tail call optimization - Page 418

Why do debug symbols so adversely affect the performance of threaded applications on Linux?

- by fluffels

Hi. I'm writing a ray tracer. Recently, I added threading to the program to exploit the additional cores on my i5 Quad Core. In a weird turn of events the debug version of the application is now running slower, but the optimized build is running faster than before I added threading. I'm passing the "-g -pg" flags to gcc for the debug build and the "-O3" flag for the optimized build. Host system: Ubuntu Linux 10.4 AMD64. I know that debug symbols add significant overhead to the program, but the relative performance has always been maintained. I.e. a faster algorithm will always run faster in both debug and optimization builds. Any idea why I'm seeing this behavior?

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Accurately and securely measure the time spent viewing a web page

- by balpha

Suppose the following: You have a web page that presents a simple game to a user (e.g. a quiz, a puzzle, etc). The user solves the puzzle, submits the result, and you want to measure as precisely as possible how long they took to solve it. Assume it's quite simple, so we're talking seconds, not hours. Also assume JavaScript is required anyway, so there's no need to think of JS-disabled browsers. Finally, assume we don't want to use anything like Flash, Silverlight, or the like. I can think of several techniques: Simply take the time between the points when the data was sent from the server and when the submission arrives. Since this is exclusively server-side, there's no chance for cheating. However, issues like network latency and page rendering time might make this unfair for users with slow computers / browsers / internet connections. On the first request, just send the page without the actual game data. When everything is loaded so far, retrieve the game data through an AJAX call and populate it into the page. This is similar to 1., but reduces some of the caveats introduced through time spent on overhead. Have the time measured on the client side using JavaScript and submitted alongside with the solution. This would theoretically be the most accurate, but it introduces the possibility of cheating, because you're relying on client data. Use the request time headers of a "ready to play" AJAX call and the result submission request. Same caveat as 3., as it is still client data. A combination of server side and client side measuring with some kind of plausibility analysis. I can't think of a good way, but maybe you can. Thoughts? Other ideas?

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Drools - Doing Complex Stuff inside a Rule Condition or Consequence

- by mfcabrera

Hello, In my company we are planning to use Drools a BRE for couple of projects. Now we trying to define some best-practices. My question is what should be and shouldn't be done inside a Rule Condition/Consequence. Given that we can write Java directly or call methods (for example From a Global object in the Working Memory). Example. Given a Rule that evaluates a generic Object (e.g. Person) have property set to true. Now, that specific propertie can only be defined for that Object going to the database and fetching that info. So we have two ways of implementing that: Alternative A: Go to the database and fetch the object property (true/false, a code) Insert the Object in the working memory Evaluate the rule Alternative B: Insert a Global Object that has a method that connects to the database and check for the property for the given object. Insert the Object to eval in Working Memory In the rule, call the Global Object and perform the access to the database Which of those is considered better? I really like A, but sometimes B is more straightforward, however what would happen if something like a Exception from the Database is raised? I have seen the alternative B implemented in the Drools 5.0 Book from Packt Publishing,however they are doing a mocking and they don't talk about the actual implications of going to the database at all. Thank you,

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How do I change the viewport of a window in win32?

- by Colen

Hi, I have a window with child windows inside in it. The child windows take up about 1000 pixels of vertical space. However, our users don't always have 1000 pixels of vertical space available - they might have as little as 500 or 600 pixels. I want to be able to display this window at a size of 500 pixels high, and have the user "scroll" up and down the window to see the full contents. The window should always be 500 pixels high, but the view within it should change. Assume I can add a scroll bar somewhere so the user can choose which part of the window he wants to see. Windows will normally paint the window contents from height 0 to height 500; how do I tell it instead to "paint from height 250 to height 750", for example? I know that I can set the viewport with functions like SetViewportOrgEx etc, but those functions require a device context - when do I call them if I want them to be "permanent"? Do I call them when I get the WM_PAINT message from windows? Or at some other time? And which functions from that family do I want to use? Thanks.

