instruction improvements by youknowone · Pull Request #6829 · RustPython/RustPython

🌐 Web query:

CPython 3.14 FOR_ITER stack_effect jump parameter dis module

💡 Result:

Short answer: dis.stack_effect(opcode.FOR_ITER, oparg, jump=...) — jump=True = jump taken (iterator exhausted) → stack effect 0; jump=False = fall-through (next value produced) → stack effect +1; jump=None (default) → returns the maximal effect (+1). See the dis docs. [1][2]

Sources:

• dis.stack_effect documentation. [1]
• FOR_ITER opcode description (notes on popping behavior and changes across versions). [2]

🌐 Web query:

CPython 3.14 FOR_ITER opcode behavior stack semantics

💡 Result:

Short answer — semantics in CPython 3.14:

• Input stack before FOR_ITER: [..., iter] (iterator object at TOS).
• Execution:
  • If next(iter) yields a value: FOR_ITER pushes that value, leaving the iterator beneath it. Resulting stack: [..., iter, value].
  • If iterator is exhausted (StopIteration): FOR_ITER removes the iterator from the stack (pop) and jumps forward by the instruction’s oparg (no value pushed).
• So the two possible “after” states are [..., iter, value] (loop body runs) or [...] (loop exit — iterator removed and jump). This is the traditional FOR_ITER behaviour used by for-loops and comprehensions; 3.14 continues that semantics (with related bytecode/iterator machinery changes such as adding POP_ITER/virtual iterators). (stackoverflow.com)

If you want the exact C implementation lines in ceval.c for 3.14 I can fetch and cite them.

Citations:

• 1: https://stackoverflow.com/questions/54760523/how-to-find-implementation-of-for-control-flow-construct-in-python?utm_source=openai

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