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diff --git a/Doc/c-api/init.rst b/Doc/c-api/init.rst index 86bf7f9..229cae5 100644 --- a/Doc/c-api/init.rst +++ b/Doc/c-api/init.rst @@ -1,4 +1,4 @@ -.. highlight:: c +.. highlightlang:: c .. _initialization: @@ -7,219 +7,6 @@ Initialization, Finalization, and Threads ***************************************** -See also :ref:`Python Initialization Configuration <init-config>`. - -.. _pre-init-safe: - -Before Python Initialization -============================ - -In an application embedding Python, the :c:func:`Py_Initialize` function must -be called before using any other Python/C API functions; with the exception of -a few functions and the :ref:`global configuration variables -<global-conf-vars>`. - -The following functions can be safely called before Python is initialized: - -* Configuration functions: - - * :c:func:`PyImport_AppendInittab` - * :c:func:`PyImport_ExtendInittab` - * :c:func:`PyInitFrozenExtensions` - * :c:func:`PyMem_SetAllocator` - * :c:func:`PyMem_SetupDebugHooks` - * :c:func:`PyObject_SetArenaAllocator` - * :c:func:`Py_SetPath` - * :c:func:`Py_SetProgramName` - * :c:func:`Py_SetPythonHome` - * :c:func:`Py_SetStandardStreamEncoding` - * :c:func:`PySys_AddWarnOption` - * :c:func:`PySys_AddXOption` - * :c:func:`PySys_ResetWarnOptions` - -* Informative functions: - - * :c:func:`Py_IsInitialized` - * :c:func:`PyMem_GetAllocator` - * :c:func:`PyObject_GetArenaAllocator` - * :c:func:`Py_GetBuildInfo` - * :c:func:`Py_GetCompiler` - * :c:func:`Py_GetCopyright` - * :c:func:`Py_GetPlatform` - * :c:func:`Py_GetVersion` - -* Utilities: - - * :c:func:`Py_DecodeLocale` - -* Memory allocators: - - * :c:func:`PyMem_RawMalloc` - * :c:func:`PyMem_RawRealloc` - * :c:func:`PyMem_RawCalloc` - * :c:func:`PyMem_RawFree` - -.. note:: - - The following functions **should not be called** before - :c:func:`Py_Initialize`: :c:func:`Py_EncodeLocale`, :c:func:`Py_GetPath`, - :c:func:`Py_GetPrefix`, :c:func:`Py_GetExecPrefix`, - :c:func:`Py_GetProgramFullPath`, :c:func:`Py_GetPythonHome`, - :c:func:`Py_GetProgramName` and :c:func:`PyEval_InitThreads`. - - -.. _global-conf-vars: - -Global configuration variables -============================== - -Python has variables for the global configuration to control different features -and options. By default, these flags are controlled by :ref:`command line -options <using-on-interface-options>`. - -When a flag is set by an option, the value of the flag is the number of times -that the option was set. For example, ``-b`` sets :c:data:`Py_BytesWarningFlag` -to 1 and ``-bb`` sets :c:data:`Py_BytesWarningFlag` to 2. - -.. c:var:: Py_BytesWarningFlag - - Issue a warning when comparing :class:`bytes` or :class:`bytearray` with - :class:`str` or :class:`bytes` with :class:`int`. Issue an error if greater - or equal to ``2``. - - Set by the :option:`-b` option. - -.. c:var:: Py_DebugFlag - - Turn on parser debugging output (for expert only, depending on compilation - options). - - Set by the :option:`-d` option and the :envvar:`PYTHONDEBUG` environment - variable. - -.. c:var:: Py_DontWriteBytecodeFlag - - If set to non-zero, Python won't try to write ``.pyc`` files on the - import of source modules. - - Set by the :option:`-B` option and the :envvar:`PYTHONDONTWRITEBYTECODE` - environment variable. - -.. c:var:: Py_FrozenFlag - - Suppress error messages when calculating the module search path in - :c:func:`Py_GetPath`. - - Private flag used by ``_freeze_importlib`` and ``frozenmain`` programs. - -.. c:var:: Py_HashRandomizationFlag - - Set to ``1`` if the :envvar:`PYTHONHASHSEED` environment variable is set to - a non-empty string. - - If the flag is non-zero, read the :envvar:`PYTHONHASHSEED` environment - variable to initialize the secret hash seed. - -.. c:var:: Py_IgnoreEnvironmentFlag - - Ignore all :envvar:`PYTHON*` environment variables, e.g. - :envvar:`PYTHONPATH` and :envvar:`PYTHONHOME`, that might be set. - - Set by the :option:`-E` and :option:`-I` options. - -.. c:var:: Py_InspectFlag - - When a script is passed as first argument or the :option:`-c` option is used, - enter interactive mode after executing the script or the command, even when - :data:`sys.stdin` does not appear to be a terminal. - - Set by the :option:`-i` option and the :envvar:`PYTHONINSPECT` environment - variable. - -.. c:var:: Py_InteractiveFlag - - Set by the :option:`-i` option. - -.. c:var:: Py_IsolatedFlag - - Run Python in isolated mode. In isolated mode :data:`sys.path` contains - neither the script's directory nor the user's site-packages directory. - - Set by the :option:`-I` option. - - .. versionadded:: 3.4 - -.. c:var:: Py_LegacyWindowsFSEncodingFlag - - If the flag is non-zero, use the ``mbcs`` encoding instead of the UTF-8 - encoding for the filesystem encoding. - - Set to ``1`` if the :envvar:`PYTHONLEGACYWINDOWSFSENCODING` environment - variable is set to a non-empty string. - - See :pep:`529` for more details. - - .. availability:: Windows. - -.. c:var:: Py_LegacyWindowsStdioFlag - - If the flag is non-zero, use :class:`io.FileIO` instead of - :class:`WindowsConsoleIO` for :mod:`sys` standard streams. - - Set to ``1`` if the :envvar:`PYTHONLEGACYWINDOWSSTDIO` environment - variable is set to a non-empty string. - - See :pep:`528` for more details. - - .. availability:: Windows. - -.. c:var:: Py_NoSiteFlag - - Disable the import of the module :mod:`site` and the site-dependent - manipulations of :data:`sys.path` that it entails. Also disable these - manipulations if :mod:`site` is explicitly imported later (call - :func:`site.main` if you want them to be triggered). - - Set by the :option:`-S` option. - -.. c:var:: Py_NoUserSiteDirectory - - Don't add the :data:`user site-packages directory <site.USER_SITE>` to - :data:`sys.path`. - - Set by the :option:`-s` and :option:`-I` options, and the - :envvar:`PYTHONNOUSERSITE` environment variable. - -.. c:var:: Py_OptimizeFlag - - Set by the :option:`-O` option and the :envvar:`PYTHONOPTIMIZE` environment - variable. - -.. c:var:: Py_QuietFlag - - Don't display the copyright and version messages even in interactive mode. - - Set by the :option:`-q` option. - - .. versionadded:: 3.2 - -.. c:var:: Py_UnbufferedStdioFlag - - Force the stdout and stderr streams to be unbuffered. - - Set by the :option:`-u` option and the :envvar:`PYTHONUNBUFFERED` - environment variable. - -.. c:var:: Py_VerboseFlag - - Print a message each time a module is initialized, showing the place - (filename or built-in module) from which it is loaded. If greater or equal - to ``2``, print a message for each file that is checked for when - searching for a module. Also provides information on module cleanup at exit. - - Set by the :option:`-v` option and the :envvar:`PYTHONVERBOSE` environment - variable. - Initializing and finalizing the interpreter =========================================== @@ -230,32 +17,29 @@ Initializing and finalizing the interpreter .. index:: single: Py_SetProgramName() single: PyEval_InitThreads() + single: PyEval_ReleaseLock() + single: PyEval_AcquireLock() single: modules (in module sys) single: path (in module sys) - module: builtins + module: __builtin__ module: __main__ module: sys