[Bug fortran/44582] New: Gfotran generates wrong results due to wrong ABI in function with array return

["yin at absoft dot com" <gcc-bugzilla at gcc dot gnu dot org>]

the function with array return must create a temporary array to hold the
returned value and transfer the value to destination array after function call.
Gfortran directly pass the destination array as the first fake argument. This
is wrong because destination is supposed to assigned to a value from the call.
If the function does nothing to the return array. the destination array will
have a wrong value. 

This is a example to show the bug

program sw

    integer,parameter::             M=500,N=60
    double precision,dimension(M,N,3)::             u
    double precision,dimension(M,N)::               dudx

    dudx(1,1) = 5.0
    dudx = ddx(u(:,:,1))

    contains


    function ddx(array)
    implicit double precision (a-h,o-z)
    double precision::          array(:,:)
    double precision::          ddx(size(array,dim=1),size(array,dim=2))

    print *, ddx(1,1)

    end function ddx

end program sw

gfortran returns 5.0
it should be 0.0 or a chaotic number.


-- 
           Summary: Gfotran generates wrong results due to wrong ABI in
                    function with array return
           Product: gcc
           Version: fortran-dev
            Status: UNCONFIRMED
          Severity: critical
          Priority: P3
         Component: fortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: yin at absoft dot com
 GCC build triplet: x86-64
  GCC host triplet: x86-64
GCC target triplet: x86-64


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44582