Use the distinguished class, ApiFailure, to signal when a Dart_Result is

runtime/include/dart_api.h

 // Copyright (c) 2011, 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.
 
 #ifndef INCLUDE_DART_API_H_
 #define INCLUDE_DART_API_H_
 
 #ifdef __cplusplus
 #define DART_EXTERN_C extern "C"
 #else
@@ skipping 35 matching lines @@
 typedef void* Dart_Handle;
 typedef void* Dart_NativeArguments;
 typedef enum {
   kRetCIntptr = 0,
   kRetCBool,
   kRetCString,
   kRetObject,
   kRetCInt64,
   kRetCDouble,
   kRetLibSpec,
-  kRetError,
 } Dart_ReturnType;
 
 typedef struct {
   Dart_ReturnType type_;
   union {
     intptr_t int_value;
     bool bool_value;
     const char* str_value;
     Dart_Handle obj_value;
     int64_t int64_value;
     double double_value;
-    const char* errmsg;
   } retval_;
 } Dart_Result;
 
 typedef enum {
   kLibraryTag = 0,
   kImportTag,
   kSourceTag,
   kCanonicalizeUrl,
 } Dart_LibraryTag;
 
@@ skipping 13 matching lines @@
 typedef void (*Dart_NativeFunction)(Dart_NativeArguments arguments);
 typedef Dart_NativeFunction (*Dart_NativeEntryResolver)(Dart_Handle name,
                                                         int num_of_arguments);
 typedef Dart_Result (*Dart_LibraryTagHandler)(Dart_LibraryTag tag,
                                               Dart_Handle library,
                                               Dart_Handle url);
 
 // TODO(iposva): This is a placeholder for the eventual external Dart API.
 
 // Return value handling after a Dart API call.
-inline bool Dart_IsValidResult(const Dart_Result& result) {
-  return (result.type_ != kRetError);
-}
+DART_EXPORT bool Dart_IsValidResult(const Dart_Result& result);
+
 inline intptr_t Dart_GetResultAsCIntptr(const Dart_Result& result) {
   assert(result.type_ == kRetCIntptr);  // Valid to access result as C int.
   return result.retval_.int_value;
 }
 inline  Dart_Result Dart_ResultAsCIntptr(intptr_t value) {
   Dart_Result result;
   result.type_ = kRetCIntptr;
   result.retval_.int_value = value;
   return result;
 }
@@ skipping 41 matching lines @@
 inline double Dart_GetResultAsCDouble(const Dart_Result& result) {
   assert(result.type_ == kRetCDouble);  // Valid to access result as C double.
   return result.retval_.double_value;
 }
 inline  Dart_Result Dart_ResultAsCDouble(double value) {
   Dart_Result result;
   result.type_ = kRetCDouble;
   result.retval_.double_value = value;
   return result;
 }
-inline const char* Dart_GetErrorCString(const Dart_Result& result) {
-  assert(result.type_ == kRetError);  // Valid to access only on failure.
-  return result.retval_.errmsg;
-}
-inline  Dart_Result Dart_ErrorResult(const char* value) {
-  // Assumes passed in string value will be available on return.
-  Dart_Result result;
-  result.type_ = kRetError;
-  result.retval_.errmsg = value;
-  return result;
-}
+DART_EXPORT const char* Dart_GetErrorCString(const Dart_Result& result);
+DART_EXPORT Dart_Result Dart_ErrorResult(const char* value);
 
 
 // Initialize the VM with commmand line flags.
 DART_EXPORT bool Dart_Initialize(int argc, char** argv,
                                  Dart_IsolateInitCallback callback);
 
 
 // Isolate handling.
 DART_EXPORT Dart_Isolate Dart_CreateIsolate(const Dart_Snapshot* snapshot,
                                             void* data);
@@ skipping 199 matching lines @@
 // External pprof support for gathering and dumping symbolic information
 // that can be used for better profile reports for dynamically generated
 // code.
 DART_EXPORT void Dart_InitPprofSupport();
 DART_EXPORT void Dart_GetPprofSymbolInfo(void** buffer, int* buffer_size);
 
 // Check set vm flags.
 DART_EXPORT bool Dart_IsVMFlagSet(const char* flag_name);
 
 #endif  // INCLUDE_DART_API_H_