PR c++/90473 - wrong code with nullptr in default argument.

	* call.c (null_ptr_cst_p): Update quote from the standard.
	* decl.c (check_default_argument): Don't return nullptr when the arg
	has side-effects.

	* g++.dg/cpp0x/nullptr42.C: New test.

From-SVN: r274382

gcc/cp/ChangeLog

 2019-08-13  Marek Polacek  <polacek@redhat.com>
 
+	PR c++/90473 - wrong code with nullptr in default argument.
+	* call.c (null_ptr_cst_p): Update quote from the standard.
+	* decl.c (check_default_argument): Don't return nullptr when the arg
+	has side-effects.
+
+2019-08-13  Marek Polacek  <polacek@redhat.com>
+
 	* cp-tree.h (DECL_MUTABLE_P): Use FIELD_DECL_CHECK.
 
 2019-08-10  Jakub Jelinek  <jakub@redhat.com>

gcc/cp/call.c

@@ -529,9 +529,8 @@ null_ptr_cst_p (tree t)
 
   /* [conv.ptr]
 
-     A null pointer constant is an integral constant expression
-     (_expr.const_) rvalue of integer type that evaluates to zero or
-     an rvalue of type std::nullptr_t. */
+     A null pointer constant is an integer literal ([lex.icon]) with value
+     zero or a prvalue of type std::nullptr_t.  */
   if (NULLPTR_TYPE_P (type))
     return true;
 

gcc/cp/decl.c

@@ -13177,7 +13177,9 @@ check_default_argument (tree decl, tree arg, tsubst_flags_t complain)
   /* Avoid redundant -Wzero-as-null-pointer-constant warnings at
      the call sites.  */
   if (TYPE_PTR_OR_PTRMEM_P (decl_type)
-      && null_ptr_cst_p (arg))
+      && null_ptr_cst_p (arg)
+      /* Don't lose side-effects as in PR90473.  */
+      && !TREE_SIDE_EFFECTS (arg))
     return nullptr_node;
 
   /* [dcl.fct.default]

gcc/testsuite/ChangeLog

+2019-08-13  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/90473 - wrong code with nullptr in default argument.
+	* g++.dg/cpp0x/nullptr42.C: New test.
+
 2019-08-13  Olivier Hainque  <hainque@adacore.com>
 
 	* gnat.dg/casesi.ad[bs], test_casesi.adb: New test.

gcc/testsuite/g++.dg/cpp0x/nullptr42.C

+// PR c++/90473 - wrong code with nullptr in default argument.
+// { dg-do run { target c++11 } }
+
+int g;
+void f() { g++; }
+
+void fn1 (void* p = (f(), nullptr)) { }
+void fn2 (int p = (f(), 0)) { }
+
+int main()
+{
+  fn1 ();
+  if (g != 1)
+    __builtin_abort ();
+  fn2 ();
+  if (g != 2)
+    __builtin_abort ();
+}