Re: [C++ Patch] PR 80956 ("[7/8 Regression] ICE with abstract class vector")

[Paolo Carlini]

Hi,

On 05/04/2018 15:56, Jason Merrill wrote:
On Thu, Apr 5, 2018 at 8:27 AM, Paolo Carlini <paolo.carl...@oracle.com> wrote:
Hi,
the main issue is already fixed in trunk but we still ICE on the reduced
testcase attached by Jakub which has a broken std::initializer_list missing
the definition. I think we can handle this case similarly to the existing
check in do_pushtag, which would be also consistent with the plain error we
give for, eg:

namespace std { template <class> class initializer_list; }

template class std::initializer_list<int>;

However, we still have the option of issuing a fatal_error, like we do in
finish_struct.
How about using complete_type_or_maybe_complain instead of a custom error?
Yes, I was about to send a message about that option, I already had it 
in the audit trail, tested too, then started fiddling with fatal_errors 
and forgot to mention it ;) Anyway, would be the below.

Thanks,
Paolo.

/////////////////////
Index: cp/call.c
===================================================================
--- cp/call.c   (revision 259124)
+++ cp/call.c   (working copy)
@@ -6880,8 +6880,12 @@ convert_like_real (conversion *convs, tree expr, t
        if (array == error_mark_node)
          return error_mark_node;
 
-       /* Build up the initializer_list object.  */
-       totype = complete_type (totype);
+       /* Build up the initializer_list object.  Note: fail gracefully
+          if the object cannot be completed because, for example, no
+          definition is provided.  */
+       totype = complete_type_or_maybe_complain (totype, NULL_TREE, complain);
+       if (!totype)
+         return error_mark_node;
        field = next_initializable_field (TYPE_FIELDS (totype));
        CONSTRUCTOR_APPEND_ELT (vec, field, array);
        field = next_initializable_field (DECL_CHAIN (field));
Index: cp/name-lookup.c
===================================================================
--- cp/name-lookup.c    (revision 259124)
+++ cp/name-lookup.c    (working copy)
@@ -6476,8 +6476,8 @@ do_pushtag (tree name, tree type, tag_scope scope)
              && init_list_identifier == DECL_NAME (TYPE_NAME (type))
              && !CLASSTYPE_TEMPLATE_INFO (type))
            {
-             error ("declaration of std::initializer_list does not match "
-                    "#include <initializer_list>, isn't a template");
+             error ("declaration of %<std::initializer_list%> does not match "
+                    "%<#include <initializer_list>%>, isn't a template");
              return error_mark_node;
            }
        }
Index: testsuite/g++.dg/cpp0x/initlist100.C
===================================================================
--- testsuite/g++.dg/cpp0x/initlist100.C        (nonexistent)
+++ testsuite/g++.dg/cpp0x/initlist100.C        (working copy)
@@ -0,0 +1,10 @@
+// PR c++/80956
+// { dg-do compile { target c++11 } }
+
+namespace std {
+template <class> class initializer_list;  // { dg-message "declaration" }
+}
+
+template <typename T> struct B { B (std::initializer_list<T>); };
+struct C { virtual int foo (); };
+struct D : C {} d { B<C> { D {} } };  // { dg-error "incomplete|no matching" }
Index: testsuite/g++.dg/cpp0x/initlist101.C
===================================================================
--- testsuite/g++.dg/cpp0x/initlist101.C        (nonexistent)
+++ testsuite/g++.dg/cpp0x/initlist101.C        (working copy)
@@ -0,0 +1,8 @@
+// PR c++/80956
+// { dg-do compile { target c++11 } }
+
+#include <initializer_list>
+
+template <typename T> struct B { B (std::initializer_list<T>); };
+struct C { virtual int foo (); };
+struct D : C {} d { B<C> { D {} } };  // { dg-error "no matching" }