[Bug sanitizer/63855] New: [5 Regression] ICE: SIGSEGV in ipa_comdats with -fsanitize=null

[zsojka at seznam dot cz]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63855

            Bug ID: 63855
           Summary: [5 Regression] ICE: SIGSEGV in ipa_comdats with
                    -fsanitize=null
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: sanitizer
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zsojka at seznam dot cz
                CC: dodji at gcc dot gnu.org, dvyukov at gcc dot gnu.org,
                    jakub at gcc dot gnu.org, kcc at gcc dot gnu.org

Created attachment 33960
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33960&action=edit
reduced testcase

$ gcc -O -fkeep-inline-functions -fsanitize=null testcase.C
==22060== Invalid read of size 8
==22060==    at 0x180E214: ipa_comdats (ipa-comdats.c:340)
==22060==    by 0x180E214: (anonymous
namespace)::pass_ipa_comdats::execute(function*) (ipa-comdats.c:381)
==22060==    by 0xCCBE78: execute_one_pass(opt_pass*) (passes.c:2269)
==22060==    by 0xCCCAD1: execute_ipa_pass_list(opt_pass*) (passes.c:2663)
==22060==    by 0x9B3B69: ipa_passes (cgraphunit.c:2088)
==22060==    by 0x9B3B69: symbol_table::compile() (cgraphunit.c:2172)
==22060==    by 0x9B5687: symbol_table::finalize_compilation_unit()
(cgraphunit.c:2325)
==22060==    by 0x785449: cp_write_global_declarations() (decl2.c:4677)
==22060==    by 0xDC3BD3: compile_file() (toplev.c:583)
==22060==    by 0x694528: do_compile (toplev.c:2020)
==22060==    by 0x694528: toplev::main(int, char**) (toplev.c:2117)
==22060==    by 0x694B78: main (main.c:38)
==22060==  Address 0x0 is not stack'd, malloc'd or (recently) free'd
==22060== 
testcase.C:5:4: internal compiler error: Segmentation fault
 B b;
    ^
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://gcc.gnu.org/bugs.html> for instructions.

Tested revisions:
r217458 - ICE
4_9 r216937 - OK