Add mj_markStack and mj_freeStack as public API functions.

Also add asan instrumentation to detect stack frame leakages (i.e. `mj_markStack` without a corresponding `mj_freeStack` in the same caller function).

PiperOrigin-RevId: 562625645
Change-Id: I4e3ff66ca0b9d08ed0a95cef45393db8e3053e22

doc/APIreference/functions.rst

@@ -1232,6 +1232,25 @@ mj_resetDataKeyframe
 
 Reset data, set fields from specified keyframe.
 
+.. _mj_markStack:
+
+mj_markStack
+~~~~~~~~~~~~
+
+.. mujoco-include:: mj_markStack
+
+Mark a new frame on the :ref:`mjData` stack.
+
+.. _mj_freeStack:
+
+mj_freeStack
+~~~~~~~~~~~~
+
+.. mujoco-include:: mj_freeStack
+
+Free the current :ref:`mjData` stack frame. All pointers returned by mj_stackAlloc since the last call
+to mj_markStack must no longer be used afterwards.
+
 .. _mj_stackAlloc:
 
 mj_stackAlloc

doc/changelog.rst

@@ -43,6 +43,8 @@ General
    functionality of allocating ``mjtNum`` arrays is still available through the new function :ref:`mj_stackAllocNum`.
 #. Renamed the ``nstack`` field in :ref:`mjModel` and :ref:`mjData` to ``narena``. Changed ``narena``, ``pstack``, and
    ``maxuse_stack`` to count number of bytes rather than number of :ref:`mjtNum` |-| s.
+#. Added new functions ``mj_markStack`` and ``mj_freeStack`` that manages ``mjData`` stack frames in a fully
+   encapsulated way (i.e. without having to introduce a local variable at the call site).
 
 Python bindings
 ^^^^^^^^^^^^^^^

doc/includes/references.h

@@ -130,6 +130,7 @@ struct mjData_ {
 
   // stack pointer
   size_t  pstack;            // first available mjtNum address in stack
+  size_t  pbase;             // value of pstack when mj_markStack was last called
 
   // arena pointer
   size_t  parena;            // first available byte in arena
@@ -2205,6 +2206,8 @@ mjData* mj_copyData(mjData* dest, const mjModel* m, const mjData* src);
 void mj_resetData(const mjModel* m, mjData* d);
 void mj_resetDataDebug(const mjModel* m, mjData* d, unsigned char debug_value);
 void mj_resetDataKeyframe(const mjModel* m, mjData* d, int key);
+void mj_markStack(mjData* d);
+void mj_freeStack(mjData* d);
 void* mj_stackAlloc(mjData* d, size_t bytes, size_t alignment);
 mjtNum* mj_stackAllocNum(mjData* d, int size);
 int* mj_stackAllocInt(mjData* d, int size);