Calling Kotlin from C++ runtime (#107)

* backend: support exporting Kotlin functions for C++ runtime

* runtime: implement several functions in Kotlin

* Throw{NullPointer,ArrayIndexOutOfBounds,ClassCast}Exception

* runtime: add literal declared in Kotlin as empty string

Also
* add corresponding test
* use empty string literal in strdedup2
  (however keep it disabled)

* fixup! runtime: add literal declared in Kotlin as empty string

* Review feedback: add more TheEmptyString() usages

Also improve string index checks in runtime

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/llvm/NameUtils.kt

@@ -4,16 +4,20 @@ import org.jetbrains.kotlin.descriptors.ClassDescriptor
 import org.jetbrains.kotlin.descriptors.ClassKind.*
 import org.jetbrains.kotlin.descriptors.FunctionDescriptor
 import org.jetbrains.kotlin.descriptors.PropertyDescriptor
+import org.jetbrains.kotlin.descriptors.annotations.AnnotationDescriptor
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.resolve.constants.StringValue
 import org.jetbrains.kotlin.resolve.descriptorUtil.fqNameSafe
 import org.jetbrains.kotlin.resolve.findOriginalTopMostOverriddenDescriptors
 import org.jetbrains.kotlin.types.KotlinType
 import org.jetbrains.kotlin.types.TypeUtils
+import org.jetbrains.kotlin.utils.addToStdlib.ifNotEmpty
 
 
 private val symbolNameAnnotation = FqName("konan.SymbolName")
 
+private val exportForCppRuntimeAnnotation = FqName("konan.internal.ExportForCppRuntime")
+
 fun typeToHashString(type: KotlinType): String {
     if (TypeUtils.isTypeParameter(type)) return "GENERIC"
 
@@ -52,18 +56,32 @@ internal val FunctionDescriptor.symbolName: String
     get() {
         this.annotations.findAnnotation(symbolNameAnnotation)?.let {
             if (this.isExternal) {
-                val nameValue = it.allValueArguments.values.single() as StringValue
+                return getStringValue(it)!!
-                return nameValue.value
             } else {
                 // ignore; TODO: report compile error
             }
         }
+
+        this.annotations.findAnnotation(exportForCppRuntimeAnnotation)?.let {
+            val name = getStringValue(it) ?: this.name.asString()
+            return name // no wrapping currently required
+        }
+
         val containingDeclarationPart = containingDeclaration.fqNameSafe.let {
             if (it.isRoot) "" else "$it."
         }
         return "kfun:$containingDeclarationPart$functionName"
     }
 
+private fun getStringValue(annotation: AnnotationDescriptor): String? {
+    annotation.allValueArguments.values.ifNotEmpty {
+        val stringValue = this.single() as StringValue
+        return stringValue.value
+    }
+
+    return null
+}
+
 internal val ClassDescriptor.symbolName: String
     get() = when (this.kind) {
         CLASS -> "kclass:"

backend.native/tests/build.gradle

@@ -323,6 +323,11 @@ task tostring2(type: RunKonanTest) {
     source = "runtime/basic/tostring2.kt"
 }
 
+task empty_substring(type: RunKonanTest) {
+    goldValue = "\n"
+    source = "runtime/basic/empty_substring.kt"
+}
+
 task array0(type: RunKonanTest) {
     goldValue = "5\n6\n7\n8\n9\n10\n11\n12\n13\n"
     source = "runtime/basic/array0.kt"
@@ -395,7 +400,9 @@ task strdedup1(type: RunKonanTest) {
 }
 
 /*
-TODO: enable after supporting Unit object
+TODO: string deduplication across several components seems to require
+linking them as bitcode modules before translating to machine code.
+
 task strdedup2(type: RunKonanTest) {
     goldValue = "true\ntrue\n"
     source = "datagen/literals/strdedup2.kt"

backend.native/tests/datagen/literals/strdedup2.kt

@@ -1,6 +1,6 @@
 fun main(args : Array<String>) {
-    val str1 = "kotlin.Unit"
+    val str1 = ""
-    val str2 = Unit.toString()
+    val str2 = "hello".subSequence(2, 2)
     println(str1 == str2)
     println(str1 === str2)
 }

backend.native/tests/runtime/basic/empty_substring.kt

@@ -0,0 +1,4 @@
+fun main(args : Array<String>) {
+    val hello = "Hello world"
+    println(hello.subSequence(1, 1).toString())
+}

runtime/src/main/cpp/Exceptions.cpp

@@ -1,41 +1,7 @@
-#include <stdio.h>
-#include <string.h>
-#include <unistd.h>
-
 #include "Assert.h"
 #include "Exceptions.h"
 #include "Types.h"
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-void ThrowNullPointerException() {
-  void* pc = __builtin_return_address(0);
-  char message[100];
-  snprintf(message, sizeof(message), "NullPointerException at %p", pc);
-  write(STDOUT_FILENO, message, strlen(message));
-  // TODO: throw it for real.
-  RuntimeAssert(false, "Throwing is unsupported");
-}
-
-void ThrowArrayIndexOutOfBoundsException() {
-  void* pc = __builtin_return_address(0);
-  char message[100];
-  snprintf(message, sizeof(message), "ArrayIndexOutOfBoundsException at %p", pc);
-  write(STDOUT_FILENO, message, strlen(message));
-  // TODO: throw it for real.
-  RuntimeAssert(false, "Throwing is unsupported");
-}
-
-void ThrowClassCastException() {
-  void* pc = __builtin_return_address(0);
-  char message[100];
-  snprintf(message, sizeof(message), "ClassCastException at %p", pc);
-  write(STDOUT_FILENO, message, strlen(message));
-  // TODO: throw it for real.
-  RuntimeAssert(false, "Throwing is unsupported");
-}
-
 class KotlinException {
  public:
 
