[K/N] Throwable.printStackTrace() should print to the stderr output

Aligns with the JVM behavior.

As a part of efforts to stabilize Native stdlib.

kotlin-native/runtime/src/main/cpp/Console.cpp

@@ -32,24 +32,40 @@
 
 using namespace kotlin;
 
-extern "C" {
+namespace {
 
-// io/Console.kt
-void Kotlin_io_Console_print(KString message) {
+std_support::string kStringToUtf8(KString message) {
     if (message->type_info() != theStringTypeInfo) {
         ThrowClassCastException(message->obj(), theStringTypeInfo);
     }
-    // TODO: system stdout must be aware about UTF-8.
     const KChar* utf16 = CharArrayAddressOfElementAt(message, 0);
     std_support::string utf8;
     utf8.reserve(message->count_);
     // Replace incorrect sequences with a default codepoint (see utf8::with_replacement::default_replacement)
     utf8::with_replacement::utf16to8(utf16, utf16 + message->count_, back_inserter(utf8));
 
+    return utf8;
+}
+
+} // namespace
+
+extern "C" {
+
+// io/Console.kt
+void Kotlin_io_Console_print(KString message) {
+    // TODO: system stdout must be aware about UTF-8.
+    auto utf8 = kStringToUtf8(message);
     kotlin::ThreadStateGuard guard(kotlin::ThreadState::kNative);
     konan::consoleWriteUtf8(utf8.c_str(), utf8.size());
 }
 
+void Kotlin_io_Console_printToStdErr(KString message) {
+    // TODO: system stderr must be aware about UTF-8.
+    auto utf8 = kStringToUtf8(message);
+    kotlin::ThreadStateGuard guard(kotlin::ThreadState::kNative);
+    konan::consoleErrorUtf8(utf8.c_str(), utf8.size());
+}
+
 void Kotlin_io_Console_println(KString message) {
     Kotlin_io_Console_print(message);
 #ifndef KONAN_ANDROID
@@ -62,11 +78,28 @@ void Kotlin_io_Console_println(KString message) {
 #endif
 }
 
+void Kotlin_io_Console_printlnToStdErr(KString message) {
+    Kotlin_io_Console_printToStdErr(message);
+#ifndef KONAN_ANDROID
+    Kotlin_io_Console_println0ToStdErr();
+#else
+    // On Android single print produces logcat entry, so no need in linefeed.
+    if (!kotlin::compiler::printToAndroidLogcat()) {
+        Kotlin_io_Console_println0ToStdErr();
+    }
+#endif
+}
+
 void Kotlin_io_Console_println0() {
     kotlin::ThreadStateGuard guard(kotlin::ThreadState::kNative);
     konan::consoleWriteUtf8("\n", 1);
 }
 
+void Kotlin_io_Console_println0ToStdErr() {
+    kotlin::ThreadStateGuard guard(kotlin::ThreadState::kNative);
+    konan::consoleErrorUtf8("\n", 1);
+}
+
 OBJ_GETTER0(Kotlin_io_Console_readLine) {
     char data[4096];
     int32_t result;

kotlin-native/runtime/src/main/cpp/Natives.h

@@ -87,6 +87,7 @@ extern "C" {
 
 OBJ_GETTER0(TheEmptyString);
 void Kotlin_io_Console_println0();
+void Kotlin_io_Console_println0ToStdErr();
 void Kotlin_NativePtrArray_set(KRef thiz, KInt index, KNativePtr value);
 KNativePtr Kotlin_NativePtrArray_get(KConstRef thiz, KInt index);
 

kotlin-native/runtime/src/main/cpp/Porting.cpp

@@ -76,7 +76,7 @@ void consoleWriteUtf8(const char* utf8, uint32_t sizeBytes) {
 #endif
 }
 
-NO_EXTERNAL_CALLS_CHECK void consoleErrorUtf8(const char* utf8, uint32_t sizeBytes) {
+void consoleErrorUtf8(const char* utf8, uint32_t sizeBytes) {
 #ifdef KONAN_ANDROID
   if (kotlin::compiler::printToAndroidLogcat()) {
     // TODO: use sizeBytes!

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

@@ -50,7 +50,7 @@ public open class Throwable(open val message: String?, open val cause: Throwable
             (0 until stackTrace.size).map { index -> stackTrace[index].toLong() }
 
     /**
-     * Prints the [detailed description][Throwable.stackTraceToString] of this throwable to the standard output.
+     * Prints the [detailed description][Throwable.stackTraceToString] of this throwable to the standard error output.
      *
      * Note that the format of the output is not stable and may change in the future.
      */
@@ -75,7 +75,7 @@ public open class Throwable(open val message: String?, open val cause: Throwable
 
         private fun StringBuilder.endln() {
             if (printOut) {
-                println(this)
+                printlnToStdErr(this.toString())
                 clear()
             } else {
                 appendLine()
@@ -169,7 +169,7 @@ private external fun getStackTraceStrings(stackTrace: NativePtrArray): Array<Str
 public actual fun Throwable.stackTraceToString(): String = dumpStackTrace()
 
 /**
- * Prints the [detailed description][Throwable.stackTraceToString] of this throwable to the standard output.
+ * Prints the [detailed description][Throwable.stackTraceToString] of this throwable to the standard error output.
  *
  * Note that the format of the output is not stable and may change in the future.
  */

kotlin-native/runtime/src/main/kotlin/kotlin/io/Console.kt

@@ -22,6 +22,10 @@ public actual fun print(message: Any?) {
 @PublishedApi
 internal external fun println(message: String)
 
+/** Prints the given [message] and the line separator to the standard error output stream. */
+@GCUnsafeCall("Kotlin_io_Console_printlnToStdErr")
+internal external fun printlnToStdErr(message: String)
+
 /** Prints the given [message] and the line separator to the standard output stream. */
 public actual fun println(message: Any?) {
     println(message.toString())