EIP-3978: Gas refunds on reverts


  Ethereum Improvement Proposals
        
        
          
            
              
            
          
        

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      🚧 Stagnant
    
    
    
    
    
      Standards Track: Core
    
  
  
    
      EIP-3978: Gas refunds on reverts
    
    
      
        
      
    
    
      
        
      
    
  

  Reprice reverted SSTORE/CREATE/SELFDESTRUCT/LOGX operations gas via gas refund mechanism

  	Authors	Anton Bukov (@k06a), Mikhail Melnik (@ZumZoom)
	Created	2021-09-16
	Discussion Link	https://ethereum-magicians.org/t/eip-3978-gas-refunds-on-reverts/7071/
	Requires	

  EIP-2929




  


  

  
    Table of Contents

    	Abstract
	Motivation
	Specification
	Rationale
	Backwards Compatibility
	Test Cases
	Reference Implementation
	Security Considerations
	Copyright



  


  
      
      
         Abstract
      
      
    


For reverted state modification operations, keep access cost, but refund modification cost.

  
    
      
      
         Motivation
      
      
    


Reverting a transaction, or any of its sub-calls, drops any state modifications that happened inside.
But now, users are being charged for the dropped modifications as if they persisted.


Since EIP-3298, the gas refund mechanism works for storage restores only inside the same transaction. But on revert, the gas refund is not increased; it is completely erased.
It can even be cheaper to transfer tokens back at the end of a transaction instead of reverting, to keep the existing gas refund.
This should be changed.


	Reverted SSTORE deserves to be repriced to SLOAD gas (100 gas)
	Reverted LOG0, LOG1, LOG2, LOG3 and LOG4 deserve to be repriced to 100 gas
	Reverted CALL with value (positive_value_cost = 9,000 gas) deserves to be repriced to 100 gas
	Reverted CALL with value and account creation (value_to_empty_account_cost = 25,000 gas) deserves to be repriced to 100 gas
	Reverted CREATE and CREATE2 (32,000 gas) deserve to be repriced to 100 gas
	Reverted SELFDESTRUCT (5,000 or 25,000 gas) deserves to be repriced to 100 gas



Moreover, it seems fair to charge CREATE and CREATE2 operations 32,000 fix price conditionally only if returned bytecode is not empty.

  
    
      
      
         Specification
      
      
    

For each callframe, track revert_gas_refund, initially 0.


The set of operations that modify revert_gas_refund are:

	SSTORE
	LOG0, LOG1, LOG2, LOG3, LOG4
	CALL
	CREATE, CREATE2
	SELFDESTRUCT



They increase revert_gas_refund as follows:

call.revert_gas_refund += operation.gas - WARM_STORAGE_READ_COST





And in case of revert let’s use this value instead of just erasing gas_refund:

if (call.reverted) {
    // existing behavior
    tx.gas_refund -= call.gas_refund;
    
    // New behavior added to existing according to the EIP-3978
    tx.gas_refund += call.revert_gas_refund;
}




  
    
      
      
         Rationale
      
      
    


Gas should reflect the cost of use.
The revert cost reflects the cost of access during execution, but not the cost of modification.

  
    
      
      
         Backwards Compatibility
      
      
    


No known backward incompatibilities.

  
    
      
      
         Test Cases
      
      
    


TBD

  
    
      
      
         Reference Implementation
      
      
    


TBD

  
    
      
      
         Security Considerations
      
      
    


TBD

  
    
      
      
         Copyright
      
      
    

Copyright and related rights waived via CC0.


  Citation

  Please cite this document as:

  
  Anton Bukov (@k06a), Mikhail Melnik (@ZumZoom), "EIP-3978: Gas refunds on reverts [DRAFT]," Ethereum Improvement Proposals, no. 3978, September 2021. [Online serial]. Available: https://eips.ethereum.org/EIPS/eip-3978.






      
    
  

  

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