segmentation fault in ADSHardware.startup()

[leigh-johnson]

Steps to reproduce:

From 6f1f6b3 with a minor revision:

diff --git a/lab_10_template.py b/lab_10_template.py
index 53623b1..acbd525 100644
--- a/lab_10_template.py
+++ b/lab_10_template.py
@@ -188,7 +188,7 @@ if __name__ == "__main__":
     try:
         ads.use_wavegen(channel=1, function=wavegen_functions["sine"], offset_v=0, freq_hz=1e3, amp_v=1)
         ### FILL IN THIS LINE FOR L10.2(a)
-        raw_data = ...
+        # raw_data = ...
         ads.close_wavegen()
 
         ### UNCOMMENT THIS CODE FOR L10.3(a)

1. Run: python lab_10_template.py (runs as expected)

2. Re-run: python lab_10_template.py
   Output:

[1]    98546 segmentation fault  python lab_10_template.py

The proximate cause is not properly tearing down handles when the __main__ block finishes running (.close_scope(), .disconnect(), etc are only called in the Exception handler).

I believe the root cause is the Waveforms SDK storing a ctype.byref memory address pointer in a Python global variable. I haven't traced the dwf.framework calls to verify, but passing around a memory address this way creates a lot of opportunities to segfault.
https://github.com/Digilent/WaveForms-SDK-Getting-Started-PY/blob/master/WF_SDK/device.py#L204
https://github.com/Digilent/WaveForms-SDK-Getting-Started-PY/blob/master/WF_SDK/device.py#L278

The device enumerator example included in the SDK works fine, so I'm ruling out any connectivity issues:

$ python ../waveforms-sdk-digilent.waveforms_v3.24.2/samples/py/Device_Enumeration.py
DWF Version: b'3.24.2'
Number of Devices: 1
------------------------------
Device 0 : 
        Name: Analog Discovery Studio SN:210384B012EE
        ID: 3 rev: C 0x403
        Configurations:
        0. AnalogIn: 2 x 8192   AnalogOut: 2 x 4096     DigitalIn: 16 x 4096    DigitalOut: 16 x 1024
        1. AnalogIn: 2 x 16384  AnalogOut: 2 x 1024     DigitalIn: 16 x 1024    DigitalOut: 0 x 0
        2. AnalogIn: 2 x 2048   AnalogOut: 2 x 16384    DigitalIn: 0 x 0        DigitalOut: 0 x 0
        3. AnalogIn: 2 x 512    AnalogOut: 2 x 256      DigitalIn: 16 x 16384   DigitalOut: 16 x 16384
        4. AnalogIn: 2 x 8192   AnalogOut: 2 x 4096     DigitalIn: 16 x 4096    DigitalOut: 16 x 1024   1V8_Digital_Input
        5. AnalogIn: 2 x 8192   AnalogOut: 4 x 4096     DigitalIn: 16 x 2048    DigitalOut: 8 x 256     Power_Supply_Waveform_Generator
        6. AnalogIn: 2 x 512    AnalogOut: 2 x 256      DigitalIn: 16 x 16384   DigitalOut: 16 x 16384  1V8_Digital_Input
        7. AnalogIn: 2 x 8192   AnalogOut: 2 x 1024     DigitalIn: 16 x 16384   DigitalOut: 8 x 256

Additional env/version info:

$ which python
/Users/leigh/Library/Caches/pypoetry/virtualenvs/phys111a-lab10-SYt7gGMh-py3.11/bin/python
$ python --version
Python 3.11.12
$ pip freeze | grep WF_SDK 
WF_SDK @ git+https://github.com/Digilent/WaveForms-SDK-Getting-Started-PY@3e5fcd1b10a6a8c83bf1e5356d6ac61f15327d52

[leigh-johnson]

Device_Emumeration.py for ref (included in the SDK/samples/py folder bundled with the MacOS installer)

