warn/Wformat-2.C: New test.

From-SVN: r258397

gcc/cp/ChangeLog

+2018-03-09  Jason Merrill  <jason@redhat.com>
+	    Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/84076
+	* call.c (convert_arg_to_ellipsis): Instead of cp_build_addr_expr
+	build ADDR_EXPR with REFERENCE_TYPE.
+	(build_over_call): For purposes of check_function_arguments, if
+	argarray[j] is ADDR_EXPR with REFERENCE_TYPE created above, use
+	its operand rather than the argument itself.
+
 2018-03-09  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c++/84724

gcc/cp/call.c

@@ -7209,7 +7209,7 @@ convert_arg_to_ellipsis (tree arg, tsubst_flags_t complain)
 		     "passing objects of non-trivially-copyable "
 		     "type %q#T through %<...%> is conditionally supported",
 		     arg_type);
-	  return cp_build_addr_expr (arg, complain);
+	  return build1 (ADDR_EXPR, build_reference_type (arg_type), arg);
 	}
       /* Build up a real lvalue-to-rvalue conversion in case the
 	 copy constructor is trivial but not callable.  */
@@ -8018,7 +8018,15 @@ build_over_call (struct z_candidate *cand, int flags, tsubst_flags_t complain)
       tree *fargs = (!nargs ? argarray
 			    : (tree *) alloca (nargs * sizeof (tree)));
       for (j = 0; j < nargs; j++)
-	fargs[j] = maybe_constant_value (argarray[j]);
+	{
+	  /* For -Wformat undo the implicit passing by hidden reference
+	     done by convert_arg_to_ellipsis.  */
+	  if (TREE_CODE (argarray[j]) == ADDR_EXPR
+	      && TREE_CODE (TREE_TYPE (argarray[j])) == REFERENCE_TYPE)
+	    fargs[j] = TREE_OPERAND (argarray[j], 0);
+	  else
+	    fargs[j] = maybe_constant_value (argarray[j]);
+	}
 
       warned_p = check_function_arguments (input_location, fn, TREE_TYPE (fn),
 					   nargs, fargs, NULL);

gcc/testsuite/ChangeLog

 2018-03-09  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/84076
+	* g++.dg/warn/Wformat-2.C: New test.
+
 	PR c++/84767
 	* g++.dg/ext/vla18.C: New test.
 

gcc/testsuite/g++.dg/warn/Wformat-2.C

+// PR c++/84076
+// { dg-do compile }
+// { dg-options "-Wformat" }
+
+struct S { ~S (); };
+struct T { T (); T (const T &); };
+
+void
+foo ()
+{
+  S s;
+  T t;
+  __builtin_printf ("%s\n", s);	// { dg-warning "format '%s' expects argument of type 'char\\*', but argument 2 has type 'S'" }
+  __builtin_printf ("%s\n", t);	// { dg-warning "format '%s' expects argument of type 'char\\*', but argument 2 has type 'T'" }
+  __builtin_printf ("%s\n", &s);// { dg-warning "format '%s' expects argument of type 'char\\*', but argument 2 has type 'S\\*'" }
+  __builtin_printf ("%s\n", &t);// { dg-warning "format '%s' expects argument of type 'char\\*', but argument 2 has type 'T\\*'" }
+}