Issue #18621: Prevent the site module's patched builtins from keeping too many references alive for too long.

Lib/_sitebuiltins.py

@@ -0,0 +1,100 @@
+"""
+The objects used by the site module to add custom builtins.
+"""
+
+# Those objects are almost immortal and they keep a reference to their module
+# globals.  Defining them in the site module would keep too many references
+# alive.
+# Note this means this module should also avoid keep things alive in its
+# globals.
+
+import sys
+
+class Quitter(object):
+    def __init__(self, name, eof):
+        self.name = name
+        self.eof = eof
+    def __repr__(self):
+        return 'Use %s() or %s to exit' % (self.name, self.eof)
+    def __call__(self, code=None):
+        # Shells like IDLE catch the SystemExit, but listen when their
+        # stdin wrapper is closed.
+        try:
+            sys.stdin.close()
+        except:
+            pass
+        raise SystemExit(code)
+
+
+class _Printer(object):
+    """interactive prompt objects for printing the license text, a list of
+    contributors and the copyright notice."""
+
+    MAXLINES = 23
+
+    def __init__(self, name, data, files=(), dirs=()):
+        import os
+        self.__name = name
+        self.__data = data
+        self.__lines = None
+        self.__filenames = [os.path.join(dir, filename)
+                            for dir in dirs
+                            for filename in files]
+
+    def __setup(self):
+        if self.__lines:
+            return
+        data = None
+        for filename in self.__filenames:
+            try:
+                with open(filename, "r") as fp:
+                    data = fp.read()
+                break
+            except OSError:
+                pass
+        if not data:
+            data = self.__data
+        self.__lines = data.split('\n')
+        self.__linecnt = len(self.__lines)
+
+    def __repr__(self):
+        self.__setup()
+        if len(self.__lines) <= self.MAXLINES:
+            return "\n".join(self.__lines)
+        else:
+            return "Type %s() to see the full %s text" % ((self.__name,)*2)
+
+    def __call__(self):
+        self.__setup()
+        prompt = 'Hit Return for more, or q (and Return) to quit: '
+        lineno = 0
+        while 1:
+            try:
+                for i in range(lineno, lineno + self.MAXLINES):
+                    print(self.__lines[i])
+            except IndexError:
+                break
+            else:
+                lineno += self.MAXLINES
+                key = None
+                while key is None:
+                    key = input(prompt)
+                    if key not in ('', 'q'):
+                        key = None
+                if key == 'q':
+                    break
+
+
+class _Helper(object):
+    """Define the builtin 'help'.
+    This is a wrapper around pydoc.help (with a twist).
+
+    """
+
+    def __repr__(self):
+        return "Type help() for interactive help, " \
+               "or help(object) for help about object."
+    def __call__(self, *args, **kwds):
+        import pydoc
+        return pydoc.help(*args, **kwds)
+

Lib/site.py

@@ -72,6 +72,7 @@ import sys
 import os
 import re
 import builtins
+import _sitebuiltins
 
 # Prefixes for site-packages; add additional prefixes like /usr/local here
 PREFIXES = [sys.prefix, sys.exec_prefix]
@@ -344,116 +345,30 @@ def setquit():
     else:
         eof = 'Ctrl-D (i.e. EOF)'
 
-    class Quitter(object):
+    builtins.quit = _sitebuiltins.Quitter('quit', eof)
-        def __init__(self, name):
+    builtins.exit = _sitebuiltins.Quitter('exit', eof)
-            self.name = name
-        def __repr__(self):
-            return 'Use %s() or %s to exit' % (self.name, eof)
-        def __call__(self, code=None):
-            # Shells like IDLE catch the SystemExit, but listen when their
-            # stdin wrapper is closed.
-            try:
-                sys.stdin.close()
-            except:
-                pass
-            raise SystemExit(code)
-    builtins.quit = Quitter('quit')
-    builtins.exit = Quitter('exit')
 
 
-class _Printer(object):
-    """interactive prompt objects for printing the license text, a list of
-    contributors and the copyright notice."""
-
-    MAXLINES = 23
-
-    def __init__(self, name, data, files=(), dirs=()):
-        self.__name = name
-        self.__data = data
-        self.__files = files
-        self.__dirs = dirs
-        self.__lines = None
-
-    def __setup(self):
-        if self.__lines:
-            return
-        data = None
-        for dir in self.__dirs:
-            for filename in self.__files:
-                filename = os.path.join(dir, filename)
-                try:
-                    with open(filename, "r") as fp:
-                        data = fp.read()
-                    break
-                except OSError:
-                    pass
-            if data:
-                break
-        if not data:
-            data = self.__data
-        self.__lines = data.split('\n')
-        self.__linecnt = len(self.__lines)
-
-    def __repr__(self):
-        self.__setup()
-        if len(self.__lines) <= self.MAXLINES:
-            return "\n".join(self.__lines)
-        else:
-            return "Type %s() to see the full %s text" % ((self.__name,)*2)
-
-    def __call__(self):
-        self.__setup()
-        prompt = 'Hit Return for more, or q (and Return) to quit: '
-        lineno = 0
-        while 1:
-            try:
-                for i in range(lineno, lineno + self.MAXLINES):
-                    print(self.__lines[i])
-            except IndexError:
-                break
-            else:
-                lineno += self.MAXLINES
-                key = None
-                while key is None:
-                    key = input(prompt)
-                    if key not in ('', 'q'):
-                        key = None
-                if key == 'q':
-                    break
-
 def setcopyright():
     """Set 'copyright' and 'credits' in builtins"""
-    builtins.copyright = _Printer("copyright", sys.copyright)
+    builtins.copyright = _sitebuiltins._Printer("copyright", sys.copyright)
     if sys.platform[:4] == 'java':
-        builtins.credits = _Printer(
+        builtins.credits = _sitebuiltins._Printer(
             "credits",
             "Jython is maintained by the Jython developers (www.jython.org).")
     else:
-        builtins.credits = _Printer("credits", """\
+        builtins.credits = _sitebuiltins._Printer("credits", """\
     Thanks to CWI, CNRI, BeOpen.com, Zope Corporation and a cast of thousands
     for supporting Python development.  See www.python.org for more information.""")
     here = os.path.dirname(os.__file__)
-    builtins.license = _Printer(
+    builtins.license = _sitebuiltins._Printer(
         "license", "See http://www.python.org/%.3s/license.html" % sys.version,
         ["LICENSE.txt", "LICENSE"],
         [os.path.join(here, os.pardir), here, os.curdir])
 
 
-class _Helper(object):
-    """Define the builtin 'help'.
-    This is a wrapper around pydoc.help (with a twist).
-
-    """
-
-    def __repr__(self):
-        return "Type help() for interactive help, " \
-               "or help(object) for help about object."
-    def __call__(self, *args, **kwds):
-        import pydoc
-        return pydoc.help(*args, **kwds)
-
 def sethelper():
-    builtins.help = _Helper()
+    builtins.help = _sitebuiltins._Helper()
 
 def enablerlcompleter():
     """Enable default readline configuration on interactive prompts, by

Misc/NEWS

@@ -19,6 +19,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #18621: Prevent the site module's patched builtins from keeping
+  too many references alive for too long.
+
 - Issue #4885: Add weakref support to mmap objects.  Patch by Valerie Lambert.
 
 - Issue #8860: Fixed rounding in timedelta constructor.