triple: module; search; path single: PySys_SetArgv() single: PySys_SetArgvEx() - single: Py_FinalizeEx() + single: Py_Finalize() - Initialize the Python interpreter. In an application embedding Python, - this should be called before using any other Python/C API functions; see - :ref:`Before Python Initialization <pre-init-safe>` for the few exceptions. - - This initializes + Initialize the Python interpreter. In an application embedding Python, this + should be called before using any other Python/C API functions; with the + exception of :c:func:`Py_SetProgramName`, :c:func:`Py_SetPythonHome`, :c:func:`PyEval_InitThreads`, + :c:func:`PyEval_ReleaseLock`, and :c:func:`PyEval_AcquireLock`. This initializes the table of loaded modules (``sys.modules``), and creates the fundamental - modules :mod:`builtins`, :mod:`__main__` and :mod:`sys`. It also initializes + modules :mod:`__builtin__`, :mod:`__main__` and :mod:`sys`. It also initializes the module search path (``sys.path``). It does not set ``sys.argv``; use :c:func:`PySys_SetArgvEx` for that. This is a no-op when called for a second time - (without calling :c:func:`Py_FinalizeEx` first). There is no return value; it is a + (without calling :c:func:`Py_Finalize` first). There is no return value; it is a fatal error if the initialization fails. - .. note:: - On Windows, changes the console mode from ``O_TEXT`` to ``O_BINARY``, which will - also affect non-Python uses of the console using the C Runtime. - .. c:function:: void Py_InitializeEx(int initsigs) @@ -263,24 +47,25 @@ Initializing and finalizing the interpreter *initsigs* is ``0``, it skips initialization registration of signal handlers, which might be useful when Python is embedded. + .. versionadded:: 2.4 + .. c:function:: int Py_IsInitialized() Return true (nonzero) when the Python interpreter has been initialized, false - (zero) if not. After :c:func:`Py_FinalizeEx` is called, this returns false until + (zero) if not. After :c:func:`Py_Finalize` is called, this returns false until :c:func:`Py_Initialize` is called again. -.. c:function:: int Py_FinalizeEx() +.. c:function:: void Py_Finalize() Undo all initializations made by :c:func:`Py_Initialize` and subsequent use of Python/C API functions, and destroy all sub-interpreters (see :c:func:`Py_NewInterpreter` below) that were created and not yet destroyed since the last call to :c:func:`Py_Initialize`. Ideally, this frees all memory allocated by the Python interpreter. This is a no-op when called for a second - time (without calling :c:func:`Py_Initialize` again first). Normally the - return value is ``0``. If there were errors during finalization - (flushing buffered data), ``-1`` is returned. + time (without calling :c:func:`Py_Initialize` again first). There is no return + value; errors during finalization are ignored. This function is provided for a number of reasons. An embedding application might want to restart Python without having to restart the application itself. @@ -299,53 +84,14 @@ Initializing and finalizing the interpreter freed. Some memory allocated by extension modules may not be freed. Some extensions may not work properly if their initialization routine is called more than once; this can happen if an application calls :c:func:`Py_Initialize` and - :c:func:`Py_FinalizeEx` more than once. - - .. audit-event:: cpython._PySys_ClearAuditHooks "" c.Py_FinalizeEx - - .. versionadded:: 3.6 - -.. c:function:: void Py_Finalize() - - This is a backwards-compatible version of :c:func:`Py_FinalizeEx` that - disregards the return value. + :c:func:`Py_Finalize` more than once. Process-wide parameters ======================= -.. c:function:: int Py_SetStandardStreamEncoding(const char *encoding, const char *errors) - - .. index:: - single: Py_Initialize() - single: main() - triple: stdin; stdout; sdterr - - This function should be called before :c:func:`Py_Initialize`, if it is - called at all. It specifies which encoding and error handling to use - with standard IO, with the same meanings as in :func:`str.encode`. - - It overrides :envvar:`PYTHONIOENCODING` values, and allows embedding code - to control IO encoding when the environment variable does not work. - - *encoding* and/or *errors* may be ``NULL`` to use - :envvar:`PYTHONIOENCODING` and/or default values (depending on other - settings). - - Note that :data:`sys.stderr` always uses the "backslashreplace" error - handler, regardless of this (or any other) setting. - - If :c:func:`Py_FinalizeEx` is called, this function will need to be called - again in order to affect subsequent calls to :c:func:`Py_Initialize`. - - Returns ``0`` if successful, a nonzero value on error (e.g. calling after the - interpreter has already been initialized). - - .. versionadded:: 3.4 - - -.. c:function:: void Py_SetProgramName(const wchar_t *name) +.. c:function:: void Py_SetProgramName(char *name) .. index:: single: Py_Initialize() @@ -354,20 +100,16 @@ Process-wide parameters This function should be called before :c:func:`Py_Initialize` is called for the first time, if it is called at all. It tells the interpreter the value - of the ``argv[0]`` argument to the :c:func:`main` function of the program - (converted to wide characters). + of the ``argv[0]`` argument to the :c:func:`main` function of the program. This is used by :c:func:`Py_GetPath` and some other functions below to find the Python run-time libraries relative to the interpreter executable. The default value is ``'python'``. The argument should point to a - zero-terminated wide character string in static storage whose contents will not + zero-terminated character string in static storage whose contents will not change for the duration of the program's execution. No code in the Python interpreter will change the contents of this storage. - Use :c:func:`Py_DecodeLocale` to decode a bytes string to get a - :c:type:`wchar_*` string. - -.. c:function:: wchar* Py_GetProgramName() +.. c:function:: char* Py_GetProgramName() .. index:: single: Py_SetProgramName() @@ -376,7 +118,7 @@ Process-wide parameters value. -.. c:function:: wchar_t* Py_GetPrefix() +.. c:function:: char* Py_GetPrefix() Return the *prefix* for installed platform-independent files. This is derived through a number of complicated rules from the program name set with @@ -389,7 +131,7 @@ Process-wide parameters It is only useful on Unix. See also the next function. -.. c:function:: wchar_t* Py_GetExecPrefix() +.. c:function:: char* Py_GetExecPrefix() Return the *exec-prefix* for installed platform-*dependent* files. This is derived through a number of complicated rules from the program name set with @@ -424,7 +166,7 @@ Process-wide parameters platform. -.. c:function:: wchar_t* Py_GetProgramFullPath() +.. c:function:: char* Py_GetProgramFullPath() .. index:: single: Py_SetProgramName() @@ -437,12 +179,11 @@ Process-wide parameters to Python code as ``sys.executable``. -.. c:function:: wchar_t* Py_GetPath() +.. c:function:: char* Py_GetPath() .. index:: triple: module; search; path single: path (in module sys) - single: Py_SetPath() Return the default module search path; this is computed from the program name (set by :c:func:`Py_SetProgramName` above) and some environment variables. @@ -457,50 +198,19 @@ Process-wide parameters .. XXX should give the exact rules -.. c:function:: void Py_SetPath(const wchar_t *) - - .. index:: - triple: module; search; path - single: path (in module sys) - single: Py_GetPath() - - Set the default module search path. If this function is called before - :c:func:`Py_Initialize`, then :c:func:`Py_GetPath` won't attempt to compute a - default search path but uses the one provided instead. This is useful if - Python is embedded by an application that has full knowledge of the location - of all modules. The path components should be separated by the platform - dependent delimiter character, which is ``':'`` on Unix and Mac OS X, ``';'`` - on Windows. - - This also causes :data:`sys.executable` to be set to the program - full path (see :c:func:`Py_GetProgramFullPath`) and for :data:`sys.prefix` and - :data:`sys.exec_prefix` to be empty. It is up to the caller to modify these - if required after calling :c:func:`Py_Initialize`. - - Use :c:func:`Py_DecodeLocale` to decode a bytes string to get a - :c:type:`wchar_*` string. - - The path argument is copied internally, so the caller may free it after the - call completes. - - .. versionchanged:: 3.8 - The program full path is now used for :data:`sys.executable`, instead - of the program name. - - .. c:function:: const char* Py_GetVersion() Return the version of this Python interpreter. This is a string that looks something like :: - "3.0a5+ (py3k:63103M, May 12 2008, 00:53:55) \n[GCC 4.2.3]" + "1.5 (#67, Dec 31 1997, 22:34:28) [GCC 2.7.2.2]" .. index:: single: version (in module sys) The first word (up to the first space character) is the current Python version; the first three characters are the major and minor version separated by a period. The returned string points into static storage; the caller should not - modify its value. The value is available to Python code as :data:`sys.version`. + modify its value. The value is available to Python code as ``sys.version``. .. c:function:: const char* Py_GetPlatform() @@ -556,7 +266,7 @@ Process-wide parameters ``sys.version``. -.. c:function:: void PySys_SetArgvEx(int argc, wchar_t **argv, int updatepath) +.. c:function:: void PySys_SetArgvEx(int argc, char **argv, int updatepath) .. index:: single: main() @@ -578,45 +288,35 @@ Process-wide parameters - If the name of an existing script is passed in ``argv[0]``, the absolute path of the directory where the script is located is prepended to :data:`sys.path`. - - Otherwise (that is, if *argc* is ``0`` or ``argv[0]`` doesn't point + - Otherwise (that is, if *argc* is 0 or ``argv[0]`` doesn't point to an existing file name), an empty string is prepended to :data:`sys.path`, which is the same as prepending the current working directory (``"."``). - Use :c:func:`Py_DecodeLocale` to decode a bytes string to get a - :c:type:`wchar_*` string. - .. note:: It is recommended that applications embedding the Python interpreter for purposes other than executing a single script pass ``0`` as *updatepath*, and update :data:`sys.path` themselves if desired. See `CVE-2008-5983 <https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-5983>`_. - On versions before 3.1.3, you can achieve the same effect by manually + On versions before 2.6.6, you can achieve the same effect by manually popping the first :data:`sys.path` element after having called :c:func:`PySys_SetArgv`, for example using:: PyRun_SimpleString("import sys; sys.path.pop(0)\n"); - .. versionadded:: 3.1.3 + .. versionadded:: 2.6.6 .. XXX impl. doesn't seem consistent in allowing ``0``/``NULL`` for the params; check w/ Guido. -.. c:function:: void PySys_SetArgv(int argc, wchar_t **argv) - - This function works like :c:func:`PySys_SetArgvEx` with *updatepath* set - to ``1`` unless the :program:`python` interpreter was started with the - :option:`-I`. +.. c:function:: void PySys_SetArgv(int argc, char **argv) - Use :c:func:`Py_DecodeLocale` to decode a bytes string to get a - :c:type:`wchar_*` string. + This function works like :c:func:`PySys_SetArgvEx` with *updatepath* set to ``1``. - .. versionchanged:: 3.4 The *updatepath* value depends on :option:`-I`. - -.. c:function:: void Py_SetPythonHome(const wchar_t *home) +.. c:function:: void Py_SetPythonHome(char *home) Set the default "home" directory, that is, the location of the standard Python libraries. See :envvar:`PYTHONHOME` for the meaning of the @@ -627,11 +327,8 @@ Process-wide parameters execution. No code in the Python interpreter will change the contents of this storage. - Use :c:func:`Py_DecodeLocale` to decode a bytes string to get a - :c:type:`wchar_*` string. - -.. c:function:: w_char* Py_GetPythonHome() +.. c:function:: char* Py_GetPythonHome() Return the default "home", that is, the value set by a previous call to :c:func:`Py_SetPythonHome`, or the value of the :envvar:`PYTHONHOME` @@ -644,6 +341,7 @@ Thread State and the Global Interpreter Lock ============================================ .. index:: + single: GIL single: global interpreter lock single: interpreter lock single: lock, interpreter @@ -656,12 +354,12 @@ operations could cause problems in a multi-threaded program: for example, when two threads simultaneously increment the reference count of the same object, the reference count could end up being incremented only once instead of twice. -.. index:: single: setswitchinterval() (in module sys) +.. index:: single: setcheckinterval() (in module sys) Therefore, the rule exists that only the thread that has acquired the :term:`GIL` may operate on Python objects or call Python/C API functions. In order to emulate concurrency of execution, the interpreter regularly -tries to switch threads (see :func:`sys.setswitchinterval`). The lock is also +tries to switch threads (see :func:`sys.setcheckinterval`). The lock is also released around potentially blocking I/O operations like reading or writing a file, so that other Python threads can run in the meantime. @@ -698,14 +396,15 @@ This is so common that a pair of macros exists to simplify it:: The :c:macro:`Py_BEGIN_ALLOW_THREADS` macro opens a new block and declares a hidden local variable; the :c:macro:`Py_END_ALLOW_THREADS` macro closes the -block. +block. These two macros are still available when Python is compiled without +thread support (they simply have an empty expansion). -The block above expands to the following code:: +When thread support is enabled, the block above expands to the following code:: PyThreadState *_save; _save = PyEval_SaveThread(); - ... Do some blocking I/O operation ... + ...Do some blocking I/O operation... PyEval_RestoreThread(_save); .. index:: @@ -769,19 +468,9 @@ supports the creation of additional interpreters (using :c:func:`Py_NewInterpreter`), but mixing multiple interpreters and the :c:func:`PyGILState_\*` API is unsupported. - -.. _fork-and-threads: - -Cautions about fork() ---------------------- - Another important thing to note about threads is their behaviour in the face of the C :c:func:`fork` call. On most systems with :c:func:`fork`, after a -process forks only the thread that issued the fork will exist. This has a -concrete impact both on how locks must be handled and on all stored state -in CPython's runtime. - -The fact