The value of the variable does not change in the while True: loops

[dlimpid]

I've read #2769, #3214, and #4535, but I'm not sure whether these are the same or not.

When I wrote the infinite loop with while True:, the value of the variable does not change (runs with no errors but the result is wrong).

@numba.njit
def foo(value):
    a = 0
    while True:
        print(a, value)
        value = value * 16807 % 2147483647
        if a > 3:
            return value
        a += 1

foo(65)

Without numba:

0 65
1 1092455
2 1181022009
3 245556042
4 1744312007

With numba:

0 65
1 65
2 65
3 65
4 65

• @numba.njit(numba.int64(numba.int64)) does not help.
• break in the while loop and return at the last of the function does not help.
• while True == True: solves the problem.

Thank you.

My env: Python 3.8.0, numba 0.46.0

[stuartarchibald]

Thanks for the report, this seems to only reproduce on Python 3.8, so would guess at it being a CFG/analysis issue from the recent rewrite of this part of the code.

CC @sklam.

[sklam]

checking this now

[sklam]

I can't replicate this on master ceab106

[sklam]

Note, the bug happens on tag 0.46.0 because at that point numba doesn't support py3.8.