Known Problems and Bugs Related to W3Kit

W3Kit Bugs

The Path2_copy() function is broken in version 2.0 (fixed in 2.1). This function is not used within the kit itself.

GNU Objective-C Bugs

Unfortunately there are currently a number of problems in GNU Objective-C related to object archiving. Since archiving is central to W3Kit, it is important to be aware of the pitfalls until these bugs are fixed. The first group of bugs will affect many application programmers:

• The archive-writing functions generally crash when archiving NULL pointers; the only exception being that nil objects are correctly archived. When archiving NULL strings or selectors, use a fallback value (e.g., an empty string) instead.
• Archiving floating point values is not currently supported. You have to archive these values as raw byte arrays:

  	float m[6];
  	objc_write_array(stream, "c", sizeof(m), &m);
  

  While that's not portable, the object archive created by W3Kit will usually be consumed by the same server that produced it.
• Compound type descriptions like "{ii}" or "[4i]" are not yet supported by most archiving functions.
• Version numbers of superclasses are not recorded in the archive, even if they are nonzero. This means that abstract classes cannot be properly versioned.

The second group of bugs will not affect as many application programmers, because the W3Input class (which acts as the base class for most of W3Kit) contains workarounds that protect its subclasses from these bugs:

• Versioning is broken; class version numbers are incorrectly recorded. The following hidden W3Kit function can be used to override and correct +setVersion:, in classes which do not derive from W3Input:

  	extern void class_set_version_fix(Class *class, unsigned num);
  

• The semantics of the +initialize method are slightly different from those under NeXTSTEP. More importantly, though, the semantics are buggy with respect to archiving: +initialize appears to only get called before the first class method is called, and unarchiving currently does not automatically invoke any class methods.

Graphics Library Bugs

• The OOGL libraries are in alpha release as standalone libraries. While they have been successfully used inside Geomview, many of the APIs are not yet well documented. There are also likely to be significant bugs in regions of the library not exercised by Geomview.
• The WriteGIF() function (copied verbatim from XV source, as required by its license) appears to get confused on images bigger than about 400 X 400. For now, keep your graphics widgets down to this size.

The Geometry Center Home Page

Author: Paul Burchard
Comments to: webmaster@geom.umn.edu
Created: Apr 18 1994 --- Last modified: Tue Jun 18 10:30:27 1996