[StdlibUnittest] Install our own handler for uncaught ObjC exceptions.

We don't want to be at the whims of the system on what to do with an
uncaught exception; we need to make sure its message gets printed to
stderr so that the parent process can check it.

(There's a bit of trickery here to see if the class looks like an
NSException; otherwise we lose the name of the exception and just get
the reason.)

stdlib/private/StdlibUnittest/CMakeLists.txt

@@ -3,7 +3,8 @@ set(swift_stdlib_unittest_module_depends
   SwiftPrivate SwiftPrivatePthreadExtras SwiftPrivateLibcExtras)
 set(swift_stdlib_unittest_framework_depends)
 set(swift_stdlib_unittest_private_link_libraries)
-set(swift_stdlib_unittest_compile_flags)
+set(swift_stdlib_unittest_compile_flags
+  "-Xfrontend" "-disable-objc-attr-requires-foundation-module")
 
 if(SWIFT_HOST_VARIANT MATCHES "${SWIFT_DARWIN_VARIANTS}")
   list(APPEND swift_stdlib_unittest_platform_sources

stdlib/private/StdlibUnittest/StdlibUnittest.swift.gyb

@@ -448,8 +448,24 @@ let _crashedPrefix = "CRASHED:"
 @_silgen_name("swift_stdlib_installTrapInterceptor")
 func _stdlib_installTrapInterceptor()
 
+@objc protocol _StdlibUnittestNSException {
+  optional var name: String { get }
+}
+
 func _childProcess() {
   _stdlib_installTrapInterceptor()
+  objc_setUncaughtExceptionHandler {
+    var stderr = _Stderr()
+    let maybeNSException = unsafeBitCast($0, to:_StdlibUnittestNSException.self)
+    if let name = maybeNSException.name {
+      print("*** [StdlibUnittest] Terminating due to uncaught exception " +
+        "\(name): \($0)",
+        to: &stderr)
+    } else {
+      print("*** [StdlibUnittest] Terminating due to uncaught exception: \($0)",
+        to: &stderr)      
+    }
+  }
   while let line = _stdlib_getline() {
     let parts = line._split(separator: ";")
     let testSuiteName = parts[0]

validation-test/stdlib/StdlibUnittestNSException.swift

@@ -0,0 +1,67 @@
+// RUN: %target-run-simple-swift 2>&1 | FileCheck %s
+// REQUIRES: executable_test
+// REQUIRES: objc_interop
+
+import StdlibUnittest
+import ObjectiveC
+import Foundation
+
+// Don't actually exit with a non-zero status, just say we're going to do it.
+_setTestSuiteFailedCallback() { print("abort()") }
+
+
+func raiseNSException() {
+  NSException(name: "Trogdor", reason: "Burnination", userInfo: nil).raise()
+}
+
+var TestSuiteCrashes = TestSuite("NSExceptionCrashes")
+
+TestSuiteCrashes.test("uncaught") {
+  print("uncaught")
+  raiseNSException()
+}
+// CHECK-LABEL: stdout>>> uncaught
+// CHECK: stderr>>> *** [StdlibUnittest] Terminating due to uncaught exception Trogdor: Burnination
+// CHECK: stderr>>> CRASHED: SIG
+// CHECK: the test crashed unexpectedly
+// CHECK: [     FAIL ] NSExceptionCrashes.uncaught
+
+TestSuiteCrashes.test("crashesAsExpected") {
+  print("crashesAsExpected")
+  expectCrashLater()
+  raiseNSException()
+}
+// CHECK-LABEL: stdout>>> crashesAsExpected
+// CHECK: stderr>>> *** [StdlibUnittest] Terminating due to uncaught exception Trogdor: Burnination
+// CHECK: stderr>>> OK: saw expected "crashed: sig
+// CHECK: [       OK ] NSExceptionCrashes.crashesAsExpected
+
+TestSuiteCrashes.test("crashesWithMessage")
+  .crashOutputMatches("libUnittest]")
+  .crashOutputMatches("Trogdor")
+  .crashOutputMatches("Burnination").code {
+  print("crashesWithMessage")
+  expectCrashLater()
+  raiseNSException()
+}
+// CHECK-LABEL: stdout>>> crashesWithMessage
+// CHECK: stderr>>> *** [StdlibUnittest] Terminating due to uncaught exception Trogdor: Burnination
+// CHECK: stderr>>> OK: saw expected "crashed: sig
+// CHECK: [       OK ] NSExceptionCrashes.crashesWithMessage
+
+TestSuiteCrashes.test("nonNSException")
+  .crashOutputMatches("countryside").code {
+  print("nonNSException")
+  expectCrashLater()
+  objc_exception_throw("countryside")
+}
+// CHECK-LABEL: stdout>>> nonNSException
+// CHECK: stderr>>> *** [StdlibUnittest] Terminating due to uncaught exception: countryside
+// CHECK: stderr>>> OK: saw expected "crashed: sig
+// CHECK: [       OK ] NSExceptionCrashes.nonNSException
+
+// CHECK: NSExceptionCrashes: Some tests failed, aborting
+// CHECK: abort()
+
+runAllTests()
+