bpo-43693 Get rid of CO_NOFREE -- it's unused (pythonGH-26839)

All uses of this flag are either setting it
or in doc or tests for it. So we should be
able to get rid of it completely.

Author: gvanrossum

Doc/library/inspect.rst

@@ -1450,10 +1450,6 @@ the following flags:
    The flag is set when the code object is a generator function, i.e.
    a generator object is returned when the code object is executed.
 
-.. data:: CO_NOFREE
-
-   The flag is set if there are no free or cell variables.
-
 .. data:: CO_COROUTINE
 
    The flag is set when the code object is a coroutine function.

Include/cpython/code.h

@@ -112,12 +112,6 @@ struct PyCodeObject {
 #define CO_VARKEYWORDS  0x0008
 #define CO_NESTED       0x0010
 #define CO_GENERATOR    0x0020
-/* The CO_NOFREE flag is set if there are no free or cell variables.
-   This information is redundant, but it allows a single flag test
-   to determine whether there is any extra work to be done when the
-   call frame it setup.
-*/
-#define CO_NOFREE       0x0040
 
 /* The CO_COROUTINE flag is set for coroutine functions (defined with
    ``async def`` keywords) */

Lib/test/test_code.py

@@ -49,7 +49,7 @@
 cellvars: ()
 freevars: ()
 nlocals: 5
-flags: 67
+flags: 3
 consts: ('None',)
 
 >>> def attrs(obj):
@@ -67,7 +67,7 @@
 cellvars: ()
 freevars: ()
 nlocals: 1
-flags: 67
+flags: 3
 consts: ('None',)
 
 >>> def optimize_away():
@@ -86,7 +86,7 @@
 cellvars: ()
 freevars: ()
 nlocals: 0
-flags: 67
+flags: 3
 consts: ("'doc string'", 'None')
 
 >>> def keywordonly_args(a,b,*,k1):
@@ -103,7 +103,7 @@
 cellvars: ()
 freevars: ()
 nlocals: 3
-flags: 67
+flags: 3
 consts: ('None',)
 
 >>> def posonly_args(a,b,/,c):
@@ -120,7 +120,7 @@
 cellvars: ()
 freevars: ()
 nlocals: 3
-flags: 67
+flags: 3
 consts: ('None',)
 
 """
@@ -199,10 +199,6 @@ class List(list):
         class_ref = function.__closure__[0].cell_contents
         self.assertIs(class_ref, List)
 
-        # Ensure the code correctly indicates it accesses a free variable
-        self.assertFalse(function.__code__.co_flags & inspect.CO_NOFREE,
-                         hex(function.__code__.co_flags))
-
         # Ensure the zero-arg super() call in the injected method works
         obj = List([1, 2, 3])
         self.assertEqual(obj[0], "Foreign getitem: 1")

Lib/test/test_dis.py

@@ -719,7 +719,7 @@ def get_disassembly(self, func, lasti=-1, wrapper=True, **kwargs):
 Kw-only arguments: 0
 Number of locals:  1
 Stack size:        3
-Flags:             OPTIMIZED, NEWLOCALS, NOFREE
+Flags:             OPTIMIZED, NEWLOCALS
 Constants:
    {code_info_consts}
 Names:
@@ -800,7 +800,7 @@ def f(c=c):
 Kw-only arguments: 0
 Number of locals:  0
 Stack size:        2
-Flags:             NOFREE
+Flags:             0x0
 Constants:
    0: 1
 Names:
@@ -814,7 +814,7 @@ def f(c=c):
 Kw-only arguments: 0
 Number of locals:  0
 Stack size:        2
-Flags:             NOFREE
+Flags:             0x0
 Constants:
    0: 1
    1: None
@@ -829,7 +829,7 @@ def f(c=c):
 Kw-only arguments: 0
 Number of locals:  0
 Stack size:        2
-Flags:             NOFREE
+Flags:             0x0
 Constants:
    0: 0
    1: 1
@@ -851,7 +851,7 @@ async def async_def():
 Kw-only arguments: 0
 Number of locals:  2
 Stack size:        10
-Flags:             OPTIMIZED, NEWLOCALS, NOFREE, COROUTINE
+Flags:             OPTIMIZED, NEWLOCALS, COROUTINE
 Constants:
    0: None
    1: 1

Objects/codeobject.c

@@ -372,13 +372,6 @@ _PyCode_New(struct _PyCodeConstructor *con)
     }
     init_code(co, con);
 
-    /* Check for any inner or outer closure references */
-    if (!co->co_ncellvars && !co->co_nfreevars) {
-        co->co_flags |= CO_NOFREE;
-    } else {
-        co->co_flags &= ~CO_NOFREE;
-    }
-
     return co;
 }
 

Programs/test_frozenmain.h

@@ -1,7 +1,7 @@
 /* Auto-generated by Programs/_freeze_importlib.c */
 const unsigned char _Py_M__hello[] = {
     99,0,0,0,0,0,0,0,0,0,0,0,0,2,0,0,
-    0,64,0,0,0,115,16,0,0,0,100,0,90,0,101,1,
+    0,0,0,0,0,115,16,0,0,0,100,0,90,0,101,1,
     100,1,131,1,1,0,100,2,83,0,41,3,84,122,12,72,
     101,108,108,111,32,119,111,114,108,100,33,78,41,2,90,11,
     105,110,105,116,105,97,108,105,122,101,100,218,5,112,114,105,