diff --git a/Doc/library/idle.rst b/Doc/library/idle.rst
index fb886a714d7471..de58f266bf5e6e 100644
--- a/Doc/library/idle.rst
+++ b/Doc/library/idle.rst
@@ -713,6 +713,10 @@ or ``print`` or ``write`` to sys.stdout or sys.stderr,
IDLE should be started in a command line window. The secondary subprocess
will then be attached to that window for input and output.
+The IDLE code running in the execution process adds frames to the call stack
+that would not be there otherwise. IDLE wraps ``sys.getrecursionlimit`` and
+``sys.setrecursionlimit`` to reduce the effect of the additional stack frames.
+
If ``sys`` is reset by user code, such as with ``importlib.reload(sys)``,
IDLE's changes are lost and input from the keyboard and output to the screen
will not work correctly.
diff --git a/Lib/idlelib/NEWS.txt b/Lib/idlelib/NEWS.txt
index 834646f7f776f8..4fad45b2de9c73 100644
--- a/Lib/idlelib/NEWS.txt
+++ b/Lib/idlelib/NEWS.txt
@@ -3,6 +3,11 @@ Released on 2019-06-24?
======================================
+bpo-26806: To compensate for stack frames added by IDLE and avoid
+possible problems with low recursion limits, add 30 to limits in the
+user code execution process. Subtract 30 when reporting recursion
+limits to make this addition mostly transparent.
+
bpo-37325: Fix tab focus traversal order for help source and custom
run dialogs.
diff --git a/Lib/idlelib/help.html b/Lib/idlelib/help.html
index 91803fd06c8f1e..cee6887df68f9d 100644
--- a/Lib/idlelib/help.html
+++ b/Lib/idlelib/help.html
@@ -14,7 +14,7 @@
-
+
@@ -135,113 +135,75 @@ Menus
diff --git a/Lib/idlelib/idle_test/test_run.py b/Lib/idlelib/idle_test/test_run.py
index 46f0235fbfdca1..d0f1e9207bb17c 100644
--- a/Lib/idlelib/idle_test/test_run.py
+++ b/Lib/idlelib/idle_test/test_run.py
@@ -6,6 +6,8 @@
from test.support import captured_stderr
import io
+import sys
+
class RunTest(unittest.TestCase):
@@ -260,5 +262,36 @@ def test_close(self):
self.assertRaises(TypeError, f.close, 1)
+class TestSysRecursionLimitWrappers(unittest.TestCase):
+
+ def test_bad_setrecursionlimit_calls(self):
+ run.install_recursionlimit_wrappers()
+ self.addCleanup(run.uninstall_recursionlimit_wrappers)
+ f = sys.setrecursionlimit
+ self.assertRaises(TypeError, f, limit=100)
+ self.assertRaises(TypeError, f, 100, 1000)
+ self.assertRaises(ValueError, f, 0)
+
+ def test_roundtrip(self):
+ run.install_recursionlimit_wrappers()
+ self.addCleanup(run.uninstall_recursionlimit_wrappers)
+
+ # check that setting the recursion limit works
+ orig_reclimit = sys.getrecursionlimit()
+ self.addCleanup(sys.setrecursionlimit, orig_reclimit)
+ sys.setrecursionlimit(orig_reclimit + 3)
+
+ # check that the new limit is returned by sys.getrecursionlimit()
+ new_reclimit = sys.getrecursionlimit()
+ self.assertEqual(new_reclimit, orig_reclimit + 3)
+
+ def test_default_recursion_limit_preserved(self):
+ orig_reclimit = sys.getrecursionlimit()
+ run.install_recursionlimit_wrappers()
+ self.addCleanup(run.uninstall_recursionlimit_wrappers)
+ new_reclimit = sys.getrecursionlimit()
+ self.assertEqual(new_reclimit, orig_reclimit)
+
+
if __name__ == '__main__':
unittest.main(verbosity=2)
diff --git a/Lib/idlelib/run.py b/Lib/idlelib/run.py
index 6b3928b7bf2bc7..c6ed76b23a2d1b 100644
--- a/Lib/idlelib/run.py
+++ b/Lib/idlelib/run.py
@@ -4,10 +4,12 @@
f'''{sys.executable} -c "__import__('idlelib.run').run.main()"'''
'.run' is needed because __import__ returns idlelib, not idlelib.run.
