Delphi in a Nutshell

Name

ErrorProc Variable

Syntax

var ErrorProc: Pointer;

procedure MyErrorProc(ErrorCode: Integer; ErrorAddr: Pointer);
begin
  ...
end;
ErrorProc := @MyErrorProc;

Description

When a runtime error occurs, and the ErrorProc variable is not nil, Delphi calls the procedure that ErrorProc points to. The procedure takes two arguments: the error number and the error address.

If ErrorProc is nil, Delphi calls RunError to issue an error message and halt the program. In a GUI application, Delphi shows the error message in a dialog box. In a console application, Delphi prints the error message to the console.

Delphi stores the error code for I/O errors separately. If ErrorCode is zero, most likely the error is an I/O error. Call IOResult to obtain the I/O error code.

Example

// Log errors in an application event log (in Windows NT). procedure LogError(ErrorCode: Integer; ErrorAddr: Pointer); var ApplicationName: string; Handle: THandle; Strings: array[0..0] of PChar; begin // Change the application path to its base name, e.g., 'App'. // The application must have created the appropriate register key. ApplicationName := ChangeFileExt(ExtractFileName(ParamStr(0)), ''); Handle := RegisterEventSource(nil, PChar(ApplicationName)); if ErrorCode = 0 then ErrorCode := IOResult; // Get the exception message. Strings[0] := PChar('Runtime error #' + IntToStr(ErrorCode)); // Define the Category elsewhere. ReportEvent(Handle, EventLog_Error_Type, Category, ErrorCode, nil, 0, 1, @Strings, nil); DeregisterEventSource(Handle); ...