This is a list of (funny) things, you have to check before you dig
into deep debugging sessions.

 * Check for assumptions about structure layout (and v-table 
   pointers)

 * Check for assumptions about bitfield layout (just the same 
   as above, but as reminder)

 * Is there code with side effects (i++=i++ or so)?

 * Some unclobbered registers or memory in inline assembly?
   - Keep in mind there was a problem on x86 with the clobber 
     list, you have to mark clobbered registers as output to 
     a dummy variable.

   - Clobbering ebp has no effects. Really! We've tried it!
     Also there is no output constraint, so if you use ebp,
     you must explicitly save/restore it.

 * Missing 'volatile' on shared and manipulated data?

 * You made assumptions about the width of native data types?


Put some printfs into the code, and hope they will not cover 
the bug. Or just use JDB and find the bug.

Remember: FIND THE BUG.