forced casts question

Hi,

How come in various places a (void *) was introduced in casts, 
apparently in order to force them?

e.g.

-    _svmt_stack_frame *frame = (_svmt_stack_frame *)
+    _svmt_stack_frame *frame = (_svmt_stack_frame *) (void *)
        (((char *) env->stack.current_frame) + offset);

I think this was to "eliminate tons of spurious warnings" (r3144), but 
why were such things causing warnings?  Isn't it good to let the 
compiler help you catch casting errors?

Chris