runtime: add trivial stack traces to exceptions

backend.native/tests/build.gradle

@@ -90,7 +90,8 @@ abstract class KonanTest extends DefaultTask {
         println "${bcFile.absolutePath} -> ${outputFile.absolutePath}"
         println "tool: ${llvmLlc}"
         project.exec {
-            commandLine "${llvmLlc}", "-o", "${outputFile.absolutePath}" , "${bcFile}"
+            commandLine "${llvmLlc}", "-o", "${outputFile.absolutePath}" , "${bcFile}",
+                    '-disable-fp-elim' // currently required for stack traces
         }
         return outputFile
     }

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

@@ -10,9 +10,9 @@ private fun Konan_start(args: Array<String>) {
         main(args)
 
     } catch (e: Throwable) {
-        // TODO: Remove .toString() when println is more capable, 
-        // and may be add some more info.
+        // TODO: may be add some more info.
         print("Uncaught exception from Kotlin's main: ")
-        println(e.toString())
+        e.printStackTrace()
+        // TODO: should exit with non-zero code.
     }
 }

runtime/src/main/cpp/Arrays.cpp

@@ -19,7 +19,7 @@ KRef Kotlin_Array_get(const ArrayHeader* obj, KInt index) {
   return *ArrayAddressOfElementAt(obj, index);
 }
 
-void Kotlin_Array_set(ArrayHeader* obj, KInt index, KRef value) {
+void Kotlin_Array_set(ArrayHeader* obj, KInt index, KConstRef value) {
   if (static_cast<uint32_t>(index) >= obj->count_) {
     ThrowArrayIndexOutOfBoundsException();
   }

runtime/src/main/cpp/Exceptions.cpp

@@ -1,5 +1,10 @@
+#include <execinfo.h>
+#include <stdlib.h>
+#include <string.h>
+
 #include "Assert.h"
 #include "Exceptions.h"
+#include "Natives.h"
 #include "Types.h"
 
 class KotlinException {
@@ -16,10 +21,54 @@ class KotlinException {
   };
 };
 
+// TODO: it seems to be very common case; does C++ std library provide something like this?
+class AutoFree {
+ private:
+  void* mem_;
+
+ public:
+  AutoFree(void* mem): mem_(mem) {}
+
+  ~AutoFree() {
+    free(mem_);
+  }
+};
+
+// TODO: this method ignores the encoding
+KString CreateKotlinStringFromCString(const char* str) {
+  int32_t length = strlen(str);
+  ArrayHeader* result = ArrayContainer(theStringTypeInfo, length).GetPlace();
+  memcpy(
+      ByteArrayAddressOfElementAt(result, 0),
+      str, length);
+  return result;
+}
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+// TODO: this implementation is just a hack, e.g. the result is inexact;
+// however it is better to have an inexact stacktrace than not to have any.
+KArrayRef GetCurrentStackTrace() {
+  const int maxSize = 32;
+  void* buffer[maxSize];
+
+  int size = backtrace(buffer, maxSize);
+  char** symbols = backtrace_symbols(buffer, size);
+  RuntimeAssert(symbols != nullptr, "Not enough memory to retrieve the stacktrace");
+
+  AutoFree autoFree(symbols);
+  KArrayRef result = AllocArrayInstance(theArrayTypeInfo, SCOPE_GLOBAL, size);
+
+  for (int i = 0; i < size; ++i) {
+    KString symbol = CreateKotlinStringFromCString(symbols[i]);
+    Kotlin_Array_set(result, i, symbol);
+  }
+
+  return result;
+}
+
 void ThrowException(KRef exception) {
   RuntimeAssert(exception != nullptr && IsInstance(exception, theThrowableTypeInfo),
                 "Throwing something non-throwable");

runtime/src/main/cpp/Exceptions.h

@@ -7,6 +7,9 @@
 extern "C" {
 #endif
 
+// Returns current stacktrace as Array<String>.
+KArrayRef GetCurrentStackTrace();
+
 // Throws arbitrary exception.
 void ThrowException(KRef exception);
 

runtime/src/main/cpp/Natives.cpp

@@ -180,4 +180,8 @@ KString Kotlin_String_subSequence(KString thiz, KInt startIndex, KInt endIndex)
   return result;
 }
 
