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Python implements debug hooks on Python memory allocators:
https://docs.python.org/dev/c-api/memory.html#c.PyMem_SetupDebugHooks
Problem: buffer understand and buffer overflow are only detected when a memory block is released, which may occur far from the code responsible to create the buffer.
Attached patch dumps the traceback where a memory block was allocated on error in malloc debug hooks. The feature requires to enable tracemalloc to record tracebacks.
test.py used in below example:
----
import _testcapi
def f():
 _testcapi.pymem_buffer_overflow()
f()
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Example:
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haypo@selma$ ./python -X tracemalloc=5 test.py 
Debug memory block at address p=0x22e8be0: API 'm'
 16 bytes originally requested
 The 7 pad bytes at p-7 are FORBIDDENBYTE, as expected.
 The 8 pad bytes at tail=0x22e8bf0 are not all FORBIDDENBYTE (0xfb):
 at tail+0: 0x78 *** OUCH
 ...
 The block was made by call #37240 to debug malloc/realloc.
 Data at p: cb cb cb cb cb cb cb cb cb cb cb cb cb cb cb cb
Memory block traceback (most recent call first):
 File "test.py", line 4
 File "test.py", line 6
Fatal Python error: bad trailing pad byte
Current thread 0x00007f4a93d9c700 (most recent call first):
 File "test.py", line 4 in f
 File "test.py", line 6 in <module>
Abandon (core dumped)
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The patch adds the "Memory block traceback" section.