bpo-9263: _PyObject_Dump() detects freed memory (GH-10061)
_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.
diff --git a/Objects/obmalloc.c b/Objects/obmalloc.c
index eb7cbfc..d58da35 100644
--- a/Objects/obmalloc.c
+++ b/Objects/obmalloc.c
@@ -2033,6 +2033,22 @@
}
+/* 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.