[Bug c++/67372] New: Functions created via cp/decl2.c:start_objects not properly registered

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67372

            Bug ID: 67372
           Summary: Functions created via cp/decl2.c:start_objects not
                    properly registered
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rguenth at gcc dot gnu.org
                CC: hubicka at gcc dot gnu.org, jason at gcc dot gnu.org
  Target Milestone: ---

Those never go through cgraph::finalize_function or rest_of_decl_compilation.
Eventually they get created a cgraph node for via c-genericize here:

  /* Dump all nested functions now.  */
  cgn = cgraph_node::get_create (fndecl);
  for (cgn = cgn->nested; cgn ; cgn = cgn->next_nested)
    c_genericize (cgn->decl);

this causes us to not generate any early debug for those functions (which
might be desired but then those decls should be DECL_IGNORED_P, not just
DECL_ARTIFICIAL - there is some ObjC use I don't grok and VTV use).

Removing the above get_create will create the cgraph node from
decl_init_priority_insert (in the VTV case) which happens via
lang_hooks.decls.post_compilation_parsing_cleanups which happens
_after_ finalizing the CU.

This is from debugging an ICE (missed early debug DIE) with LTO early debug
and g++.dg/ubsan/pr59437.C

STH is rotten here regarding to symtab correctness I think.  Not sure what
debug info we want for DECL_ARTIFICIAL functions that do not have an
(non-artificial) abstract origin but are not DECL_IGNORED_P.