LiveTests: Properly print unrecognized errors and wasm tags

A live test failing due to a too high failure rate reports sth. like:
  Observed failures:
      10x RuntimeError: memory access out of bounds
      9x Error: Timed out
      4x RuntimeError: float unrepresentable in integer range

If the runner did not include any line containing "Error:", these
failures would just not appear in the "Observed failures" (but they'd
still be included in the failure rate).

With this change the observed failures list will contain an extra entry
for failures without such "Error:"-line (if there is any).

An extra magic entry is added for uncaught wasm exceptions from the
exception-handling proposal. As these are opaque objects in JS, they
don't create a nice error message nor do they have a proper stack
trace.

Change-Id: I838857c0ec38c91a4085c61b1e9aae2f98b50daf
Reviewed-on: https://chrome-internal-review.googlesource.com/c/v8/fuzzilli/+/7967828
Auto-Submit: Matthias Liedtke <[email protected]>
Reviewed-by: Carl Smith <[email protected]>
Commit-Queue: Carl Smith <[email protected]>

Author: Liedtke

Tests/FuzzilliTests/LiveTests.swift

@@ -17,7 +17,7 @@ import XCTest
 
 class LiveTests: XCTestCase {
     enum ExecutionResult {
-        case failed(failureMessage: String?)
+        case failed(failureMessage: String)
         case succeeded
     }
 
@@ -142,9 +142,7 @@ class LiveTests: XCTestCase {
                     programs[i].program.storeToDisk(atPath: path.appendingPathComponent("failure_\(i).fzil").path)
                 }
                 failures += 1
-                if let message = message {
-                    failureMessages[message] = (failureMessages[message] ?? 0) + 1
-                }
+                failureMessages[message] = (failureMessages[message] ?? 0) + 1
             case .succeeded:
                 break
             }
@@ -180,6 +178,12 @@ class LiveTests: XCTestCase {
                     if line.contains("Error:") {
                         // Remove anything after a potential 2nd ":", which is usually testcase dependent content, e.g. "SyntaxError: Invalid regular expression: /ep{}[]Z7/: Incomplete quantifier"
                         signature = line.split(separator: ":")[0...1].joined(separator: ":")
+                    } else if line.contains("[object WebAssembly.Exception]") {
+                        // An uncaught thrown wasm tag results in an output like this in d8:
+                        //   undefined:0: [object WebAssembly.Exception]
+                        // Treat anything that contains the WebAssembly.Exception object as one
+                        // special signature.
+                        signature = "<Uncaught WebAssembly.Exception>"
                     }
                 }
 
@@ -193,7 +197,7 @@ class LiveTests: XCTestCase {
                     print(fuzzilProgram)
                 }
 
-                return .failed(failureMessage: signature)
+                return .failed(failureMessage: signature ?? "<Unrecognized error>")
             }
         } catch {
             XCTFail("Could not execute script: \(error)")