pythongh-107954: Add PyInitConfig C API

Add PyInitConfig functions:

* PyInitConfig_Python_New()
* PyInitConfig_Isolated_New()
* PyInitConfig_Free(config)
* PyInitConfig_SetInt(config, key, value)
* PyInitConfig_SetStr(config, key, value)
* PyInitConfig_SetWStr(config, key, value)
* PyInitConfig_SetStrList(config, key, length, items)
* PyInitConfig_SetWStrList(config, key, length, items)
* PyInitConfig_GetErrorMsg(config)

Add also functions using it:

* Py_InitializeFromInitConfig(config)
* Py_ExitWithInitConfig(config)

* Add functions to get runtime config:

  * PyConfig_GetInt()
  * PyConfig_GetStr()
  * PyConfig_GetStrList()

Add these functions to the limited C API.

Changes:

* Add Doc/c-api/config.rst.
* Add Include/initconfig.h header.
* Add Modules/_testcapi/config.c
* Add Lib/test/test_capi/test_config.py.

Author: vstinner

Doc/c-api/config.rst

@@ -0,0 +1,201 @@
+.. highlight:: c
+
+.. _config-c-api:
+
+********************
+Python Configuration
+********************
+
+.. versionadded:: 3.13
+
+API part of the limited C API version 3.13 to configure the Python
+initialization and get the Python runtime configuration.
+
+See also :ref:`Python Initialization Configuration <init-config>`.
+
+
+Initialize Python
+=================
+
+.. c:struct:: PyInitConfig
+
+   Opaque structure to configure the Python initialization.
+
+
+.. c:function:: PyInitConfig* PyInitConfig_Python_New(void)
+
+   Create a new initialization configuration using :ref:`Python Configuration
+   <init-python-config>` default values.
+
+   It must be freed by c:func:`PyInitConfig_Free`.
+
+   Return ``NULL`` on memory allocation failure.
+
+
+.. c:function:: PyInitConfig* PyInitConfig_Isolated_New(void)
+
+   Similar to :c:func:`PyInitConfig_Python_New`, but use :ref:`Isolated
+   Configuration <init-isolated-conf>` default values.
+
+
+.. c:function:: void PyInitConfig_Free(PyInitConfig *config)
+
+   Free memory of a initialization configuration.
+
+
+.. c:function:: int PyInitConfig_SetInt(PyInitConfig *config, const char *key, int64_t value)
+
+   Set an integer configuration option.
+
+   Return 0 on success, or return -1 on error.
+
+
+.. c:function:: int PyInitConfig_SetStr(PyInitConfig *config, const char *key, const char *value)
+
+   Set a string configuration option from a bytes string.
+
+   The bytes string is decoded by Py_DecodeLocale(). Preinitialize Python if
+   needed to ensure that encodings are properly configured.
+
+   Return 0 on success, or return -1 on error.
+
+.. c:function:: int PyInitConfig_SetWStr(PyInitConfig *config, const char *key, const wchar_t *value)
+
+   Set a string configuration option from a wide string.
+
+   Preinitialize Python if needed.
+
+   Return ``0`` on success, or return ``-1`` on error.
+
+
+.. c:function:: int PyInitConfig_SetStrList(PyInitConfig *config, const char *key, size_t length, char * const *items)
+
+   Set a string list configuration option from bytes strings.
+
+   The bytes strings are decoded by Py_DecodeLocale(). Preinitialize Python if
+   needed to ensure that encodings are properly configured.
+
+   Return ``0`` on success, or return ``-1`` on error.
+
+
+.. c:function:: int PyInitConfig_SetWStrList(PyInitConfig *config, const char *key, size_t length, wchar_t * const *items)
+
+   Set a string list configuration option from a wide strings.
+   Preinitialize Python if needed.
+   Return 0 on success, or return -1 on error.
+
+
+.. c:function:: int Py_InitializeFromInitConfig(PyInitConfig *config)
+
+   Initialize Python from the initialization configuration.
+
+   Return ``0`` on success.
+
+   Return ``-1`` if Python wants to exit and on error. Call
+   :c:func:`Py_ExitWithInitConfig` in this case.
+
+
+.. c:function:: char* PyInitConfig_GetErrorMsg(PyInitConfig* config)
+
+   Get the current error message.
+
+   Return a UTF-8 string allocated by ``malloc()``. It must be released by
+   ``free()``.
+
+   Return ``NULL`` on memory allocation failure.
+
+
+.. c:function:: void Py_ExitWithInitConfig(PyInitConfig *config)
+
+   Exit Python and free memory of a initialization configuration.
+
+   The function does not return.
+
+Example
+-------
+
+Code::
+
+    void init_python(void)
+    {
+        PyInitConfig *config = PyInitConfig_Python_New();
+        if (config == NULL) {
+            printf("Init allocation error\n");
+            return;
+        }
+
+        if (PyInitConfig_SetInt(config, "dev_mode", 1) < 0) {
+            goto error;
+        }
+
+        // Set a list of wide strings (argv)
+        wchar_t *argv[] = {L"my_program"", L"-c", L"pass"};
+        if (PyInitConfig_SetWStrList(config, "argv",
+                                     Py_ARRAY_LENGTH(argv), argv) < 0) {
+            goto error;
+        }
+
+        // Set a wide string (program_name)
+        if (PyInitConfig_SetWStr(config, "program_name", L"my_program") < 0) {
+            goto error;
+        }
+
+        // Set a list of bytes strings (xoptions)
+        char* xoptions[] = {"faulthandler"};
+        if (PyInitConfig_SetStrList(config, "xoptions",
+                                    Py_ARRAY_LENGTH(xoptions), xoptions) < 0) {
+            goto error;
+        }
+
+        if (Py_InitializeFromInitConfig(config) < 0) {
+            Py_ExitWithInitConfig(config);
+        }
+        PyInitConfig_Free(config);
+    }
+
+
+Get the current Python configuration
+====================================
+
+.. c:function:: int PyConfig_GetInt(const char *key, int64_t *value)
+
+   Get an integer configuration option.
+
+   Return ``0`` and set *\*value* on success.
+
+   Raise an exception return ``-1`` on error.
+
+
+.. c:function:: int PyConfig_GetStr(const char *key, PyObject **value)
+
+   Get a string configuration option.
+
+   Return ``0`` and set *\*value* on success. *\*value* can be set to a Python
+   :class:`str` object or to ``None``.
+
+   Raise an exception return ``-1`` on error.
+
+
+.. c:function:: int PyConfig_GetStrList(const char *key, PyObject **value)
+
+   Get a string configuration option.
+
+   Return ``0`` and set *\*value* to a Python list on success.
+
+   Raise an exception return ``-1`` on error.
+
+Example
+-------
+
+Code::
+
+    static int get_bytes_warning(void)
+    {
+        int64_t bytes_warning;
+        if (PyConfig_GetInt("bytes_warning", &bytes_warning) < 0) {
+            // Silently ignore the error
+            PyErr_Clear();
+            return -1;
+        }
+        return (int)bytes_warning;
+    }

