Front page | perl.perl5.porters |
Postings from October 2000
On Sun, 01 Oct 2000 16:58:04 BST, Alan Burlison wrote: >I think I've managed to track down where self-ties are broken. It is in >pp_hot.c in pp_aelem, 4 lines from the bottom of the function: > > if (!lval && SvGMAGICAL(sv)) /* see note in pp_helem() */ > sv = sv_mortalcopy(sv); > >This was added I believe as part of change 1307, to get local to work on >tied hashes. However, in the case of self-ties it doesn't work, as the >call to sv_mortalcopy then calls mg_get, which then recurses into >pp_aelem with inevitable consequences. I've tried temporarily removing >the call to sv_mortalcopy, but that still doesn't fix the problem, >although I'm not quite sure why. I'm assuming the correct fix is to >disable magic for the tied array for the duration of the call to >sv_mortalcopy, but the save_magic and restore_magic functions are local >to mg.c. I'm a bit wary of promoting them to be global, as they should >probably be renamed (mg_save/mg_restore?) which involves changing >embed.pl > >I'd like some help and advice from someone please - Gurusamay, as your >name is against the changes in this area (761, 802 and 1307) could you >advise? I know it is a long time ago, but you probably have a far >better idea than I do of the correct fix. I doubt that change#1307 is the problem--we call sv_mortalcopy() in lots of other situations. IIRC, Chip did the work to support self-ties (prompted by Joshua's reports, maybe). I remember thinking at the time that the patch that we added might not really support self-referential ties in general (as opposed a variable tied to itself, in particular). I'm not sure about the details now, but it may have been something to do with scenarios like A-tiedto-B-tiedto-C-tiedto...tiedto-A not working. Whittling it down to a small test case may prove educational. Sarathy gsar@ActiveState.comThread Previous | Thread Next