[Bug fortran/84412] New: Erroneous "Inquire statement identifies an internal file" error

[abensonca at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84412

            Bug ID: 84412
           Summary: Erroneous "Inquire statement identifies an internal
                    file" error
           Product: gcc
           Version: 8.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: abensonca at gmail dot com
  Target Milestone: ---

Using gfortran 8.0.1 (r257607) the following produces an erroneous error of
"Inquire statement identifies an internal file":

program bug
  implicit none
  integer          :: i
  character(len=1) :: s
  write (s,'(i1)') 0
  open(newUnit=i,file='bug.txt',status='unknown')
  inquire(unit=i)
end program bug

$ gfortran -v
Using built-in specs.
COLLECT_GCC=gfortran
COLLECT_LTO_WRAPPER=/home/abenson/Galacticus/Tools/libexec/gcc/x86_64-pc-linux-gnu/8.0.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-trunk/configure --prefix=/home/abenson/Galacticus/Tools
--enable-languages=c,c++,fortran --disable-multilib
Thread model: posix
gcc version 8.0.1 20180212 (experimental) (GCC) 

$ gfortran bug.F90

$ a.out 
At line 7 of file bug.F90
Fortran runtime error: Inquire statement identifies an internal file

Error termination. Backtrace:
#0  0x7fd470750d44 in inquire_via_unit
        at ../../../gcc-trunk/libgfortran/io/inquire.c:47
#1  0x400969 in ???
#2  0x4009a0 in ???
#3  0x7fd46fb7ed0c in __libc_start_main
        at /data001/abenson/Galacticus/Tools/glibc-2.12.1/csu/libc-start.c:226
#4  0x4006f8 in ???

If the WRITE statement is removed the error does not occur.