[Bug libfortran/80365] New: undefined memcpy while writing zero length array on unformatted stream in unix.c

["zeccav at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80365

            Bug ID: 80365
           Summary: undefined memcpy while writing zero length array on
                    unformatted stream in unix.c
           Product: gcc
           Version: 7.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libfortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zeccav at gmail dot com
  Target Milestone: ---
              Host: x86_64-pc-linux-gnu
            Target: x86_64-pc-linux-gnu

! undefined memcpy writing zero length array on unformatted stream
! must be compiled and run
! ../../../gcc-trunk-246751/libgfortran/io/unix.c:596:7: runtime error: null
pointer passed as argument 2, which is declared to never be null
! unix.c:596 is "memcpy (s->buffer + (s->logical_offset - s->buffer_offset),
buf, nbyte);"
! buf is zero but luckily nbyte is zero as well
! just in case I suggest putting "assert(buf || !nbyte);" before memcpy
      real v(1:0)
      open(1,form='unformatted',access='stream')
      write(unit=1,pos=1) v
      end

This is related to bug 67536