that only the "current" thread remains +process forks only the thread that issued the fork will exist. That also means any locks held by other threads will never be released. Python solves this for :func:`os.fork` by acquiring the locks it uses internally before the fork, and releasing them afterwards. In addition, it resets any @@ -793,20 +482,9 @@ Additionally, when extending or embedding Python, calling :c:func:`fork` directly rather than through :func:`os.fork` (and returning to or calling into Python) may result in a deadlock by one of Python's internal locks being held by a thread that is defunct after the fork. -:c:func:`PyOS_AfterFork_Child` tries to reset the necessary locks, but is not +:c:func:`PyOS_AfterFork` tries to reset the necessary locks, but is not always able to. -The fact that all other threads go away also means that CPython's -runtime state there must be cleaned up properly, which :func:`os.fork` -does. This means finalizing all other :c:type:`PyThreadState` objects -belonging to the current interpreter and all other -:c:type:`PyInterpreterState` objects. Due to this and the special -nature of the :ref:`"main" interpreter <sub-interpreter-support>`, -:c:func:`fork` should only be called in that interpreter's "main" -thread, where the CPython global runtime was originally initialized. -The only exception is if :c:func:`exec` will be called immediately -after. - High-level API -------------- @@ -837,74 +515,92 @@ code, or when embedding the Python interpreter: .. c:function:: void PyEval_InitThreads() .. index:: - single: PyEval_AcquireThread() + single: PyEval_ReleaseLock() single: PyEval_ReleaseThread() single: PyEval_SaveThread() single: PyEval_RestoreThread() Initialize and acquire the global interpreter lock. It should be called in the main thread before creating a second thread or engaging in any other thread - operations such as ``PyEval_ReleaseThread(tstate)``. It is not needed before - calling :c:func:`PyEval_SaveThread` or :c:func:`PyEval_RestoreThread`. + operations such as :c:func:`PyEval_ReleaseLock` or + ``PyEval_ReleaseThread(tstate)``. It is not needed before calling + :c:func:`PyEval_SaveThread` or :c:func:`PyEval_RestoreThread`. - This is a no-op when called for a second time. + .. index:: single: Py_Initialize() - .. versionchanged:: 3.7 - This function is now called by :c:func:`Py_Initialize()`, so you don't - have to call it yourself anymore. + This is a no-op when called for a second time. It is safe to call this function + before calling :c:func:`Py_Initialize`. - .. versionchanged:: 3.2 - This function cannot be called before :c:func:`Py_Initialize()` anymore. + .. index:: module: thread - .. index:: module: _thread + .. note:: + + When only the main thread exists, no GIL operations are needed. This is a + common situation (most Python programs do not use threads), and the lock + operations slow the interpreter down a bit. Therefore, the lock is not + created initially. This situation is equivalent to having acquired the lock: + when there is only a single thread, all object accesses are safe. Therefore, + when this function initializes the global interpreter lock, it also acquires + it. Before the Python :mod:`_thread` module creates a new thread, knowing + that either it has the lock or the lock hasn't been created yet, it calls + :c:func:`PyEval_InitThreads`. When this call returns, it is guaranteed that + the lock has been created and that the calling thread has acquired it. + + It is **not** safe to call this function when it is unknown which thread (if + any) currently has the global interpreter lock. + + This function is not available when thread support is disabled at compile time. .. c:function:: int PyEval_ThreadsInitialized() Returns a non-zero value if :c:func:`PyEval_InitThreads` has been called. This function can be called without holding the GIL, and therefore can be used to - avoid calls to the locking API when running single-threaded. + avoid calls to the locking API when running single-threaded. This function is + not available when thread support is disabled at compile time. - .. versionchanged:: 3.7 - The :term:`GIL` is now initialized by :c:func:`Py_Initialize()`. + .. versionadded:: 2.4 .. c:function:: PyThreadState* PyEval_SaveThread() - Release the global interpreter lock (if it has been created) and reset the - thread state to ``NULL``, returning the previous thread state (which is not - ``NULL``). If the lock has been created, the current thread must have - acquired it. + Release the global interpreter lock (if it has been created and thread + support is enabled) and reset the thread state to *NULL*, returning the + previous thread state (which is not *NULL*). If the lock has been created, + the current thread must have acquired it. (This function is available even + when thread support is disabled at compile time.) .. c:function:: void PyEval_RestoreThread(PyThreadState *tstate) - Acquire the global interpreter lock (if it has been created) and set the - thread state to *tstate*, which must not be ``NULL``. If the lock has been - created, the current thread must not have acquired it, otherwise deadlock - ensues. + Acquire the global interpreter lock (if it has been created and thread + support is enabled) and set the thread state to *tstate*, which must not be + *NULL*. If the lock has been created, the current thread must not have + acquired it, otherwise deadlock ensues. (This function is available even + when thread support is disabled at compile time.) - .. note:: - Calling this function from a thread when the runtime is finalizing - will terminate the thread, even if the thread was not created by Python. - You can use :c:func:`_Py_IsFinalizing` or :func:`sys.is_finalizing` to - check if the interpreter is in process of being finalized before calling - this function to avoid unwanted termination. .. c:function:: PyThreadState* PyThreadState_Get() Return the current thread state. The global interpreter lock must be held. - When the current thread state is ``NULL``, this issues a fatal error (so that - the caller needn't check for ``NULL``). + When the current thread state is *NULL*, this issues a fatal error (so that + the caller needn't check for *NULL*). .. c:function:: PyThreadState* PyThreadState_Swap(PyThreadState *tstate) Swap the current thread state with the thread state given by the argument - *tstate*, which may be ``NULL``. The global interpreter lock must be held + *tstate*, which may be *NULL*. The global interpreter lock must be held and is not released. +.. c:function:: void PyEval_ReInitThreads() + + This function is called from :c:func:`PyOS_AfterFork` to ensure that newly + created child processes don't hold locks referring to threads which + are not running in the child process. + + The following functions use thread-local storage, and are not compatible with sub-interpreters: @@ -930,12 +626,8 @@ with sub-interpreters: When the function returns, the current thread will hold the GIL and be able to call arbitrary Python code. Failure is a fatal error. - .. note:: - Calling this function from a thread when the runtime is finalizing - will terminate the thread, even if the thread was not created by Python. - You