What causes the 'type and size of dynamic symbol ... not defined'warning?

[Richard Frith-Macdonald]

Since I got RedHat-6, I have been getting warning messages like -

  /usr/bin/ld: warning: type and size of dynamic symbol
  `__objc_class_name_NSObject' are not defined

Whenever I build an objective-c program.

The compiler version is -
gcc version egcs-2.91.66 19990314/Linux (egcs-1.1.2 release)

Can anyone enlighten me as to what exactly is causing these warnings, and how
they can be fixed?

Presumably this is a bug in either egcs or ld - my guess being that it is an
egcs bug, but perhaps a long-standing one that has been exposed by a change in
ld?