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All ABBYY FineReader Engine interface methods and properties return a value of the HRESULT type. The HRESULT (for “result handle”) is a way of returning success, warning, and error values. HRESULTs are really not handles to anything; they are only 32-bit values with several fields encoded in the value. A zero result indicates success and a non-zero result indicates failure. If a method or property call was not successful, this method or property returns an HRESULT code that indicates the failure. Besides, it provides a more detailed description of the error through the IErrorInfo interface.
For Windows : Please refer to the documentation on COM for detailed description of error handling.
  • C#. (Windows only) Automatically generated wrappers for COM interfaces detect errors and translate them to standard exceptions. Enclose a sequence of ABBYY FineReader Engine methods by the statements:
try
{
    ...
}
catch( Exception e )
{
    ...
}
  • C++ with the Native COM support (Windows). The Native COM support technology translates the HRESULT codes of interface functions into exceptions of a special type (_com_error) and automatically uses information from IErrorInfo. Thus, a sequence of FineReader Engine methods may be enclosed by the statements:
try {
    ...
}
catch (_com_error& e) {
    ...
}
Generally, error handling with the Native COM support may be performed in a way standard for any C++ code using functions that may throw exceptions.
  • Raw C++ / C++. FineReader Engine interface methods and properties cannot throw exceptions but return HRESULTs. The most important means for handling these return codes are the SUCCEEDED and FAILED macros. They test the HRESULT value and deduce from it what was the result of the operation — success or failure. To get a pointer to the IErrorInfo object’s interface, use the following API functions:
    • GetErrorInfo for Windows
    • GetFREngineErrorInfo for Linux and macOS:
wchar_t* GetErrorMessage() {
   IErrorInfo* errorInfo;
   if( GetFREngineErrorInfo( 0, &errorInfo ) == S_OK && errorInfo != 0 ) {
      // Get error description 
      wchar_t* description;
      errorInfo->GetDescription( &description );
      errorInfo->Release();
      return description;
   } else {
      return L"Unknown error";
   }
}
  • Java (Linux and Windows only). See Using ABBYY FineReader Engine in Java for advice on error handling in Java.
  • Visual Basic (Windows only). Visual Basic users may access the HRESULT code through the Number property of the Err object. Other attributes of the Err object are initialized with the information from IErrorInfo. Error handling here is performed with the use of the On Error statement. If you do not use the On Error Resume Next statement anywhere in your code, any run-time error that occurs can cause an error message from IErrorInfo to be displayed and code execution stopped.

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See also

Standard Return Codes