[Bug fortran/51589] Modification of loop index variable by intent(out) or intent(inout) procedures

["burnus at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51589

Tobias Burnus <burnus at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |diagnostic
                 CC|                            |burnus at gcc dot gnu.org

--- Comment #4 from Tobias Burnus <burnus at gcc dot gnu.org> 2011-12-17 09:15:44 UTC ---
As Harald already mentioned, GCC 4.5 (or later) support -fcheck=do to find
modifications to the DO variables at run time.

 * * *

Currently, the do-variable check is done only at parse time via
"gfc_check_do_variable"; it uses gfc_state_stack to save the information about
the do variables [gfc_state_stack(->previous...)->do_variable], but this
information is lost at resolution time - on the other hand, the INTENT_OUT is
often not known at parse time.

One possibility is to generate a stack of do variables and save a link to it,
e.g., in gfc_code. Something like:

struct gfc_do_var_list {
 struct gfc_do_var_list *previous;
 gfc_symbol *do_var;
}
struct gfc_do_var_list *gfc_current_do_var = NULL;

The gfc_current_do_var is saved in gfc_code; every time a new DO loop is
started, a new item is generated and assigned to gfc_current_do_var - after the
DO loop, one sets gfc_current_do_var = gfc_current_do_var->previous. That will
generate a tree-like structure, which looks like a stack. (One probably needs
another linked list to store the gfc_current_do_var - as chain not as tree -
for freeing the list.)