Re: Patch: fix up Syscall a bit

[Phil Muldoon <pmuldoon at redhat dot com>]

My only general concern is the over-use of throwing exceptions in 
syscall look-ups. (I realize, Tom., that you just changed the Exception 
and did not put the original Exception in there). I thought this would 
be a good place to ask the question as it is in the patch. In the location:
> @@ -259,24 +260,21 @@
>  	syscallList = task.getIsa().getSyscallList ();
>  	unknownSyscalls = task.getIsa().getUnknownSyscalls ();
>        }
> -    catch (Exception e)
> +    catch (TaskException e)
>        {
> -	throw new RuntimeException ("Could not get the isa");
> +	throw new RuntimeException ("Could not get the isa", e);
>        }
>  
>      if (num < 0)
>        {
> -	throw new RuntimeException ("Negative Syscall Number:" + 
> -				    Integer.toString(num));
> +	throw new RuntimeException ("Negative syscall number: " + num);
>        }
>      else if (num >= syscallList.length)
>        {
> -	synchronized (Syscall.class)
> +	synchronized (unknownSyscalls)
>  	  {
>  	    Integer key = new Integer(num);
> -	    if (unknownSyscalls == null)
> -	      unknownSyscalls = new HashMap();
> -	    else if (unknownSyscalls.containsKey(key))
> +	    if (unknownSyscalls.containsKey(key))
>  	      return (Syscall) unknownSyscalls.get(key);
>  	    
>  	    class UnknownSyscall

And here:
>  	    
> @@ -327,9 +324,9 @@
>        {
>  	syscall = task.getIsa().syscallByName(name);
>        }
> -    catch (Exception e)
> +    catch (TaskException e)
>        {
> -	throw new RuntimeException ("Could not get the name of isa");
> +	throw new RuntimeException ("Could not get the name of isa", e);
>        }
>  
>      return syscall;
>   

This exception will stop the event loop for implementing clients (and as 
the exception is unchecked, very hard to check on the severity). Would 
it be better to return null in these places instead of completely 
aborting with a throw?

Regards

Phil