gh-114099: Add documentation for iOS platform

Doc/includes/wasm-ios-notavail.rst

@@ -0,0 +1,8 @@
+.. include for modules that don't work on WASM or iOS
+
+.. availability:: not Emscripten, not WASI, not iOS.
+
+   This module does not work or is not available on WebAssembly platforms
+   ``wasm32-emscripten`` and ``wasm32-wasi``, or on iOS. See
+   :ref:`wasm-availability` for more information on WASM availability; see
+   :ref:`iOS-availability` for more information on iOS availability.

Doc/library/curses.rst

@@ -16,6 +16,8 @@
 The :mod:`curses` module provides an interface to the curses library, the
 de-facto standard for portable advanced terminal handling.
 
+.. include:: ../includes/wasm-ios-notavail.rst
+
 While curses is most widely used in the Unix environment, versions are available
 for Windows, DOS, and possibly other systems as well.  This extension module is
 designed to match the API of ncurses, an open-source curses library hosted on

Doc/library/dbm.rst

@@ -10,6 +10,8 @@
 
 :mod:`dbm` is a generic interface to variants of the DBM database:
 
+.. include:: ../includes/wasm-ios-notavail.rst
+
 * :mod:`dbm.sqlite3`
 * :mod:`dbm.gnu`
 * :mod:`dbm.ndbm`
@@ -455,4 +457,3 @@ The :mod:`!dbm.dumb` module defines the following:
    .. method:: dumbdbm.close()
 
       Close the database.
-

Doc/library/ensurepip.rst

@@ -38,7 +38,7 @@ when creating a virtual environment) or after explicitly uninstalling
    :pep:`453`: Explicit bootstrapping of pip in Python installations
       The original rationale and specification for this module.
 
-.. include:: ../includes/wasm-notavail.rst
+.. include:: ../includes/wasm-ios-notavail.rst
 
 Command line interface
 ----------------------

Doc/library/grp.rst

@@ -10,7 +10,7 @@
 This module provides access to the Unix group database. It is available on all
 Unix versions.
 
-.. availability:: Unix, not Emscripten, not WASI.
+.. availability:: Unix, not Emscripten, not WASI, not iOS.
 
 Group database entries are reported as a tuple-like object, whose attributes
 correspond to the members of the ``group`` structure (Attribute field below, see

Doc/library/intro.rst

@@ -58,7 +58,7 @@ Notes on availability
   operating system.
 
 * If not separately noted, all functions that claim "Availability: Unix" are
-  supported on macOS, which builds on a Unix core.
+  supported on macOS and iOS, both of which build on a Unix core.
 
 * If an availability note contains both a minimum Kernel version and a minimum
   libc version, then both conditions must hold. For example a feature with note
@@ -119,3 +119,44 @@ DOM APIs as well as limited networking capabilities with JavaScript's
 .. _wasmtime: https://wasmtime.dev/
 .. _Pyodide: https://pyodide.org/
 .. _PyScript: https://pyscript.net/
+
+.. _iOS-availability:
+
+iOS
+---
+
+iOS is, in most respects, a POSIX operating system. File I/O, socket handling,
+and threading all behave as they would on any POSIX operating system. However,
+there are several major differences between iOS and other POSIX systems.
+
+* iOS can only use Python in "embedded" mode. There is no Python REPL, and no
+  ability to execute binaries that are part of the normal Python developer
+  experience, such as ``pip``. To add Python code to your iOS app, you must use
+  the :ref:`Python embedding API <embedding>` to add a Python interpreter to an
+  iOS app created with Xcode. See the :ref:`iOS usage guide <using-ios>` for
+  more details.
+
+* An iOS app cannot use any form of subprocessing, background processing, or
+  inter-process communication. If an iOS app attempts to create a subprocess,
+  the process creating the subprocess will either lock up, or crash. An iOS app
+  has no visibility of other applications that are running, nor any ability to
+  communicate with other running applications, outside of the iOS-specific APIs
+  that exist for this purpose.
+
+* iOS apps have limited access to modify system resources (such as the system
+  clock). These resources will often be *readable*, but attempts to modify
+  those resources will usually fail.
+
+* iOS apps have a limited concept of console input and output. ``stdout`` and
+  ``stderr`` *exist*, and content written to ``stdout`` and ``stderr`` will be
+  visible in logs when running in Xcode, but this content *won't* be recorded
+  in the system log. If a user who has installed your app provides their app
+  logs as a diagnostic aid, they will not include any detail written to
+  ``stdout`` or ``stderr``.
+
+  iOS apps have no concept of  ``stdin`` at all. While iOS apps can have a
+  keyboard, this is a software feature, not something that is attached to
+  ``stdin``.
+
+  As a result, Python library that involve console manipulation (such as
+  :mod:`curses` and :mod:`readline`) are not available on iOS.

Doc/library/multiprocessing.rst

@@ -8,7 +8,7 @@
 
 --------------
 
-.. include:: ../includes/wasm-notavail.rst
+.. include:: ../includes/wasm-ios-notavail.rst
 
 Introduction
 ------------