[Bug libfortran/59513] [4.8/4.9/4.10 Regression] Fortran runtime error: Sequential READ or WRITE not allowed after EOF marker, possibly use REWIND or BACKSPACE

[jvdelisle at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59513

--- Comment #20 from Jerry DeLisle <jvdelisle at gcc dot gnu.org> ---
I think gfortran behavior is correct.  The problem with the sample code is in
the lack of handling in subroutine BOTTOM.  The loop is reading past the end of
the file. END= is not a true error condition, but a file condition. One can not
just ignore it, the read has gone past the End-Of-File marker.  It is necessary
to position the file.

Also, this is really not good coding practice to do nothing on ERR=. ERR=
really is an ERROR.


      SUBROUTINE BOTTOM(LU)
      CHARACTER*1 DUMMY

 10   READ(LU,1000,END=90,ERR=90) DUMMY
 1000 FORMAT(A)
      GO TO 10

 90   BACKSPACE(LU)
      RETURN
      END

Fortran 2003 Standard:  9.2.3.2 File position prior to data transfer

If the file contains an endfile record, the file shall not be positioned after
the endfile record prior to data transfer. However, a REWIND or BACKSPACE
statement may be used to reposition the file.

Based on this I believe the resolution of this bug is 'INVALID'.  The bug is in
xfoil.  We could choose to disable the error on -std=legacy.  I do not know
what the old g77 did.  I will check that.