Mention NULL in SetStr() documentation

Author: vstinner

Doc/c-api/init_config.rst

@@ -204,6 +204,9 @@ only implemented when ``Py_InitializeFromInitConfig()`` is called, not by the
    Set a string configuration option from a null-terminated UTF-8
    encoded string. The string is copied.
 
+   Options documented with the type ``str | None`` in the :ref:`Configuration
+   Options <pyinitconfig-opts>` table can be set to ``NULL``.
+
    * Return ``0`` on success.
    * Set an error in *config* and return ``-1`` on error.
 
@@ -275,15 +278,15 @@ Configuration Options
      - Public
    * - ``"base_exec_prefix"``
      - :c:member:`base_exec_prefix <PyConfig.base_exec_prefix>`
-     - ``str``
+     - ``str | None``
      - Public
    * - ``"base_executable"``
      - :c:member:`base_executable <PyConfig.base_executable>`
-     - ``str``
+     - ``str | None``
      - Public
    * - ``"base_prefix"``
      - :c:member:`base_prefix <PyConfig.base_prefix>`
-     - ``str``
+     - ``str | None``
      - Public
    * - ``"buffered_stdio"``
      - :c:member:`buffered_stdio <PyConfig.buffered_stdio>`
@@ -331,15 +334,15 @@ Configuration Options
      - Read-only
    * - ``"dump_refs_file"``
      - :c:member:`dump_refs_file <PyConfig.dump_refs_file>`
-     - ``str``
+     - ``str | None``
      - Read-only
    * - ``"exec_prefix"``
      - :c:member:`exec_prefix <PyConfig.exec_prefix>`
-     - ``str``
+     - ``str | None``
      - Public
    * - ``"executable"``
      - :c:member:`executable <PyConfig.executable>`
-     - ``str``
+     - ``str | None``
      - Public
    * - ``"faulthandler"``
      - :c:member:`faulthandler <PyConfig.faulthandler>`
@@ -359,7 +362,7 @@ Configuration Options
      - Read-only
    * - ``"home"``
      - :c:member:`home <PyConfig.home>`
-     - ``str``
+     - ``str | None``
      - Read-only
    * - ``"import_time"``
      - :c:member:`import_time <PyConfig.import_time>`
@@ -431,35 +434,35 @@ Configuration Options
      - Public
    * - ``"prefix"``
      - :c:member:`prefix <PyConfig.prefix>`
-     - ``str``
+     - ``str | None``
      - Public
    * - ``"program_name"``
      - :c:member:`program_name <PyConfig.program_name>`
      - ``str``
      - Read-only
    * - ``"pycache_prefix"``
      - :c:member:`pycache_prefix <PyConfig.pycache_prefix>`
-     - ``str``
+     - ``str | None``
      - Public
    * - ``"quiet"``
      - :c:member:`quiet <PyConfig.quiet>`
      - ``bool``
      - Public
    * - ``"run_command"``
      - :c:member:`run_command <PyConfig.run_command>`
-     - ``str``
+     - ``str | None``
      - Read-only
    * - ``"run_filename"``
      - :c:member:`run_filename <PyConfig.run_filename>`
-     - ``str``
+     - ``str | None``
      - Read-only
    * - ``"run_module"``
      - :c:member:`run_module <PyConfig.run_module>`
-     - ``str``
+     - ``str | None``
      - Read-only
    * - ``"run_presite"``
      - :c:member:`run_presite <PyConfig.run_presite>`
-     - ``str``
+     - ``str | None``
      - Read-only
    * - ``"safe_path"``
      - :c:member:`safe_path <PyConfig.safe_path>`
@@ -479,15 +482,15 @@ Configuration Options
      - Read-only
    * - ``"stdio_encoding"``
      - :c:member:`stdio_encoding <PyConfig.stdio_encoding>`
-     - ``str``
+     - ``str | None``
      - Read-only
    * - ``"stdio_errors"``
      - :c:member:`stdio_errors <PyConfig.stdio_errors>`
      - ``str``
      - Read-only
    * - ``"stdlib_dir"``
      - :c:member:`stdlib_dir <PyConfig.stdlib_dir>`
-     - ``str``
+     - ``str | None``
      - Public
    * - ``"tracemalloc"``
      - :c:member:`tracemalloc <PyConfig.tracemalloc>`
@@ -542,6 +545,8 @@ Configuration Options
      - ``bool``
      - Read-only
 
+The type ``str | None`` means that a string can be ``NULL``.
+
 Visibility:
 
 * Public: Can be retrieved by :c:func:`PyConfig_Get` and set by