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Recursion limitation in Python 3.13 #114413
Description
Bug report
Every recursive call of Python function increases the recursion_depth counter. Some recursive calls of C functions also increase it. A RecursionError is raised when it exceed the limit (sys.getrecursionlimit()).
The following code expectedly prints a value close to 1/2 of sys.getrecursionlimit() in all Python versions before 3.7 (including 2.7):
def test(n):
if n > 0:
a = []
a.extend(test(n-1) for _ in [1])
for i in range(1000):
try:
test(i)
except RecursionError:
print(i)
breakOne for every test() function call and one for every generator expression. Both are shown in a traceback.
In Python 3.7 to 3.11 it prints 1/3 of the limit. Perhaps it adds one level for every list.extend() call?
In Python 3.12 it returns to 1/2 of the limit.
But in the main branch it only prints 1/6 of the limit. How can it increase the recursion_depth counter 6 times per the recursion level? It is a regression, because now the code that was successfully passed in previous versions starts to raise a RecursionError. See #111803 for example.
Activity
serhiy-storchaka commentedon Jan 22, 2024
Other example that involves only one Python (generator) function call per recursion level:
It prints the whole limit in Python before 3.7, 1/2 of the limit in Python 3.7 to 3.12 (no difference between 3.11 and 3.12!), and only 1/6 of the limit in the main branch.
terryjreedy commentedon Jan 22, 2024
On installed 3.13.0a3, (tags/v3.13.0a3:f009305, Jan 17 2024, 13:25:20), I get 513: IDLE, Win10, rc=1000. With debug no-gil build, (heads/main-dirty:b04c5005cc, Jan 21 2024, 02:00:08), I get 165 (rc same). Recompile plain build.bat, 513 again. Recompile with -d, back to 165.
brettcannon commentedon Jan 22, 2024
Under a debug build of WASI w/ a modification to print before calling
list(test(i)), I got to 58 onmainand then the call stack was exhausted (i.e. the WASI host killed the run beforeRecursionErrorwas reached). A non-debug build gets to 167 and doesn't crash. 3.12 non-debug is 165. For a non-debug build of 3.11 it's 198.GH-114456: lower the recursion limit under WASI for debug builds (GH-…
pythonGH-114456: lower the recursion limit under WASI for debug builds (
pythonGH-114456: lower the recursion limit under WASI for debug builds (