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[docs] Clarify stack restoration when catching exceptions from JS #27748

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[docs] Clarify stack restoration when catching exceptions from JS #27748

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8 changes: 4 additions & 4 deletions site/source/docs/porting/exceptions.rst
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Expand Up @@ -149,10 +149,10 @@ exception thrown``, this code will print ``MyException,My exception thrown``.
true at ``-O0``. At ``-O1`` or above, you can export it separately by
``-sEXPORTED_RUNTIME_METHODS=getExceptionMessage,decrementExceptionRefcount``.

If the stack pointer has been moved due to stack allocations within the Wasm
function before an exception is thrown, you can use ``stackSave()`` and
``stackRestore()`` to restore the stack pointer so that no stack memory is
leaked.
Emscripten does not automatically restore the shadow stack pointer during
exception unwinding. Therefore, whenever you catch an exception in JavaScript
and intend to continue using the module, you should use ``stackSave()`` and
``stackRestore()`` around the call to prevent stack memory from leaking.

.. note:: If you catch a Wasm exception and do not rethrow it, you need to free
the storage associated with the exception in JS using
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