Replace some libstdc++ functions by simpler implementations

This helps to avoid linking large libstdc++ parts,
thus reducing the binary size.

runtime/src/main/cpp/StdCppStubs.cpp

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2010-2018 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "Assert.h"
+#include "Porting.h"
+#include "Common.h"
+
+// This function replaces `__cxa_demangle` defined in GNU libstdc++
+// by adding `--defsym` flag in `konan.properties`.
+// This allows to avoid linking `__cxa_demangle` and its dependencies, thus reducing binary size.
+RUNTIME_USED extern "C" char* Konan_cxa_demangle(
+    const char* __mangled_name, char* __output_buffer,
+    size_t* __length, int* __status
+) {
+  *__status = -2; // __mangled_name is not a valid name under the C++ ABI mangling rules.
+  return nullptr;
+}
+
+namespace std {
+  void __throw_length_error(const char* __s __attribute__((unused))) {
+    RuntimeAssert(false, __s);
+  }
+}