gh-105145: Remove old functions to config Python init (#105154)

Remove the following old functions to configure the Python
initialization, deprecated in Python 3.11:

* PySys_AddWarnOptionUnicode()
* PySys_AddWarnOption()
* PySys_AddXOption()
* PySys_HasWarnOptions()
* PySys_SetArgvEx()
* PySys_SetArgv()
* PySys_SetPath()
* Py_SetPath()
* Py_SetProgramName()
* Py_SetPythonHome()
* Py_SetStandardStreamEncoding()
* _Py_SetProgramFullPath()

Most of these functions are kept in the stable ABI, except:

* Py_SetStandardStreamEncoding()
* _Py_SetProgramFullPath()

Update Doc/extending/embedding.rst and Doc/extending/extending.rst to
use the new PyConfig API.

_testembed.c:

* check_stdio_details() now sets stdio_encoding and stdio_errors
  of PyConfig.
* Add definitions of functions removed from the API but kept in the
  stable ABI.
* test_init_from_config() and test_init_read_set() now use
  PyConfig_SetString() instead of PyConfig_SetBytesString().

Remove _Py_ClearStandardStreamEncoding() internal function.

2 files changed, 41 insertions, 18 deletions

diff --git a/Doc/extending/embedding.rst b/Doc/extending/embedding.rst
index e64db37..1470029 100644
--- a/Doc/extending/embedding.rst
+++ b/Doc/extending/embedding.rst
@@ -59,24 +59,36 @@ perform some operation on a file. ::
    int
    main(int argc, char *argv[])
    {
-       wchar_t *program = Py_DecodeLocale(argv[0], NULL);
-       if (program == NULL) {
-           fprintf(stderr, "Fatal error: cannot decode argv[0]\n");
-           exit(1);
+       PyStatus status;
+       PyConfig config;
+       PyConfig_InitPythonConfig(&config);
+
+       /* optional but recommended */
+       status = PyConfig_SetBytesString(&config, &config.program_name, argv[0]);
+       if (PyStatus_Exception(status)) {
+           goto exception;
        }
-       Py_SetProgramName(program);  /* optional but recommended */
-       Py_Initialize();
+
+       status = Py_InitializeFromConfig(&config);
+       if (PyStatus_Exception(status)) {
+           goto exception;
+       }
+       PyConfig_Clear(&config);
+
        PyRun_SimpleString("from time import time,ctime\n"
                           "print('Today is', ctime(time()))\n");
        if (Py_FinalizeEx() < 0) {
            exit(120);
        }
-       PyMem_RawFree(program);
        return 0;
+
+     exception:
+        PyConfig_Clear(&config);
+        Py_ExitStatusException(status);
    }
 
-The :c:func:`Py_SetProgramName` function should be called before
-:c:func:`Py_Initialize` to inform the interpreter about paths to Python run-time
+Setting :c:member:`PyConfig.program_name` should be called before
+:c:func:`Py_InitializeFromConfig` to inform the interpreter about paths to Python run-time
 libraries.  Next, the Python interpreter is initialized with
 :c:func:`Py_Initialize`, followed by the execution of a hard-coded Python script
 that prints the date and time.  Afterwards, the :c:func:`Py_FinalizeEx` call shuts
diff --git a/Doc/extending/extending.rst b/Doc/extending/extending.rst
index c37b69f..ef93848 100644
--- a/Doc/extending/extending.rst
+++ b/Doc/extending/extending.rst
@@ -383,14 +383,15 @@ automatically unless there's an entry in the :c:data:`PyImport_Inittab` table.
 To add the module to the initialization table, use :c:func:`PyImport_AppendInittab`,
 optionally followed by an import of the module::
 
+   #define PY_SSIZE_T_CLEAN
+   #include <Python.h>
+
    int
    main(int argc, char *argv[])
    {
-       wchar_t *program = Py_DecodeLocale(argv[0], NULL);
-       if (program == NULL) {
-           fprintf(stderr, "Fatal error: cannot decode argv[0]\n");
-           exit(1);
-       }
+       PyStatus status;
+       PyConfig config;
+       PyConfig_InitPythonConfig(&config);
 
        /* Add a built-in module, before Py_Initialize */
        if (PyImport_AppendInittab("spam", PyInit_spam) == -1) {
@@ -399,11 +400,18 @@ optionally followed by an import of the module::
        }
 
        /* Pass argv[0] to the Python interpreter */
-       Py_SetProgramName(program);
+       status = PyConfig_SetBytesString(&config, &config.program_name, argv[0]);
+       if (PyStatus_Exception(status)) {
+           goto exception;
+       }
 
        /* Initialize the Python interpreter.  Required.
           If this step fails, it will be a fatal error. */
-       Py_Initialize();
+       status = Py_InitializeFromConfig(&config);
+       if (PyStatus_Exception(status)) {
+           goto exception;
+       }
+       PyConfig_Clear(&config);
 
        /* Optionally import the module; alternatively,
           import can be deferred until the embedded script
@@ -414,10 +422,13 @@ optionally followed by an import of the module::
            fprintf(stderr, "Error: could not import module 'spam'\n");
        }
 
-       ...
+       // ... use Python C API here ...
 
-       PyMem_RawFree(program);
        return 0;
+
+     exception:
+        PyConfig_Clear(&config);
+        Py_ExitStatusException(status);
    }
 
 .. note::