Simulator with print() in a tight loop consumes all RAM and page becomes unresponsive

[martinwork]

Bug Description

Arising from support ticket https://support.microbit.org/helpdesk/tickets/99552 (private)

Running the simulator with a tight loop using print() consumes all RAM in less than a minute, and the page becomes unresponsive after another minute or two.

The support ticket owner reports using Linux with Firefox, and printing compass.heading()

from microbit import *
while True:
    print(compass.heading())

When I test in Windows Chrome, printing a fixed string has the same effect.

from microbit import *
while True:
    print("0"))

I don't see any RAM increase with a sleep in the loop, unless it's sleep(0).

from microbit import *
while True:
    print("0")
    sleep(1)

How To Reproduce

Steps to reproduce the behavior:

1. Go to https://python.microbit.org/
2. Use the code above
3. Monitor memory consumption
4. See error

Expected behavior

The page does not become unresponsive.

Screenshots

Environment

Desktop (please complete the following information):

• OS: [e.g. iOS] Windows 11
• Browser [e.g. chrome, safari] Chrome
• Version [e.g. 22] 148