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how to convert video from one format to another using php

- by Meena

hi i want to include the vedio download option in my webpage. I am using ffmpeg, but it seems to work very slow. Is there is any other way to do this or how to spead up the ffmpeg. i am using this code to get the frames from the vedio. to convert the vedio $call="ffmpeg -i ".$_SESSION['video_to_convert']." -vcodec libvpx -r 30 -b ".$quality." -acodec libvorbis -ab 128000 -ar ".$audio." -ac 2 -s ".$size." ".$converted_vids.$name.".".$type." -y 2> log/".$name.".txt"; $convert = (popen("start /b ".$call, "r")); pclose($convert); to get the frame from the vedio exec("ffmpeg -vframes 1 -ss ".$time_in_seconds." -i $converted_vids video_images.jpg -y 2>); but this code does not generate any error its loading continously.

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Access is denied. Javascript error on request to secured page

- by ihorko

On SomePage.aspx page by javascript (XMLHttpRequest) I call SecuredPage.aspx used next code: var httpRequest = GetXmlHttp(); var url = "https://myhost.com/SecuredPage.aspx"; var params = "param1=" + document.getElementById('param1').value + "&param2=" + document.getElementById('param2').value; httpRequest.open("POST", url, true); httpRequest.setRequestHeader("Content-Type", "application/x-www-form-urlencoded"); httpRequest.onreadystatechange = function() { //Call a function when the state changes. if (httpRequest.readyState == 4 && httpRequest.status == 200) { alert(httpRequest.responseText); } } httpRequest.send(params); // HERE ACCESS IS DENIED //--------------------------------------------- function GetXmlHttp() { var xmlhttp = false; if (window.XMLHttpRequest) { xmlhttp = new XMLHttpRequest(); } else if (window.ActiveXObject) // code for IE { try { xmlhttp = new ActiveXObject("Msxml2.XMLHTTP"); } catch (e) { try { xmlhttp = new ActiveXObject("Microsoft.XMLHTTP"); } catch (E) { xmlhttp = false; } } } return xmlhttp; } It throws Access is denied error. if send to http (http://myhost.com/SecuredPage.aspx), it works fine. How is it possible to resolve that problem. Thanks!

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Using *.html extension in dynamic URL's for SEO

- by lostaman

Hi all My situation is. I have a project planned to be built on ASP.NET MVC 2. And one of the major requirements is SEO optimization. A customer wants to use static-like URLs that end up with .html extension for this project that make URLs more SEO friendly. E.g. "mysite.com/about.html " or "mysite.com/items/getitem/5.html" etc. I wonder is there any benefit from SEO perspective to use .html extension in dynamic URLs? Are Google and other search engines rank work better with such URLs?

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unexpected behaviour of object stored in web service Session

- by draconis

Hi. I'm using Session variables inside a web service to maintain state between successive method calls by an external application called QBWC. I set this up by decorating my web service methods with this attribute: [WebMethod(EnableSession = true)] I'm using the Session variable to store an instance of a custom object called QueueManager. The QueueManager has a property called ChangeQueue which looks like this: [Serializable] public class QueueManager { ... public Queue<QBChange> ChangeQueue { get; set; } ... where QBChange is a custom business object belonging to my web service. Now, every time I get a call to a method in my web service, I use this code to retrieve my QueueManager object and access my queue: QueueManager qm = (QueueManager)Session[ticket]; then I remove an object from the queue, using qm.dequeue() and then I save the modified query manager object (modified because it contains one less object in the queue) back to the Session variable, like so: Session[ticket] = qm; ready for the next web service method call using the same ticket. Now here's the thing: if I comment out this last line //Session[ticket] = qm; , then the web service behaves exactly the same way, reducing the size of the queue between method calls. Now why is that? The web service seems to be updating a class contained in serialized form in a Session variable without being asked to. Why would it do that? When I deserialize my Queuemanager object, does the qm variable hold a reference to the serialized object inside the Session[ticket] variable?? This seems very unlikely.

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How would a user stay logged in to a REST-based website?

- by unforgiven3

A year or so ago I asked this question: Can you help me understand this? “Common REST Mistakes: Sessions are irrelevant”. My question was essentially this: Okay, I get that HTTP authentication is done automatically on every message - but how? Is the username/password sent with every request? Doesn't that just increase attack surface area? I feel like I'm missing part of the puzzle. The answers I received made perfect sense in the context of a mobile (iPhone, Android, WP7) app - when talking to a REST service, the app would just send user credentials along with each request. That worked great for me. But now, I would like to better understand how one would secure a REST-like website, like StackOverflow itself or something like Reddit. How would things work if it was a user logged in via a web browser instead of logged in via an iPhone app? What happens when a user logs in? Are the credentials saved in the browser somehow? How would the browser know what credentials to send with subsequent REST requests? What if it's a JavaScript call to a webservice? How would the JavaScript call include user credentials? I'll be quite frank: my understanding of security when it comes to websites is pretty limited. I enjoyed working with REST services from an app perspective, but now I want to try and build a website that is based on REST principles, and I'm finding myself to be pretty lost. If there is anything in the above question that is unclear that you'd like me to clarify, please leave a comment and I'll address it.

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Jquery Ajax + PHP

- by Kris.Mitchell

I am having problems with jQuery Ajax and PHP I have my php file set up to echo the data I am gathering from a mysql database. I have verified that the database is returning something and that the string at the end of the function actually contains data. What is happening though, is that it looks like the php echo is happening before the ajax call, causing the php data to be displayed at the top of the page, and not below in proper div. I think it might have something to do with timing of the ajax and the php call, but I am not sure. So, why is the data not getting caught by the .ajax and thrown into the div? Thanks for the help! jQuery $(document).ready(function() { $.ajax({ url: "../database_functions.php", type: "GET", data: "cat=jw&sub=pi&sort=no", cache: false, success: function (html) { alert("Success!"); $('#product-list').html(html); } }); }); PHP echo "Hello World";

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Thread mutex behaviour

- by Alberteddu

Hi there, I'm learning C. I'm writing an application with multiple threads; I know that when a variable is shared between two or more threads, it is better to lock/unlock using a mutex to avoid deadlock and inconsistency of variables. This is very clear when I want to change or view one variable. int i = 0; /** Global */ static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER; /** Thread 1. */ pthread_mutex_lock(&mutex); i++; pthread_mutex_unlock(&mutex); /** Thread 2. */ pthread_mutex_lock(&mutex); i++; pthread_mutex_unlock(&mutex); This is correct, I think. The variable i, at the end of the executions, contains the integer 2. Anyway, there are some situations in which I don't know exactly where to put the two function calls. For example, suppose you have a function obtain(), which returns a global variable. I need to call that function from within the two threads. I have also two other threads that call the function set(), defined with a few arguments; this function will set the same global variable. The two functions are necessary when you need to do something before getting/setting the var. /** (0) */ /** Thread 1, or 2, or 3... */ if(obtain() == something) { if(obtain() == somethingElse) { // Do this, sometimes obtain() and sometimes set(random number) (1) } else { // Do that, just obtain(). (2) } } else { // Do this and do that (3) // If # of thread * 3 > 10, then set(3*10) For example. (4) } /** (5) */ Where I have to lock, and where I have to unlock? The situation can be, I think, even more complex. I will appreciate an exhaustive answer. Thank you in advance. —Alberto

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C++ - Basic WinAPI question

- by HardCoder1986

Hello! I am now working on a some sort of a game engine and I had an idea to put everything engine-related into a static library and then link it to my actual problem. Right now I achieved it and actually link that library and every functions seem to work fine, except those, which are windows-related. I have a chunk of code in my library that looks like this: hWnd = CreateWindow(className, "Name", WS_OVERLAPPED | WS_CAPTION | WS_EX_TOPMOST, 0, 0, 800, 600, NULL, NULL, GetModuleHandle(NULL), this); if (hWnd) { ShowWindow(hWnd, SW_NORMAL); UpdateWindow(hWnd); } else { MessageBox(NULL, "Internal program error", "Error", MB_OK | MB_ICONERROR); return; } When this code was not in the library, but in the actual project, it worked fine, created the window and everything was ok. Right now (when I'm linking to my library that contains this code) CreateWindow(...) call returns NULL and GetLastError() returns "Operation succesfully completed" (wtf?). Could anybody help me with this? Is it possible to create a window and display it using a static library call and why could my code fail? Thank you.

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Compiler turning a string& into a basic_string<>&

- by Shtong

Hello I'm coming back to C++ after long years spent on other technologies and i'm stuck on some weird behavior when calling some methods taking std::string as parameters : An example of call : LocalNodeConfiguration *LocalNodeConfiguration::ReadFromFile(std::string & path) { // ... throw configuration_file_error(string("Configuration file empty"), path); // ... } When I compile I get this (I cropped file names for readability) : /usr/bin/g++ -g -I/home/shtong/Dev/OmegaNoc/build -I/usr/share/include/boost-1.41.0 -o CMakeFiles/OmegaNocInternals.dir/configuration/localNodeConfiguration.cxx.o -c /home/shtong/Dev/OmegaNoc/source/configuration/localNodeConfiguration.cxx .../localNodeConfiguration.cxx: In static member function ‘static OmegaNoc::LocalNodeConfiguration* OmegaNoc::LocalNodeConfiguration::ReadFromFile(std::string&)’: .../localNodeConfiguration.cxx:72: error: no matching function for call to ‘OmegaNoc::configuration_file_error::configuration_file_error(std::string, std::basic_string<char, std::char_traits<char>, std::allocator<char> >&)’ .../configurationManager.hxx:25: note: candidates are: OmegaNoc::configuration_file_error::configuration_file_error(std::string&, std::string&) .../configurationManager.hxx:22: note: OmegaNoc::configuration_file_error::configuration_file_error(const OmegaNoc::configuration_file_error&) So as I understand it, the compiler is considering that my path parameter turned into a basic_string at some point, thus not finding the constructor overload I want to use. But I don't really get why this transformation happened. Some search on the net suggested me to use g++ but I was already using it. So any other advice would be appreciated :) Thanks

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incorrect height in Chrome when "-webkit-appearance: none" and value="" on <input> tag

- by Avi Steiner

In Chrome v17.0.963.79 on Windows 7, I seem to be having an inexplicable problem when applying the -webkit-appearance: none style to an <input> tag. The problem is as follows: I have a stylesheet, let's call it potatofoot.css, which consists of the code .tbl { display: table; } .tblRow { display: table-row; } .tblCell { display: table-cell; } input { -webkit-appearance: none; }? and I have an html file, let's call it blech.html, which contains the code <div class="tbl"> <div class="tblRow"> <label class="tblCell">Name</label> <input type="text" class="tblCell" value="I'M NOT EMPTY! OH, YEAH!"> </div> </div> This displays fine (see this jsfiddle). But when I empty the value attribute, as in this jsfiddle, the entire table grows from a height of 26px to a height of 31px, the label moves to the bottom, and the input stays at the top. However, if I remove -webkit-appearance: none;, everything shows up the same with and without out the value attribute being filled. What's going on?

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Where is the chink in Google Chrome's armor?

- by kudlur

While browsing with Chrome, I noticed that it responds extremely fast (in comparison with IE and Firefox on my laptop) in terms of rendering pages, including JavaScript heavy sites like gmail. This is what googlebook on Chrome has to say tabs are hosted in process rather than thread. compile javascript using V8 engine as opposed to interpreting. Introduce new virtual machine to support javascript heavy apps introduce "hidden class transitions" and apply dynamic optimization to speed up things. Replace inefficient "Conservative garbage colllection" scheme with more precise garbage collection scheme. Introduce their own task scheduler and memory manager to manage the browser environment. All this sounds so familiar, and Microsoft has been doing such things for long time.. Windows os, C++, C# etc compilers, CLR, and so on. So why isn't Microsoft or any other browser vendor taking Chrome's approach? Is there a flaw in Chrome's approach? If not, is the rest of browser vendor community caught unaware with Google's approach?

