feat(spec-specs): SSTORE 0 to x to 0 refunds state gas to reservoir

spencer-tb · spencer-tb · commit 162802007c90 · 2026-04-19T14:11:39.000+02:00
diff --git a/src/ethereum/forks/amsterdam/vm/__init__.py b/src/ethereum/forks/amsterdam/vm/__init__.py
@@ -173,6 +173,7 @@ class Evm:
     accessed_storage_keys: Set[Tuple[Address, Bytes32]]
     regular_gas_used: Uint = Uint(0)
     state_gas_used: Uint = Uint(0)
+    state_gas_refund: Uint = Uint(0)
 
 
 def incorporate_child_on_success(evm: Evm, child_evm: Evm) -> None:
@@ -196,6 +197,7 @@ def incorporate_child_on_success(evm: Evm, child_evm: Evm) -> None:
     evm.accessed_storage_keys.update(child_evm.accessed_storage_keys)
     evm.regular_gas_used += child_evm.regular_gas_used
     evm.state_gas_used += child_evm.state_gas_used
+    evm.state_gas_refund += child_evm.state_gas_refund
 
 
 def incorporate_child_on_error(
@@ -210,6 +212,12 @@ def incorporate_child_on_error(
     that spilled into `gas_left`, is restored to the parent's reservoir and
     the child's `state_gas_used` is not accumulated.
 
+    Inline state-gas refunds (SSTORE 0 to x to 0) accumulated in the child or
+    its successful descendants are dropped: `state_gas_refund` is subtracted
+    from the amount returned to the parent's reservoir and is not propagated.
+    This matches `refund_counter`'s error-path behavior and keeps the refund
+    frame-scoped.
+
     Parameters
     ----------
     evm :
@@ -219,5 +227,9 @@ def incorporate_child_on_error(
 
     """
     evm.gas_left += child_evm.gas_left
-    evm.state_gas_left += child_evm.state_gas_used + child_evm.state_gas_left
+    evm.state_gas_left += (
+        child_evm.state_gas_used
+        + child_evm.state_gas_left
+        - child_evm.state_gas_refund
+    )
     evm.regular_gas_used += child_evm.regular_gas_used
diff --git a/src/ethereum/forks/amsterdam/vm/instructions/storage.py b/src/ethereum/forks/amsterdam/vm/instructions/storage.py
@@ -127,13 +127,16 @@ def sstore(evm: Evm) -> None:
         if original_value == new_value:
             # Storage slot being restored to its original value
             if original_value == 0:
-                # Slot was originally empty and was SET earlier.
-                # Refund state gas and the write cost (the write
-                # is cancelled — clients batch trie writes to slot
-                # boundaries, so no IO actually happens).
+                # Slot set then cleared: refund state gas to the
+                # reservoir and regular cost via refund_counter. The
+                # state-gas credit is tracked in state_gas_refund so it
+                # can be unwound on revert or exceptional halt of this
+                # frame or any ancestor that inherits it.
+                evm.state_gas_left += state_gas_storage_set
+                evm.state_gas_used -= state_gas_storage_set
+                evm.state_gas_refund += state_gas_storage_set
                 evm.refund_counter += int(
-                    state_gas_storage_set
-                    + GAS_STORAGE_UPDATE
+                    GAS_STORAGE_UPDATE
                     - GAS_COLD_STORAGE_ACCESS
                     - GAS_WARM_ACCESS
                 )
diff --git a/src/ethereum/forks/amsterdam/vm/instructions/system.py b/src/ethereum/forks/amsterdam/vm/instructions/system.py
@@ -124,6 +124,7 @@ def generic_create(
         # No account created — refund state gas to reservoir.
         evm.state_gas_left += create_account_state_gas
         evm.state_gas_used -= create_account_state_gas
+        evm.state_gas_refund += create_account_state_gas
         push(evm.stack, U256(0))
         return
 
@@ -138,6 +139,7 @@ def generic_create(
         # Address collision — no account created, refund state gas.
         evm.state_gas_left += create_account_state_gas
         evm.state_gas_used -= create_account_state_gas
+        evm.state_gas_refund += create_account_state_gas
         push(evm.stack, U256(0))
         return
 
@@ -170,6 +172,7 @@ def generic_create(
         # No account created, refund parent's CREATE state gas.
         evm.state_gas_left += create_account_state_gas
         evm.state_gas_used -= create_account_state_gas
+        evm.state_gas_refund += create_account_state_gas
         evm.return_data = child_evm.output
         push(evm.stack, U256(0))
     else:
