fix(evm): rescue gas before inspector callback to preserve remaining gas#171
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fix(evm): rescue gas before inspector callback to preserve remaining gas#171
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…ue_gas GasInspector::call_end (revm) calls gas.spend_all() on error results such as OutOfGas. This is called from frame_end in inspect_frame_run and inspect_frame_init, before frame_return_result has a chance to call rescue_gas(). The rescue_gas mechanism saves the remaining gas of a frame halted by MegaETH's additional limits (e.g. state growth limit) so it can be refunded to the sender in last_frame_result. With the inspector path, spend_all() zeroes gas.remaining() first, so rescue_gas() reads 0 and the refund is lost. This causes different gas_used values compared to the non-inspector path, resulting in a receipts root mismatch when validating blocks. Fix: save gas.remaining() before calling frame_end, then restore it afterwards if the inspector callback reduced it. The inspector still receives the unmodified (pre-spend_all) gas value for its callbacks, which is fine since GasInspector computes last_gas_cost from the delta between step() and step_end() readings rather than from the final remaining value.
flyq
approved these changes
Feb 27, 2026
Move rescue_gas to happen before the inspector's frame_end callback instead of saving/restoring gas around it. This is structurally correct because TX-level limit exceeds are always detected during execution, never newly discovered in before_frame_return_result. - Add try_rescue_gas method on AdditionalLimit that checks check_limit() - Call try_rescue_gas in after_frame_run and frame_init (before_frame_init early-return path) - Remove rescue_gas from before_frame_return_result - Remove save/restore gas pattern from inspect_frame_run and inspect_frame_init - Add tests with GasSpendingInspector covering both inspect_frame_init and inspect_frame_run paths
Troublor
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Summary
Move
rescue_gasto happen before the inspector'sframe_endcallback instead of saving/restoring gas around it.This prevents inspectors like
TracerEip3155(which callsGas::spend_all()on error results incall_end) from zeroinggas.remaining()before rescue_gas captures it.Changes
try_rescue_gasmethod onAdditionalLimitthat checkscheck_limit()and rescues gas if a TX-level limit was exceededtry_rescue_gasinafter_frame_run(coversframe_runandinspect_frame_runpaths) and inframe_init(before_frame_initearly-return path)rescue_gasfrombefore_frame_return_result— just mark the result as exceeding limitinspect_frame_runandinspect_frame_initGasSpendingInspectortest inspector and two tests covering bothinspect_frame_initandinspect_frame_runpaths