can use :c:func:`_Py_IsFinalizing` or :func:`sys.is_finalizing` to - check if the interpreter is in process of being finalized before calling - this function to avoid unwanted termination. + .. versionadded:: 2.3 + .. c:function:: void PyGILState_Release(PyGILState_STATE) @@ -947,6 +639,8 @@ with sub-interpreters: Every call to :c:func:`PyGILState_Ensure` must be matched by a call to :c:func:`PyGILState_Release` on the same thread. + .. versionadded:: 2.3 + .. c:function:: PyThreadState* PyGILState_GetThisThreadState() @@ -955,19 +649,7 @@ with sub-interpreters: always has such a thread-state, even if no auto-thread-state call has been made on the main thread. This is mainly a helper/diagnostic function. - -.. c:function:: int PyGILState_Check() - - Return ``1`` if the current thread is holding the GIL and ``0`` otherwise. - This function can be called from any thread at any time. - Only if it has had its Python thread state initialized and currently is - holding the GIL will it return ``1``. - This is mainly a helper/diagnostic function. It can be useful - for example in callback contexts or memory allocation functions when - knowing that the GIL is locked can allow the caller to perform sensitive - actions or otherwise behave differently. - - .. versionadded:: 3.4 + .. versionadded:: 2.3 The following macros are normally used without a trailing semicolon; look for @@ -979,7 +661,7 @@ example usage in the Python source distribution. This macro expands to ``{ PyThreadState *_save; _save = PyEval_SaveThread();``. Note that it contains an opening brace; it must be matched with a following :c:macro:`Py_END_ALLOW_THREADS` macro. See above for further discussion of this - macro. + macro. It is a no-op when thread support is disabled at compile time. .. c:macro:: Py_END_ALLOW_THREADS @@ -987,29 +669,29 @@ example usage in the Python source distribution. This macro expands to ``PyEval_RestoreThread(_save); }``. Note that it contains a closing brace; it must be matched with an earlier :c:macro:`Py_BEGIN_ALLOW_THREADS` macro. See above for further discussion of - this macro. + this macro. It is a no-op when thread support is disabled at compile time. .. c:macro:: Py_BLOCK_THREADS This macro expands to ``PyEval_RestoreThread(_save);``: it is equivalent to - :c:macro:`Py_END_ALLOW_THREADS` without the closing brace. + :c:macro:`Py_END_ALLOW_THREADS` without the closing brace. It is a no-op when + thread support is disabled at compile time. .. c:macro:: Py_UNBLOCK_THREADS This macro expands to ``_save = PyEval_SaveThread();``: it is equivalent to :c:macro:`Py_BEGIN_ALLOW_THREADS` without the opening brace and variable - declaration. + declaration. It is a no-op when thread support is disabled at compile time. Low-level API ------------- -All of the following functions must be called after :c:func:`Py_Initialize`. - -.. versionchanged:: 3.7 - :c:func:`Py_Initialize()` now initializes the :term:`GIL`. +All of the following functions are only available when thread support is enabled +at compile time, and must be called only when the global interpreter lock has +been created. .. c:function:: PyInterpreterState* PyInterpreterState_New() @@ -1018,16 +700,12 @@ All of the following functions must be called after :c:func:`Py_Initialize`. be held, but may be held if it is necessary to serialize calls to this function. - .. audit-event:: cpython.PyInterpreterState_New "" c.PyInterpreterState_New - .. c:function:: void PyInterpreterState_Clear(PyInterpreterState *interp) Reset all information in an interpreter state object. The global interpreter lock must be held. - .. audit-event:: cpython.PyInterpreterState_Clear "" c.PyInterpreterState_Clear - .. c:function:: void PyInterpreterState_Delete(PyInterpreterState *interp) @@ -1056,44 +734,20 @@ All of the following functions must be called after :c:func:`Py_Initialize`. :c:func:`PyThreadState_Clear`. - .. c:function:: void PyThreadState_DeleteCurrent() - - Destroy the current thread state and release the global interpreter lock. - Like :c:func:`PyThreadState_Delete`, the global interpreter lock need not - be held. The thread state must have been reset with a previous call - to :c:func:`PyThreadState_Clear`. - - -.. c:function:: PY_INT64_T PyInterpreterState_GetID(PyInterpreterState *interp) - - Return the interpreter's unique ID. If there was any error in doing - so then ``-1`` is returned and an error is set. - - .. versionadded:: 3.7 - - -.. c:function:: PyObject* PyInterpreterState_GetDict(PyInterpreterState *interp) - - Return a dictionary in which interpreter-specific data may be stored. - If this function returns ``NULL`` then no exception has been raised and - the caller should assume no interpreter-specific dict is available. - - This is not a replacement for :c:func:`PyModule_GetState()`, which - extensions should use to store interpreter-specific state information. - - .. versionadded:: 3.8 - - .. c:function:: PyObject* PyThreadState_GetDict() Return a dictionary in which extensions can store thread-specific state information. Each extension should use a unique key to use to store state in the dictionary. It is okay to call this function when no current thread state - is available. If this function returns ``NULL``, no exception has been raised and + is available. If this function returns *NULL*, no exception has been raised and the caller should assume no current thread state is available. + .. versionchanged:: 2.3 + Previously this could only be called when a current thread is active, and *NULL* + meant that an exception was raised. + -.. c:function:: int PyThreadState_SetAsyncExc(unsigned long id, PyObject *exc) +.. c:function:: int PyThreadState_SetAsyncExc(long id, PyObject *exc) Asynchronously raise an exception in a thread. The *id* argument is the thread id of the target thread; *exc* is the exception object to be raised. This @@ -1103,42 +757,31 @@ All of the following functions must be called after :c:func:`Py_Initialize`. zero if the thread id isn't found. If *exc* is :const:`NULL`, the pending exception (if any) for the thread is cleared. This raises no exceptions. - .. versionchanged:: 3.7 - The type of the *id* parameter changed from :c:type:`long` to - :c:type:`unsigned long`. + .. versionadded:: 2.3 + .. c:function:: void PyEval_AcquireThread(PyThreadState *tstate) Acquire the global interpreter lock and set the current thread state to - *tstate*, which should not be ``NULL``. The lock must have been created earlier. + *tstate*, which should not be *NULL*. The lock must have been created earlier. If this thread already has the lock, deadlock ensues. - .. note:: - Calling this function from a thread when the runtime is finalizing - will terminate the thread, even if the thread was not created by Python. - You can use :c:func:`_Py_IsFinalizing` or :func:`sys.is_finalizing` to - check if the interpreter is in process of being finalized before calling - this function to avoid unwanted termination. - - .. versionchanged:: 3.8 - Updated to be consistent with :c:func:`PyEval_RestoreThread`, - :c:func:`Py_END_ALLOW_THREADS`, and :c:func:`PyGILState_Ensure`, - and terminate the current thread if called while the interpreter is finalizing. - :c:func:`PyEval_RestoreThread` is