MemoryError goes away when program is changed slightly

[dhalbert]

From https://forums.adafruit.com/viewtopic.php?t=218315

A program mentioned in the thread above happens to trigger a MemoryError in recent 10.0.0 alpha builds. Very slight changes cause the error to go away. This seems like it might be some kind of edge case related to the recent gc changes.

Program is below. This is running on a CPX with 10.0.0-alpha.6. As is, it causes:

MemoryError: memory allocation failed, allocating 1472 bytes

If the line

### a=1 ### uncommenting this causes MemoryError to go away

is uncommented, the error does not occur.

code.py:

# SPDX-FileCopyrightText: 2017 Limor Fried for Adafruit Industries
#
# SPDX-License-Identifier: MIT

# Circuit Playground digitalio example
# Rick Pump

import time
import board
import digitalio
import countio
import neopixel
a=1 ### uncommenting this causes MemoryError to go away

# start neopixel
pixels = neopixel.NeoPixel(board.NEOPIXEL, 10, brightness=0.01, auto_write=False)
RED = (255, 0, 0)
YELLOW = (255, 150, 0)
# GREEN = (0, 255, 0)
# CYAN = (0, 255, 255)
# BLUE = (0, 0, 255)
# PURPLE = (180, 0, 255)
# WHITE = (255, 255, 255)
OFF = (0, 0, 0)
# end neopixel

# Create PIN
testbtn = digitalio.DigitalInOut(board.BUTTON_A)
testbtn.switch_to_input(pull=digitalio.Pull.DOWN)
vcmtimebtn = countio.Counter(board.BUTTON_B, edge=countio.Edge.RISE)
ctsw = digitalio.DigitalInOut(board.A1)
ctsw.switch_to_input(pull=digitalio.Pull.DOWN)
vcmsw = digitalio.DigitalInOut(board.A6)
vcmsw.switch_to_input(pull=digitalio.Pull.DOWN)
fltrsw = digitalio.DigitalInOut(board.A5)
fltrsw.switch_to_input(pull=digitalio.Pull.DOWN)
led = digitalio.DigitalInOut(board.D13)
led.switch_to_output()
rly = digitalio.DigitalInOut(board.A2)
rly.switch_to_output()

vcm = 0
vcmtime = (60.0)  # 5 min test - 3600 sec = 1 hour
vcmoveride = (60.0)  # 55 min test - 86400 sec = 24 hour (86400 - vctime)
dbt = (3)  # debounce

while True:
    if vcm == 1:  # vacuum is commanded
        led.value = True
        rly.value = True
        print("Vacuum Time", vcmtime)
        time.sleep(vcmtime)
        print("Vacuum Done")
        led.value = False
        rly.value = False
        print("Vacuum Overide", vcmoveride)
        time.sleep(vcmoveride)
        print("Vacuum TimeOut")
        vcm = 0
    elif testbtn.value or ctsw.value or vcmsw.value:  # button is pushed
        # time.sleep(dbt)
        vcm = 1
        print("Vacuum Start")
    elif vcmtimebtn.count == 1:
        time.sleep(dbt)
        pixels.fill(OFF)  # turn all neopixels off
        pixels[9] = YELLOW
        pixels.show()
        vcmtime = 5
        print("Vacuum Time Set", vcmtime)
        time.sleep(dbt)
    elif vcmtimebtn.count == 2:
        time.sleep(dbt)
        pixels.fill(OFF)  # turn all neopixels off
        pixels[8] = YELLOW
        pixels.show()
        vcmtime = 10
        print("Vacuum Time Set", vcmtime)
        time.sleep(dbt)
    elif vcmtimebtn.count == 3:
        time.sleep(dbt)
        pixels.fill(OFF)  # turn all neopixels off
        pixels[7] = YELLOW
        pixels.show()
        vcmtime = 15
        print("Vacuum Time Set", vcmtime)
        time.sleep(dbt)
    elif vcmtimebtn.count == 4:
        time.sleep(dbt)
        pixels.fill(OFF)  # turn all neopixels off
        pixels[6] = YELLOW
        pixels.show()
        vcmtime = 20
        print("Vacuum Time Set", vcmtime)
        time.sleep(dbt)
    elif vcmtimebtn.count == 5:
        time.sleep(dbt)
        pixels.fill(OFF)  # turn all neopixels off
        pixels[5] = YELLOW
        pixels.show()
        vcmtime = 25
        print("Vacuum Time Set", vcmtime)
        time.sleep(dbt)
    elif vcmtimebtn.count == 6:
        time.sleep(5)
        pixels.fill(OFF)  # turn all neopixels off
        pixels[9] = YELLOW
        pixels[8] = YELLOW
        pixels[7] = YELLOW
        pixels[6] = YELLOW
        pixels[5] = YELLOW
        pixels.show()
        vcmtime = 30
        print("Vacuum Time Set", vcmtime)
        time.sleep(5)
    elif vcmtimebtn.count == 7:
        time.sleep(dbt)
        pixels.fill(OFF)  # turn all neopixels off
        pixels[4] = YELLOW
        pixels.show()
        vcmtime = 35
        print("Vacuum Time Set", vcmtime)
        time.sleep(dbt)
    elif vcmtimebtn.count == 8:
        time.sleep(dbt)
        pixels.fill(OFF)  # turn all neopixels off
        pixels[3] = YELLOW
        pixels.show()
        vcmtime = 40
        print("Vacuum Time Set", vcmtime)
        time.sleep(dbt)
    elif vcmtimebtn.count == 9:
        time.sleep(dbt)
        pixels.fill(OFF)  # turn all neopixels off
        pixels[2] = YELLOW
        pixels.show()
        vcmtime = 45
        print("Vacuum Time Set", vcmtime)
        time.sleep(dbt)
    elif vcmtimebtn.count == 10:
        time.sleep(dbt)
        pixels.fill(OFF)  # turn all neopixels off
        pixels[1] = YELLOW
        pixels.show()
        vcmtime = 50
        print("Vacuum Time Set", vcmtime)
        time.sleep(dbt)
    elif vcmtimebtn.count == 11:
        time.sleep(dbt)
        pixels.fill(OFF)  # turn all neopixels off
        pixels[0] = YELLOW
        pixels.show()
        vcmtime = 55
        print("Vacuum Time Set", vcmtime)
        time.sleep(dbt)
    elif vcmtimebtn.count == 12:
        time.sleep(dbt)
        pixels.fill(OFF)  # turn all neopixels off
        pixels.fill(YELLOW)
        pixels.show()
        vcmtime = 60
        print("Vacuum Time Set", vcmtime)
        time.sleep(dbt)
    elif vcmtimebtn.count == 13:
        time.sleep(5)
        pixels.fill(OFF)  # turn all neopixels off
        pixels.show()
        time.sleep(1)
        pixels.fill(RED)  # turn all neopixels off
        pixels.show()
        time.sleep(1)
        pixels.fill(OFF)  # turn all neopixels off
        pixels.show()
        vcmtimebtn.reset()
        print("Vacuum Time Reset", vcmtime)
        time.sleep(5)
    else:
        led.value = False
        pixels.fill(OFF)
        pixels.show()
        print("Vacuum Time Set", vcmtime)
        time.sleep(dbt)

[dhalbert]

After some more thorough testing, this appears just to be a program that is too big. The current behavior is a bit idiosyncratic, but when re-testing on a Metro M0, it's clear that a slightly smaller or larger program affects whether the MemoryError occurs.