bpo-32124: Document C functions safe before init (#4540)

Explicitly document C functions and C variables that can be set
before Py_Initialize().
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Victor Stinner 2017-11-24 22:30:27 +01:00 committed by GitHub
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@ -7,6 +7,213 @@
Initialization, Finalization, and Threads
*****************************************
.. _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`
* Informative functions:
* :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_GetProgramName`
* :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` and
:c:func:`Py_GetProgramFullPath` and :c:func:`Py_GetPythonHome`.
.. _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
===========================================
@ -27,9 +234,11 @@ Initializing and finalizing the interpreter
single: PySys_SetArgvEx()
single: Py_FinalizeEx()
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` and :c:func:`Py_SetPath`. This initializes
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
the table of loaded modules (``sys.modules``), and creates the fundamental
modules :mod:`builtins`, :mod:`__main__` and :mod:`sys`. It also initializes
the module search path (``sys.path``). It does not set ``sys.argv``; use

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@ -212,7 +212,7 @@ Miscellaneous options
.. cmdoption:: -d
Turn on parser debugging output (for wizards only, depending on compilation
Turn on parser debugging output (for expert only, depending on compilation
options). See also :envvar:`PYTHONDEBUG`.

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@ -124,7 +124,7 @@ This terminates the option list (following options are passed as
arguments to the command).
.TP
.B \-d
Turn on parser debugging output (for wizards only, depending on
Turn on parser debugging output (for expert only, depending on
compilation options).
.TP
.B \-E