On Fri, 05 Apr 2013 23:31:44 +0600, Sturla Molden <stu...@molden.no> wrote:
offsetof() is not supported by current Cython, and I have not found any workaround (except hardcoding offsets for a specific architecture and compiler, but this is obviously wrong).offsetof() would certainly be very useful, but in the meantime offsetof(Struct, field) can be replaced with: <Py_ssize_t>&(<Struct*>NULL).field It's not ANSI C, but is portable enough.This will dereference a NULL pointer.
Nope it won't. It is purely an address calculation. Works fine in both msvc and gcc. offsetof is a builtin in gcc, but msvc implements it as a macro similar to the above.
Also, Py_ssize_t is not guaranteed to be long enough to store a pointer (but Py_intptr_t is). Use Py_intptr_t when you cast pointers to integers.
Thanks, Py_intptr_t is indeed more appropriate. I didn't know it existed.
Another option (for extern or public structs only) is to abuse renaming: enum: Struct_offsetof_field1 "offsetof(Struct, field1)"This will fail if "Struct" is name mangled by Cython. Basically it requires that it is defined outside of the Cython code, e.g. in a header file.
Please note "(for extern or public structs only)". These are not mangled. Best regards, Nikita Nemkin _______________________________________________ cython-devel mailing list cython-devel@python.org http://mail.python.org/mailman/listinfo/cython-devel
