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import { logUtils } from '@0x/utils';
import { OpCode, StructLog } from 'ethereum-types';
import * as _ from 'lodash';
import { EvmCallStack } from './types';
import { utils } from './utils';
/**
* Converts linear trace to a call stack by following calls and returns
* @param structLogs Linear trace
* @param startAddress The address of initial context
*/
export function getRevertTrace(structLogs: StructLog[], startAddress: string): EvmCallStack {
const evmCallStack: EvmCallStack = [];
const addressStack = [startAddress];
if (_.isEmpty(structLogs)) {
return [];
}
const normalizedStructLogs = utils.normalizeStructLogs(structLogs);
// tslint:disable-next-line:prefer-for-of
for (let i = 0; i < normalizedStructLogs.length; i++) {
const structLog = normalizedStructLogs[i];
if (structLog.depth !== addressStack.length - 1) {
throw new Error("Malformed trace. Trace depth doesn't match call stack depth");
}
// After that check we have a guarantee that call stack is never empty
// If it would: callStack.length - 1 === structLog.depth === -1
// That means that we can always safely pop from it
if (utils.isCallLike(structLog.op)) {
const currentAddress = _.last(addressStack) as string;
const jumpAddressOffset = 1;
const newAddress = utils.getAddressFromStackEntry(
structLog.stack[structLog.stack.length - jumpAddressOffset - 1],
);
// Sometimes calls don't change the execution context (current address). When we do a transfer to an
// externally owned account - it does the call and immediately returns because there is no fallback
// function. We manually check if the call depth had changed to handle that case.
const nextStructLog = normalizedStructLogs[i + 1];
if (nextStructLog.depth !== structLog.depth) {
addressStack.push(newAddress);
evmCallStack.push({
address: currentAddress,
structLog,
});
}
} else if (utils.isEndOpcode(structLog.op) && structLog.op !== OpCode.Revert) {
// Just like with calls, sometimes returns/stops don't change the execution context (current address).
const nextStructLog = normalizedStructLogs[i + 1];
if (_.isUndefined(nextStructLog) || nextStructLog.depth !== structLog.depth) {
evmCallStack.pop();
addressStack.pop();
}
if (structLog.op === OpCode.SelfDestruct) {
// After contract execution, we look at all sub-calls to external contracts, and for each one, fetch
// the bytecode and compute the coverage for the call. If the contract is destroyed with a call
// to `selfdestruct`, we are unable to fetch it's bytecode and compute coverage.
// TODO: Refactor this logic to fetch the sub-called contract bytecode before the selfdestruct is called
// in order to handle this edge-case.
logUtils.warn(
"Detected a selfdestruct. We currently do not support that scenario. We'll just skip the trace part for a destructed contract",
);
}
} else if (structLog.op === OpCode.Revert) {
evmCallStack.push({
address: _.last(addressStack) as string,
structLog,
});
return evmCallStack;
} else if (structLog.op === OpCode.Create) {
// TODO: Extract the new contract address from the stack and handle that scenario
logUtils.warn(
"Detected a contract created from within another contract. We currently do not support that scenario. We'll just skip that trace",
);
return [];
} else {
if (structLog !== _.last(normalizedStructLogs)) {
const nextStructLog = normalizedStructLogs[i + 1];
if (nextStructLog.depth === structLog.depth) {
continue;
} else if (nextStructLog.depth === structLog.depth - 1) {
addressStack.pop();
} else {
throw new Error('Malformed trace. Unexpected call depth change');
}
}
}
}
if (evmCallStack.length !== 0) {
logUtils.warn('Malformed trace. Call stack non empty at the end. (probably out of gas)');
}
return [];
}
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