move exception handler deeper in the EVM

nimbus/vm/computation.nim

@@ -167,6 +167,24 @@ proc transferBalance(computation: BaseComputation, opCode: static[Op]) =
       db.subBalance(computation.msg.sender, computation.msg.value)
       db.addBalance(computation.msg.storageAddress, computation.msg.value)
 
+template continuation*(comp: BaseComputation, body: untyped) =
+  var tmpNext = comp.nextProc
+  comp.nextProc = proc() =
+    body
+    tmpNext()
+
+proc postExecuteVM(computation: BaseComputation) =
+  if computation.isSuccess and computation.msg.isCreate:
+    let fork = computation.getFork
+    let contractFailed = not computation.writeContract(fork)
+    if contractFailed and fork == FkHomestead:
+      computation.setError(&"writeContract failed, depth={computation.msg.depth}", true)
+
+  if computation.isSuccess:
+    computation.commit()
+  else:
+    computation.rollback()
+
 proc executeOpcodes*(computation: BaseComputation) {.gcsafe.}
 
 proc applyMessage*(computation: BaseComputation, opCode: static[Op]) =
@@ -182,25 +200,9 @@ proc applyMessage*(computation: BaseComputation, opCode: static[Op]) =
   if computation.gasMeter.gasRemaining < 0:
     computation.commit()
     return
-    
-  let fork = computation.getFork
-  
-  try:
-    if not computation.execPrecompiles(fork):
-      executeOpcodes(computation)
-  except:
-    let msg = getCurrentExceptionMsg()
-    computation.setError(&"applyMessage Error msg={msg}, depth={computation.msg.depth}", true)
 
-  if computation.isSuccess and computation.msg.isCreate:    
-    let contractFailed = not computation.writeContract(fork)
-    if contractFailed and fork == FkHomestead:
-      computation.setError(&"writeContract failed, depth={computation.msg.depth}", true)
-
-  if computation.isSuccess:
-    computation.commit()
-  else:
-    computation.rollback()
+  executeOpcodes(computation)
+  postExecuteVM(computation)
 
 proc addChildComputation*(computation: BaseComputation, child: BaseComputation) =
   if child.isError:

nimbus/vm/interpreter_dispatch.nim

@@ -231,14 +231,23 @@ proc opTableToCaseStmt(opTable: array[Op, NimNode], computation: NimNode): NimNo
 
   # Wrap the case statement in while true + computed goto
   result = quote do:
-    if `computation`.tracingEnabled:
-      `computation`.prepareTracer()
-    `computation`.instr = `computation`.code.next()
-    while true:
-      {.computedGoto.}
-      # TODO lots of macro magic here to unravel, with chronicles...
-      # `computation`.logger.log($`computation`.stack & "\n\n", fgGreen)
-      `result`
+    try:
+      let fork = `computation`.getFork
+      if `computation`.execPrecompiles(fork):
+        return
+
+      if `computation`.tracingEnabled:
+        `computation`.prepareTracer()
+      `computation`.instr = `computation`.code.next()
+      while true:
+        {.computedGoto.}
+        # TODO lots of macro magic here to unravel, with chronicles...
+        # `computation`.logger.log($`computation`.stack & "\n\n", fgGreen)
+        `result`
+    except:
+      let msg = getCurrentExceptionMsg()
+      let errorMsg = "Opcode Dispatch Error msg=" & msg & ", depth=" & $computation.msg.depth
+      `computation`.setError(errorMsg, true)
 
 macro genFrontierDispatch(computation: BaseComputation): untyped =
   result = opTableToCaseStmt(FrontierOpDispatch, computation)

nimbus/vm_types.nim

@@ -67,6 +67,7 @@ type
     dbsnapshot*:            Snapshot
     instr*:                 Op
     opIndex*:               int
+    nextProc*:              proc()
 
   Error* = ref object
     info*:                  string

tests/test_vm_json.nim

@@ -56,11 +56,8 @@ proc testFixture(fixtures: JsonNode, testStatusIMPL: var TestStatus) =
                                   createAddress = toAddress))
 
   var computation = newBaseComputation(vmState, header.blockNumber, message)
-  try:
-    computation.executeOpcodes()
-  except VMError:
-    computation.error = Error(info: getCurrentExceptionMsg())
-
+  computation.executeOpcodes()
+  
   if not fixture{"post"}.isNil:
     # Success checks
     check(not computation.isError)