AoU: ETAS_RTACAR_SM_OS_223
**************************

This AoU checks that calls to ``GetResource()`` and ``ReleaseResource()`` are correctly paired and strictly nested
along all feasible execution paths, according to the ETAS_RTACAR_SM_OS_223 requirement and ISO 17356.

The validation procedure simulates a resource stack and verifies that:

- Every ``GetResource()`` call is matched by a corresponding ``ReleaseResource()`` call.
- ``ReleaseResource()`` always matches the most-recent outstanding ``GetResource()`` for the same resource (LIFO order).
- No path reaches a function exit point with an unmatched ``GetResource()`` call still outstanding.
- Nested acquisition of the same resource (e.g., ``GetResource(R)`` followed by another ``GetResource(R)``) is flagged as a violation per ISO 17356.

.. include:: restricted_os_regions_common_rationale.rst

.. important:: Os API call region delimiters

   The tool detects the start of a resource critical region when a call to the **Os_GetResource()** (or ``GetResource()``)
   function is made. The end of the critical region is detected when a corresponding call to **Os_ReleaseResource()** (or
   ``ReleaseResource()``) is made.

.. attention:: Resource identifier resolution

   The tool does not resolve resource identifiers during analysis. Rules that require matching a specific resource
   identifier are therefore applied without identifier verification. When call targets are unresolved (function pointers,
   external calls), the tool marks the affected path result as ambiguous.

.. include:: ../rules/ETAS_RTACAR_SM_OS_223.rst