https://github.com/python/cpython/commit/3359cab038968935b40344fad7c30d211f9... commit: 3359cab038968935b40344fad7c30d211f9692e4 branch: master author: Victor Stinner <vstinner@python.org> committer: vstinner <vstinner@python.org> date: 2021-04-02T15:45:37+02:00 summary: bpo-43688: Support the limited C API in debug mode (GH-25131) The limited C API is now supported if Python is built in debug mode (if the Py_DEBUG macro is defined). In the limited C API, the Py_INCREF() and Py_DECREF() functions are now implemented as opaque function calls, rather than accessing directly the PyObject.ob_refcnt member, if Python is built in debug mode and the Py_LIMITED_API macro targets Python 3.10 or newer. It became possible to support the limited C API in debug mode because the PyObject structure is the same in release and debug mode since Python 3.8 (see bpo-36465). The limited C API is still not supported in the --with-trace-refs special build (Py_TRACE_REFS macro). files: A Misc/NEWS.d/next/C API/2021-04-01-09-10-42.bpo-43688.G4gs6k.rst M Doc/whatsnew/3.10.rst M Include/object.h M Objects/object.c M PC/python3dll.c M setup.py diff --git a/Doc/whatsnew/3.10.rst b/Doc/whatsnew/3.10.rst index a8ff56745c758..b84bcf93edb1e 100644 --- a/Doc/whatsnew/3.10.rst +++ b/Doc/whatsnew/3.10.rst @@ -1315,6 +1315,18 @@ New Features to simulate. (Contributed by Antoine Pitrou in :issue:`43356`.) +* The limited C API is now supported if Python is built in debug mode (if the + ``Py_DEBUG`` macro is defined). In the limited C API, the :c:func:`Py_INCREF` + and :c:func:`Py_DECREF` functions are now implemented as opaque function + calls, rather than accessing directly the :c:member:`PyObject.ob_refcnt` + member, if Python is built in debug mode and the ``Py_LIMITED_API`` macro + targets Python 3.10 or newer. It became possible to support the limited C API + in debug mode because the :c:type:`PyObject` structure is the same in release + and debug mode since Python 3.8 (see :issue:`36465`). + + The limited C API is still not supported in the ``--with-trace-refs`` special + build (``Py_TRACE_REFS`` macro). + (Contributed by Victor Stinner in :issue:`43688`.) Porting to Python 3.10 ---------------------- diff --git a/Include/object.h b/Include/object.h index 14545839341f4..3138db0a0a3e4 100644 --- a/Include/object.h +++ b/Include/object.h @@ -54,11 +54,11 @@ whose size is determined when the object is allocated. /* Py_DEBUG implies Py_REF_DEBUG. */ #if defined(Py_DEBUG) && !defined(Py_REF_DEBUG) -#define Py_REF_DEBUG +# define Py_REF_DEBUG #endif -#if defined(Py_LIMITED_API) && defined(Py_REF_DEBUG) -#error Py_LIMITED_API is incompatible with Py_DEBUG, Py_TRACE_REFS, and Py_REF_DEBUG +#if defined(Py_LIMITED_API) && defined(Py_TRACE_REFS) +# error Py_LIMITED_API is incompatible with Py_TRACE_REFS #endif /* PyTypeObject structure is defined in cpython/object.h. @@ -74,8 +74,8 @@ typedef struct _typeobject PyTypeObject; #define _PyObject_EXTRA_INIT 0, 0, #else -#define _PyObject_HEAD_EXTRA -#define _PyObject_EXTRA_INIT +# define _PyObject_HEAD_EXTRA +# define _PyObject_EXTRA_INIT #endif /* PyObject_HEAD defines the initial segment of every PyObject. */ @@ -427,21 +427,46 @@ PyAPI_FUNC(void) _Py_NegativeRefcount(const char *filename, int lineno, PyAPI_FUNC(void) _Py_Dealloc(PyObject *); +/* +These are provided as conveniences to Python runtime embedders, so that +they can have object code that is not dependent on Python compilation flags. +*/ +PyAPI_FUNC(void) Py_IncRef(PyObject *); +PyAPI_FUNC(void) Py_DecRef(PyObject *); + +// Similar to Py_IncRef() and Py_DecRef() but the argument must be non-NULL. +// Private functions used by Py_INCREF() and Py_DECREF(). +PyAPI_FUNC(void) _Py_IncRef(PyObject *); +PyAPI_FUNC(void) _Py_DecRef(PyObject *); + static inline void _Py_INCREF(PyObject *op) { +#if defined(Py_REF_DEBUG) && defined(Py_LIMITED_API) && Py_LIMITED_API+0 >= 0x030A0000 + // Stable ABI for Python 3.10 built in debug mode. + _Py_IncRef(op); +#else + // Non-limited C API and limited C API for Python 3.9 and older access + // directly PyObject.ob_refcnt. #ifdef Py_REF_DEBUG _Py_RefTotal++; #endif op->ob_refcnt++; +#endif } #define Py_INCREF(op) _Py_INCREF(_PyObject_CAST(op)) static inline void _Py_DECREF( -#ifdef Py_REF_DEBUG +#if defined(Py_REF_DEBUG) && !