Bug report

Bug description:

Bug report

Bug description:

In Modules/_io/bufferedio.c, the buffered_iternext function has a fast path that calls _buffered_readline directly to avoid method call overhead.
However, due to an incorrect type check, this fast path is never executed.

    tp = Py_TYPE(self);
    if (Py_IS_TYPE(tp, state->PyBufferedReader_Type) ||
        Py_IS_TYPE(tp, state->PyBufferedRandom_Type))

because Py_IS_TYPE will call Py_TYPE internally, will cause Py_TYPE(Py_TYPE(ob)) == type,
<class 'type'> != state->PyBufferedReader_Type

All iteration over buffered binary files is affected:

with open('data.txt', 'rb') as f:
    for line in f:
        process(line)

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Linked PRs

• gh-144380: Fix incorrect type check in buffered_iternext() #144381
• [3.14] gh-144380: Fix incorrect type check in buffered_iternext() (GH-144381) #144389
• [3.13] gh-144380: Fix incorrect type check in buffered_iternext() (GH-144381) #144390