Add Py_GetConstant() and Py_GetConstantBorrowed() functions.
In the limited C API version 3.13, getting Py_None, Py_False,
Py_True, Py_Ellipsis and Py_NotImplemented singletons is now
implemented as function calls at the stable ABI level to hide
implementation details. Getting these constants still return borrowed
references.
Add _testlimitedcapi/object.c and test_capi/test_object.py to test
Py_GetConstant() and Py_GetConstantBorrowed() functions.
* gh-112529: Remove PyGC_Head from object pre-header in free-threaded build
This avoids allocating space for PyGC_Head in the free-threaded build.
The GC implementation for free-threaded CPython does not use the
PyGC_Head structure.
* The trashcan mechanism uses the `ob_tid` field instead of `_gc_prev`
in the free-threaded build.
* The GDB libpython.py file now determines the offset of the managed
dict field based on whether the running process is a free-threaded
build. Those are identified by the `ob_ref_local` field in PyObject.
* Fixes `_PySys_GetSizeOf()` which incorrectly incorrectly included the
size of `PyGC_Head` in the size of static `PyTypeObject`.
* gh-112529: Implement GC for free-threaded builds
This implements a mark and sweep GC for the free-threaded builds of
CPython. The implementation relies on mimalloc to find GC tracked
objects (i.e., "containers").
If Py_NOGIL is defined and Py_SET_REFCNT() is called with a reference
count larger than UINT32_MAX, make the object immortal.
Set _Py_IMMORTAL_REFCNT constant type to Py_ssize_t to fix the
following compiler warning:
Include/internal/pycore_global_objects_fini_generated.h:14:24:
warning: comparison of integers of different signs: 'Py_ssize_t'
(aka 'long') and 'unsigned int' [-Wsign-compare]
if (Py_REFCNT(obj) < _Py_IMMORTAL_REFCNT) {
~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~
Critical sections are helpers to replace the global interpreter lock
with finer grained locking. They provide similar guarantees to the GIL
and avoid the deadlock risk that plain locking involves. Critical
sections are implicitly ended whenever the GIL would be released. They
are resumed when the GIL would be acquired. Nested critical sections
behave as if the sections were interleaved.
On a Python built in debug mode, Py_DECREF() now calls
_Py_NegativeRefcount() if the object is a dangling pointer to
deallocated memory: memory filled with 0xDD "dead byte" by the debug
hook on memory allocators. The fix is to check the reference count
*before* checking for _Py_IsImmortal().
Add test_decref_freed_object() to test_capi.test_misc.
* Move <ctype.h>, <limits.h> and <stdarg.h> standard includes to
Python.h.
* Move "pystats.h" include from object.h to Python.h.
* Remove redundant "pymem.h" include in objimpl.h and "pyport.h"
include in pymem.h; Python.h already includes them earlier.
* Remove redundant <wchar.h> include in unicodeobject.h; Python.h
already includes it.
* Move _SGI_MP_SOURCE define from Python.h to pyport.h.
* pycore_condvar.h includes explicitly <unistd.h> for the
_POSIX_THREADS macro.
Python built with "configure --with-trace-refs" (tracing references)
is now ABI compatible with Python release build and debug build.
Moreover, it now also supports the Limited API.
Change Py_TRACE_REFS build:
* Remove _PyObject_EXTRA_INIT macro.
* The PyObject structure no longer has two extra members (_ob_prev
and _ob_next).
* Use a hash table (_Py_hashtable_t) to trace references (all
objects): PyInterpreterState.object_state.refchain.
* Py_TRACE_REFS build is now ABI compatible with release build and
debug build.
* Limited C API extensions can now be built with Py_TRACE_REFS:
xxlimited, xxlimited_35, _testclinic_limited.
* No longer rename PyModule_Create2() and PyModule_FromDefAndSpec2()
functions to PyModule_Create2TraceRefs() and
PyModule_FromDefAndSpec2TraceRefs().
* _Py_PrintReferenceAddresses() is now called before
finalize_interp_delete() which deletes the refchain hash table.
* test_tracemalloc find_trace() now also filters by size to ignore
the memory allocated by _PyRefchain_Trace().
Test changes for Py_TRACE_REFS:
* Add test.support.Py_TRACE_REFS constant.
* Add test_sys.test_getobjects() to test sys.getobjects() function.
* test_exceptions skips test_recursion_normalizing_with_no_memory()
and test_memory_error_in_PyErr_PrintEx() if Python is built with
Py_TRACE_REFS.
* test_repl skips test_no_memory().
* test_capi skisp test_set_nomemory().
* Convert PyObject_DelAttr() and PyObject_DelAttrString() macros to
functions.
* Add PyObject_DelAttr() and PyObject_DelAttrString() functions to
the stable ABI.
* Replace PyObject_SetAttr(obj, name, NULL) with
PyObject_DelAttr(obj, name).
When Python is built in debug mode (Py_REF_DEBUG macro), Py_INCREF()
and Py_DECREF() of the limited C API 3.9 (and older) now call
Py_IncRef() and Py_DecRef(), since _Py_IncRef() and _Py_DecRef() were
added to Python 3.10.
When Python is built in debug mode (if the Py_REF_DEBUG macro is
defined), the Py_INCREF() and Py_DECREF() function are now always
implemented as opaque functions to avoid leaking implementation
details like the "_Py_RefTotal" variable or the
_Py_DecRefTotal_DO_NOT_USE_THIS() function.
* Remove _Py_IncRefTotal_DO_NOT_USE_THIS() and
_Py_DecRefTotal_DO_NOT_USE_THIS() from the stable ABI.
* Remove _Py_NegativeRefcount() from limited C API.
This is the implementation of PEP683
Motivation:
The PR introduces the ability to immortalize instances in CPython which bypasses reference counting. Tagging objects as immortal allows up to skip certain operations when we know that the object will be around for the entire execution of the runtime.
Note that this by itself will bring a performance regression to the runtime due to the extra reference count checks. However, this brings the ability of having truly immutable objects that are useful in other contexts such as immutable data sharing between sub-interpreters.
Sam Gross
Mark Shannon
Victor Stinner
Ken Jin
mpage
Donghee Na
Furkan Onder
Hugo van Kemenade
Serhiy Storchaka
brandonardenwalli
Eric Snow
Petr Viktorin
Eddie Elizondo