re PR c++/92666 (bogus -Wunused-but-set-variable in gcov.c with -Wno-restrict)

	PR c++/92666
	* call.c (convert_arg_to_ellipsis): For floating point or
	decltype(nullptr) arguments call mark_rvalue_use.

	* g++.dg/warn/Wunused-var-36.C: New test.

From-SVN: r279681

gcc/cp/ChangeLog

 2019-12-20  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/92666
+	* call.c (convert_arg_to_ellipsis): For floating point or
+	decltype(nullptr) arguments call mark_rvalue_use.
+
 	PR c++/92992
 	* call.c (convert_arg_to_ellipsis): For decltype(nullptr) arguments
 	that have side-effects use cp_build_compound_expr.

gcc/cp/call.c

@@ -7819,10 +7819,12 @@ convert_arg_to_ellipsis (tree arg, tsubst_flags_t complain)
 		    "implicit conversion from %qH to %qI when passing "
 		    "argument to function",
 		    arg_type, double_type_node);
+      arg = mark_rvalue_use (arg);
       arg = convert_to_real_nofold (double_type_node, arg);
     }
   else if (NULLPTR_TYPE_P (arg_type))
     {
+      arg = mark_rvalue_use (arg);
       if (TREE_SIDE_EFFECTS (arg))
 	arg = cp_build_compound_expr (arg, null_pointer_node, complain);
       else

gcc/testsuite/ChangeLog

 2019-12-20  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/92666
+	* g++.dg/warn/Wunused-var-36.C: New test.
+
 	PR c++/92992
 	* g++.dg/cpp0x/nullptr45.C: New test.
 

gcc/testsuite/g++.dg/warn/Wunused-var-36.C

+// PR c++/92666
+// { dg-do compile }
+// { dg-options "-Wunused-but-set-variable" }
+
+int bar (int, ...);
+#if __cplusplus >= 201103L
+enum class E : int { F = 0, G = 1 };
+#endif
+struct S { int s; };
+
+void
+foo ()
+{
+  float r = 1.0f;			// { dg-bogus "set but not used" }
+  int i = 2;				// { dg-bogus "set but not used" }
+#if __cplusplus >= 201103L
+  decltype(nullptr) n = nullptr;	// { dg-bogus "set but not used" }
+  E e = E::F;				// { dg-bogus "set but not used" }
+#else
+  void *n = (void *) 0;
+  int e = 4;
+#endif
+  S s = { 3 };				// { dg-bogus "set but not used" }
+  bar (0, r, i, n, e, s);
+}