This variant of maxloc_bounds_4.f90

module tst
contains
  subroutine foo(res)
    integer(kind=4), allocatable :: f(:,:)
    integer(kind=8) , dimension(:) :: res
    allocate (f(2,5))
    f = 3
    res = maxloc(f)
  end subroutine foo

end module tst
program main
  use tst
  implicit none
  integer(kind=8) :: res(3)
  call foo(res)
end program main

does not trigger a bounds check with -fcheck=all.

It is translated to

    ASSIGN foo:res(FULL) __convert_i4_i8[[((_gfortran_maxloc0_4_i4[[((foo:f(FULL)) ((arg not-present)) ((arg not-present)))]]))]]

and the __convert_i4_i8 call hides the conversion from the
library code for bounds checking, and does not do any bounds
checking by itself.