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Fix ThrowRef execution semantics #330

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Sep 13, 2024
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Fix ThrowRef execution semantics #330

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46 changes: 23 additions & 23 deletions document/core/exec/instructions.rst
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Expand Up @@ -2757,75 +2757,75 @@ Control Instructions
:math:`\THROWREF`
.................

1. Let :math:`F` be the :ref:`current <exec-notation-textual>` :ref:`frame <syntax-frame>`.

2. Assert: due to :ref:`validation <valid-throw_ref>`, a :ref:`reference <syntax-ref>` is on the top of the stack.
1. Assert: due to :ref:`validation <valid-throw_ref>`, a :ref:`reference <syntax-ref>` is on the top of the stack.

3. Pop the reference :math:`\reff` from the stack.
2. Pop the reference :math:`\reff` from the stack.

4. If :math:`\reff` is :math:`\REFNULL~\X{ht}`, then:
3. If :math:`\reff` is :math:`\REFNULL~\X{ht}`, then:

a. Trap.

5. Assert: due to :ref:`validation <valid-throw_ref>`, :math:`\reff` is an :ref:`exception reference <syntax-ref.exn-addr>`.
4. Assert: due to :ref:`validation <valid-throw_ref>`, :math:`\reff` is an :ref:`exception reference <syntax-ref.exn-addr>`.

6. Let :math:`\REFEXNADDR~\X{ea}` be :math:`\reff`.
5. Let :math:`\REFEXNADDR~\X{ea}` be :math:`\reff`.

7. Assert: due to :ref:`validation <valid-throw_ref>`, :math:`S.\SEXNS[\X{ea}]` exists.
6. Assert: due to :ref:`validation <valid-throw_ref>`, :math:`S.\SEXNS[\X{ea}]` exists.

8. Let :math:`\X{exn}` be the :ref:`exception instance <syntax-exninst>` :math:`S.\SEXNS[\X{ea}]`.
7. Let :math:`\X{exn}` be the :ref:`exception instance <syntax-exninst>` :math:`S.\SEXNS[\X{ea}]`.

9. Let :math:`a` be the :ref:`tag address <syntax-tagaddr>` :math:`\X{exn}.\EITAG`.
8. Let :math:`a` be the :ref:`tag address <syntax-tagaddr>` :math:`\X{exn}.\EITAG`.

10. While the stack is not empty and the top of the stack is not an :ref:`exception handler <syntax-handler>`, do:
9. While the stack is not empty and the top of the stack is not an :ref:`exception handler <syntax-handler>`, do:

a. Pop the top element from the stack.

11. Assert: the stack is now either empty, or there is an exception handler on the top of the stack.
10. Assert: the stack is now either empty, or there is an exception handler on the top of the stack.

12. If the stack is empty, then:
11. If the stack is empty, then:

a. Return the exception :math:`(\REFEXNADDR~a)` as a :ref:`result <syntax-result>`.

13. Assert: there is an :ref:`exception handler <syntax-handler>` on the top of the stack.
12. Assert: there is an :ref:`exception handler <syntax-handler>` on the top of the stack.

14. Pop the exception handler :math:`\HANDLER_n\{\catch^\ast\}` from the stack.
13. Pop the exception handler :math:`\HANDLER_n\{\catch^\ast\}` from the stack.

15. If :math:`\catch^\ast` is empty, then:
14. If :math:`\catch^\ast` is empty, then:

a. Push the exception reference :math:`\REFEXNADDR~\X{ea}` back to the stack.

b. Execute the instruction |THROWREF| again.

16. Else:
15. Else:

a. Let :math:`F` be the :ref:`current <exec-notation-textual>` :ref:`frame <syntax-frame>`.

a. Let :math:`\catch_1` be the first :ref:`catch clause <syntax-catch>` in :math:`\catch^\ast` and :math:`{\catch'}^\ast` the remaining clauses.
b. Let :math:`\catch_1` be the first :ref:`catch clause <syntax-catch>` in :math:`\catch^\ast` and :math:`{\catch'}^\ast` the remaining clauses.

b. If :math:`\catch_1` is of the form :math:`\CATCH~x~l` and the :ref:`tag address <syntax-tagaddr>` :math:`a` equals :math:`F.\AMODULE.\MITAGS[x]`, then:
c. If :math:`\catch_1` is of the form :math:`\CATCH~x~l` and the :ref:`tag address <syntax-tagaddr>` :math:`a` equals :math:`F.\AMODULE.\MITAGS[x]`, then:

i. Push the values :math:`\X{exn}.\EIFIELDS` to the stack.

ii. Execute the instruction :math:`\BR~l`.

c. Else if :math:`\catch_1` is of the form :math:`\CATCHREF~x~l` and the :ref:`tag address <syntax-tagaddr>` :math:`a` equals :math:`F.\AMODULE.\MITAGS[x]`, then:
d. Else if :math:`\catch_1` is of the form :math:`\CATCHREF~x~l` and the :ref:`tag address <syntax-tagaddr>` :math:`a` equals :math:`F.\AMODULE.\MITAGS[x]`, then:

i. Push the values :math:`\X{exn}.\EIFIELDS` to the stack.

ii. Push the exception reference :math:`\REFEXNADDR~\X{ea}` to the stack.

iii. Execute the instruction :math:`\BR~l`.

d. Else if :math:`\catch_1` is of the form :math:`\CATCHALL~l`, then:
e. Else if :math:`\catch_1` is of the form :math:`\CATCHALL~l`, then:

i. Execute the instruction :math:`\BR~l`.

e. Else if :math:`\catch_1` is of the form :math:`\CATCHALLREF~l`, then:
f. Else if :math:`\catch_1` is of the form :math:`\CATCHALLREF~l`, then:

i. Push the exception reference :math:`\REFEXNADDR~\X{ea}` to the stack.

ii. Execute the instruction :math:`\BR~l`.

f. Else:
g. Else:

1. Push the modified handler :math:`\HANDLER_n\{{\catch'}^\ast\}` back to the stack.

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