[C++ Patch] PR 85014 ("[7/8/9 Regression] internal compiler error: in lookup_base, at cp/search.c:185")

[Paolo Carlini]

Hi,

another - rather long standing - error-recovery regression, where, in 
some rather special circumstances, we end up passing the FUNCTION_DECL 
representing the operator () of the lambda to maybe_dummy_object and 
obviously we almost immediately crash. Not sure how much we want to dig 
- but simply checking that context_for_name_lookup is actually returning 
a type appears to work fine, the error_mark_node then propagates back to 
cp_parser_late_parse_one_default_arg and so on. In the special 
circumstances of the testcase, context_for_name_lookup finds 
ANON_AGGR_TYPE_P set for the DECL_CONTEXT of 'b' and iterates to its 
TYPE_CONTEXT which is the FUNCTION_DECL representing the operator () of 
the lambda. This is because we just called check_tag_decl on that 
anonymous type as part of calling shadow_tag on the abstract 
declaration. Tested x86_64-linux.

Thanks, Paolo.

////////////////////

/cp
2019-03-15  Paolo Carlini  <paolo.carl...@oracle.com>

        PR c++/85014
        * semantics.c (finish_non_static_data_member): Check return value
        of context_for_name_lookup and immediately return error_mark_node
        if isn't a type.

/testsuite
2019-03-15  Paolo Carlini  <paolo.carl...@oracle.com>

        PR c++/85014
        * g++.dg/cpp0x/pr85014.C: New.
Index: cp/semantics.c
===================================================================
--- cp/semantics.c      (revision 269693)
+++ cp/semantics.c      (working copy)
@@ -1828,7 +1828,15 @@ finish_non_static_data_member (tree decl, tree obj
     {
       tree scope = qualifying_scope;
       if (scope == NULL_TREE)
-       scope = context_for_name_lookup (decl);
+       {
+         scope = context_for_name_lookup (decl);
+         if (!TYPE_P (scope))
+           {
+             /* Can happen during error recovery (c++/85014).  */
+             gcc_assert (seen_error ());
+             return error_mark_node;
+           }
+       }
       object = maybe_dummy_object (scope, NULL);
     }
 
Index: testsuite/g++.dg/cpp0x/pr85014.C
===================================================================
--- testsuite/g++.dg/cpp0x/pr85014.C    (nonexistent)
+++ testsuite/g++.dg/cpp0x/pr85014.C    (working copy)
@@ -0,0 +1,10 @@
+// { dg-do compile { target c++11 } }
+// { dg-options "" }
+
+struct {
+  short a[__builtin_constant_p([] {
+    struct {
+      int b = b;
+      };  // { dg-error "abstract declarator" }
+  })];
+};  // { dg-error "abstract declarator" }