circuitpython: BLE start_scan on 5.3.0 dies with MemoryError: memory allocation failed, allocating 65536 bytes - also 42241 bytes

I had a spate of these a fortnight ago and I just got one now on a CLUE running 5.3.0 and fairly recent libs (20200625). I’ve touched nothing near this part of my application recently. This is with active=False if it makes any difference and I have been using buffer_size=1536 for some time.

Listening for (<class 'Advertisement'>,)
Traceback (most recent call last):
  File "code.py", line 1520, in <module>
  File "code.py", line 914, in broadcastAndReceive
  File "code.py", line 691, in startScan
  File "adafruit_ble/__init__.py", line 235, in start_scan
MemoryError: memory allocation failed, allocating 65536 bytes

That number is clearly suspicious for being so large and for being 2^16.

Minor possibility this is data driven, perhaps a rogue received BLE packet could cause the library to do some unwise size allocations? Three other devices running same code at same time weren’t affected.

About this issue

Original URL
State: closed
Created 4 years ago
Comments: 31 (1 by maintainers)

Most upvoted comments

The normal way we would debug this is to set a breakpoint on the exception handler and look at the backtrace. That requires connecting a J-Link or similar to the board. That’s why I was hoping for a simpler example that occurs often enough to catch this, but I’m not sure that’s possible here. Do you think any of that is possible?

The other thing I am looking at is generating and printing a stack trace when these exceptions happen. It looks like this is possible, if we add -funwind-tables or the equivalent: https://www.google.com/search?q=backtrace+arm-none-eabi-gcc https://github.com/red-rocket-computing/backtrace etc.

dhalbert on Jul 9, 2020