Patch #1680961: remove sys.exitfunc and replace it with a private C API. Also, reimplement atexit in C so it can take advantage of this private API.

Author: collinw

Doc/lib/libatexit.tex

@@ -1,32 +1,21 @@
 \section{\module{atexit} ---
          Exit handlers}
 
-\declaremodule{standard}{atexit}
+\declaremodule{builtin}{atexit}
 \moduleauthor{Skip Montanaro}{skip@mojam.com}
 \sectionauthor{Skip Montanaro}{skip@mojam.com}
 \modulesynopsis{Register and execute cleanup functions.}
 
 \versionadded{2.0}
 
-The \module{atexit} module defines a single function to register
-cleanup functions.  Functions thus registered are automatically
-executed upon normal interpreter termination.
 
-Note: the functions registered via this module are not called when the program is killed by a
-signal, when a Python fatal internal error is detected, or when
-\function{os._exit()} is called.
+The \module{atexit} module defines functions to register and
+unregister cleanup functions.  Functions thus registered are
+automatically executed upon normal interpreter termination.
 
-This is an alternate interface to the functionality provided by the
-\code{sys.exitfunc} variable.
-\withsubitem{(in sys)}{\ttindex{exitfunc}}
-
-Note: This module is unlikely to work correctly when used with other code
-that sets \code{sys.exitfunc}.  In particular, other core Python modules are
-free to use \module{atexit} without the programmer's knowledge.  Authors who
-use \code{sys.exitfunc} should convert their code to use
-\module{atexit} instead.  The simplest way to convert code that sets
-\code{sys.exitfunc} is to import \module{atexit} and register the function
-that had been bound to \code{sys.exitfunc}.
+Note: the functions registered via this module are not called when
+the program is killed by a signal, when a Python fatal internal
+error is detected, or when \function{os._exit()} is called.
 
 \begin{funcdesc}{register}{func\optional{, *args\optional{, **kargs}}}
 Register \var{func} as a function to be executed at termination.  Any
@@ -47,7 +36,16 @@ \section{\module{atexit} ---
 
 \versionchanged[This function now returns \var{func} which makes it
                 possible to use it as a decorator without binding the
-		original name to \code{None}]{2.6}
+                original name to \code{None}]{2.6}
+\end{funcdesc}
+
+\begin{funcdesc}{unregister}{func}
+Remove a function \var{func} from the list of functions to be run at
+interpreter-shutdown.  After calling \function{unregister()},
+\var{func} is guaranteed not to be called when the interpreter
+shuts down.
+
+\versionadded{3.0}
 \end{funcdesc}
 
 

Doc/lib/libsys.tex

@@ -218,19 +218,6 @@ \section{\module{sys} ---
   program when an error occurs.
 \end{funcdesc}
 
-\begin{datadesc}{exitfunc}
-  This value is not actually defined by the module, but can be set by
-  the user (or by a program) to specify a clean-up action at program
-  exit.  When set, it should be a parameterless function.  This
-  function will be called when the interpreter exits.  Only one
-  function may be installed in this way; to allow multiple functions
-  which will be called at termination, use the \refmodule{atexit}
-  module.  \note{The exit function is not called when the program is
-  killed by a signal, when a Python fatal internal error is detected,
-  or when \code{os._exit()} is called.}
-  \deprecated{2.4}{Use \refmodule{atexit} instead.}
-\end{datadesc}
-
 \begin{funcdesc}{getcheckinterval}{}
   Return the interpreter's ``check interval'';
   see \function{setcheckinterval()}.

Include/pythonrun.h

@@ -69,6 +69,10 @@ PyAPI_FUNC(void) PyErr_Print(void);
 PyAPI_FUNC(void) PyErr_PrintEx(int);
 PyAPI_FUNC(void) PyErr_Display(PyObject *, PyObject *, PyObject *);
 
+/* Py_PyAtExit is for the atexit module, Py_AtExit is for low-level
+ * exit functions.
+ */
+PyAPI_FUNC(void) _Py_PyAtExit(void (*func)(void));
 PyAPI_FUNC(int) Py_AtExit(void (*func)(void));
 
 PyAPI_FUNC(void) Py_Exit(int);

Lib/atexit.py

@@ -48,7 +48,6 @@ def test_all(self):
         self.check_all("StringIO")
         self.check_all("UserString")
         self.check_all("aifc")
-        self.check_all("atexit")
         self.check_all("audiodev")
         self.check_all("base64")
         self.check_all("bdb")

Lib/test/test___all__.py

@@ -4,97 +4,112 @@
 import atexit
 from test import test_support
 
-class TestCase(unittest.TestCase):
-    def test_args(self):
-        # be sure args are handled properly
-        s = StringIO.StringIO()
-        sys.stdout = sys.stderr = s
-        save_handlers = atexit._exithandlers
-        atexit._exithandlers = []
-        try:
-            atexit.register(self.h1)
-            atexit.register(self.h4)
-            atexit.register(self.h4, 4, kw="abc")
-            atexit._run_exitfuncs()
-        finally:
-            sys.stdout = sys.__stdout__
-            sys.stderr = sys.__stderr__
-            atexit._exithandlers = save_handlers
-        self.assertEqual(s.getvalue(), "h4 (4,) {'kw': 'abc'}\nh4 () {}\nh1\n")
+### helpers
+def h1():
+    print("h1")
 
-    def test_order(self):
-        # be sure handlers are executed in reverse order
-        s = StringIO.StringIO()
-        sys.stdout = sys.stderr = s
-        save_handlers = atexit._exithandlers
-        atexit._exithandlers = []
-        try:
-            atexit.register(self.h1)
-            atexit.register(self.h2)
-            atexit.register(self.h3)
-            atexit._run_exitfuncs()
-        finally:
-            sys.stdout = sys.__stdout__
-            sys.stderr = sys.__stderr__
-            atexit._exithandlers = save_handlers
-        self.assertEqual(s.getvalue(), "h3\nh2\nh1\n")
+def h2():
+    print("h2")
 