(defined(Py_LIMITED_API) && Py_LIMITED_API+0 >= 0x030A0000) const char *filename, int lineno, #endif PyObject *op) { +#if defined(Py_REF_DEBUG) && defined(Py_LIMITED_API) && Py_LIMITED_API+0 >= 0x030A0000 + // Stable ABI for Python 3.10 built in debug mode. + _Py_DecRef(op); +#else + // Non-limited C API and limited C API for Python 3.9 and older access + // directly PyObject.ob_refcnt. #ifdef Py_REF_DEBUG _Py_RefTotal--; #endif @@ -455,8 +480,9 @@ static inline void _Py_DECREF( else { _Py_Dealloc(op); } +#endif } -#ifdef Py_REF_DEBUG +#if defined(Py_REF_DEBUG) && !(defined(Py_LIMITED_API) && Py_LIMITED_API+0 >= 0x030A0000) # define Py_DECREF(op) _Py_DECREF(__FILE__, __LINE__, _PyObject_CAST(op)) #else # define Py_DECREF(op) _Py_DECREF(_PyObject_CAST(op)) @@ -525,13 +551,6 @@ static inline void _Py_XDECREF(PyObject *op) #define Py_XDECREF(op) _Py_XDECREF(_PyObject_CAST(op)) -/* -These are provided as conveniences to Python runtime embedders, so that -they can have object code that is not dependent on Python compilation flags. -*/ -PyAPI_FUNC(void) Py_IncRef(PyObject *); -PyAPI_FUNC(void) Py_DecRef(PyObject *); - // Create a new strong reference to an object: // increment the reference count of the object and return the object. PyAPI_FUNC(PyObject*) Py_NewRef(PyObject *obj); diff --git a/Misc/NEWS.d/next/C API/2021-04-01-09-10-42.bpo-43688.G4gs6k.rst b/Misc/NEWS.d/next/C API/2021-04-01-09-10-42.bpo-43688.G4gs6k.rst new file mode 100644 index 0000000000000..6b1d44ee17686 --- /dev/null +++ b/Misc/NEWS.d/next/C API/2021-04-01-09-10-42.bpo-43688.G4gs6k.rst @@ -0,0 +1,13 @@ +The limited C API is now supported if Python is built in debug mode (if the +``Py_DEBUG`` macro is defined). In the limited C API, the :c:func:`Py_INCREF` +and :c:func:`Py_DECREF` functions are now implemented as opaque function calls, +rather than accessing directly the :c:member:`PyObject.ob_refcnt` member, if +Python is built in debug mode and the ``Py_LIMITED_API`` macro targets Python +3.10 or newer. It became possible to support the limited C API in debug mode +because the :c:type:`PyObject` structure is the same in release and debug mode +since Python 3.8 (see :issue:`36465`). + +The limited C API is still not supported in the ``--with-trace-refs`` special +build (``Py_TRACE_REFS`` macro). + +Patch by Victor Stinner. diff --git a/Objects/object.c b/Objects/object.c index 0a8621b3503b3..0845966c5fe9d 100644 --- a/Objects/object.c +++ b/Objects/object.c @@ -13,6 +13,11 @@ #include "frameobject.h" #include "interpreteridobject.h" +#ifdef Py_LIMITED_API + // Prevent recursive call _Py_IncRef() <=> Py_INCREF() +# error "Py_LIMITED_API macro must not be defined" +#endif + #ifdef __cplusplus extern "C" { #endif @@ -136,6 +141,18 @@ Py_DecRef(PyObject *o) Py_XDECREF(o); } +void +_Py_IncRef(PyObject *o) +{ + Py_INCREF(o); +} + +void +_Py_DecRef(PyObject *o) +{ + Py_DECREF(o); +} + PyObject * PyObject_Init(PyObject *op, PyTypeObject *tp) { diff --git a/PC/python3dll.c b/PC/python3dll.c index 1567ac159168a..b5735e81e81ae 100644 --- a/PC/python3dll.c +++ b/PC/python3dll.c @@ -36,6 +36,8 @@ EXPORT_FUNC(_PyTrash_deposit_object) EXPORT_FUNC(_PyTrash_destroy_chain) EXPORT_FUNC(_PyTrash_thread_deposit_object) EXPORT_FUNC(_PyTrash_thread_destroy_chain) +EXPORT_FUNC(_Py_IncRef) +EXPORT_FUNC(_Py_DecRef) EXPORT_FUNC(Py_AddPendingCall) EXPORT_FUNC(Py_AtExit) EXPORT_FUNC(Py_BuildValue) diff --git a/setup.py b/setup.py index 75bd16375063a..3b4e7ae70a4ec 100644 --- a/setup.py +++ b/setup.py @@ -1864,17 +1864,11 @@ def detect_modules(self): ## # Uncomment these lines if you want to play with xxmodule.c ## self.add(Extension('xx', ['xxmodule.c'])) - if 'd' not in sysconfig.get_config_var('ABIFLAGS'): - # Non-debug mode: Build xxlimited with limited API - self.add(Extension('xxlimited', ['xxlimited.c'], - define_macros=[('Py_LIMITED_API', '0x030a0000')])) - self.add(Extension('xxlimited_35', ['xxlimited_35.c'], - define_macros=[('Py_LIMITED_API', '0x03050000')])) - else: - # Debug mode: Build xxlimited with the full API - # (which is compatible with the limited one) - self.add(Extension('xxlimited', ['xxlimited.c'])) - self.add(Extension('xxlimited_35', ['xxlimited_35.c'])) + # Limited C API + self.add(Extension('xxlimited', ['xxlimited.c'], + define_macros=[('Py_LIMITED_API', '0x030a0000')])) + self.add(Extension('xxlimited_35', ['xxlimited_35.c'], + define_macros=[('Py_LIMITED_API', '0x03050000')])) def detect_tkinter_fromenv(self): # Build _tkinter using the Tcl/Tk locations specified by