re PR c++/92992 (Side-effects dropped when decltype(nullptr) typed expression is passed to ellipsis)

PR c++/92992
	* call.c (convert_arg_to_ellipsis): For decltype(nullptr) arguments
	that have side-effects use cp_build_compound_expr.

	* g++.dg/cpp0x/nullptr45.C: New test.

From-SVN: r279680

gcc/cp/ChangeLog

@@ -1,3 +1,9 @@
+2019-12-20  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/92992
+	* call.c (convert_arg_to_ellipsis): For decltype(nullptr) arguments
+	that have side-effects use cp_build_compound_expr.
+
 2019-12-20  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* decl2.c (c_parse_final_cleanups): Always call collect_source_ref on

gcc/cp/call.c

@@ -7822,7 +7822,12 @@ convert_arg_to_ellipsis (tree arg, tsubst_flags_t complain)
       arg = convert_to_real_nofold (double_type_node, arg);
     }
   else if (NULLPTR_TYPE_P (arg_type))
-    arg = null_pointer_node;
+    {
+      if (TREE_SIDE_EFFECTS (arg))
+	arg = cp_build_compound_expr (arg, null_pointer_node, complain);
+      else
+	arg = null_pointer_node;
+    }
   else if (INTEGRAL_OR_ENUMERATION_TYPE_P (arg_type))
     {
       if (SCOPED_ENUM_P (arg_type))

gcc/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2019-12-20  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/92992
+	* g++.dg/cpp0x/nullptr45.C: New test.
+
 2019-12-20  Jonathan Wakely  <jwakely@redhat.com>
 
 	PR fortran/69497

gcc/testsuite/g++.dg/cpp0x/nullptr45.C

@@ -0,0 +1,24 @@
+// PR c++/92992
+// { dg-do run { target c++11 } }
+
+int a;
+
+void
+bar (int, ...)
+{
+}
+
+decltype (nullptr)
+baz ()
+{
+  a++;
+  return nullptr;
+}
+
+int
+main ()
+{
+  bar (0, baz ());
+  if (a != 1)
+    __builtin_abort ();
+}