@@ -50,6 +16,10 @@ class KotlinException {
   };
 };
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 void ThrowException(KRef exception) {
   RuntimeAssert(exception != nullptr && IsInstance(exception, theThrowableTypeInfo),
                 "Throwing something non-throwable");

runtime/src/main/cpp/Exceptions.h

@@ -6,6 +6,12 @@
 #ifdef __cplusplus
 extern "C" {
 #endif
+
+// Throws arbitrary exception.
+void ThrowException(KRef exception);
+
+// The functions below are implemented in Kotlin (at package konan.internal).
+
 // Throws null pointer exception. Context is evaluated from caller's address.
 void ThrowNullPointerException();
 // Throws array index out of bounds exception.
@@ -13,8 +19,6 @@ void ThrowNullPointerException();
 void ThrowArrayIndexOutOfBoundsException();
 // Throws class cast exception.
 void ThrowClassCastException();
-// Throws arbitrary exception.
-void ThrowException(KRef exception);
 
 #ifdef __cplusplus
 } // extern "C"

runtime/src/main/cpp/Natives.cpp

@@ -11,9 +11,6 @@
 
 extern "C" {
 
-// TODO: remove, once can generate empty string constant in compile time.
-KString theEmptyString = nullptr;
-
 // Any.kt
 KBoolean Kotlin_Any_equals(KConstRef thiz, KConstRef other) {
   return thiz == other;
@@ -82,9 +79,14 @@ KInt Kotlin_String_getStringLength(KString thiz) {
 KString Kotlin_String_fromUtf8Array(
     const ArrayHeader* array, KInt start, KInt size) {
   RuntimeAssert(array->type_info() == theByteArrayTypeInfo, "Must use a byte array");
-  if (start < 0 || start + size > array->count_) {
+  if (start < 0 || size < 0 || start + size > array->count_) {
     ThrowArrayIndexOutOfBoundsException();
   }
+
+  if (size == 0) {
+    return TheEmptyString();
+  }
+
   // TODO: support full UTF-8.
   ArrayHeader* result = ArrayContainer(theStringTypeInfo, size).GetPlace();
   memcpy(
@@ -97,9 +99,14 @@ KString Kotlin_String_fromUtf8Array(
 KString Kotlin_String_fromCharArray(
     const ArrayHeader* array, KInt start, KInt size) {
   RuntimeAssert(array->type_info() == theCharArrayTypeInfo, "Must use a byte array");
-  if (start < 0 || start + size > array->count_) {
+  if (start < 0 || size < 0 || start + size > array->count_) {
     ThrowArrayIndexOutOfBoundsException();
   }
+
+  if (size == 0) {
+    return TheEmptyString();
+  }
+
   // TODO: support full UTF-8.
   ArrayHeader* result = ArrayContainer(theStringTypeInfo, size).GetPlace();
   for (KInt index = 0; index < size; ++index) {
@@ -162,7 +169,7 @@ KString Kotlin_String_subSequence(KString thiz, KInt startIndex, KInt endIndex)
     ThrowArrayIndexOutOfBoundsException();
   }
   if (startIndex == endIndex) {
-    return theEmptyString;
+    return TheEmptyString();
   }
   // TODO: support UTF-8.
   KInt length = endIndex - startIndex;

runtime/src/main/cpp/Natives.h

@@ -37,7 +37,7 @@ inline const KRef* ArrayAddressOfElementAt(const ArrayHeader* obj, KInt index) {
 extern "C" {
 #endif
 
-extern KString theEmptyString;
+KString TheEmptyString();
 
 // Any.kt
 KBoolean Kotlin_Any_equals(KConstRef thiz, KConstRef other);

runtime/src/main/kotlin/konan/internal/Annotations.kt

@@ -0,0 +1,13 @@
+package konan.internal
+
+/**
+ * Makes this function to be possible to call by given name from C++ part of runtime using C ABI.
+ * The parameters are mapped in an implementation-dependent manner.
+ *
+ * The function to call from C++ can be a wrapper around the original function.
+ *
+ * If the name is not specified, the function to call will be available by its Kotlin unqualified name.
+ */
+//@Target(AnnotationTarget.FUNCTION)
+//@Retention(AnnotationRetention.SOURCE)
+annotation class ExportForCppRuntime(val name: String = "")

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

@@ -0,0 +1,19 @@
+package konan.internal
+
+@ExportForCppRuntime
+internal fun ThrowNullPointerException() {
+    throw NullPointerException()
+}
+
+@ExportForCppRuntime
+internal fun ThrowArrayIndexOutOfBoundsException() {
+    throw IndexOutOfBoundsException()
+}
+
+@ExportForCppRuntime
+internal fun ThrowClassCastException() {
+    throw ClassCastException()
+}
+
+@ExportForCppRuntime
+internal fun TheEmptyString() = ""