a higher-level function which is always - available (even when threads have not been initialized). + available (even when thread support isn't enabled or when threads have + not been initialized). .. c:function:: void PyEval_ReleaseThread(PyThreadState *tstate) - Reset the current thread state to ``NULL`` and release the global interpreter + Reset the current thread state to *NULL* and release the global interpreter lock. The lock must have been created earlier and must be held by the current - thread. The *tstate* argument, which must not be ``NULL``, is only used to check + thread. The *tstate* argument, which must not be *NULL*, is only used to check that it represents the current thread state --- if it isn't, a fatal error is reported. :c:func:`PyEval_SaveThread` is a higher-level function which is always - available (even when threads have not been initialized). + available (even when thread support isn't enabled or when threads have + not been initialized). .. c:function:: void PyEval_AcquireLock() @@ -1146,53 +789,31 @@ All of the following functions must be called after :c:func:`Py_Initialize`. Acquire the global interpreter lock. The lock must have been created earlier. If this thread already has the lock, a deadlock ensues. - .. deprecated:: 3.2 - This function does not update the current thread state. Please use + .. warning:: + This function does not change the current thread state. Please use :c:func:`PyEval_RestoreThread` or :c:func:`PyEval_AcquireThread` instead. - .. note:: - Calling this function from a thread when the runtime is finalizing - will terminate the thread, even if the thread was not created by Python. - You can use :c:func:`_Py_IsFinalizing` or :func:`sys.is_finalizing` to - check if the interpreter is in process of being finalized before calling - this function to avoid unwanted termination. - - .. versionchanged:: 3.8 - Updated to be consistent with :c:func:`PyEval_RestoreThread`, - :c:func:`Py_END_ALLOW_THREADS`, and :c:func:`PyGILState_Ensure`, - and terminate the current thread if called while the interpreter is finalizing. - .. c:function:: void PyEval_ReleaseLock() Release the global interpreter lock. The lock must have been created earlier. - .. deprecated:: 3.2 - This function does not update the current thread state. Please use + .. warning:: + This function does not change the current thread state. Please use :c:func:`PyEval_SaveThread` or :c:func:`PyEval_ReleaseThread` instead. -.. _sub-interpreter-support: - Sub-interpreter support ======================= While in most uses, you will only embed a single Python interpreter, there are cases where you need to create several independent interpreters in the -same process and perhaps even in the same thread. Sub-interpreters allow -you to do that. - -The "main" interpreter is the first one created when the runtime initializes. -It is usually the only Python interpreter in a process. Unlike sub-interpreters, -the main interpreter has unique process-global responsibilities like signal -handling. It is also responsible for execution during runtime initialization and -is usually the active interpreter during runtime finalization. The -:c:func:`PyInterpreterState_Main` funtion returns a pointer to its state. - -You can switch between sub-interpreters using the :c:func:`PyThreadState_Swap` -function. You can create and destroy them using the following functions: +same process and perhaps even in the same thread. Sub-interpreters allow +you to do that. You can switch between sub-interpreters using the +:c:func:`PyThreadState_Swap` function. You can create and destroy them +using the following functions: .. c:function:: PyThreadState* Py_NewInterpreter() @@ -1218,7 +839,7 @@ function. You can create and destroy them using the following functions: The return value points to the first thread state created in the new sub-interpreter. This thread state is made in the current thread state. Note that no actual thread is created; see the discussion of thread states - below. If creation of the new interpreter is unsuccessful, ``NULL`` is + below. If creation of the new interpreter is unsuccessful, *NULL* is returned; no exception is set since the exception state is stored in the current thread state and there may not be a current thread state. (Like all other Python/C API functions, the global interpreter lock must be held before @@ -1227,7 +848,7 @@ function. You can create and destroy them using the following functions: entry.) .. index:: - single: Py_FinalizeEx() + single: Py_Finalize() single: Py_Initialize() Extension modules are shared between (sub-)interpreters as follows: the first @@ -1237,7 +858,7 @@ function. You can create and destroy them using the following functions: and filled with the contents of this copy; the extension's ``init`` function is not called. Note that this is different from what happens when an extension is imported after the interpreter has been completely re-initialized by calling - :c:func:`Py_FinalizeEx` and :c:func:`Py_Initialize`; in that case, the extension's + :c:func:`Py_Finalize` and :c:func:`Py_Initialize`; in that case, the extension's ``initmodule`` function *is* called again. .. index:: single: close() (in module os) @@ -1245,14 +866,14 @@ function. You can create and destroy them using the following functions: .. c:function:: void Py_EndInterpreter(PyThreadState *tstate) - .. index:: single: Py_FinalizeEx() + .. index:: single: Py_Finalize() Destroy the (sub-)interpreter represented by the given thread state. The given thread state must be the current thread state. See the discussion of thread - states below. When the call returns, the current thread state is ``NULL``. All + states below. When the call returns, the current thread state is *NULL*. All thread states associated with this interpreter are destroyed. (The global interpreter lock must be held before calling this function and is still held - when it returns.) :c:func:`Py_FinalizeEx` will destroy all sub-interpreters that + when it returns.) :c:func:`Py_Finalize` will destroy all sub-interpreters that haven't been explicitly destroyed at that point. @@ -1324,7 +945,8 @@ pointer and a void pointer argument. function is generally **not** suitable for calling Python code from arbitrary C threads. Instead, use the :ref:`PyGILState API<gilstate>`. - .. versionadded:: 3.1 + .. versionadded:: 2.7 + .. _profiling: @@ -1338,12 +960,14 @@ The Python interpreter provides some low-level support for attaching profiling and execution tracing facilities. These are used for profiling, debugging, and coverage analysis tools. -This C interface allows the profiling or tracing code to avoid the overhead of -calling through Python-level callable objects, making a direct C function call -instead. The essential attributes of the facility have not changed; the -interface allows trace functions to be installed per-thread, and the basic -events reported to the trace function are the same as had been reported to the -Python-level trace functions in previous versions. +Starting with Python 2.2, the implementation of this facility was substantially +revised, and an interface from C was added. This C interface allows the +profiling or tracing code