[Bug fortran/67939] New: ICE on using data with negative substring range

[gerhard.steinmetz.fortran@t-online.de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67939

            Bug ID: 67939
           Summary: ICE on using data with negative substring range
           Product: gcc
           Version: 5.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gerhard.steinmetz.fortran@t-online.de
  Target Milestone: ---

Depending on compiler options the following codes
show different reactions (sometimes with hanging process).
Depending on environment settings too (e.g. $LANG, $LC_ALL).
All suffer from a negative substring-range (length < -1).


$ cat z1.f90
program p
   character(100) :: x
   data x(998:99) /'ab'/
end


$ cat z2.f90
program p
   character(2) :: x
   data x(:-1) /'ab'/
end


$ gfortran -c z1.f90
z1.f90:3:20:

    data x(998:99) /'ab'/
                    1
Warning: Initialization string starting at (1) was truncated to fit the
variable (-898/2)
f951: internal compiler error: Segmentation fault


$ gfortran -c z2.f90
z2.f90:3:17:

    data x(:-1) /'ab'/
                 1
Warning: Initialization string starting at (1) was truncated to fit the
variable (-1/2)
*** Error in `/usr/lib64/gcc/x86_64-suse-linux/5/f951': malloc(): memory
corruption (fast): 0x0000000001c03420 ***


$ gfortran -g -O0 -Wall -fcheck=all -fno-frontend-optimize -c z2.f90
z2.f90:3:17:

    data x(:-1) /'ab'/
                 1
Warning: Initialization string starting at (1) was truncated to fit the
variable (-1/2)
*** Error in `/usr/lib64/gcc/x86_64-suse-linux/5/f951': corrupted double-linked
list: 0x00000000036d5db0 ***