or C<PERL_MAGIC_uvar> magic, it is important for extensions to take
extra care to avoid conflict. Typically only using the magic on
objects blessed into the same class as the extension is sufficient.
-For C<PERL_MAGIC_ext> magic, it may also be appropriate to add an I32
-'signature' at the top of the private data area and check that.
+For C<PERL_MAGIC_ext> magic, it is usually a good idea to define an
+C<MGVTBL>, even if all its fields will be C<0>, so that individual
+C<MAGIC> pointers can be identified as a particular kind of magic
+using their C<mg_virtual> field.
+
+ STATIC MGVTBL my_vtbl = { 0, 0, 0, 0, 0, 0, 0, 0 };
+
+ MAGIC *mg;
+ for (mg = SvMAGIC(sv); mg; mg = mg->mg_moremagic) {
+ if (mg->mg_type == PERL_MAGIC_ext && mg->mg_virtual == &my_vtbl) {
+ /* this is really ours, not another module's PERL_MAGIC_ext */
+ my_priv_data_t *priv = (my_priv_data_t *)mg->mg_ptr;
+ }
+ }
Also note that the C<sv_set*()> and C<sv_cat*()> functions described
earlier do B<not> invoke 'set' magic on their targets. This must