Constructing an A301 on a Motioncore bus segfaults in sim #387

The first::a301::A301 constructor segfaults in simulation when passed a Motioncore CAN bus ID.

I encountered this when updating robotpy-rev to the latest REVLib today. I haven't attempted to reproduce this on real hardware (as I don't have an A301 or Motioncore).

In C++ this might look like:

#include "first/A301.h"
#include "wpi/framework/TimedRobot.hpp"
#include "wpi/hardware/bus/CANPort.hpp"

class Robot : public wpi::TimedRobot {
  first::a301::A301 motor1{wpi::CANPort::CAN_D0};
  first::a301::A301 motor2{wpi::CANPort::CAN_D19, 1};
}

With the builds from robotpy/robotpy-rev#94 calling it from a REPL is also enough to reproduce:

import rev
import wpilib

rev.A301(wpilib.CANPort.CAN_D0)
rev.A301(wpilib.CANPort.CAN_D1, 1)

This segfault doesn't occur with a SparkMax, nor does it occur when instantiating an A301 on a Systemcore CAN bus (as exercised by robotpy-rev tests); it's specific to specifying a Motioncore bus.

Here's a backtrace from gdb:

#0  0x00007fffe4a1dca4 in (anonymous namespace)::A301_AutoDetectDeviceId(int) ()
   from /home/davo/git/robotpy/robotpy-rev/rev/_rev.cpython-312-x86_64-linux-gnu.so
#1  0x00007fffe4a1e8b5 in c_A301_RegisterId () from /home/davo/git/robotpy/robotpy-rev/rev/_rev.cpython-312-x86_64-linux-gnu.so
#2  0x00007fffe4a04de2 in first::a301::internal::A301::A301(int, int) ()
   from /home/davo/git/robotpy/robotpy-rev/rev/_rev.cpython-312-x86_64-linux-gnu.so
#3  0x00007fffe4a0498c in first::a301::A301::A301(wpi::CANPort, int) ()
   from /home/davo/git/robotpy/robotpy-rev/rev/_rev.cpython-312-x86_64-linux-gnu.so

• REVLib 2027.0.0-alpha-7
• Linux (Fedora 44, also reproducible in a Debian 13 container)