Haven't checked CPython's extension API but Java's JNI does not allow exceptions to propagate through native code. When you call a Java method from JNI it will

Haven't checked CPython's extension API but Java's JNI does not allow exceptions to propagate through native code. When you call a Java method from JNI it will return and you have to check whether there is a pending exception, and do whatever is sensible in your native library. If a native library called from Java throws an exception that is not caught in that library then I think all bets are off - it probably depends on your language/platform ABI. The best case scenario would be that your Java stack gets nicely unwound in some way, but given it wouldn't be a Java exception object being thrown up the stack I'm really not sure what would happen. Unwinding the stack through native library or language boundaries is fraught with potential problems and language interop APIs have to be designed carefully round that sort of thing.