-    def test_sys_override(self):
-        # be sure a preset sys.exitfunc is handled properly
-        s = StringIO.StringIO()
-        sys.stdout = sys.stderr = s
-        save_handlers = atexit._exithandlers
-        atexit._exithandlers = []
-        exfunc = sys.exitfunc
-        sys.exitfunc = self.h1
-        reload(atexit)
-        try:
-            atexit.register(self.h2)
-            atexit._run_exitfuncs()
-        finally:
-            sys.stdout = sys.__stdout__
-            sys.stderr = sys.__stderr__
-            atexit._exithandlers = save_handlers
-            sys.exitfunc = exfunc
-        self.assertEqual(s.getvalue(), "h2\nh1\n")
+def h3():
+    print("h3")
 
-    def test_raise(self):
-        # be sure raises are handled properly
-        s = StringIO.StringIO()
-        sys.stdout = sys.stderr = s
-        save_handlers = atexit._exithandlers
-        atexit._exithandlers = []
-        try:
-            atexit.register(self.raise1)
-            atexit.register(self.raise2)
-            self.assertRaises(TypeError, atexit._run_exitfuncs)
-        finally:
-            sys.stdout = sys.__stdout__
-            sys.stderr = sys.__stderr__
-            atexit._exithandlers = save_handlers
+def h4(*args, **kwargs):
+    print("h4", args, kwargs)
+
+def raise1():
+    raise TypeError
 
-    ### helpers
-    def h1(self):
-        print("h1")
+def raise2():
+    raise SystemError
 
-    def h2(self):
-        print("h2")
+class TestCase(unittest.TestCase):
+    def setUp(self):
+        self.stream = StringIO.StringIO()
+        sys.stdout = sys.stderr = self.stream
+        atexit._clear()
+        
+    def tearDown(self):
+        sys.stdout = sys.__stdout__
+        sys.stderr = sys.__stderr__
+        atexit._clear()
 
-    def h3(self):
-        print("h3")
+    def test_args(self):
+        # be sure args are handled properly
+        atexit.register(h1)
+        atexit.register(h4)
+        atexit.register(h4, 4, kw="abc")
+        atexit._run_exitfuncs()
 
-    def h4(self, *args, **kwargs):
-        print("h4", args, kwargs)
+        self.assertEqual(self.stream.getvalue(),
+                            "h4 (4,) {'kw': 'abc'}\nh4 () {}\nh1\n")
 
-    def raise1(self):
-        raise TypeError
+    def test_order(self):
+        # be sure handlers are executed in reverse order
+        atexit.register(h1)
+        atexit.register(h2)
+        atexit.register(h3)
+        atexit._run_exitfuncs()
+            
+        self.assertEqual(self.stream.getvalue(), "h3\nh2\nh1\n")
 
-    def raise2(self):
-        raise SystemError
+    def test_raise(self):
+        # be sure raises are handled properly
+        atexit.register(raise1)
+        atexit.register(raise2)
+        
+        self.assertRaises(TypeError, atexit._run_exitfuncs)
+        
+    def test_stress(self):
+        a = [0]
+        def inc():
+            a[0] += 1
+    
+        for i in range(128):
+            atexit.register(inc)
+        atexit._run_exitfuncs()
+        
+        self.assertEqual(a[0], 128)
+        
+    def test_clear(self):
+        a = [0]
+        def inc():
+            a[0] += 1
+            
+        atexit.register(inc)
+        atexit._clear()
+        atexit._run_exitfuncs()
+        
+        self.assertEqual(a[0], 0)
+        
+    def test_unregister(self):
+        a = [0]
+        def inc():
+            a[0] += 1
+        def dec():
+            a[0] -= 1
+        
+        for i in range(4):    
+            atexit.register(inc)
+        atexit.register(dec)
+        atexit.unregister(inc)
+        atexit._run_exitfuncs()
+        
+        self.assertEqual(a[0], -1)
+        
+    def test_bound_methods(self):
+        l = []
+        atexit.register(l.append, 5)
+        atexit._run_exitfuncs()
+        self.assertEqual(l, [5])
+        
+        atexit.unregister(l.append)
+        atexit._run_exitfuncs()
+        self.assertEqual(l, [5])
+        
 
 def test_main():
     test_support.run_unittest(TestCase)
 
-
 if __name__ == "__main__":
     test_main()

Lib/test/test_atexit.py

@@ -28,6 +28,9 @@ TO DO
 Core and Builtins
 -----------------
 
+- Patch #1680961: sys.exitfunc has been removed and replaced with a private
+  C-level API.
+
 - PEP 3115: new metaclasses: the metaclass is now specified as a
   keyword arg in the class statement, which can now use the full syntax of
   a parameter list. Also, the metaclass can implement a __prepare__ function
@@ -156,6 +159,8 @@ Extension Modules
 Library
 -------
 
+- Patch #1680961: atexit has been reimplemented in C.
+
 - Removed all traces of the sets module.
 
 Build

Misc/NEWS

@@ -176,6 +176,7 @@ GLHACK=-Dclear=__GLclear
 #collections collectionsmodule.c # Container types
 #itertools itertoolsmodule.c	# Functions creating iterators for efficient looping 
 #strop stropmodule.c		# String manipulations
+#atexit atexitmodule.c      # Register functions to be run at interpreter-shutdown
 
 #unicodedata unicodedata.c    # static Unicode character database