Exception Handling

All Recursion Software toolkits use the ANSI/ISO C++ exception mechanism to report errors. Each toolkit has a specialized error class that it uses to encapsulate the problem details. The exception class provided in Platform<ToolKit> for UNIX is os_unix_toolkit_error . This represents an error condition in Platform<ToolKit> for UNIX.

To detect and recover from errors in any Recursion Software toolkit, you must place C++ try...catch blocks in your code. Failure to catch an exception invokes the global function uncaught_exception() , usually followed by a call to terminate() . Both of these global functions are included in your compiler's C++ runtime library and are not part of any Recursion Software toolkit. The call to terminate() forces your application to abort and is unrecoverable. It is usually better to provide your own exception handler that safely shuts down your application in case an unexpected error condition is encountered.

The following code fragment illustrates several techniques for handling errors in Recursion Software toolkits.


try
  {
  // Sleep for three seconds.
  os_this_process::sleep( 3 );

  // assume an exception was thrown - this code never executes.
  cout << "awake" << endl;
  }
catch ( os_unix_toolkit_error& error )
  {
  // This will catch an error generated by a
  // Platform<ToolKit> for UNIX object.
  cout << "Caught error: " << error.what() << endl;
  }
catch ( os_toolkit_error& error )
  {
  // This will catch any error generated by an Recursion Software ToolKit,
  // excluding the ANSI/ISO components found in Standards<ToolKit>.
  cout << "Caught error: " << error.what() << endl;
  }
catch ( ... )
 {
 // This catch block will handle any thrown exception, although
 // you are not able to query any information about it. This is
 // often used as a "last resort" to keep your application from
 // crashing abnormally.
 }