Support LOWER optional argument in C_F_POINTER interface

[bcornille]

Fortran 2023 introduced the LOWER optional argument to C_F_POINTER. It would be useful for this to be supported in flang.
Example:

program CPointersLB
  use iso_c_binding
  implicit none

  real, allocatable, target :: A(:,:,:)
  type(c_ptr) :: ptr
  integer :: nx, ny, nz, i
  real, pointer :: chunk(:,:)

  nx = 10
  ny = 10
  nz = 10

  allocate(A(nx, ny, nz))

  A = reshape([(real(i), i=1, nx*ny*nz)], shape(A))

  ptr = c_loc(A(1,1,1))

  call c_f_pointer(ptr, chunk, [nx, ny], [0, 0])

  print *, chunk(0,1)

  deallocate(A)
end program

[llvmbot]

@llvm/issue-subscribers-flang-frontend

Author: Brian Cornille (bcornille)

Fortran 2023 introduced the LOWER optional argument to C_F_POINTER. It would be useful for this to be supported in flang. Example: ``` program CPointersLB use iso_c_binding implicit none

real, allocatable, target :: A(:,:,:)
type(c_ptr) :: ptr
integer :: nx, ny, nz, i
real, pointer :: chunk(:,:)

nx = 10
ny = 10
nz = 10

allocate(A(nx, ny, nz))

A = reshape([(real(i), i=1, nxnynz)], shape(A))

ptr = c_loc(A(1,1,1))

call c_f_pointer(ptr, chunk, [nx, ny], [0, 0])

print *, chunk(0,1)

deallocate(A)
end program

</details>

[klausler]

what other Fortran compilers support this feature?

[bcornille]

ifx supports it as of 2024.1.0
https://www.intel.com/content/www/us/en/developer/articles/technical/fortran-language-and-openmp-features-in-ifx.html

[mjklemm]

I can have a look at this.

[c8ef]

Resolved by #149870.