> I wouldn't mind letting Cython special case subtypes of str (or unicode in > Py3) *somehow*, as long as this "somewhow" proves to be a viable solution that > only applies to exactly those types *and* can be done realiably for subtypes > of subtypes. I'm just not aware of such a solution.
As people have pointed out: add new fields *after* the variable-sized members. To access it, you need to compute the length of the base object, and then cast the pointer to an extension struct. That extends to further subtypes, too. Access is slightly slower, i.e. it's not a compile-time constant, but base_address + base_address[ob_len]*elem_size - more_fields_size This still compiles efficiently, e.g. on x86, gcc compiles a struct field access to movl 20(%eax), %eax and an access with a var-sized offset into movl 8(%eax), %edx; fetch length into edx movl -20(%eax,%edx,2), %eax; access 20-byte sized struct, assuming elements of size 2 > This does sound interesting, but I will have to look into the implications. As > I said, it has to be a viable solution without (noticeable) impact on other > types. I'm not sure how this would interact with subtypes of subtypes, and > what the memory layout would be in that case. See above. Regards, Martin _______________________________________________ Python-3000 mailing list Python-3000@python.org http://mail.python.org/mailman/listinfo/python-3000 Unsubscribe: http://mail.python.org/mailman/options/python-3000/archive%40mail-archive.com
