doc: posix: mark posix signals supported with undefined behaviour

Mark the POSIX_SIGNALS Option Group as supported to the extent
possible under Zephyr, as Zephyr does not yet support processes.

Signed-off-by: Chris Friedt <cfriedt@tenstorrent.com>

doc/services/portability/posix/aep/index.rst

@@ -50,8 +50,8 @@ The *Minimal Realtime System Profile* (PSE51) includes all of the
 
     :ref:`POSIX_C_LANG_JUMP <posix_option_group_c_lang_jump>`, yes,
     :ref:`POSIX_C_LANG_SUPPORT <posix_option_group_c_lang_support>`, yes,
-    :ref:`POSIX_DEVICE_IO <posix_option_group_device_io>`, yes, :kconfig:option:`CONFIG_POSIX_DEVICE_IO`
-    :ref:`POSIX_SIGNALS <posix_option_group_signals>`,, :kconfig:option:`CONFIG_POSIX_SIGNALS`
+    :ref:`POSIX_DEVICE_IO <posix_option_group_device_io>`,yes, :kconfig:option:`CONFIG_POSIX_DEVICE_IO`
+    :ref:`POSIX_SIGNALS <posix_option_group_signals>`, yes, :kconfig:option:`CONFIG_POSIX_SIGNALS` :ref:`†<posix_undefined_behaviour>`
     :ref:`POSIX_SINGLE_PROCESS <posix_option_group_single_process>`, yes, :kconfig:option:`CONFIG_POSIX_SINGLE_PROCESS`
     :ref:`XSI_THREADS_EXT <posix_option_group_xsi_threads_ext>`, yes, :kconfig:option:`CONFIG_XSI_THREADS_EXT`
 

doc/services/portability/posix/option_groups/index.rst

@@ -244,26 +244,34 @@ POSIX_SIGNALS
 Signal services are a basic mechanism within POSIX-based systems and are
 required for error and event handling.
 
+.. note::
+   As processes are not yet supported in Zephyr, the ISO C functions ``abort()``, ``signal()``,
+   and ``raise()``, as well as the other POSIX functions listed below, may exhibit undefined
+   behaviour. The POSIX functions ``kill()``, ``pause()``, ``sigaction()``, ``sigpending()``,
+   ``sigsuspend()``, and ``sigwait()`` are implemented to ensure that conformant applications can
+   link, but they are expected to fail, setting errno to ``ENOSYS``
+   :ref:`†<posix_undefined_behaviour>`.
+
 .. csv-table:: POSIX_SIGNALS
    :header: API, Supported
    :widths: 50,10
 
-    abort(),yes
-    alarm(),
-    kill(),
-    pause(),
-    raise(),
-    sigaction(),
+    abort(),yes :ref:`†<posix_undefined_behaviour>`
+    alarm(),yes :ref:`†<posix_undefined_behaviour>`
+    kill(),yes :ref:`†<posix_undefined_behaviour>`
+    pause(),yes :ref:`†<posix_undefined_behaviour>`
+    raise(),yes :ref:`†<posix_undefined_behaviour>`
+    sigaction(),yes :ref:`†<posix_undefined_behaviour>`
     sigaddset(),yes
     sigdelset(),yes
     sigemptyset(),yes
     sigfillset(),yes
     sigismember(),yes
-    signal(),
-    sigpending(),
+    signal(),yes :ref:`†<posix_undefined_behaviour>`
+    sigpending(),yes :ref:`†<posix_undefined_behaviour>`
     sigprocmask(),yes
-    sigsuspend(),
-    sigwait(),
+    sigsuspend(),yes :ref:`†<posix_undefined_behaviour>`
+    sigwait(),yes :ref:`†<posix_undefined_behaviour>`
     strsignal(),yes
 
 .. _posix_option_group_device_io: