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  • In Asp.net (c#) i'm not able to catch any exception properly????

    - by Anand
    In Asp.net (c#),i'm not able to catch exception(FileNotFoundException) properly... i don't know the reason..Actually File s not there..But catch statement fails to catch the exception.. here is the code.. try { System.Drawing.Image imgg1 = System.Drawing.Image.FromFile(Server.MapPath("").ToString() + "\\images\\img1.jpg"); } catch (FileNotFoundException) { Response.Write("<script>alert('Please Select and upload Student's Photo');</script>"); }

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  • MSTest Test Context Exception Handling

    - by Flip
    Is there a way that I can get to the exception that was handled by the MSTest framework using the TestContext or some other method on a base test class? If an unhandled exception occurs in one of my tests, I'd like to spin through all the items in the exception.Data dictionary and display them to the test result to help me figure out why the test failed (we usually add data to the exception to help us debug in the production env, so I'd like to do the same for testing). Note: I am not testing that an exception was SUPPOSED TO HAPPEN (I have other tests for that), I am testing a valid case, I just need to see the exception data. Here is a code example of what I'm talking about. [TestMethod] public void IsFinanceDeadlineDateValid() { var target = new BusinessObject(); SetupBusinessObject(target); //How can I capture this in the text context so I can display all the data //in the exception in the test result... var expected = 100; try { Assert.AreEqual(expected, target.PerformSomeCalculationThatMayDivideByZero()); } catch (Exception ex) { ex.Data.Add("SomethingImportant", "I want to see this in the test result, as its important"); ex.Data.Add("Expected", expected); throw ex; } } I understand there are issues around why I probably shouldn't have such an encapsulating method, but we also have sub tests to test all the functionality of PerformSomeCalculation... However, if the test fails, 99% of the time, I rerun it passes, so I can't debug anything without this information. I would also like to do this on a GLOBAL level, so that if any test fails, I get the information in the test results, as opposed to doing it for each individual test. Here is the code that would put the exception info in the test results. public void AddDataFromExceptionToResults(Exception ex) { StringBuilder whereAmI = new StringBuilder(); var holdException = ex; while (holdException != null) { Console.WriteLine(whereAmI.ToString() + "--" + holdException.Message); foreach (var item in holdException.Data.Keys) { Console.WriteLine(whereAmI.ToString() + "--Data--" + item + ":" + holdException.Data[item]); } holdException = holdException.InnerException; } }

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  • correct way to store an exception in a variable

    - by Evan Teran
    I have an API which internally has some exceptions for error reporting. The basic structure is that it has a root exception object which inherits from std::exception, then it will throw some subclass of that. Since catching an exception thrown in one library and catching it in another can lead to undefined behavior (at least Qt complains about it and disallows it in many contexts). I would like to wrap the library calls in functions which will return a status code, and if an exception occurred, a copy of the exception object. What is the best way to store an exception (with it's polymorphic behavior) for later use? I believe that the c++0x futures API makes use of something like this. So what is the best approach? The best I can think of is to have a clone() method in each exception class which will return a pointer to an exception of the same type. But that's not very generic and doesn't deal with standard exceptions at all. Any thoughts?

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  • error catching exception while System.out.print

    - by user1702633
    I have 2 classes, one that implements a double lookup( int i); and one where I use that lookup(int i) in solving a question, or in this case printing the lookup values. This case is for an array. So I read the exception documentation or google/textbook and come with the following code: public double lookup(int i) throws Exception { if( i > numItems) throw new Exception("out of bounds"); return items[i]; } and take it over to my class and try to print my set, where set is a name of the object type I define in the class above. public void print() { for (int i = 0; i < set.size() - 1; i++) { System.out.print(set.lookup(i) + ","); } System.out.print(set.lookup(set.size())); } I'm using two print()'s to avoid the last "," in the print, but am getting an unhandled exception Exception (my exception's name was Exception) I think I have to catch my exception in my print() but cannot find the correct formatting online. Do I have to write catch exception Exception? because that gives me a syntax error saying invalid type on catch. Sources like http://docs.oracle.com/javase/tutorial/essential/exceptions/ are of little help to me, I'm can't seem to grasp what the text is telling me. I'm also having trouble finding sources with multiple examples where I can actually understand the coding in the examples. so could anybody give me a source/example for the above catch phrase and perhaps a decent source of examples for new Java programmers? my book is horrendous and I cannot seem to find an understandable example for the above catch phrase online.

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  • Exception Handling in ASP.NET MVC and Ajax - [HandleException] filter

    - by Graham
    All, I'm learning MVC and using it for a business app (MVC 1.0). I'm really struggling to get my head around exception handling. I've spent a lot of time on the web but not found anything along the lines of what I'm after. We currently use a filter attribute that implements IExceptionFilter. We decorate a base controller class with this so all server side exceptions are nicely routed to an exception page that displays the error and performs logging. I've started to use AJAX calls that return JSON data but when the server side implementation throws an error, the filter is fired but the page does not redirect to the Error page - it just stays on the page that called the AJAX method. Is there any way to force the redirect on the server (e.g. a ASP.NET Server.Transfer or redirect?) I've read that I must return a JSON object (wrapping the .NET Exception) and then redirect on the client, but then I can't guarantee the client will redirect... but then (although I'm probably doing something wrong) the server attempts to redirect but then gets an unauthorised exception (the base controller is secured but the Exception controller is not as it does not inherit from this) Has anybody please got a simple example (.NET and jQuery code). I feel like I'm randomly trying things in the hope it will work Exception Filter so far... public class HandleExceptionAttribute : FilterAttribute, IExceptionFilter { #region IExceptionFilter Members public void OnException(ExceptionContext filterContext) { if (filterContext.ExceptionHandled) { return; } filterContext.Controller.TempData[CommonLookup.ExceptionObject] = filterContext.Exception; if (filterContext.HttpContext.Request.IsAjaxRequest()) { filterContext.Result = AjaxException(filterContext.Exception.Message, filterContext); } else { //Redirect to global handler filterContext.Result = new RedirectToRouteResult(new RouteValueDictionary(new { controller = AvailableControllers.Exception, action = AvailableActions.HandleException })); filterContext.ExceptionHandled = true; filterContext.HttpContext.Response.Clear(); } } #endregion private JsonResult AjaxException(string message, ExceptionContext filterContext) { if (string.IsNullOrEmpty(message)) { message = "Server error"; //TODO: Replace with better message } filterContext.HttpContext.Response.StatusCode = (int)HttpStatusCode.InternalServerError; filterContext.HttpContext.Response.TrySkipIisCustomErrors = true; //Needed for IIS7.0 return new JsonResult { Data = new { ErrorMessage = message }, ContentEncoding = Encoding.UTF8, }; } }

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  • Java: exception-throwing class?

    - by HH
    I have classes DirReader and Search. The search uses DirReader. I want the search to know when DirReader throws exception. So how can I have class throwing exception? Currently, I use initCorrect -dummy var. Exception-style method may be more appropriate. Simplified Example Error $ javac ExceptionStatic.java ExceptionStatic.java:4: '{' expected public class ExceptionStatic throws Exception{ ^ 1 error Code import java.util.*; import java.io.*; // THIS PART NEEDS TO BE FIXED: public class ExceptionStatic throws Exception{ private static boolean initCorrect = false; public static String hello; static{ try{ hello = "hallo"; //some other conditionals in real code if( true) throw new Exception(); initCorrect=true; }catch(Exception e){ e.printStackTrace(); } } public static void main(String[] args){ if(initCorrect) System.out.println(hello); } }

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  • How to create custom exception handler for custom controls or extension methods.

    - by Shantanu Gupta
    I am creating an extension method in C# to retrieve some value from datagridview. Here if a user gives column name that doesnot exists then i want this function to throw an exception that can be handled at the place where this function will be called. How can i achieve this. public static T Value<T>(this DataGridView dgv, int RowNo, string ColName) { if (!dgv.Columns.Contains(ColName)) throw new ArgumentException("Column Name " + ColName + " doesnot exists in DataGridView."); return (T)Convert.ChangeType(dgv.Rows[RowNo].Cells[ColName].Value, typeof(T)); }

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  • Method with throws Exception: Where is it actually handled?

    - by Esq
    Here is an example code, I am throwing an exception here, it works perfectly fine without the try/catch block of code for some reason. Do I have to handle this inside this method "EntryDelete" or Do I have to handle this where the method is called from? If so can I see an example, what do I have to import in there? What is the acceptable syntax or method to do this? public boolean EntryDelete(int entryId) throws SQLException{ this.open(); kDatabase.delete(kENTRY_TABLE, kENTRY_ENTRY_ID + "=" + entryId, null); this.close(); return true; } Thanks

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  • Exception wrapping and HTML pages

    - by dotnetdev
    Hi, We have a sharepoint 2007 project at work. The exception handling policy is to log to the Sharepoint logs. In this case, would the best approach be to call that method and then rethrow the exception higher up? Except if I rethrow it to be caught higher up, there is no other exception handling code so what would happen in this case? Also, if you are going to display a more friendly error to the user (which uses information in the exception object), then this would be a good use of exception wrapping. Would it be a good idea to make a custom aspx page and add these to customerrors, so that on init (not sure of the exact event), I can display exception info in the passed parameter on the page. However, a static html page can't do this so I don't see the point in wrapping exceptions (unless there is a page or alert which uses the exception object). So if a project uses html pages for errors, is there a point in wrapping exceptions? Thanks

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  • Strange IIS/Asp.net Exception Message

    - by Element
    I have a standard asp.net 2.0 application running on IIS 6. I have noticed some strange exception messages in the logs. They seem to be caused by random spam bots trying to submit forms. They are strange because the request string is huge and all the exception details in the event manager are messed up, they have been replaced with %21,%22, etc.. as seen in the screen shot. Is this some kind of exploit or just a bug in the asp.net exception handler/logger ? UPDATE: I traced the requests that are causing this strange log event to a bug in IE8 that causes it to request scriptresource.axd?d={html from page} as described in these links: MS Connect SO - Invalid Webresource.axd SO - IE8 Dropping Memory Pages I am still not sure why these requests would break the IIS log event like seen above, they are just long strings of jiberish being sent to the server, maybe someone reading this can shed some light on it.

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  • Exception handling protocol for methods

    - by athena
    Is there any specific protocol for handling exceptions in public methods? Consider this eg. public int someMethod() { try{ code that might throw an exception } catch(Exception e) { log the exception } } Say that this method might throw an ArrayIndexOutOfBoundsException. So, is it correct to handle this Exception in the method itself (as in the example) or throw it and assume that the calling method will handle the Exception?

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  • Subterranean IL: Filter exception handlers

    - by Simon Cooper
    Filter handlers are the second type of exception handler that aren't accessible from C#. Unlike the other handler types, which have defined conditions for when the handlers execute, filter lets you use custom logic to determine whether the handler should be run. However, similar to a catch block, the filter block does not get run if control flow exits the block without throwing an exception. Introducing filter blocks An example of a filter block in IL is the following: .try { // try block } filter { // filter block endfilter }{ // filter handler } or, in v1 syntax, TryStart: // try block TryEnd: FilterStart: // filter block HandlerStart: // filter handler HandlerEnd: .try TryStart to TryEnd filter FilterStart handler HandlerStart to HandlerEnd In the v1 syntax there is no end label specified for the filter block. This is because the filter block must come immediately before the filter handler; the end of the filter block is the start of the filter handler. The filter block indicates to the CLR whether the filter handler should be executed using a boolean value on the stack when the endfilter instruction is run; true/non-zero if it is to be executed, false/zero if it isn't. At the start of the filter block, and the corresponding filter handler, a reference to the exception thrown is pushed onto the stack as a raw object (you have to manually cast to System.Exception). The allowed IL inside a filter block is tightly controlled; you aren't allowed branches outside the block, rethrow instructions, and other exception handling clauses. You can, however, use call and callvirt instructions to call other methods. Filter block logic To demonstrate filter block logic, in this example I'm filtering on whether there's a particular key in the Data dictionary of the thrown exception: .try { // try block } filter { // Filter starts with exception object on stack // C# code: ((Exception)e).Data.Contains("MyExceptionDataKey") // only execute handler if Contains returns true castclass [mscorlib]System.Exception callvirt instance class [mscorlib]System.Collections.IDictionary [mscorlib]System.Exception::get_Data() ldstr "MyExceptionDataKey" callvirt instance bool [mscorlib]System.Collections.IDictionary::Contains(object) endfilter }{ // filter handler // Also starts off with exception object on stack callvirt instance string [mscorlib]System.Object::ToString() call void [mscorlib]System.Console::WriteLine(string) } Conclusion Filter exception handlers are another exception handler type that isn't accessible from C#, however, just like fault handlers, the behaviour can be replicated using a normal catch block: try { // try block } catch (Exception e) { if (!FilterLogic(e)) throw; // handler logic } So, it's not that great a loss, but it's still annoying that this functionality isn't directly accessible. Well, every feature starts off with minus 100 points, so it's understandable why something like this didn't make it into the C# compiler ahead of a different feature.

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  • Subterranean IL: Exception handler semantics

    - by Simon Cooper
    In my blog posts on fault and filter exception handlers, I said that the same behaviour could be replicated using normal catch blocks. Well, that isn't entirely true... Changing the handler semantics Consider the following: .try { .try { .try { newobj instance void [mscorlib]System.Exception::.ctor() // IL for: // e.Data.Add("DictKey", true) throw } fault { ldstr "1: Fault handler" call void [mscorlib]System.Console::WriteLine(string) endfault } } filter { ldstr "2a: Filter logic" call void [mscorlib]System.Console::WriteLine(string) // IL for: // (bool)((Exception)e).Data["DictKey"] endfilter }{ ldstr "2b: Filter handler" call void [mscorlib]System.Console::WriteLine(string) leave.s Return } } catch object { ldstr "3: Catch handler" call void [mscorlib]System.Console::WriteLine(string) leave.s Return } Return: // rest of method If the filter handler is engaged (true is inserted into the exception dictionary) then the filter handler gets engaged, and the following gets printed to the console: 2a: Filter logic 1: Fault handler 2b: Filter handler and if the filter handler isn't engaged, then the following is printed: 2a:Filter logic 1: Fault handler 3: Catch handler Filter handler execution The filter handler is executed first. Hmm, ok. Well, what happens if we replaced the fault block with the C# equivalent (with the exception dictionary value set to false)? .try { // throw exception } catch object { ldstr "1: Fault handler" call void [mscorlib]System.Console::WriteLine(string) rethrow } we get this: 1: Fault handler 2a: Filter logic 3: Catch handler The fault handler is executed first, instead of the filter block. Eh? This change in behaviour is due to the way the CLR searches for exception handlers. When an exception is thrown, the CLR stops execution of the thread, and searches up the stack for an exception handler that can handle the exception and stop it propagating further - catch or filter handlers. It checks the type clause of catch clauses, and executes the code in filter blocks to see if the filter can handle the exception. When the CLR finds a valid handler, it saves the handler's location, then goes back to where the exception was thrown and executes fault and finally blocks between there and the handler location, discarding stack frames in the process, until it reaches the handler. So? By replacing a fault with a catch, we have changed the semantics of when the filter code is executed; by using a rethrow instruction, we've split up the exception handler search into two - one search to find the first catch, then a second when the rethrow instruction is encountered. This is only really obvious when mixing C# exception handlers with fault or filter handlers, so this doesn't affect code written only in C#. However it could cause some subtle and hard-to-debug effects with object initialization and ordering when using and calling code written in a language that can compile fault and filter handlers.

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  • Exception Handling And Other Contentious Political Topics

    - by Justin Jones
    So about three years ago, around the time of my last blog post, I promised a friend I would write this post. Keeping promises is a good thing, and this is my first step towards easing back into regular blogging. I fully expect him to return from Pennsylvania to buy me a beer over this. However, it’s been an… ahem… eventful three years or so, and blogging, unfortunately, got pushed to the back burner on my priority list, along with a few other career minded activities. Now that the personal drama of the past three years is more or less resolved, it’s time to put a few things back on the front burner. What I consider to be proper exception handling practices is relatively well known these days. There are plenty of blog posts out there already on this topic which more or less echo my opinions on this topic. I’ll try to include a few links at the bottom of the post. Several years ago I had an argument with a co-worker who posited that exceptions should be caught at every level and logged. This might seem like sanity on the surface, but the resulting error log looked something like this: Error: System.SomeException Followed by small stack trace. Error: System.SomeException Followed by slightly bigger stack trace. Error: System.SomeException Followed by slightly bigger stack trace. Error: System.SomeException Followed by slightly bigger stack trace. Error: System.SomeException Followed by slightly bigger stack trace. Error: System.SomeException Followed by slightly bigger stack trace. Error: System.SomeException Followed by slightly bigger stack trace. Error: System.SomeException Followed by slightly bigger stack trace.   These were all the same exception. The problem with this approach is that the error log, if you run any kind of analytics on in, becomes skewed depending on how far up the stack trace your exception was thrown. To mitigate this problem, we came up with the concept of the “PreLoggedException”. Basically, we would log the exception at the very top level and subsequently throw the exception back up the stack encapsulated in this pre-logged type, which our logging system knew to ignore. Now the error log looked like this: Error: System.SomeException Followed by small stack trace. Much cleaner, right? Well, there’s still a problem. When your exception happens in production and you go about trying to figure out what happened, you’ve lost more or less all context for where and how this exception was thrown, because all you really know is what method it was thrown in, but really nothing about who was calling the method or why. What gives you this clue is the entire stack trace, which we’re losing here. I believe that was further mitigated by having the logging system pull a system stack trace and add it to the log entry, but what you’re actually getting is the stack for how you got to the logging code. You’re still losing context about the actual error. Not to mention you’re executing a whole slew of catch blocks which are sloooooooowwwww……… In other words, we started with a bad idea and kept band-aiding it until it didn’t suck quite so bad. When I argued for not catching exceptions at every level but rather catching them following a certain set of rules, my co-worker warned me “do yourself a favor, never express that view in any future interviews.” I suppose this is my ultimate dismissal of that advice, but I’m not too worried. My approach for exception handling follows three basic rules: Only catch an exception if 1. You can do something about it. 2. You can add useful information to it. 3. You’re at an application boundary. Here’s what that means: 1. Only catch an exception if you can do something about it. We’ll start with a trivial example of a login system that uses a file. Please, never actually do this in production code, it’s just concocted example. So if our code goes to open a file and the file isn’t there, we get a FileNotFound exception. If the calling code doesn’t know what to do with this, it should bubble up. However, if we know how to create the file from scratch we can create the file and continue on our merry way. When you run into situations like this though, What should really run through your head is “How can I avoid handling an exception at all?” In this case, it’s a trivial matter to simply check for the existence of the file before trying to open it. If we detect that the file isn’t there, we can accomplish the same thing without having to handle in in a catch block. 2. Only catch an exception if you can do something about it. Continuing with the poorly thought out file based login system we contrived in part 1, if the code calls a Login(…) method and the FileNotFound exception is thrown higher up the stack, the code that calls Login must account for a FileNotFound exception. This is kind of counterintuitive because the calling code should not need to know the internals of the Login method, and the data file is an implementation detail. What makes more sense, assuming that we didn’t implement any of the good advice from step 1, is for Login to catch the FileNotFound exception and wrap it in a new exception. For argument’s sake we’ll say LoginSystemFailureException. (Sorry, couldn’t think of anything better at the moment.) This gives us two stack traces, preserving the original stack trace in the inner exception, and also is much more informative to the calling code. 3. Only catch an exception if you’re at an application boundary. At some point we have to catch all the exceptions, even the ones we don’t know what to do with. WinForms, ASP.Net, and most other UI technologies have some kind of built in mechanism for catching unhandled exceptions without fatally terminating the application. It’s still a good idea to somehow gracefully exit the application in this case if possible though, because you can no longer be sure what state your application is in, but nothing annoys a user more than an application just exploding. These unhandled exceptions need to be logged, and this is a good place to catch them. Ideally you never want this option to be exercised, but code as though it will be. When you log these exceptions, give them a “Fatal” status (e.g. Log4Net) and make sure these bugs get handled in your next release. That’s it in a nutshell. If you do it right each exception will only get logged once and with the largest stack trace possible which will make those 2am emergency severity 1 debugging sessions much shorter and less frustrating. Here’s a few people who also have interesting things to say on this topic:  http://blogs.msdn.com/b/ericlippert/archive/2008/09/10/vexing-exceptions.aspx http://www.codeproject.com/Articles/9538/Exception-Handling-Best-Practices-in-NET I know there’s more but I can’t find them at the moment.

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  • Are there legitimate reasons for returning exception objects instead of throwing them?

    - by stakx
    This question is intended to apply to any OO programming language that supports exception handling; I am using C# for illustrative purposes only. Exceptions are usually intended to be raised when an problem arises that the code cannot immediately handle, and then to be caught in a catch clause in a different location (usually an outer stack frame). Q: Are there any legitimate situations where exceptions are not thrown and caught, but simply returned from a method and then passed around as error objects? This question came up for me because .NET 4's System.IObserver<T>.OnError method suggests just that: exceptions being passed around as error objects. Let's look at another scenario, validation. Let's say I am following conventional wisdom, and that I am therefore distinguishing between an error object type IValidationError and a separate exception type ValidationException that is used to report unexpected errors: partial interface IValidationError { } abstract partial class ValidationException : System.Exception { public abstract IValidationError[] ValidationErrors { get; } } (The System.Component.DataAnnotations namespace does something quite similar.) These types could be employed as follows: partial interface IFoo { } // an immutable type partial interface IFooBuilder // mutable counterpart to prepare instances of above type { bool IsValid(out IValidationError[] validationErrors); // true if no validation error occurs IFoo Build(); // throws ValidationException if !IsValid(…) } Now I am wondering, could I not simplify the above to this: partial class ValidationError : System.Exception { } // = IValidationError + ValidationException partial interface IFoo { } // (unchanged) partial interface IFooBuilder { bool IsValid(out ValidationError[] validationErrors); IFoo Build(); // may throw ValidationError or sth. like AggregateException<ValidationError> } Q: What are the advantages and disadvantages of these two differing approaches?

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  • Problem in linking an nasm code

    - by Stefano
    I'm using a computer with an Intel Core 2 CPU and 2GB of RAM. The SO is Ubuntu 9.04. When I try to compile this code: ;programma per la simulazione di un terminale su PC, ottenuto utilizzando l'8250 ;in condizione di loopback , cioè Tx=Rx section .code64 section .data TXDATA EQU 03F8H ;TRASMETTITORE RXDATA EQU 03F8H ;RICEVITORE BAUDLSB EQU 03F8H ;DIVISORE DI BAUD RATE IN LSB BAUDMSB EQU 03F9H ;DIVISORE DI BAUD RATE IN MSB INTENABLE EQU 03F9H ;REGISTRO DI ABILITAZIONE DELL'INTERRUZIONE INTIDENTIF EQU 03FAH ;REGISTRO DI IDENTIFICAZIONE DELL'INTERRUZIONE LINECTRL EQU 03FBH ;REGISTRO DI CONTROLLO DELLA LINEA MODEMCTRL EQU 03FCH ;REGISTRO DI CONTROLLO DEL MODEM LINESTATUS EQU 03FDH ;REGISTRO DI STATO DELLA LINEA MODEMSTATUS EQU 03FEH ;REGISTRO DI STATO DEL MODEM BAUDRATEDIV DW 0060H ;DIVISOR: LOW=60, HIGH=00 -BAUD =9600 COUNTERCHAR DB 0 ;CHARACTER COUNTER ;DW 256 DUP (?) section .text global _start _start: ;PROGRAMMAZIONE 8250 MOV DX,LINECTRL MOV AL,80H ;BIT 7=1 PER INDIRIZZARE IL BAUD RATE OUT DX,AL MOV DX,BAUDLSB MOV AX,BAUDRATEDIV ;DEFINISCO FATTORE DI DIVISIONE OUT DX,AL MOV DX,BAUDMSB MOV AL,AH OUT DX,AL ;MSB MOV DX,LINECTRL MOV AL,00000011B ;8 BIT DATO, 1 STOP, PARITA' NO OUT DX,AL MOV DX,MODEMCTRL MOV AL,00010011B ;BIT 4=0 PER NO LOOPBACK OUT DX,AL MOV DX,INTENABLE XOR AL,AL ;DISABILITO TUTTI GLI INTERRUPTS OUT DX,AL CICLO: MOV DX,LINESTATUS IN AL,DX ;LEGGO IL REGISTRO DI STATO DELLA LINEA TEST AL,00011110B ;VERIFICO GLI ERRORI (4 TIPI) JNE ERRORI TEST AL,01H ;VERIFICO Rx PRONTO JNE LEGGOCHAR TEST AL,20H ;VERIFICO Tx VUOTO JE CICLO ;SE SI ARRIVA A QUESTO PUNTO ALLORA L'8250 è PRONTO PER TRASMETTERE UN NUOVO CARATTERE MOV AH,1 INT 80H JE CICLO ;SE SI ARRIVA A QUESTO PUNTO SIGNIFICA CHE ESISTE UN CARATTERE DA TASTIERA MOV AH,0 INT 80H ;Al CONTIENE IL CARATTERE DELLA TASTIERA MOV DX,3F8H OUT DX,AL JMP CICLO LEGGOCHAR: MOV AL,[COUNTERCHAR] INC AL CMP AL,15 JE FINE MOV [COUNTERCHAR],AL MOV DX,TXDATA IN AL,DX ;AL CONTIENE IL CARATTERE RICEVUTO AND AL,7FH ;POICHè VI SONO 7 BIT DI DATO ;VISUALIZZAZIONE DEL CARATTERE MOV BX,0 MOV AH,14 INT 80H POP AX CMP AL,0DH ;CONTROLLO SE RETURN JNE CICLO ;CAMBIO RIGA DI VISUALIZZAZIONE MOV AL,0AH MOV BX,0 MOV AH,14 ;INT 10H INT 80H JMP CICLO ;GESTIONE ERRORI ERRORI: MOV DX,3F8H IN AL,DX MOV AL,'?' MOV BX,0 MOV AH,14 INT 80H JMP CICLO FINE: XOR AH,AH MOV AL,03 INT 80H When I compile this code "NASM -f bin UARTLOOP.asm", the compiler can create the UARTLOOP.o file without any error. When I try to link the .o file with "ld UARTLOOP.o" it tells: UARTLOOP.o: In function `_start': UARTLOOP.asm:(.text+0xd): relocation truncated to fit: R_X86_64_16 against `.data' Have u got some ideas to solve this problem? Thx =)

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  • HttpWebRequest.GetResponse() - what specific status codes cause an exception to be thrown?

    - by H. Morrow
    I've hunted around for some definitive documentation on this but haven't had much luck finding any. Basically - the question is - for which HTTP Status codes coming back from the server will HttpWebRequest.GetResponse() generate a WebException after doing something like say, a POST? Specifically - will it generate a WebException for anything other than status 200 OK? Or will it only generate a WebException for say, 400, 404, and 500 (for the sake of argument). I want to know since, the server I'm communicating with defines anything other than HTTP 200 OK coming back as an error condition - and the key is, can I rely on a WebException being generated for anything other than 200? (I've currently written my code so that it'll actually check the return status code everytime to ensure it's 200 OK and if it's not, take appropriate action - but it's alot of duplication between that, and the catch block for a WebException, and I'm hoping to clean it up...) Any relevant links to documentation would be most appreciated. Thanks!

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  • Should Java IOException have been an unchecked RuntimeException?

