From 7ab921669bf52c1cb2d43350b2cccc8efe91bdbd Mon Sep 17 00:00:00 2001
From: Alex Browne <stephenalexbrowne@gmail.com>
Date: Thu, 14 Jun 2018 13:58:28 -0700
Subject: Introduce subprovider for printing revert stack traces

---
 packages/sol-cov/src/revert_trace.ts | 82 ++++++++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)
 create mode 100644 packages/sol-cov/src/revert_trace.ts

(limited to 'packages/sol-cov/src/revert_trace.ts')

diff --git a/packages/sol-cov/src/revert_trace.ts b/packages/sol-cov/src/revert_trace.ts
new file mode 100644
index 000000000..59edf5db4
--- /dev/null
+++ b/packages/sol-cov/src/revert_trace.ts
@@ -0,0 +1,82 @@
+import { logUtils } from '@0xproject/utils';
+import { OpCode, StructLog } from 'ethereum-types';
+
+import * as _ from 'lodash';
+
+import { EvmCallStack, EvmCallStackEntry } from './types';
+import { utils } from './utils';
+
+export function getRevertTrace(structLogs: StructLog[], startAddress: string): EvmCallStack {
+    const evmCallStack: EvmCallStack = [];
+    let currentAddress = 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 !== evmCallStack.length) {
+            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
+
+        // TODO(albrow): split out isCallLike and isEndOpcode
+        if (utils.isCallLike(structLog.op)) {
+            const evmCallStackEntry = _.last(evmCallStack) as EvmCallStackEntry;
+            const prevAddress = _.isUndefined(evmCallStackEntry) ? currentAddress : evmCallStackEntry.address;
+            const jumpAddressOffset = 1;
+            currentAddress = utils.getAddressFromStackEntry(
+                structLog.stack[structLog.stack.length - jumpAddressOffset - 1],
+            );
+
+            if (structLog === _.last(normalizedStructLogs)) {
+                throw new Error('Malformed trace. CALL-like opcode can not be the last one');
+            }
+            // 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) {
+                evmCallStack.push({
+                    address: prevAddress,
+                    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();
+            }
+            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. Sol-cov currently doesn't support that scenario. We'll just skip the trace part for a destructed contract",
+                );
+            }
+        } else if (structLog.op === OpCode.Revert) {
+            evmCallStack.push({
+                address: currentAddress,
+                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. Sol-cov currently doesn't support that scenario. We'll just skip that trace",
+            );
+            return [];
+        }
+    }
+    if (evmCallStack.length !== 0) {
+        logUtils.warn('Malformed trace. Call stack non empty at the end. (probably out of gas)');
+    }
+    return [];
+}
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