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bpo-39947: Hide implementation detail of trashcan macros (GH-18971) 

Py_TRASHCAN_BEGIN_CONDITION and Py_TRASHCAN_END macro no longer
access PyThreadState attributes, but call new private
_PyTrash_begin() and _PyTrash_end() functions which hide
implementation details.
This commit is contained in:
Victor Stinner 2020-03-13 16:51:52 +01:00 committed by GitHub
parent 309d7cc5df
commit 38965ec541
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GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 45 additions and 15 deletions
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33
Include/cpython/object.h
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@ -385,11 +385,6 @@ PyAPI_DATA(PyTypeObject) _PyNotImplemented_Type;
*/
PyAPI_DATA(int) _Py_SwappedOp[];
/* This is the old private API, invoked by the macros before 3.2.4.
Kept for binary compatibility of extensions using the stable ABI. */
PyAPI_FUNC(void) _PyTrash_deposit_object(PyObject*);
PyAPI_FUNC(void) _PyTrash_destroy_chain(void);
PyAPI_FUNC(void)
_PyDebugAllocatorStats(FILE *out, const char *block_name, int num_blocks,
size_t sizeof_block);
@ -507,10 +502,23 @@ partially-deallocated object. To check this, the tp_dealloc function must be
passed as second argument to Py_TRASHCAN_BEGIN().
*/
/* The new thread-safe private API, invoked by the macros below. */
/* This is the old private API, invoked by the macros before 3.2.4.
Kept for binary compatibility of extensions using the stable ABI. */
PyAPI_FUNC(void) _PyTrash_deposit_object(PyObject*);
PyAPI_FUNC(void) _PyTrash_destroy_chain(void);
/* This is the old private API, invoked by the macros before 3.9.
Kept for binary compatibility of extensions using the stable ABI. */
PyAPI_FUNC(void) _PyTrash_thread_deposit_object(PyObject*);
PyAPI_FUNC(void) _PyTrash_thread_destroy_chain(void);
/* Forward declarations for PyThreadState */
struct _ts;
/* Python 3.9 private API, invoked by the macros below. */
PyAPI_FUNC(int) _PyTrash_begin(struct _ts *tstate, PyObject *op);
PyAPI_FUNC(void) _PyTrash_end(struct _ts *tstate);
#define PyTrash_UNWIND_LEVEL 50
#define Py_TRASHCAN_BEGIN_CONDITION(op, cond) \
@ -520,24 +528,19 @@ PyAPI_FUNC(void) _PyTrash_thread_destroy_chain(void);
* is run normally without involving the trashcan */ \
if (cond) { \
_tstate = PyThreadState_GET(); \
if (_tstate->trash_delete_nesting >= PyTrash_UNWIND_LEVEL) { \
/* Store the object (to be deallocated later) and jump past \
* Py_TRASHCAN_END, skipping the body of the deallocator */ \
_PyTrash_thread_deposit_object(_PyObject_CAST(op)); \
if (_PyTrash_begin(_tstate, _PyObject_CAST(op))) { \
break; \
} \
++_tstate->trash_delete_nesting; \
}
/* The body of the deallocator is here. */
#define Py_TRASHCAN_END \
if (_tstate) { \
--_tstate->trash_delete_nesting; \
if (_tstate->trash_delete_later && _tstate->trash_delete_nesting <= 0) \
_PyTrash_thread_destroy_chain(); \
_PyTrash_end(_tstate); \
} \
} while (0);
#define Py_TRASHCAN_BEGIN(op, dealloc) Py_TRASHCAN_BEGIN_CONDITION(op, \
#define Py_TRASHCAN_BEGIN(op, dealloc) \
Py_TRASHCAN_BEGIN_CONDITION(op, \
Py_TYPE(op)->tp_dealloc == (destructor)(dealloc))
/* For backwards compatibility, these macros enable the trashcan

3
Misc/NEWS.d/next/C API/2020-03-12-23-47-57.bpo-39947.-nCdFV.rst Normal file
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@ -0,0 +1,3 @@
Py_TRASHCAN_BEGIN_CONDITION and Py_TRASHCAN_END macro no longer access
PyThreadState attributes, but call new private _PyTrash_begin() and
_PyTrash_end() functions which hide implementation details.

24
Objects/object.c
View File

@ -2116,6 +2116,30 @@ _PyTrash_thread_destroy_chain(void)
}
int
_PyTrash_begin(PyThreadState *tstate, PyObject *op)
{
if (tstate->trash_delete_nesting >= PyTrash_UNWIND_LEVEL) {
/* Store the object (to be deallocated later) and jump past
* Py_TRASHCAN_END, skipping the body of the deallocator */
_PyTrash_thread_deposit_object(op);
return 1;
}
++tstate->trash_delete_nesting;
return 0;
}
void
_PyTrash_end(PyThreadState *tstate)
{
--tstate->trash_delete_nesting;
if (tstate->trash_delete_later && tstate->trash_delete_nesting <= 0) {
_PyTrash_thread_destroy_chain();
}
}
void _Py_NO_RETURN
_PyObject_AssertFailed(PyObject *obj, const char *expr, const char *msg,
const char *file, int line, const char *function)