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bpo-9263: _PyObject_Dump() detects freed memory (GH-10061)

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_PyObject_Dump() now uses an heuristic to check if the object memory
has been freed: log "<freed object>" in that case.

The heuristic rely on the debug hooks on Python memory allocators
which fills the memory with DEADBYTE (0xDB) when memory is
deallocated. Use PYTHONMALLOC=debug to always enable these debug
hooks.
This commit is contained in:
Victor Stinner 2018-10-23 17:39:40 +02:00 • committed by GitHub
parent 96f2c73954
commit 82af0b63b0
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4 changed files with 75 additions and 24 deletions
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16
Objects/obmalloc.c
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@ -2033,6 +2033,22 @@ _PyMem_DebugRawCalloc(void *ctx, size_t nelem, size_t elsize)
}
/* Heuristic checking if the memory has been freed. Rely on the debug hooks on
Python memory allocators which fills the memory with DEADBYTE (0xDB) when
memory is deallocated. */
int
_PyMem_IsFreed(void *ptr, size_t size)
{
unsigned char *bytes = ptr;
for (size_t i=0; i < size; i++) {
if (bytes[i] != DEADBYTE) {
return 0;
}
}
return 1;
}
/* The debug free first checks the 2*SST bytes on each end for sanity (in
particular, that the FORBIDDENBYTEs with the api ID are still intact).
Then fills the original bytes with DEADBYTE.