https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78670
Bug ID: 78670
Summary: Incorrect file position with namelist read under DTIO
Product: gcc
Version: 7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: ian_harvey at bigpond dot com
Target Milestone: ---
When compiled with recent trunk, the attached demonstrates that the position of
a file is incorrect when a user defined derived type input procedure is invoked
to process namelist input. The character read from the file by the user
defined derived type input procedure appears to be the `=` character that
separates the object designator from the value in the namelist input. The file
position when the user defined derived type input procedure is invoked should
be after that `=`.
(As a result of picking up the `=` the defined input procedure leaves the file
positioned prior to the value `a`, which then confuses the Fortran runtime and
results in an end of file condition - that's not a problem in itself.)
MODULE m
IMPLICIT NONE
TYPE :: t
CHARACTER :: c
CONTAINS
PROCEDURE :: read_formatted
GENERIC :: READ(FORMATTED) => read_formatted
! Work around for PR78659.
PROCEDURE :: write_formatted
GENERIC :: WRITE(FORMATTED) => write_formatted
END TYPE t
CONTAINS
! Workaround for PR78659.
SUBROUTINE write_formatted(dtv, unit, iotype, v_list, iostat, iomsg)
CLASS(t), INTENT(IN) :: dtv
INTEGER, INTENT(IN) :: unit
CHARACTER(*), INTENT(IN) :: iotype
INTEGER, INTENT(IN) :: v_list(:)
INTEGER, INTENT(OUT) :: iostat
CHARACTER(*), INTENT(INOUT) :: iomsg
iostat = 0
END SUBROUTINE write_formatted
SUBROUTINE read_formatted(dtv, unit, iotype, v_list, iostat, iomsg)
CLASS(t), INTENT(INOUT) :: dtv
INTEGER, INTENT(IN) :: unit
CHARACTER(*), INTENT(IN) :: iotype
INTEGER, INTENT(IN) :: v_list(:)
INTEGER, INTENT(OUT) :: iostat
CHARACTER(*), INTENT(INOUT) :: iomsg
CHARACTER :: ch
dtv%c = ''
DO
READ (unit, "(A)", IOSTAT=iostat, IOMSG=iomsg) ch
IF (iostat /= 0) RETURN
! for debugging only.
print "('Got ''',A,'''')", ch
! Store first non-blank
IF (ch /= '') THEN
dtv%c = ch
RETURN
END IF
END DO
READ (unit, "(A)", IOSTAT=iostat, IOMSG=iomsg) dtv%c
END SUBROUTINE read_formatted
END MODULE m
PROGRAM p
USE m
IMPLICIT NONE
TYPE(t) :: x
NAMELIST /nml/ x
INTEGER :: unit
OPEN(NEWUNIT=unit, STATUS='SCRATCH', ACTION='READWRITE')
WRITE (unit, "(A)") '&nml'
WRITE (unit, "(A)") 'x = a'
WRITE (unit, "(A)") '/'
REWIND (unit)
READ (unit, nml)
PRINT *, x%c ! expect `a`.
END PROGRAM p
$ gfortran -g 2016-12-04\ namelist3.f90 && ./a.out
Got '='
At line 72 of file 2016-12-04 namelist3.f90
Fortran runtime error: End of file
Error termination. Backtrace:
#0 0x7f19aad29321 in nml_get_obj_data
at ../../.././vanilla/libgfortran/io/list_read.c:3494
#1 0x7f19aad31700 in finalize_transfer
at ../../.././vanilla/libgfortran/io/transfer.c:3813
#2 0x40101e in p
at /home/MEGMS2/ian/srv/home/projects/FortranMisc/2016/2016-12-04
namelist3.f90:72
#3 0x4010b5 in main
at /home/MEGMS2/ian/srv/home/projects/FortranMisc/2016/2016-12-04
namelist3.f90:58
(The program is technically non-conforming because it executes an output
statement to an external unit while parent READ statement is active, if
necessary the print statement in read_formatted can be removed and the value of
dtv%c in the read_formatted procedure inspected after a read using a debugger.)
