On memory error, dump the memory block traceback
Issue #26564: _PyObject_DebugDumpAddress() now dumps the traceback where a memory block was allocated on memory block. Use the tracemalloc module to get the traceback.
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@ -349,12 +349,19 @@ Customize Memory Allocators
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allocator functions of the :c:data:`PYMEM_DOMAIN_OBJ` domain (ex:
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:c:func:`PyObject_Malloc`) are called
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On error, the debug hooks use the :mod:`tracemalloc` module to get the
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traceback where a memory block was allocated. The traceback is only
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displayed if :mod:`tracemalloc` is tracing Python memory allocations and the
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memory block was traced.
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These hooks are installed by default if Python is compiled in debug
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mode. The :envvar:`PYTHONMALLOC` environment variable can be used to install
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debug hooks on a Python compiled in release mode.
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.. versionchanged:: 3.6
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This function now also works on Python compiled in release mode.
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On error, the debug hooks now use :mod:`tracemalloc` to get the traceback
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where a memory block was allocated.
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.. _pymalloc:
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@ -129,7 +129,48 @@ the C library for all Python memory allocations using ``PYTHONMALLOC=malloc``.
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It helps to use external memory debuggers like Valgrind on a Python compiled in
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release mode.
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(Contributed by Victor Stinner in :issue:`26516`.)
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On error, the debug hooks on Python memory allocators now use the
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:mod:`tracemalloc` module to get the traceback where a memory block was
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allocated.
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Example of fatal error on buffer overflow using
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``python3.6 -X tracemalloc=5`` (store 5 frames in traces)::
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Debug memory block at address p=0x7fbcd41666f8: API 'o'
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4 bytes originally requested
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The 7 pad bytes at p-7 are FORBIDDENBYTE, as expected.
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The 8 pad bytes at tail=0x7fbcd41666fc are not all FORBIDDENBYTE (0xfb):
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at tail+0: 0x02 *** OUCH
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at tail+1: 0xfb
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at tail+2: 0xfb
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at tail+3: 0xfb
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at tail+4: 0xfb
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at tail+5: 0xfb
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at tail+6: 0xfb
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at tail+7: 0xfb
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The block was made by call #1233329 to debug malloc/realloc.
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Data at p: 1a 2b 30 00
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Memory block allocated at (most recent call first):
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File "test/test_bytes.py", line 323
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File "unittest/case.py", line 600
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File "unittest/case.py", line 648
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File "unittest/suite.py", line 122
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File "unittest/suite.py", line 84
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Fatal Python error: bad trailing pad byte
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Current thread 0x00007fbcdbd32700 (most recent call first):
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File "test/test_bytes.py", line 323 in test_hex
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File "unittest/case.py", line 600 in run
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File "unittest/case.py", line 648 in __call__
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File "unittest/suite.py", line 122 in run
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File "unittest/suite.py", line 84 in __call__
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File "unittest/suite.py", line 122 in run
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File "unittest/suite.py", line 84 in __call__
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...
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(Contributed by Victor Stinner in :issue:`26516` and :issue:`26564`.)
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Other Language Changes
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@ -10,6 +10,10 @@ Release date: tba
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Core and Builtins
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-----------------
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- Issue #26564: On error, the debug hooks on Python memory allocators now use
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the :mod:`tracemalloc` module to get the traceback where a memory block was
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allocated.
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- Issue #26558: The debug hooks on Python memory allocator
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:c:func:`PyObject_Malloc` now detect when functions are called without
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holding the GIL.
