https://github.com/python/cpython/commit/10eac0269bce4e2ba575e5b549d3dd9a6da9349a commit: 10eac0269bce4e2ba575e5b549d3dd9a6da9349a branch: main author: Irit Katriel <[email protected]> committer: iritkatriel <[email protected]> date: 2024-06-05T16:28:47+01:00 summary:
gh-119786: add links to code in exception handling doc (#120077) files: M InternalDocs/exception_handling.md diff --git a/InternalDocs/exception_handling.md b/InternalDocs/exception_handling.md index 22d9c3bf7933f1..ec09e0769929fa 100644 --- a/InternalDocs/exception_handling.md +++ b/InternalDocs/exception_handling.md @@ -67,14 +67,18 @@ handler located at label `L1`. Handling Exceptions ------------------- -At runtime, when an exception occurs, the interpreter looks up -the offset of the current instruction in the exception table. If -it finds a handler, control flow transfers to it. Otherwise, the +At runtime, when an exception occurs, the interpreter calls +``get_exception_handler()`` in +[Python/ceval.c](https://github.com/python/cpython/blob/main/Python/ceval.c) +to look up the offset of the current instruction in the exception +table. If it finds a handler, control flow transfers to it. Otherwise, the exception bubbles up to the caller, and the caller's frame is checked for a handler covering the `CALL` instruction. This repeats until a handler is found or the topmost frame is reached. If no handler is found, the program terminates. During unwinding, -the traceback is constructed as each frame is added to it. +the traceback is constructed as each frame is added to it by +``PyTraceBack_Here()``, which is in +[Python/traceback.c](https://github.com/python/cpython/blob/main/Python/traceback.c). Along with the location of an exception handler, each entry of the exception table also contains the stack depth of the `try` instruction @@ -169,33 +173,12 @@ which is then encoded as: for a total of five bytes. +The code to construct the exception table is in ``assemble_exception_table()`` +in [Python/assemble.c](https://github.com/python/cpython/blob/main/Python/assemble.c). -Script to parse the exception table ------------------------------------ - -``` -def parse_varint(iterator): - b = next(iterator) - val = b & 63 - while b&64: - val <<= 6 - b = next(iterator) - val |= b&63 - return val -``` -``` -def parse_exception_table(code): - iterator = iter(code.co_exceptiontable) - try: - while True: - start = parse_varint(iterator)*2 - length = parse_varint(iterator)*2 - end = start + length - 2 # Present as inclusive, not exclusive - target = parse_varint(iterator)*2 - dl = parse_varint(iterator) - depth = dl >> 1 - lasti = bool(dl&1) - yield start, end, target, depth, lasti - except StopIteration: - return -``` +The interpreter's function to lookup the table by instruction offset is +``get_exception_handler()`` in +[Python/ceval.c](https://github.com/python/cpython/blob/main/Python/ceval.c). +The Python function ``_parse_exception_table()`` in +[Lib/dis.py](https://github.com/python/cpython/blob/main/Lib/dis.py) +returns the exception table content as a list of namedtuple instances. _______________________________________________ Python-checkins mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3/lists/python-checkins.python.org/ Member address: [email protected]
