Crash report

What happened?

This snippet causes a segfault on current main:

importtypeslst= []classX:def__repr__(self):lst.clear()return"x"lst+= [X(),1]ga=types.GenericAlias(int,lst)print(repr(ga))

This is because thega_repr_items_list() function does not properly handle the case where the list is mutated while we're iterating over it.

Similar to#143635 but a distinct code path.

CPython versions tested on:

CPython main branch, 3.14

Operating systems tested on:

macOS

Output from running 'python -VV' on the command line:

Python 3.15.0a4+ (heads/main:1857a40807d, Jan 13 2026, 19:01:52) [Clang 15.0.0 (clang-1500.3.9.4)]