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Problem with function calls [javascript]

- by Samuel

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How to write a "thread safe" function in C ?

- by Andrei Ciobanu

Hello I am writing some data structures in C, and I've realized that their associated functions aren't thread safe. The i am writing code uses only standard C, and I want to achieve some sort of 'synchronization'. I was thinking to do something like this: enum sync_e { TRUE, FALSE }; typedef enum sync_e sync; struct list_s { //Other stuff struct list_node_s *head; struct list_node_s *tail; enum sync_e locked; }; typedef struct list_s list; , to include a "boolean" field in the list structure that indicates the structures state: locked, unlocked. For example an insertion function will be rewritten this way: int list_insert_next(list* l, list_node *e, int x){ while(l->locked == TRUE){ /* Wait */ } l->locked = TRUE; /* Insert element */ /* -------------- */ l->locked = FALSE; return (0); } While operating on the list the 'locked' field will be set to TRUE, not allowing any other alterations. After operation completes the 'locked' field will be again set to 'TRUE'. Is this approach good ? Do you know other approaches (using only standard C).

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SQL Server 2008 Stored Proc suddenly returns -1

- by aaginor

I use the following stored procedure from my SQL Server 2008 database to return a value to my C#-Program ALTER PROCEDURE [dbo].[getArticleBelongsToCatsCount] @id int AS BEGIN SET NOCOUNT ON; DECLARE @result int; set @result = (SELECT COUNT(*) FROM art_in_cat WHERE child_id = @id); return @result; END I use a SQLCommand-Object to call this Stored Procedure public int ExecuteNonQuery() { try { return _command.ExecuteNonQuery(); } catch (Exception e) { Logger.instance.ErrorRoutine(e, "Text: " + _command.CommandText); return -1; } } Till recently, everything works fine. All of a sudden, the stored procedure returned -1. At first, I suspected, that the ExecuteNonQuery-Command would have caused and Exception, but when stepping through the function, it shows that no Exception is thrown and the return value comes directly from return _command.ExecuteNonQuery(); I checked following parameters and they were as expected: - Connection object was set to the correct database with correct access values - the parameter for the SP was there and contained the right type, direction and value Then I checked the SP via SQLManager, I used the same value for the parameter like the one for which my C# brings -1 as result (btw. I checked some more parameter values in my C' program and they ALL returned -1) but in the manager, the SP returns the correct value. It looks like the call from my C# prog is somehow bugged, but as I don't get any error (it's just the -1 from the SP), I have no idea, where to look for a solution.

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Pass arguments to a parameter class object

- by David R

This is undoubtedly a simple question. I used to do this before, but it's been around 10 years since I worked in C++ so I can't remember properly and I can't get a simple constructor call working. The idea is that instead of parsing the args in main, main would create an object specifically designed to parse the arguments and return them as required. So: Parameters params = new Parameters(argc, argv) then I can call things like params.getfile() Only problem is I'm getting a complier error in Visual Studio 2008 and I'm sure this is simple, but I think my mind is just too rusty. What I've got so far is really basic: In the main: #include "stdafx.h" #include "Parameters.h" int _tmain(int argc, _TCHAR* argv[]) { Parameters params = new Parameters(argc, argv); return 0; } Then in the Parameters header: #pragma once class Parameters { public: Parameters(int, _TCHAR*[]); ~Parameters(void); }; Finally in the Parameters class: include "Stdafx.h" #include "Parameters.h" Parameters::Parameters(int argc, _TCHAR* argv[]) { } Parameters::~Parameters(void) { } I would appreciate if anyone could see where my ageing mind has missed the really obvious. Thanks in advance.

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Using groovy ws with enum types?

