Custom exception reporter. (#2604)

backend.native/tests/build.gradle

@@ -2036,6 +2036,13 @@ task extend_exception(type: RunKonanTest) {
     source = "runtime/exceptions/extend0.kt"
 }
 
+task custom_hook(type: RunStandaloneKonanTest) {
+    disabled = (project.testTarget == 'wasm32') // Uses exceptions.
+    goldValue = "value 42: Error\n"
+    expectedExitStatus = 1
+    source = "runtime/exceptions/custom_hook.kt"
+}
+
 task runtime_math_exceptions(type: RunKonanTest) {
     disabled = (project.testTarget == 'wasm32')
     source = "stdlib_external/numbers/MathExceptionTest.kt"

backend.native/tests/runtime/exceptions/custom_hook.kt

@@ -0,0 +1,22 @@
+/*
+ * Copyright 2010-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the LICENSE file.
+ */
+import kotlin.test.*
+
+import kotlin.native.concurrent.*
+
+fun main(args : Array<String>) {
+    assertFailsWith<InvalidMutabilityException> {
+        setUnhandledExceptionHook { _ -> println("wrong") }
+    }
+
+    val x = 42
+    val old = setUnhandledExceptionHook({
+        throwable: Throwable -> println("value $x: ${throwable::class.simpleName}")
+    }.freeze())
+
+    assertNull(old)
+
+    throw Error("an error")
+}

runtime/src/launcher/kotlin/konan/start.kt

@@ -12,18 +12,17 @@ import kotlin.native.internal.ExportForCppRuntime
 @SymbolName("EntryPointSelector")
 external fun EntryPointSelector(args: Array<String>)
 
+@SymbolName("OnUnhandledException")
+external private fun OnUnhandledException(throwable: Throwable)
+
 @ExportForCppRuntime
 private fun Konan_start(args: Array<String>): Int {
     try {
         EntryPointSelector(args)
-
         // Successfully finished:
         return 0
-
     } catch (e: Throwable) {
-        // TODO: may be add some more info.
-        print("Uncaught exception from Kotlin's main: ")
-        e.printStackTrace()
+        OnUnhandledException(e)
         return 1
     }
 }

runtime/src/main/cpp/Exceptions.cpp

@@ -58,6 +58,13 @@ class AutoFree {
   }
 };
 
+// RuntimeUtiks.kt
+extern "C" void ReportUnhandledException(KRef throwable);
+extern "C" void ExceptionReporterLaunchpad(KRef reporter, KRef throwable);
+
+KRef currentUnhandledExceptionHook = nullptr;
+int32_t currentUnhandledExceptionHookLock = 0;
+
 #if USE_GCC_UNWIND
 struct Backtrace {
   Backtrace(int count, int skip) : index(0), skipCount(skip) {
@@ -206,10 +213,24 @@ void ThrowException(KRef exception) {
 #endif
 }
 
-void ReportUnhandledException(KRef e);
+OBJ_GETTER(Kotlin_setUnhandledExceptionHook, KRef hook) {
+  RETURN_RESULT_OF(SwapRefLocked,
+    &currentUnhandledExceptionHook, currentUnhandledExceptionHook, hook, &currentUnhandledExceptionHookLock);
+}
 
-RUNTIME_NORETURN void TerminateWithUnhandledException(KRef e) {
-  ReportUnhandledException(e);
+void OnUnhandledException(KRef throwable) {
+  ObjHolder handlerHolder;
+  auto* handler = SwapRefLocked(&currentUnhandledExceptionHook, currentUnhandledExceptionHook, nullptr,
+     &currentUnhandledExceptionHookLock, handlerHolder.slot());
+  if (handler == nullptr) {
+    ReportUnhandledException(throwable);
+  } else {
+    ExceptionReporterLaunchpad(handler, throwable);
+  }
+}
+
+RUNTIME_NORETURN void TerminateWithUnhandledException(KRef throwable) {
+  OnUnhandledException(throwable);
   konan::abort();
 }
 

runtime/src/main/kotlin/kotlin/native/Runtime.kt

@@ -4,6 +4,9 @@
  */
 package kotlin.native
 
+import kotlin.native.concurrent.isFrozen
+import kotlin.native.concurrent.InvalidMutabilityException
+
 /**
  * Initializes Kotlin runtime for the current thread, if not inited already.
  */
@@ -23,4 +26,27 @@ public class IncorrectDereferenceException : RuntimeException {
     constructor() : super()
 
     constructor(message: String) : super(message)
-}
+}
+
+/**
+ * Typealias describing custom exception reporting hook.
+ */
+public typealias ReportUnhandledExceptionHook = Function1<Throwable, Unit>
+
+/**
+ * Install custom unhandled exception hook. Returns old hook, or null if it was not specified.
+ * Hook is invoked whenever there's uncaught exception reaching boundaries of the Kotlin world,
+ * i.e. top level main(), or when Objective-C to Kotlin call not marked with @Throws throws an exception.
+ * Hook must be a frozen lambda, so that it could be called from any thread/worker.
+ * Hook is invoked once, and is cleared afterwards, so that memory leak detection works as expected even
+ * with custom exception hooks.
+ */
+public fun setUnhandledExceptionHook(hook: ReportUnhandledExceptionHook): ReportUnhandledExceptionHook? {
+    if (!hook.isFrozen) {
+        throw InvalidMutabilityException("Unhandled exception hook must be frozen")
+    }
+    return setUnhandledExceptionHook0(hook)
+}
+
+@SymbolName("Kotlin_setUnhandledExceptionHook")
+external private fun setUnhandledExceptionHook0(hook: ReportUnhandledExceptionHook): ReportUnhandledExceptionHook?

runtime/src/main/kotlin/kotlin/native/internal/RuntimeUtils.kt

@@ -86,9 +86,18 @@ internal fun PrintThrowable(throwable: Throwable) {
 }
 
 @ExportForCppRuntime
-internal fun ReportUnhandledException(e: Throwable) {
+internal fun ReportUnhandledException(throwable: Throwable) {
     print("Uncaught Kotlin exception: ")
-    e.printStackTrace()
+    throwable.printStackTrace()
+}
+
+@ExportForCppRuntime
+internal fun ExceptionReporterLaunchpad(reporter: (Throwable) -> Unit, throwable: Throwable) {
+    try {
+        reporter(throwable)
+    } catch (t: Throwable) {
+        ReportUnhandledException(t)
+    }
 }
 
 @ExportForCppRuntime