Re: [C++ PATCH] Fix ICE in C++14 with null RETURN_EXPR (PR c++/65202)

[Marek Polacek]

On Thu, Feb 26, 2015 at 08:35:00AM -0500, Jason Merrill wrote:
> On 02/26/2015 07:22 AM, Marek Polacek wrote:
> >-  if (t == error_mark_node)
> >+  if (t == NULL_TREE || t == error_mark_node)
> >      {
> >        *non_constant_p = true;
> 
> No, we don't want an empty return to make the call non-constant, it's
> perfectly valid.  Let's handle this specifically in the RETURN_EXPR case.

Sorry about that.  So like this?

2015-02-26  Marek Polacek  <pola...@redhat.com>

        PR c++/65202
        * constexpr.c (cxx_eval_constant_expression): Don't evaluate
        a RETURN_EXPR if its operand is null.

        * g++.dg/cpp1y/pr65202.C: New test.

diff --git gcc/cp/constexpr.c gcc/cp/constexpr.c
index 32a23ff7..f7e8ce9 100644
--- gcc/cp/constexpr.c
+++ gcc/cp/constexpr.c
@@ -3113,9 +3113,10 @@ cxx_eval_constant_expression (const constexpr_ctx *ctx, 
tree t,
       break;
 
     case RETURN_EXPR:
-      r = cxx_eval_constant_expression (ctx, TREE_OPERAND (t, 0),
-                                       lval,
-                                       non_constant_p, overflow_p);
+      if (TREE_OPERAND (t, 0) != NULL_TREE)
+       r = cxx_eval_constant_expression (ctx, TREE_OPERAND (t, 0),
+                                         lval,
+                                         non_constant_p, overflow_p);
       *jump_target = t;
       break;
 
diff --git gcc/testsuite/g++.dg/cpp1y/pr65202.C 
gcc/testsuite/g++.dg/cpp1y/pr65202.C
index e69de29..602b264 100644
--- gcc/testsuite/g++.dg/cpp1y/pr65202.C
+++ gcc/testsuite/g++.dg/cpp1y/pr65202.C
@@ -0,0 +1,26 @@
+// // PR c++/65202
+// { dg-do compile { target c++14 } }
+
+template <typename T> struct is_move_constructible;
+template <typename T> struct is_move_assignable;
+template <int, typename T> using enable_if_t = int;
+namespace adl {
+template <
+    typename L, typename R,
+    enable_if_t<is_move_constructible<L>() && is_move_assignable<L>(), int>...>
+constexpr auto adl_swap(L &l, R &r) -> decltype(swap(l, r)) {
+  return;
+}
+template <typename L, typename R>
+auto swap(L &l, R &r) noexcept(noexcept(adl::adl_swap(l, r)))
+    -> decltype(adl::adl_swap(l, r));
+namespace ns {
+template <typename T> struct foo {};
+template <typename T> void swap(foo<T> &, foo<T> &);
+struct bar;
+
+int main()
+{
+    foo<ns::bar> f;
+    adl::swap(f, f)
+} // { dg-error "" }


        Marek