RP2: Global variable lost/distorted after start_new_thread() with try/except
import _thread
from time import sleep_ms
a = b = 1 # these have to be 2 variables, for the bug to occur
def test():
global a
try: # the try / except block has to be there too
a = 2
except Exception as e:
print(e)
_thread.start_new_thread(test,())
c = 5 # and also this variable has to be here, before the sleep_ms()
sleep_ms(10)
print("a is "+str(a))
reports
a is 1 which should be a is 2.
@pdg137 found even that a is __main__may be reported in a similar setup, with MicroPython v1.21.0 on 2023-10-06 or older.
This issue is a reincarnation of https://github.com/micropython/micropython/issues/10621 in a more minimal setting (thanks to @pdg137), so hopefully it will be easier to trace the bug.
Maintainers: If it was the wrong policy to raise a new issue, please give a short feedback, then I may delete this one and rename https://github.com/micropython/micropython/issues/10621.
RP2: global variable lost at maximum recursion depth in second thread
A global variable reportedly is not there (NameError: name 'a' isn't defined) although it should be there.
This occurs in a setting of a recursion test function that hits the limit of 19 recursions on the second thread/core on a RPi2040.
The global variable, a, is updated in this function.
Strangely this only occurs if also two other global variables are defined, sleep_ms is imported as a single import and the maximum recursion depth exception is catched with try/except.
The code is as follows:
import _thread
from time import sleep_ms #, sleep_us # if more than one functions imported there is no NameError
a = 0
b = 0
def recursionTest():
global a
a += 1
try:
recursionTest()
except Exception as errorMsg:
print(errorMsg)
_thread.start_new_thread(recursionTest,())
c = 0
sleep_ms(10)
print('recursion depth:', a)
The output is as follows:
Unhandled exception in thread started by <function recursionTest at 0x20008d50>
Traceback (most recent call last):
File "<stdin>", line 9, in recursionTest
NameError: name 'a' isn't defined
recursion depth: 0
If c = 0, for example is commented out the output changes to (correct);
maximum recursion depth exceeded
recursion depth: 19
This was on `MicroPython v1.19.1 on 2022-07-27; Raspberry Pi Pico with RP2040