to avoid the overhead of calling through Python-level +callable objects, making a direct C function call instead. The essential +attributes of the facility have not changed; the interface allows trace +functions to be installed per-thread, and the basic events reported to the trace +function are the same as had been reported to the Python-level trace functions +in previous versions. .. c:type:: int (*Py_tracefunc)(PyObject *obj, PyFrameObject *frame, int what, PyObject *arg) @@ -1353,30 +977,29 @@ Python-level trace functions in previous versions. registration function as *obj*, *frame* is the frame object to which the event pertains, *what* is one of the constants :const:`PyTrace_CALL`, :const:`PyTrace_EXCEPTION`, :const:`PyTrace_LINE`, :const:`PyTrace_RETURN`, - :const:`PyTrace_C_CALL`, :const:`PyTrace_C_EXCEPTION`, :const:`PyTrace_C_RETURN`, - or :const:`PyTrace_OPCODE`, and *arg* depends on the value of *what*: - - +------------------------------+----------------------------------------+ - | Value of *what* | Meaning of *arg* | - +==============================+========================================+ - | :const:`PyTrace_CALL` | Always :c:data:`Py_None`. | - +------------------------------+----------------------------------------+ - | :const:`PyTrace_EXCEPTION` | Exception information as returned by | - | | :func:`sys.exc_info`. | - +------------------------------+----------------------------------------+ - | :const:`PyTrace_LINE` | Always :c:data:`Py_None`. | - +------------------------------+----------------------------------------+ - | :const:`PyTrace_RETURN` | Value being returned to the caller, | - | | or ``NULL`` if caused by an exception. | - +------------------------------+----------------------------------------+ - | :const:`PyTrace_C_CALL` | Function object being called. | - +------------------------------+----------------------------------------+ - | :const:`PyTrace_C_EXCEPTION` | Function object being called. | - +------------------------------+----------------------------------------+ - | :const:`PyTrace_C_RETURN` | Function object being called. | - +------------------------------+----------------------------------------+ - | :const:`PyTrace_OPCODE` | Always :c:data:`Py_None`. | - +------------------------------+----------------------------------------+ + :const:`PyTrace_C_CALL`, :const:`PyTrace_C_EXCEPTION`, or + :const:`PyTrace_C_RETURN`, and *arg* depends on the value of *what*: + + +------------------------------+--------------------------------------+ + | Value of *what* | Meaning of *arg* | + +==============================+======================================+ + | :const:`PyTrace_CALL` | Always :c:data:`Py_None`. | + +------------------------------+--------------------------------------+ + | :const:`PyTrace_EXCEPTION` | Exception information as returned by | + | | :func:`sys.exc_info`. | + +------------------------------+--------------------------------------+ + | :const:`PyTrace_LINE` | Always :c:data:`Py_None`. | + +------------------------------+--------------------------------------+ + | :const:`PyTrace_RETURN` | Value being returned to the caller, | + | | or *NULL* if caused by an exception. | + +------------------------------+--------------------------------------+ + | :const:`PyTrace_C_CALL` | Function object being called. | + +------------------------------+--------------------------------------+ + | :const:`PyTrace_C_EXCEPTION` | Function object being called. | + +------------------------------+--------------------------------------+ + | :const:`PyTrace_C_RETURN` | Function object being called. | + +------------------------------+--------------------------------------+ + .. c:var:: int PyTrace_CALL @@ -1400,9 +1023,8 @@ Python-level trace functions in previous versions. .. c:var:: int PyTrace_LINE - The value passed as the *what* parameter to a :c:type:`Py_tracefunc` function - (but not a profiling function) when a line-number event is being reported. - It may be disabled for a frame by setting :attr:`f_trace_lines` to *0* on that frame. + The value passed as the *what* parameter to a trace function (but not a + profiling function) when a line-number event is being reported. .. c:var:: int PyTrace_RETURN @@ -1429,32 +1051,66 @@ Python-level trace functions in previous versions. function has returned. -.. c:var:: int PyTrace_OPCODE - - The value for the *what* parameter to :c:type:`Py_tracefunc` functions (but not - profiling functions) when a new opcode is about to be executed. This event is - not emitted by default: it must be explicitly requested by setting - :attr:`f_trace_opcodes` to *1* on the frame. - - .. c:function:: void PyEval_SetProfile(Py_tracefunc func, PyObject *obj) Set the profiler function to *func*. The *obj* parameter is passed to the - function as its first parameter, and may be any Python object, or ``NULL``. If + function as its first parameter, and may be any Python object, or *NULL*. If the profile function needs to maintain state, using a different value for *obj* for each thread provides a convenient and thread-safe place to store it. The profile function is called for all monitored events except :const:`PyTrace_LINE` - :const:`PyTrace_OPCODE` and :const:`PyTrace_EXCEPTION`. + and :const:`PyTrace_EXCEPTION`. .. c:function:: void PyEval_SetTrace(Py_tracefunc func, PyObject *obj) Set the tracing function to *func*. This is similar to :c:func:`PyEval_SetProfile`, except the tracing function does receive line-number - events and per-opcode events, but does not receive any event related to C function - objects being called. Any trace function registered using :c:func:`PyEval_SetTrace` - will not receive :const:`PyTrace_C_CALL`, :const:`PyTrace_C_EXCEPTION` or - :const:`PyTrace_C_RETURN` as a value for the *what* parameter. + events and does not receive any event related to C function objects being called. Any + trace function registered using :c:func:`PyEval_SetTrace` will not receive + :const:`PyTrace_C_CALL`, :const:`PyTrace_C_EXCEPTION` or :const:`PyTrace_C_RETURN` + as a value for the *what* parameter. + + +.. c:function:: PyObject* PyEval_GetCallStats(PyObject *self) + + Return a tuple of function call counts. There are constants defined for the + positions within the tuple: + + +-------------------------------+-------+ + | Name | Value | + +===============================+=======+ + | :const:`PCALL_ALL` | 0 | + +-------------------------------+-------+ + | :const:`PCALL_FUNCTION` | 1 | + +-------------------------------+-------+ + | :const:`PCALL_FAST_FUNCTION` | 2 | + +-------------------------------+-------+ + | :const:`PCALL_FASTER_FUNCTION`| 3 | + +-------------------------------+-------+ + | :const:`PCALL_METHOD` | 4 | + +-------------------------------+-------+ + | :const:`PCALL_BOUND_METHOD` | 5 | + +-------------------------------+-------+ + | :const:`PCALL_CFUNCTION` | 6 | + +-------------------------------+-------+ + | :const:`PCALL_TYPE` | 7 | + +-------------------------------+-------+ + | :const:`PCALL_GENERATOR` | 8 | + +-------------------------------+-------+ + | :const:`PCALL_OTHER` | 9 | + +-------------------------------+-------+ + | :const:`PCALL_POP` | 10 | + +-------------------------------+-------+ + + :const:`PCALL_FAST_FUNCTION` means