"""
   DWF Python Example
   Author:  Digilent, Inc.
   Revision:  2018-07-19

   Requires:                       
       Python 2.7, 3
"""

from ctypes import *
import sys
from dwfconstants import *

if sys.platform.startswith("win"):
    dwf = cdll.dwf
elif sys.platform.startswith("darwin"):
    dwf = cdll.LoadLibrary("/Library/Frameworks/dwf.framework/dwf")
else:
    dwf = cdll.LoadLibrary("libdwf.so")

#check library loading errors
szerr = create_string_buffer(512)
dwf.FDwfGetLastErrorMsg(szerr)
if szerr[0] != b'\0':
    print(str(szerr.value))

#declare ctype variables
hdwf = c_int()
cDevice = c_int()
cConfig = c_int()
cInfo = c_int()
iDevId = c_int()
iDevRev = c_int()

#declare string variables
devicename = create_string_buffer(64)
serialnum = create_string_buffer(16)

#print DWF version
version = create_string_buffer(16)
dwf.FDwfGetVersion(version)
print("DWF Version: "+str(version.value))

#enumerate and print device information
dwf.FDwfEnum(enumfilterAll, byref(cDevice))
#dwf.FDwfEnum(devidDiscovery2, byref(cDevice)) only Analog Discovery 2 devices
#dwf.FDwfEnum(c_int(enumfilterType.value|enumfilterUSB.value), byref(cDevice)) # only USB devices
print("Number of Devices: "+str(cDevice.value))

for iDev in range(0, cDevice.value):
    dwf.FDwfEnumDeviceName (c_int(iDev), devicename)
    dwf.FDwfEnumSN (c_int(iDev), serialnum)
    dwf.FDwfEnumDeviceType (c_int(iDev), byref(iDevId), byref(iDevRev))
    others = create_string_buffer(128)
    print("------------------------------")
    print("Device "+str(iDev)+" : ")
    print("\tName: " + str(devicename.value.decode()) + " " + str(serialnum.value.decode()))
    print("\tID: "+str(iDevId.value)+" rev: "+chr(0x40+(iDevRev.value&0xF))+" "+hex(iDevRev.value)) # LSbits of rev represent 1=A, 2=B

    print("\tConfigurations:")
    dwf.FDwfEnumConfig(c_int(iDev), byref(cConfig))
    for iCfg in range (0, cConfig.value):
        sz = "\t"+str(iCfg)+"."
        dwf.FDwfEnumConfigInfo(c_int(iCfg), c_int(1), byref(cInfo)) # DECIAnalogInChannelCount
        sz += " AnalogIn: "+str(cInfo.value)
        dwf.FDwfEnumConfigInfo(c_int(iCfg), c_int(7), byref(cInfo)) # DECIAnalogInBufferSize
        sz += " x "+str(cInfo.value)
        dwf.FDwfEnumConfigInfo(c_int(iCfg), c_int(2), byref(cInfo)) # DECIAnalogOutChannelCount
        sz += " \tAnalogOut: "+str(cInfo.value)
        dwf.FDwfEnumConfigInfo(c_int(iCfg), c_int(8), byref(cInfo)) # DECIAnalogOutBufferSize
        sz += " x "+str(cInfo.value)
        dwf.FDwfEnumConfigInfo(c_int(iCfg), c_int(4), byref(cInfo)) # DECIDigitalInChannelCount
        sz += " \tDigitalIn: "+str(cInfo.value)
        dwf.FDwfEnumConfigInfo(c_int(iCfg), c_int(9), byref(cInfo)) # DECIDigitalInBufferSize
        sz += " x "+str(cInfo.value)
        dwf.FDwfEnumConfigInfo(c_int(iCfg), c_int(5), byref(cInfo)) # DECIDigitalOutChannelCount
        sz += " \tDigitalOut: "+str(cInfo.value)
        dwf.FDwfEnumConfigInfo(c_int(iCfg), c_int(10), byref(cInfo)) # DECIDigitalOutBufferSize
        sz += " x "+str(cInfo.value)
        dwf.FDwfEnumConfigInfo(c_int(iCfg), c_int(-2), byref(others)) # other text info
        szothers = str(others.value.decode())
        if len(szothers) > 1 : sz += " \t"+szothers
        print(sz)