Fix for issue 23908 - error message reports the exact error when a native extension fails to load.

runtime/bin/extensions.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "bin/extensions.h"
 
 #include <stdio.h>
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/globals.h"
 #include "bin/dartutils.h"
 #include "bin/file.h"
 
 
 namespace dart {
 namespace bin {
 
 Dart_Handle Extensions::LoadExtension(const char* extension_directory,
                                       const char* extension_file,
                                       const char* extension_name,
                                       Dart_Handle parent_library) {
   if (strncmp(extension_directory, "http://", 7) == 0 ||
       strncmp(extension_directory, "https://", 8) == 0) {
     return Dart_NewApiError("Cannot load native extensions over http:");
   }
   const char* library_strings[] = { extension_directory, extension_file, NULL };
   char* library_file = Concatenate(library_strings);
-  void* library_handle = LoadExtensionLibrary(library_file);
+  void* library_handle = NULL;
+  Dart_Handle result = LoadExtensionLibrary(library_file, &library_handle);
   free(library_file);
-  if (library_handle == NULL) {
-    return Dart_NewApiError("Cannot find extension library");
+  if (Dart_IsError(result)) {
+    return result;
   }
+  ASSERT(library_handle != NULL);
 
   const char* strings[] = { extension_name, "_Init", NULL };
   char* init_function_name = Concatenate(strings);
+  void* init_function = NULL;
+  result = ResolveSymbol(library_handle, init_function_name, &init_function);
+  free(init_function_name);
+  if (Dart_IsError(result)) {
+    return result;
+  }
+  ASSERT(init_function != NULL);
   typedef Dart_Handle (*InitFunctionType)(Dart_Handle import_map);
-  InitFunctionType fn = reinterpret_cast<InitFunctionType>(
-      ResolveSymbol(library_handle, init_function_name));
-  free(init_function_name);
-
-  if (fn == NULL) {
-    return Dart_NewApiError("Cannot find initialization function in extension");
-  }
+  InitFunctionType fn = reinterpret_cast<InitFunctionType>(init_function);
   return (*fn)(parent_library);
 }
 
 
 // Concatenates a NULL terminated array of strings.
 // The returned string must be freed.
 char* Extensions::Concatenate(const char** strings) {
   int size = 1;  // null termination.
   for (int i = 0; strings[i] != NULL; i++) {
     size += strlen(strings[i]);
   }
   char* result = reinterpret_cast<char*>(malloc(size));
   int index = 0;
   for (int i = 0; strings[i] != NULL; i++) {
     index += snprintf(result + index, size - index, "%s", strings[i]);
   }
   ASSERT(index == size - 1);
   ASSERT(result[size - 1] == '\0');
   return result;
 }
 
 }  // namespace bin
 }  // namespace dart