http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38536
--- Comment #19 from Tobias Burnus <burnus at gcc dot gnu.org> 2011-01-14 09:00:20 UTC --- (In reply to comment #18) > (I asked on comp.lang.fortran) Cf. http://groups.google.com/group/comp.lang.fortran/browse_thread/thread/4b65b1cd206ce9fe Or from the standard (F2008): "15.2.3.6 C LOC (X)": "Argument. X [...] shall not be a coindexed object. [...] If it is an array, it shall be contiguous and have nonzero size." > We just have to check for array sections along the references, and error > out if there are any. I was about to suggest to use gfc_simply_contiguous() but I then realized that -- for a simply contiguous array "array" -- also the following array section array([1,2,3,4]) is contiguous - even though it is not simply contiguous and in the general case the contiguity is not compile-time checkable. (vector-subscripts are notoriously difficult to check at compile time) Similarly, c_loc(comp(1:2)%elem) is valid as long as "elem" is the only item in the derived type *and* no padding is happening. (As padding often occurs, one could always reject it.) And comp(1:1)%elem is always contiguous - but that's also a strange way of writing it. (Actually, I think that comp(1:1)%elem _is_ simply contiguous - though I am not sure gfc_simply_contiguous does detect this.) Personally, I think one should give some diagnostic as soon as the argument is not simply contiguous -- be it a warning or an error. At least I cannot imagine any sensible program using non-simply contiguous arrays as argument for C_LOC. (The term simply contiguous is defined in section 6.5.4.) * * * When you add another check for C_LOC, can you include one for the following? You just need to add a "gfc_is_coindexed (expr)". use iso_c_binding type t integer :: A end type t type(t), target, allocatable :: x(:)[:] type(c_ptr) :: cptr allocate(x(1)[*]) cptr = c_loc(x(1)%a) ! OK cptr = c_loc(x(1)[1]%a) ! Invalid end
