[Bug fortran/77972] New: ICE on broken character continuation with -Wall etc.

["gerhard dot steinmetz dot fortran at t-online dot de" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77972

            Bug ID: 77972
           Summary: ICE on broken character continuation with -Wall etc.
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gerhard.steinmetz.fortran@t-online.de
  Target Milestone: ---

ICEs down to at least 4.8; gcc-7 in combination with option -Wall,
or one of -pedantic, -std=f95, -std=f2003, -std=f2008, ...
Follow-up of pr71686.


$ cat z1.f90
program p
   character(8) :: z
   z = 'abc&
!end


$ cat z2.f90
program p
   character(8) :: z = 'abc&
!end


$ gfortran-7-20161009 -Wall z1.f90
0x68903e gfc_format_decoder
        ../../gcc/fortran/error.c:935
0x13c9bff pp_format(pretty_printer*, text_info*)
        ../../gcc/pretty-print.c:660
0x13bd020 diagnostic_report_diagnostic(diagnostic_context*, diagnostic_info*)
        ../../gcc/diagnostic.c:945
0x688d4f gfc_warning
        ../../gcc/fortran/error.c:792
0x6899e6 gfc_warning(int, char const*, ...)
        ../../gcc/fortran/error.c:823
0x6fecb8 gfc_next_char_literal(gfc_instring)
        ../../gcc/fortran/scanner.c:1424
0x6de738 next_string_char
        ../../gcc/fortran/primary.c:903
0x6e06a7 match_string_constant
        ../../gcc/fortran/primary.c:1102
0x6e06a7 gfc_match_literal_constant(gfc_expr**, int)
        ../../gcc/fortran/primary.c:1455
0x6bc01f match_primary
        ../../gcc/fortran/matchexp.c:149
0x6bc01f match_level_1
        ../../gcc/fortran/matchexp.c:211
0x6bc01f match_mult_operand
        ../../gcc/fortran/matchexp.c:267
0x6bc308 match_add_operand
        ../../gcc/fortran/matchexp.c:356
0x6bc59c match_level_2
        ../../gcc/fortran/matchexp.c:480
0x6bc6f2 match_level_3
        ../../gcc/fortran/matchexp.c:551
0x6bc804 match_level_4
        ../../gcc/fortran/matchexp.c:599
0x6bc804 match_and_operand
        ../../gcc/fortran/matchexp.c:693
0x6bc9c2 match_or_operand
        ../../gcc/fortran/matchexp.c:722
0x6bcab2 match_equiv_operand
        ../../gcc/fortran/matchexp.c:765
0x6bcba2 match_level_5
        ../../gcc/fortran/matchexp.c:811