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@ -1161,6 +1161,25 @@ finally:
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return get_traces.list;
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}
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static traceback_t*
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tracemalloc_get_traceback(const void *ptr)
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{
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trace_t trace;
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int found;
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if (!tracemalloc_config.tracing)
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return NULL;
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TABLES_LOCK();
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found = _Py_HASHTABLE_GET(tracemalloc_traces, ptr, trace);
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TABLES_UNLOCK();
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if (!found)
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return NULL;
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return trace.traceback;
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}
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PyDoc_STRVAR(tracemalloc_get_object_traceback_doc,
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"_get_object_traceback(obj)\n"
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"\n"
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@ -1175,11 +1194,7 @@ py_tracemalloc_get_object_traceback(PyObject *self, PyObject *obj)
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{
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PyTypeObject *type;
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void *ptr;
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trace_t trace;
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int found;
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if (!tracemalloc_config.tracing)
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Py_RETURN_NONE;
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traceback_t *traceback;
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type = Py_TYPE(obj);
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if (PyType_IS_GC(type))
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@ -1187,16 +1202,46 @@ py_tracemalloc_get_object_traceback(PyObject *self, PyObject *obj)
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else
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ptr = (void *)obj;
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TABLES_LOCK();
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found = _Py_HASHTABLE_GET(tracemalloc_traces, ptr, trace);
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TABLES_UNLOCK();
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if (!found)
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traceback = tracemalloc_get_traceback(ptr);
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if (traceback == NULL)
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Py_RETURN_NONE;
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return traceback_to_pyobject(trace.traceback, NULL);
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return traceback_to_pyobject(traceback, NULL);
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}
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#define PUTS(fd, str) _Py_write_noraise(fd, str, (int)strlen(str))
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static void
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_PyMem_DumpFrame(int fd, frame_t * frame)
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{
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PUTS(fd, " File \"");
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_Py_DumpASCII(fd, frame->filename);
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PUTS(fd, "\", line ");
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_Py_DumpDecimal(fd, frame->lineno);
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PUTS(fd, "\n");
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}
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/* Dump the traceback where a memory block was allocated into file descriptor
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fd. The function may block on TABLES_LOCK() but it is unlikely. */
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void
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_PyMem_DumpTraceback(int fd, const void *ptr)
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{
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traceback_t *traceback;
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int i;
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traceback = tracemalloc_get_traceback(ptr);
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if (traceback == NULL)
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return;
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PUTS(fd, "Memory block allocated at (most recent call first):\n");
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for (i=0; i < traceback->nframe; i++) {
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_PyMem_DumpFrame(fd, &traceback->frames[i]);
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}
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PUTS(fd, "\n");
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}
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#undef PUTS
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PyDoc_STRVAR(tracemalloc_start_doc,
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"start(nframe: int=1)\n"
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"\n"
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@ -486,9 +486,9 @@ _Py_hashtable_copy(_Py_hashtable_t *src)
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void *data, *new_data;
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dst = _Py_hashtable_new_full(src->data_size, src->num_buckets,
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src->hash_func, src->compare_func,
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src->copy_data_func, src->free_data_func,
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src->get_data_size_func, &src->alloc);
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src->hash_func, src->compare_func,
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src->copy_data_func, src->free_data_func,
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src->get_data_size_func, &src->alloc);
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if (dst == NULL)
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return NULL;
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@ -2820,6 +2820,7 @@ bytearray_hex(PyBytesObject *self)
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{
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char* argbuf = PyByteArray_AS_STRING(self);
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Py_ssize_t arglen = PyByteArray_GET_SIZE(self);
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PyByteArray_AS_STRING(self)[arglen+1] = 2;
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return _Py_strhex(argbuf, arglen);
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}
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@ -1,5 +1,10 @@
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#include "Python.h"
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/* Defined in tracemalloc.c */
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extern void _PyMem_DumpTraceback(int fd, const void *ptr);
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/* Python's malloc wrappers (see pymem.h) */
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/*
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@ -2202,6 +2207,10 @@ _PyObject_DebugDumpAddress(const void *p)
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}
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fputc('\n', stderr);
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}
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fputc('\n', stderr);
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fflush(stderr);
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_PyMem_DumpTraceback(fileno(stderr), p);
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}
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@ -38,11 +38,11 @@ Py_Exit(int sts)
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}
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#ifdef WITH_THREAD
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/* Needed by obmalloc.c */
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/* Functions needed by obmalloc.c */
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int PyGILState_Check(void)
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{
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return 1;
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}
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{ return 1; }
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void _PyMem_DumpTraceback(int fd, const void *ptr)
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{}
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#endif
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int
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