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Stack map frames: append mutates earlier frames' locals · case 04

Frames recorded before an append frame suddenly list the appended locals too.

Member previewVariant 4 · 3 implementations · 9 checks per implementation

Case contract

Expand compressed stack map frames. Types: 0-63 same (delta = type), 64-127 same_locals_1_stack_item (delta = type - 64, one stack item), 128-246 reserved (["ClassFormatError", index]), 247 extended one item [247, delta, item], 248-250 chop 251-type locals [t, delta], 251 same extended [251, delta], 252-254 append type-251 locals [t, delta, items...], 255 full [255, delta, locals, stack]. The first frame's offset is its delta; each later offset is previous + delta + 1. Chopping more locals than exist is an error. Return [offset, locals, stack] for every frame; each frame's locals are an independent snapshot.

Why this case matters

Verifiers reconstruct per-offset types from this compressed encoding; any slip mistypes locals.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression: every compressed frame kind	`[[5, ["I", "Object", "F"], []], [16, ["I", "Object", "F"], ["I"]], [20, ["I", "Object", "F"], []], [23, ["I"], []], [324, ["I"], []], [326, ["I"], ["Object", "J"]]]`	`[[5, ["I", "Object"], []], [16, ["I", "Object"], ["I"]], [20, ["I", "Object", "F"], []], [23, ["I"], []], [324, ["I"], []], [326, ["I"], ["Object", "J"]]]`	Failed

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