Remove obselete memoryview getbuffer fallback code (GH-4685)

It appears to have been be used for Python < 2.6 (which didn't have the new buffer protocol).
Most of the mechanism had already been removed, but the capsule attributes that it relied on were still generated.

Also removed some utility code that was only used for this feature.

Cython/Compiler/MemoryView.py

@@ -852,7 +852,7 @@ view_utility_code = load_memview_cy_utility(
                   is_contig_utility,
                   overlapping_utility,
                   copy_contents_new_utility,
-                  ModuleNode.capsule_utility_code],
+                  ],
 )
 view_utility_allowlist = ('array', 'memoryview', 'array_cwrapper',
                           'generic', 'strided', 'indirect', 'contiguous',

Cython/Compiler/ModuleNode.py

@@ -3918,5 +3918,3 @@ packed_struct_utility_code = UtilityCode(proto="""
 #define __Pyx_PACKED
 #endif
 """, impl="", proto_block='utility_code_proto_before_types')
-
-capsule_utility_code = UtilityCode.load("Capsule", "Capsule.c")

Cython/Utility/Capsule.c

-//////////////// Capsule.proto ////////////////
-
-/* Todo: wrap the rest of the functionality in similar functions */
-static CYTHON_INLINE PyObject *__pyx_capsule_create(void *p, const char *sig);
-
-//////////////// Capsule ////////////////
-
-static CYTHON_INLINE PyObject *
-__pyx_capsule_create(void *p, const char *sig)
-{
-    return PyCapsule_New(p, sig, NULL);
-}

Cython/Utility/MemoryView.pyx

@@ -78,10 +78,6 @@ cdef extern from *:
     ctypedef struct __Pyx_TypeInfo:
         pass
 
-    cdef object capsule "__pyx_capsule_create" (void *p, char *sig)
-    cdef int __pyx_array_getbuffer(PyObject *obj, Py_buffer view, int flags)
-    cdef int __pyx_memoryview_getbuffer(PyObject *obj, Py_buffer view, int flags)
-
 cdef extern from *:
     ctypedef int __pyx_atomic_int
     {{memviewslice_name}} slice_copy_contig "__pyx_memoryview_copy_new_contig"(
@@ -202,8 +198,6 @@ cdef class array:
         info.format = self.format if flags & PyBUF_FORMAT else NULL
         info.obj = self
 
-    __pyx_getbuffer = capsule(<void *> &__pyx_array_getbuffer, "getbuffer(obj, view, flags)")
-
     def __dealloc__(array self):
         if self.callback_free_data != NULL:
             self.callback_free_data(self.data)
@@ -560,8 +554,6 @@ cdef class memoryview:
         info.readonly = self.view.readonly
         info.obj = self
 
-    __pyx_getbuffer = capsule(<void *> &__pyx_memoryview_getbuffer, "getbuffer(obj, view, flags)")
-
     # Some properties that have the same semantics as in NumPy
     @property
     def T(self):
@@ -1004,8 +996,6 @@ cdef class _memoryviewslice(memoryview):
     cdef _get_base(self):
         return self.from_object
 
-    __pyx_getbuffer = capsule(<void *> &__pyx_memoryview_getbuffer, "getbuffer(obj, view, flags)")
-
 
 @cname('__pyx_memoryview_fromslice')
 cdef memoryview_fromslice({{memviewslice_name}} memviewslice,

tests/compile/fused_redeclare_T3111.pyx

@@ -27,12 +27,12 @@ _WARNINGS = """
 36:10: 'cpdef_cname_method' redeclared
 
 # from MemoryView.pyx
-329:0: The 'DEF' statement is deprecated and will be removed in a future Cython version. Consider using global variables, constants, and in-place literals instead. See https://github.com/cython/cython/issues/4310
-329:0: The 'DEF' statement is deprecated and will be removed in a future Cython version. Consider using global variables, constants, and in-place literals instead. See https://github.com/cython/cython/issues/4310
-987:29: Ambiguous exception value, same as default return value: 0
-987:29: Ambiguous exception value, same as default return value: 0
-1014:46: Ambiguous exception value, same as default return value: 0
-1014:46: Ambiguous exception value, same as default return value: 0
-1104:29: Ambiguous exception value, same as default return value: 0
-1104:29: Ambiguous exception value, same as default return value: 0
+323:0: The 'DEF' statement is deprecated and will be removed in a future Cython version. Consider using global variables, constants, and in-place literals instead. See https://github.com/cython/cython/issues/4310
+323:0: The 'DEF' statement is deprecated and will be removed in a future Cython version. Consider using global variables, constants, and in-place literals instead. See https://github.com/cython/cython/issues/4310
+979:29: Ambiguous exception value, same as default return value: 0
+979:29: Ambiguous exception value, same as default return value: 0
+1004:46: Ambiguous exception value, same as default return value: 0
+1004:46: Ambiguous exception value, same as default return value: 0
+1094:29: Ambiguous exception value, same as default return value: 0
+1094:29: Ambiguous exception value, same as default return value: 0
 """