[Bug ada/72740] New: gnat.dg/specs/access[12].ads ICE when compiling with -g

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=72740

            Bug ID: 72740
           Summary: gnat.dg/specs/access[12].ads ICE when compiling with
                    -g
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: ada
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rguenth at gcc dot gnu.org
  Target Milestone: ---

/home/abuild/rguenther/obj-early-lto-debug-g/gcc/gnat1 -I
/space/rguenther/src/svn/early-lto-debug/gcc/testsuite/gnat.dg/specs/ -I -
-quiet -dumpbase access2.ads -auxbase access2 -gnatez -fdiagnostics-color=never
-gnatea
-fRTS=/home/abuild/rguenther/obj-early-lto-debug-g/x86_64-pc-linux-gnu/./libada
-fno-diagnostics-show-caret -g -gnatez -mtune=generic -march=x86-64
/space/rguenther/src/svn/early-lto-debug/gcc/testsuite/gnat.dg/specs/access2.ads
-o access2.s

raised STORAGE_ERROR : stack overflow or erroneous memory access
gnatmake:
"/space/rguenther/src/svn/early-lto-debug/gcc/testsuite/gnat.dg/specs/access2.ads"
compilation error

the issue is that we have recursive pointer types and blow the stack when
dwarf2out calls verify_type which calls variably_modified_type_p:

(gdb) p type->typed.type->typed.type
$3 = <pointer_type 0x7ffff6525a80 access2__inc>
(gdb) p type->typed.type->typed.type->typed.type
$4 = <pointer_type 0x7ffff6525888 access2__priv>
(gdb) p type->typed.type->typed.type->typed.type->typed.type
$5 = <pointer_type 0x7ffff6525a80 access2__inc>

not sure how to best represent such a structure.  Maybe
variably_modified_type_p
needs adjustment?