FA-90054 / Bytecode virtual machines / Member archive

Method descriptors: instance methods lose the this slot · case 04

Local 0 of instance methods is assigned to the first declared parameter.

Member previewVariant 4 · 3 implementations · 9 checks per implementation

Case contract

Parse a method descriptor "(args)ret". Field types: B C D F I J S Z, L<binary name>; with a non-empty name, and up to 255 leading "[" dimensions. V is allowed only as a non-array return type. Local-slot count: one extra slot for "this" unless static; J and D take two slots unless they are array element types. Return {args (readable names, "[]" per dimension), slots, ret} or ["ClassFormatError", position].

Why this case matters

Frame sizes and argument placement in bytecode VMs are derived from descriptors.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
instance method reserves this slot	`{"args": ["long", "double", "int", "int", "int", "int"], "ret": "long", "slots": 8}`	`{"args": ["long", "double", "int", "int", "int", "int"], "ret": "long", "slots": 9}`	Failed

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