318) Why does my callback's client data structure contain incorrect

values when the callback is called?  I created a structure and used a pointer
to it as callback client data.
[Last modified: Apr 95]

Answer: If your structure is declared as automatic, the callback will probably
not be executed within the structure's scope, so the pointer to the structure
will become invalid.  You can avoid this problem by declaring your structure
external or by allocating with malloc or (in C++) new.

Ken Lee