Re: [Gretl-devel] global series penetrating into functions problem

On Sat, 13 Oct 2018, oleg_komashko(a)ukr.net wrote: > Dear all, > Below is a script illustrating the problem > > # creates list of all global series > function list fun1(void) > list retlist = seq(1,$nvars-1) > return retlist > end function > # identity list function > function list fun2(list a_list) > return a_list > end function > # checking function > function void fu(string name) > catch eval @name > err = $error > if err > printf "Variable %s is not defined\n", name > endif > end function > > #contaminating function > > function void spoil(void) > list list1 = fun1() > list list2 = fun2(list1) > end function > > ###### example > > nulldata 20 > set seed 13 > x1 = normal() > # before > fu("x1") > # looking at x1 > print x1 > > # spoiling > spoil() > # after > fu("x1") > > > On the first run fu("x1") does not know > global series 'x1' but after running spoil() > fu("x1") knows and evaluates x1 Thanks for the report. The primary source of mischief here is the ability, within a function, to create a list that includes series that were not given as arguments in any shape or form (neither as "pointer"-form series arguments nor as members of a list argument), by the simple expedient of referring to the series by their ID numbers -- with the $nvars accessor providing a handy upper bound! I've been aware of this possibility for a while but I didn't think it was a high priority for fixing, since it seemed excessively "tricksy" and unlikely to arise in practice. Now it has if fact arisen, the loophole is closed in git. You can now put into a list by ID number only series that satisfy one of these criteria: 1. the series was given to the function via a "pointer-to-series" argument, 2. the series was given to the function as a member of a list argument, or 3. the series was newly defined after the function began executing. This means that the statement in fun1() above, list retlist = seq(1,$nvars-1) will fail right away (since fun1 is not passed any arguments, let alone references to series), and therefore the mischief will not get started. Allin _______________________________________________ Gretl-devel mailing list Gretl-devel(a)lists.wfu.edu http://lists.wfu.edu/mailman/listinfo/gretl-devel