Defensive bipolar check in twist engine (#7413)

The twist engine lacked a defensive test for the bipolar detector
which meant some automation events which didn't load an entire
oscillator state could result in an out of boudns read.

Closes #7410

scripts/osc-tests/OSC_test.py

@@ -0,0 +1,100 @@
+from osc4py3.as_eventloop import *
+from osc4py3 import oscbuildparse as obp
+from osc4py3.oscmethod import *
+import time
+from threading import Thread
+
+ip = "127.0.0.1"
+surgeOSCInPort = 53280	#Surge XT default OSC in port
+surgeOSCOutPort = 53281	#Surge XT default OSC out port
+
+def freqNote(freq, vel, noteid):
+    msg = obp.OSCMessage("/fnote", ",fff", [freq, vel, noteid])
+    osc_send(msg, "oscout")
+    osc_process()
+
+def freqNoteRelease(freq, vel, noteid):
+    msg = obp.OSCMessage("/fnote/rel", ",fff", [freq, vel, noteid])
+    osc_send(msg, "oscout")
+    osc_process()
+
+def midiNote(freq, vel, noteid):
+    msg = obp.OSCMessage("/mnote", ",fff", [freq, vel, noteid])
+    osc_send(msg, "oscout")
+    osc_process()
+
+def midiNoteRelease(freq, vel, noteid):
+    msg = obp.OSCMessage("/mnote/rel", ",fff", [freq, vel, noteid])
+    osc_send(msg, "oscout")
+    osc_process()
+
+def notesTest():
+    freqNote(218.022, 100, 1)
+    freqNote(261.626, 100, 2)
+    freqNote(348.834, 100, 3)
+
+    time.sleep(3)
+
+    freqNoteRelease(0, 127, 1)
+    freqNoteRelease(0, 127, 2)
+    freqNoteRelease(0, 127, 3)
+
+    time.sleep(2)
+
+    midiNote(60, 100, 1)
+    midiNote(65, 100, 2)
+    midiNote(72, 100, 3)
+
+    time.sleep(3)
+
+    midiNoteRelease(0, 127, 1)
+    midiNoteRelease(0, 127, 2)
+    midiNoteRelease(0, 127, 3) 
+
+def handlerfunction(*args):
+    """for arg in args:
+        print(arg + " ", end="")
+    print()"""
+
+def endless_while():
+    global thread_running
+    while thread_running:
+        osc_process()
+        time.sleep(0.1)
+
+def get_input():
+    user_input = input('Listening for OSC messages from Surge (hit any key, and return, to quit) \n')
+    print('Exiting...')
+
+
+osc_startup()
+osc_udp_client(ip, surgeOSCInPort, "oscout")
+osc_udp_server(ip, surgeOSCOutPort, "oscin")
+osc_method("/*/*", handlerfunction, argscheme=OSCARG_ADDRESS + OSCARG_DATAUNPACK)
+
+def trigger_crash():
+    msg = obp.OSCMessage("/param/a/osc/1/type", ",f", [9.0])
+    osc_send(msg, "oscout")
+    osc_process()
+
+    msg = obp.OSCMessage("/param/a/osc/1/type", ",f", [10.0])
+    osc_send(msg, "oscout")
+    osc_process()
+
+    msg = obp.OSCMessage("/q/all_params", ",", [])
+    osc_send(msg, "oscout")
+    osc_process()
+
+notesTest()
+trigger_crash()
+thread_running = True
+
+if __name__ == '__main__':
+    t1 = Thread(target=endless_while)
+    t2 = Thread(target=get_input)
+
+    t1.start()
+    t2.start()
+
+    t2.join()
+    thread_running = False

src/common/dsp/oscillators/TwistOscillator.cpp

@@ -199,7 +199,10 @@ static struct EngineDynamicBipolar : public ParameterDynamicBoolFunction
             return false;
         }
         auto idx = (p - engp);
-
+        if (idx < 0 || idx >= engineBipolars[eng].size())
+        {
+            return false;
+        }
         bool res = engineBipolars[eng][idx - 1];
         if (idx == TwistOscillator::twist_aux_mix)
             res = p->extend_range;