Doc/c-api/init.rst

@@ -7,7 +7,8 @@
 Initialization, Finalization, and Threads
 *****************************************
 
-See also :ref:`Python Initialization Configuration <init-config>`.
+See also the :ref:`Python Initialization Configuration <init-config>`
+and the :ref:`Python Configuration <config-c-api>`
 
 .. _pre-init-safe:
 

Doc/c-api/init_config.rst

@@ -27,7 +27,8 @@ There are two kinds of configuration:
 The :c:func:`Py_RunMain` function can be used to write a customized Python
 program.
 
-See also :ref:`Initialization, Finalization, and Threads <initialization>`.
+See also :ref:`Initialization, Finalization, and Threads <initialization>`
+and the :ref:`Python Configuration <config-c-api>`.
 
 .. seealso::
    :pep:`587` "Python Initialization Configuration".

Doc/data/stable_abi.dat

@@ -1230,6 +1230,30 @@ New Features
   :exc:`KeyError` if the key missing.
   (Contributed by Stefan Behnel and Victor Stinner in :gh:`111262`.)
 
+* Add functions to the limited C API to configure the Python initialization:
+
+  * :c:func:`PyInitConfig_Python_New`
+  * :c:func:`PyInitConfig_Isolated_New`
+  * :c:func:`PyInitConfig_Free`
+  * :c:func:`PyInitConfig_SetInt`
+  * :c:func:`PyInitConfig_SetStr`
+  * :c:func:`PyInitConfig_SetWStr`
+  * :c:func:`PyInitConfig_SetStrList`
+  * :c:func:`PyInitConfig_SetWStrList`
+  * :c:func:`PyInitConfig_GetErrorMsg`
+  * :c:func:`Py_InitializeFromInitConfig`
+  * :c:func:`Py_ExitWithInitConfig`
+
+  (Contributed by Victor Stinner in :gh:`107954`.)
+
+* Add functions to get the current Python configuration:
+
+  * :c:func:`PyConfig_GetInt`
+  * :c:func:`PyConfig_GetStr`
+  * :c:func:`PyConfig_GetStrList`
+
+  (Contributed by Victor Stinner in :gh:`107954`.)
+
 
 Porting to Python 3.13
 ----------------------

Doc/whatsnew/3.13.rst

@@ -88,7 +88,7 @@
 #include "sliceobject.h"
 #include "cpython/cellobject.h"
 #include "iterobject.h"
-#include "cpython/initconfig.h"
+#include "initconfig.h"
 #include "pystate.h"
 #include "cpython/genobject.h"
 #include "descrobject.h"

Include/Python.h

@@ -1,8 +1,5 @@
-#ifndef Py_PYCORECONFIG_H
-#define Py_PYCORECONFIG_H
-#ifndef Py_LIMITED_API
-#ifdef __cplusplus
-extern "C" {
+#ifndef Py_CPYTHON_INITCONFIG_H
+#  error "this header file must not be included directly"
 #endif
 
 /* --- PyStatus ----------------------------------------------- */
@@ -263,9 +260,3 @@ PyAPI_FUNC(PyStatus) PyConfig_SetWideStringList(PyConfig *config,
 
    See also PyConfig.orig_argv. */
 PyAPI_FUNC(void) Py_GetArgcArgv(int *argc, wchar_t ***argv);
-
-#ifdef __cplusplus
-}
-#endif
-#endif /* !Py_LIMITED_API */
-#endif /* !Py_PYCORECONFIG_H */