René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"SystemExit.code is read-only; CPython allows assignment","articleBody":"# Summary\n\n`SystemExit.code` is read-only in RustPython, but it is a writable member in CPython:\n\n```python\nclass MyExit(SystemExit):\n    pass\n\nm = MyExit(1)\nm.code = 42\n# AttributeError: attribute 'code' of 'MyExit' objects is not writable\n```\n\nCPython 3.14.2 accepts the assignment (`code` is a `PyMemberDef` on `SystemExit`, i.e. a writable data descriptor; same as assigning on `SystemExit` itself). Verified on `main` @ 7044fdcc8.\n\nNote the neighboring exception members are already correct — e.g. `OSError().errno = 5` works — it's specifically `SystemExit.code` that was made read-only.\n\n# Cause\n\n`crates/vm/src/exceptions.rs:965`:\n\n```rust\n\"code\" =\u003e ctx.new_readonly_getset(\"code\", excs.system_exit, system_exit_code),\n```\n\nShould be a getset with a setter (or member-style storage) writing through to the instance, like the `errno`/`filename`/etc. attributes on `OSError`. `sys.exit()`/`SystemExit.__init__` derive `code` from `args`, and CPython keeps `code` as an independent writable slot after construction.\n\n---\n*Found while running synthetic benchmark/compat suites; researched and reported by Claude on behalf of @youknowone.*\n","author":{"url":"https://github.com/youknowone","@type":"Person","name":"youknowone"},"datePublished":"2026-07-06T15:34:35.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/8230/RustPython/issues/8230"}