+KArrayRef Kotlin_getCurrentStackTrace() {
+  return GetCurrentStackTrace();
+}
+
 }  // extern "C"

runtime/src/main/cpp/Natives.h

@@ -37,8 +37,8 @@ inline const T* PrimitiveArrayAddressOfElementAt(
   return reinterpret_cast<const T*>(obj + 1) + index;
 }
 
-inline KRef* ArrayAddressOfElementAt(ArrayHeader* obj, KInt index) {
-  return reinterpret_cast<KRef*>(obj + 1) + index;
+inline KConstRef* ArrayAddressOfElementAt(ArrayHeader* obj, KInt index) {
+  return reinterpret_cast<KConstRef*>(obj + 1) + index;
 }
 
 inline const KRef* ArrayAddressOfElementAt(const ArrayHeader* obj, KInt index) {
@@ -60,7 +60,7 @@ KString Kotlin_Any_toString(KConstRef thiz);
 // TODO: those must be compiler intrinsics afterwards.
 ArrayHeader* Kotlin_Array_clone(const ArrayHeader* thiz);
 KRef Kotlin_Array_get(const ArrayHeader* thiz, KInt index);
-void Kotlin_Array_set(ArrayHeader* thiz, KInt index, KRef value);
+void Kotlin_Array_set(ArrayHeader* thiz, KInt index, KConstRef value);
 KInt Kotlin_Array_getArrayLength(const ArrayHeader* thiz);
 
 ArrayHeader* Kotlin_ByteArray_clone(const ArrayHeader* thiz);
@@ -98,6 +98,8 @@ KString Kotlin_String_plusImpl(KString thiz, KString other);
 KInt Kotlin_String_getStringLength(KString thiz);
 KString Kotlin_String_subSequence(KString thiz, KInt startIndex, KInt endIndex);
 
+KArrayRef Kotlin_getCurrentStackTrace();
+
 #ifdef __cplusplus
 }
 #endif

runtime/src/main/cpp/Types.h

@@ -15,6 +15,7 @@ typedef float   KFloat;
 typedef double  KDouble;
 
 typedef ObjHeader* KRef;
+typedef ArrayHeader* KArrayRef;
 typedef const ObjHeader* KConstRef;
 typedef const ArrayHeader* KString;
 

runtime/src/main/kotlin/kotlin/Throwable.kt

@@ -8,16 +8,35 @@ package kotlin
  */
 @ExportTypeInfo("theThrowableTypeInfo")
 public open class Throwable(open val message: String?, open val cause: Throwable?) {
+
     constructor(message: String?) : this(message, null)
 
     constructor(cause: Throwable?) : this(cause?.toString(), cause)
 
     constructor() : this(null, null)
 
+    private val stacktrace: Array<String> = getCurrentStackTrace()
+
+    fun printStackTrace() {
+        println(this.toString())
+        for (element in stacktrace) {
+            println("        at " + element)
+        }
+
+        this.cause?.printEnclosedStackTrace(this)
+    }
+
+    private fun printEnclosedStackTrace(enclosing: Throwable) {
+        // TODO: should skip common stack frames
+        print("Caused by: ")
+        this.printStackTrace()
+    }
+
     override fun toString(): String {
-        /* enable, once codegen is improved.
-        val s = "Throwable"
-        return if (message != null) s + ": " + message.toString() else s */
-        return "Throwable"
+        val s = "Throwable" // TODO: should be class name
+        return if (message != null) s + ": " + message.toString() else s
     }
 }
+
+@SymbolName("Kotlin_getCurrentStackTrace")
+private external fun getCurrentStackTrace(): Array<String>