[Bug debug/66535] New: segfault in gen_subprogram_die after debug-early merge

["ebotcazou at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66535

            Bug ID: 66535
           Summary: segfault in gen_subprogram_die after debug-early merge
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: debug
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ebotcazou at gcc dot gnu.org
                CC: aldyh at gcc dot gnu.org
  Target Milestone: ---

Created attachment 35776
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35776&action=edit
Testcase to be gnatchop'ed

The debug-early merge has introduced a crash on the attached Ada testcase:

eric@polaris:~/build/gcc/native> gcc/xgcc -Bgcc -S debug4.adb -g

raised STORAGE_ERROR : stack overflow or erroneous memory access

Program received signal SIGSEGV, Segmentation fault.
0x0000000000b3685c in gen_subprogram_die (decl=0x7ffff53928c0, context_die=0x0)
    at /home/eric/gnat/gnat-head/src/gcc/dwarf2out.c:18793
18793              || old_die->die_parent->die_tag == DW_TAG_module

old_die->die_parent is NULL.

The testcase can be added as-is to the gnat.dg/ testsuite:

  gnat.dg/debug4.adb
  gnat.dg/debug4_pkg.adb
  gnat.dg/debug4_pkg.ads