"""
+import functools
import io
import linecache
import queue
import sys
+import textwrap
import time
import traceback
import _thread as thread
@@ -305,6 +307,64 @@ def fix_scaling(root):
font['size'] = round(-0.75*size)
+RECURSIONLIMIT_DELTA = 30
+def install_recursionlimit_wrappers():
+ """Install wrappers to always add 30 to the recursion limit."""
+ # see: bpo-26806
+
+ @functools.wraps(sys.setrecursionlimit)
+ def setrecursionlimit(*args, **kwargs):
+ # mimic the original sys.setrecursionlimit()'s input handling
+ if kwargs:
+ raise TypeError(
+ "setrecursionlimit() takes no keyword arguments")
+ try:
+ limit, = args
+ except ValueError:
+ raise TypeError(f"setrecursionlimit() takes exactly one "
+ f"argument ({len(args)} given)")
+ if not limit > 0:
+ raise ValueError(
+ "recursion limit must be greater or equal than 1")
+
+ return setrecursionlimit.__wrapped__(limit + RECURSIONLIMIT_DELTA)
+
+ setrecursionlimit.__doc__ += "\n\n" + textwrap.fill(textwrap.dedent(f"""\
+ This IDLE wrapper adds {RECURSIONLIMIT_DELTA} to prevent possible
+ uninterruptible loops.
+ """).strip())
+
+ @functools.wraps(sys.getrecursionlimit)
+ def getrecursionlimit():
+ return getrecursionlimit.__wrapped__() - RECURSIONLIMIT_DELTA
+
+ getrecursionlimit.__doc__ += "\n\n" + textwrap.fill(textwrap.dedent(f"""\
+ This IDLE wrapper subtracts {RECURSIONLIMIT_DELTA} to compensate for
+ the {RECURSIONLIMIT_DELTA} IDLE adds when setting the limit.
+ """).strip())
+
+ # add the delta to the default recursion limit, to compensate
+ sys.setrecursionlimit(sys.getrecursionlimit() + RECURSIONLIMIT_DELTA)
+
+ sys.setrecursionlimit = setrecursionlimit
+ sys.getrecursionlimit = getrecursionlimit
+
+
+def uninstall_recursionlimit_wrappers():
+ """Uninstall the recursion limit wrappers from the sys module.
+
+ IDLE only uses this for tests. Users can import run and call
+ this to remove the wrapping.
+ """
+ if (
+ getattr(sys.setrecursionlimit, '__wrapped__', None) and
+ getattr(sys.getrecursionlimit, '__wrapped__', None)
+ ):
+ sys.setrecursionlimit = sys.setrecursionlimit.__wrapped__
+ sys.getrecursionlimit = sys.getrecursionlimit.__wrapped__
+ sys.setrecursionlimit(sys.getrecursionlimit() - RECURSIONLIMIT_DELTA)
+
+
class MyRPCServer(rpc.RPCServer):
def handle_error(self, request, client_address):
@@ -448,6 +508,8 @@ def handle(self):
# sys.stdin gets changed from within IDLE's shell. See issue17838.
self._keep_stdin = sys.stdin
+ install_recursionlimit_wrappers()
+
self.interp = self.get_remote_proxy("interp")
rpc.RPCHandler.getresponse(self, myseq=None, wait=0.05)
diff --git a/Misc/NEWS.d/next/IDLE/2019-06-10-22-48-50.bpo-26806.Zltkum.rst b/Misc/NEWS.d/next/IDLE/2019-06-10-22-48-50.bpo-26806.Zltkum.rst
new file mode 100644
index 00000000000000..8514bb9292fec8
--- /dev/null
+++ b/Misc/NEWS.d/next/IDLE/2019-06-10-22-48-50.bpo-26806.Zltkum.rst
@@ -0,0 +1,4 @@
+To compensate for stack frames added by IDLE and avoid possible problems
+with low recursion limits, add 30 to limits in the user code execution
+process. Subtract 30 when reporting recursion limits to make this addition
+mostly transparent.