    - by Derek Mahar
    Do you agree that the designers of Java class java.io.IOException should have made it an unchecked run-time exception derived from java.lang.RuntimeException instead of a checked exception derived only from java.lang.Exception? I think that class IOException should have been an unchecked exception because there is little that an application can do to resolve problems like file system errors. However, in When You Can't Throw An Exception, Elliotte Rusty Harold claims that most I/O errors are transient and so you can retry an I/O operation several times before giving up: For instance, an IOComparator might not take an I/O error lying down, but — because many I/O problems are transient — you can retry a few times, as shown in Listing 7: Is this generally the case? Can a Java application correct I/O errors or wait for the system to recover? If so, then it is reasonable for IOException to be checked, but if it is not the case, then IOException should be unchecked so that business logic can delegate handling this exception to a separate system error handler.

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  • Why does a looser specification in an overriding method compile after the exception specification fo

    - by Everyone
    The code below has an overridden method with a looser exception specification as compared to the method being overridden. //AnotherMain.java public class AnotherMain { public void dummyMethod( String args[] ) throws IOException{ throw new IOException(); } } //SubAnotherMain.java public class SubAnotherMain extends AnotherMain{ @Override public void dummyMethod( String[] args ) throws Exception { // To get this to compile, change the above - throws IOException, Exception super.dummyMethod(args); throw new Exception("This will not compile unless the exception specification has IOException too"); } } Afaik, the overriding method should not compile at all as the looser specification might break substitutability. Why does it compile after the original exception specification is included in the override? What have I misunderstood?

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  • Python: User-Defined Exception That Proves The Rule

    - by bandana
    Python documentations states: Exceptions should typically be derived from the Exception class, either directly or indirectly. the word 'typically' leaves me in an ambiguous state. consider the code: class good(Exception): pass class bad(object): pass Heaven = good() Hell = bad() >>> raise Heaven Traceback (most recent call last): File "<pyshell#163>", line 1, in <module> raise Heaven good >>> raise Hell Traceback (most recent call last): File "<pyshell#171>", line 1, in <module> raise Hell TypeError: exceptions must be classes or instances, not bad so when reading the python docs, should i change 'typically' with ''? what if i have a class hierarchy that has nothing to do with the Exception class, and i want to 'raise' objects belonging to the hierarchy? i can always raise an exception with an argument: raise Exception, Hell This seems slightly awkward to me What's so special about the Exception class, that only its family members can be raised?

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  • Should class IOException in Java have been an unchecked RuntimeException?

    - by Derek Mahar
    Do you agree that the designers of Java class java.io.IOException should have made it an unchecked run-time exception derived from java.lang.RuntimeException instead of a checked exception derived only from java.lang.Exception? I think that class IOException should have been an unchecked exception because there is little that an application can do to resolve problems like file system errors. However, in When You Can't Throw An Exception, Elliotte Rusty Harold claims that most I/O errors are transient and so you can retry an I/O operation several times before giving up: For instance, an IOComparator might not take an I/O error lying down, but — because many I/O problems are transient — you can retry a few times, as shown in Listing 7: Is this generally the case? Can a Java application correct I/O errors or wait for the system to recover? If so, then it is reasonable for IOException to be checked, but if it is not the case, then IOException should be unchecked so that business logic can delegate handling of this exception to a separate system error handler.

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  • Exception and Inheritance in JAVA

    - by user1759950
    Suppose we have this problem public class Father{ public void method1(){...} } public class Child1 extends Father{ public void method1() throws Exception{ super.method1(); ... } } Child1 extends Father and override method1 but given implementation Child1.method1 now throws a exception, this wont compile as override method can't throw new exceptions. What is the best solution? Propagate the required exception to the Father.. to me this is against encapsulation, inheritance and general OOP ( the father potentially throw and exception that will never happen ) Use a RuntimeException instead? This solution wont propagate the Exception to the father but I read In Oracle docs and others sources states class of exceptions should be used when "Client code cannot do anything" this is not that case, this exception will b useful to recover blablabla ( why is wrong to use RuntimeException instead? ) Other.. thanks, Federico

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