[Bug fortran/97046] New: Bad interaction between lbound/ubound, allocatable arrays and bind(C) subroutine with dimension(..) parameter

["igor.gayday at mu dot edu" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97046

            Bug ID: 97046
           Summary: Bad interaction between lbound/ubound, allocatable
                    arrays and bind(C) subroutine with dimension(..)
                    parameter
           Product: gcc
           Version: 10.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: igor.gayday at mu dot edu
  Target Milestone: ---

Consider the following code:

MODULE FOO
INTERFACE
SUBROUTINE dummyc(x0) BIND(C, name="sync")
type(*), dimension(..) :: x0
END SUBROUTINE
END INTERFACE
contains
SUBROUTINE dummy(x0)
type(*), dimension(..) :: x0
call dummyc(x0)
END SUBROUTINE
END MODULE

PROGRAM main
    USE FOO
    IMPLICIT NONE
    integer :: before(2), after(2)

    INTEGER, parameter :: n = 1

    DOUBLE PRECISION, ALLOCATABLE :: buf(:)
    DOUBLE PRECISION :: buf2(n)

    ALLOCATE(buf(n))
    before(1) = LBOUND(buf,1)
    before(2) = UBOUND(buf,1)
    CALL dummy (buf)
    after(1) = LBOUND(buf,1)
    after(2) = UBOUND(buf,1)

    if (before(1) .NE. after(1)) stop 1
    if (before(2) .NE. after(2)) stop 2

    before(1) = LBOUND(buf2,1)
    before(2) = UBOUND(buf2,1)
    CALL dummy (buf2)
    after(1) = LBOUND(buf2,1)
    after(2) = LBOUND(buf2,1)

    if (before(1) .NE. after(1)) stop 3
    if (before(2) .NE. after(2)) stop 4

END PROGRAM

lbound() and ubound() of an allocatable array return different values 
before and after a Fortran subroutine with dimension(..) parameter (that 
in turns invokes a bind(C) subroutine) is invoked.

Note that if the main program directly CALL dummyc(buf) (instead of 
dummy(buf)), then the error does not occur.

gcc versions 9.2.0, 10.2.0 and the latest master branch are all affected.

In particular, this causes issues with mpi_f08 module, see:
https://stackoverflow.com/questions/63824065/lbound-of-an-array-changes-after-call-to-mpi-gatherv-when-using-mpi-f08-module

This might be a duplicate of Bug #94070.