incomplete fix for memory leak in array.array

[YuanchengJiang]

Bug report

Bug description:

#140474

The array.array constructor leaks a range_iterator object (64 bytes) when it is given an invalid typecode along with a range object as the initializer. The constructor calls PyObject_GetIter() on the initializer before validating the typecode, allocating a range_iterator via fast_range_iter. When the typecode validation subsequently fails with ValueError: bad typecode, the iterator is not decremented and is leaked.

import array

array.array('\u200e', range(5))

ValueError: bad typecode (must be b, B, u, w, h, H, i, I, l, L, q, Q, f or d)

=================================================================
==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 64 byte(s) in 1 object(s) allocated from:
    #0 malloc
    #1 _PyMem_DebugRawAlloc  Objects/obmalloc.c:3097
    #2 _PyObject_New          Objects/object.c:556
    #3 fast_range_iter        Objects/rangeobject.c:1024
    #4 PyObject_GetIter       Objects/abstract.c:2825
    #5 cfunction_vectorcall_FASTCALL  Objects/methodobject.c:449

SUMMARY: AddressSanitizer: 64 byte(s) leaked in 1 allocation(s).

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

[skirpichev]

I suspect it's just missing decref:

diff --git a/Modules/arraymodule.c b/Modules/arraymodule.c
index a86a7561271..6e097d90756 100644
--- a/Modules/arraymodule.c
+++ b/Modules/arraymodule.c
@@ -3136,6 +3136,7 @@ array_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
             return a;
         }
     }
+    Py_XDECREF(it);
     PyErr_SetString(PyExc_ValueError,
         "bad typecode (must be b, B, u, w, h, H, i, I, l, L, q, Q, f or d)");
     return NULL;