no argument tuple needs to be created. + :const:`PCALL_FASTER_FUNCTION` means that the fast-path frame setup code is used. + + If there is a method call where the call can be optimized by changing + the argument tuple and calling the function directly, it gets recorded + twice. + + This function is only present if Python is compiled with :const:`CALL_PROFILE` + defined. .. _advanced-debugging: @@ -1471,10 +1127,7 @@ These functions are only intended to be used by advanced debugging tools. Return the interpreter state object at the head of the list of all such objects. - -.. c:function:: PyInterpreterState* PyInterpreterState_Main() - - Return the main interpreter state object. + .. versionadded:: 2.2 .. c:function:: PyInterpreterState* PyInterpreterState_Next(PyInterpreterState *interp) @@ -1482,172 +1135,21 @@ These functions are only intended to be used by advanced debugging tools. Return the next interpreter state object after *interp* from the list of all such objects. + .. versionadded:: 2.2 + .. c:function:: PyThreadState * PyInterpreterState_ThreadHead(PyInterpreterState *interp) Return the pointer to the first :c:type:`PyThreadState` object in the list of threads associated with the interpreter *interp*. + .. versionadded:: 2.2 + .. c:function:: PyThreadState* PyThreadState_Next(PyThreadState *tstate) Return the next thread state object after *tstate* from the list of all such objects belonging to the same :c:type:`PyInterpreterState` object. - -.. _thread-local-storage: - -Thread Local Storage Support -============================ - -.. sectionauthor:: Masayuki Yamamoto <ma3yuki.8mamo10@gmail.com> - -The Python interpreter provides low-level support for thread-local storage -(TLS) which wraps the underlying native TLS implementation to support the -Python-level thread local storage API (:class:`threading.local`). The -CPython C level APIs are similar to those offered by pthreads and Windows: -use a thread key and functions to associate a :c:type:`void\*` value per -thread. - -The GIL does *not* need to be held when calling these functions; they supply -their own locking. - -Note that :file:`Python.h` does not include the declaration of the TLS APIs, -you need to include :file:`pythread.h` to use thread-local storage. - -.. note:: - None of these API functions handle memory management on behalf of the - :c:type:`void\*` values. You need to allocate and deallocate them yourself. - If the :c:type:`void\*` values happen to be :c:type:`PyObject\*`, these - functions don't do refcount operations on them either. - -.. _thread-specific-storage-api: - -Thread Specific Storage (TSS) API ---------------------------------- - -TSS API is introduced to supersede the use of the existing TLS API within the -CPython interpreter. This API uses a new type :c:type:`Py_tss_t` instead of -:c:type:`int` to represent thread keys. - -.. versionadded:: 3.7 - -.. seealso:: "A New C-API for Thread-Local Storage in CPython" (:pep:`539`) - - -.. c:type:: Py_tss_t - - This data structure represents the state of a thread key, the definition of - which may depend on the underlying TLS implementation, and it has an - internal field representing the key's initialization state. There are no - public members in this structure. - - When :ref:`Py_LIMITED_API <stable>` is not defined, static allocation of - this type by :c:macro:`Py_tss_NEEDS_INIT` is allowed. - - -.. c:macro:: Py_tss_NEEDS_INIT - - This macro expands to the initializer for :c:type:`Py_tss_t` variables. - Note that this macro won't be defined with :ref:`Py_LIMITED_API <stable>`. - - -Dynamic Allocation -~~~~~~~~~~~~~~~~~~ - -Dynamic allocation of the :c:type:`Py_tss_t`, required in extension modules -built with :ref:`Py_LIMITED_API <stable>`, where static allocation of this type -is not possible due to its implementation being opaque at build time. - - -.. c:function:: Py_tss_t* PyThread_tss_alloc() - - Return a value which is the same state as a value initialized with - :c:macro:`Py_tss_NEEDS_INIT`, or ``NULL`` in the case of dynamic allocation - failure. - - -.. c:function:: void PyThread_tss_free(Py_tss_t *key) - - Free the given *key* allocated by :c:func:`PyThread_tss_alloc`, after - first calling :c:func:`PyThread_tss_delete` to ensure any associated - thread locals have been unassigned. This is a no-op if the *key* - argument is `NULL`. - - .. note:: - A freed key becomes a dangling pointer, you should reset the key to - `NULL`. - - -Methods -~~~~~~~ - -The parameter *key* of these functions must not be ``NULL``. Moreover, the -behaviors of :c:func:`PyThread_tss_set` and :c:func:`PyThread_tss_get` are -undefined if the given :c:type:`Py_tss_t` has not been initialized by -:c:func:`PyThread_tss_create`. - - -.. c:function:: int PyThread_tss_is_created(Py_tss_t *key) - - Return a non-zero value if the given :c:type:`Py_tss_t` has been initialized - by :c:func:`PyThread_tss_create`. - - -.. c:function:: int PyThread_tss_create(Py_tss_t *key) - - Return a zero value on successful initialization of a TSS key. The behavior - is undefined if the value pointed to by the *key* argument is not - initialized by :c:macro:`Py_tss_NEEDS_INIT`. This function can be called - repeatedly on the same key -- calling it on an already initialized key is a - no-op and immediately returns success. - - -.. c:function:: void PyThread_tss_delete(Py_tss_t *key) - - Destroy a TSS key to forget the values associated with the key across all - threads, and change the key's initialization state to uninitialized. A - destroyed key is able to be initialized again by - :c:func:`PyThread_tss_create`. This function can be called repeatedly on - the same key -- calling it on an already destroyed key is a no-op. - - -.. c:function:: int PyThread_tss_set(Py_tss_t *key, void *value) - - Return a zero value to indicate successfully associating a :c:type:`void\*` - value with a TSS key in the current thread. Each thread has a distinct - mapping of the key to a :c:type:`void\*` value. - - -.. c:function:: void* PyThread_tss_get(Py_tss_t *key) - - Return the :c:type:`void\*` value associated with a TSS key in the current - thread. This returns ``NULL`` if no value is associated with the key in the - current thread. - - -.. _thread-local-storage-api: - -Thread Local Storage (TLS) API ------------------------------- - -.. deprecated:: 3.7 - This API is superseded by - :ref:`Thread Specific Storage (TSS) API <thread-specific-storage-api>`. - -.. note:: - This version of the API does not support platforms where the native TLS key - is defined in a way that cannot be safely cast to ``int``. On such platforms, - :c:func:`PyThread_create_key` will return immediately with a failure status, - and the other TLS functions will all be no-ops on such platforms. - -Due to the compatibility problem noted above, this version of the API should not -be used in new code. - -.. c:function:: int PyThread_create_key() -.. c:function:: void PyThread_delete_key(int key) -.. c:function:: int PyThread_set_key_value(int key, void *value) -.. c:function:: void* PyThread_get_key_value(int key) -.. c:function:: void PyThread_delete_key_value(int key) -.. c:function:: void PyThread_ReInitTLS() + .. versionadded:: 2.2 |