1.2.3 What are these type and size warnings?

These warnings:

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

are a common occurence and are due to a mismatch between gcc and ld. They don’t do any harm so they can be safely ignored. They have been fixed in GCC version 3.1.