- by Jared

I'm trying to use groovy ws to call a webservice. One of the properties of the generated class is it's self a class with an enum type. Although the debug messages show that the com.test.FinalActionType is created at runtime when the WSDL is read I can't create an instance of it using code like proxy.create("com.test.FinalActionType") When I try and assign a string to my class uin place of an instance of FinalActionType groovy is not able to do the conversion. How can I get an instance of this class to use in a webservice call? I've pasted the important part of the WSDL below. <xsd:simpleType name="FinalActionType"> <xsd:restriction base="xsd:string"> <xsd:enumeration value="stop"/> <xsd:enumeration value="quit"/> <xsd:enumeration value="continue"/> <xsd:whiteSpace value="collapse"/> </xsd:restriction> </xsd:simpleType>

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Member function overloading/template specialization issue

- by Ferruccio

I've been trying to call the overloaded table::scan_index(std::string, ...) member function without success. For the sake of clarity, I have stripped out all non-relevant code. I have a class called table which has an overloaded/templated member function named scan_index() in order to handle strings as a special case. class table : boost::noncopyable { public: template <typename T> void scan_index(T val, std::function<bool (uint recno, T val)> callback) { // code } void scan_index(std::string val, std::function<bool (uint recno, std::string val)> callback) { // code } }; Then there is a hitlist class which has a number of templated member functions which call table::scan_index(T, ...) class hitlist { public: template <typename T> void eq(uint fieldno, T value) { table* index_table = db.get_index_table(fieldno); // code index_table->scan_index<T>(value, [&](uint recno, T n)->bool { // code }); } }; And, finally, the code which kicks it all off: hitlist hl; // code hl.eq<std::string>(*fieldno, p1.to_string()); The problem is that instead of calling table::scan_index(std::string, ...), it calls the templated version. I have tried using both overloading (as shown above) and a specialized function template (below), but nothing seems to work. After staring at this code for a few hours, I feel like I'm missing something obvious. Any ideas? template <> void scan_index<std::string>(std::string val, std::function<bool (uint recno, std::string val)> callback) { // code }

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How to catch unintentional function interpositioning with GCC?

- by SiegeX

Reading through my book Expert C Programming, I came across the chapter on function interpositioning and how it can lead to some serious hard to find bugs if done unintentionally. The example given in the book is the following: my_source.c mktemp() { ... } main() { mktemp(); getwd(); } libc mktemp(){ ... } getwd(){ ...; mktemp(); ... } According to the book, what happens in main() is that mktemp() (a standard C library function) is interposed by the implementation in my_source.c. Although having main() call my implementation of mktemp() is intended behavior, having getwd() (another C library function) also call my implementation of mktemp() is not. Apparently, this example was a real life bug that existed in SunOS 4.0.3's version of lpr. The book goes on to explain the fix was to add the keyword static to the definition of mktemp() in my_source.c; although changing the name altogether should have fixed this problem as well. This chapter leaves me with some unresolved questions that I hope you guys could answer: Should our software group adopt the practice of putting the keyword static in front of all functions that we don't want to be exposed? Does GCC have a way to warn about function interposition? We certainly don't ever intend on this happening and I'd like to know about it if it does. Can interposition happen with functions introduced by static libraries? Thanks for the help.

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Dynamic Select boxes page load

- by Chris

Hello, I have a dynamic chained select box that I am attempting to show the value of on a page load. In my chained select box, it will default to the first option within the select box on page load, could anyone provide assitance? I stumbled upon this thread, but I can't seem to translate what they are doing with that answer to my language of CF. Dynamic chained drop downs on page refresh Here is the JS script I am using. function dynamicSelect(id1, id2) { // Feature test to see if there is enough W3C DOM support if (document.getElementById && document.getElementsByTagName) { // Obtain references to both select boxes var sel1 = document.getElementById(id1); var sel2 = document.getElementById(id2); // Clone the dynamic select box var clone = sel2.cloneNode(true); // Obtain references to all cloned options var clonedOptions = clone.getElementsByTagName("option"); // Onload init: call a generic function to display the related options in the dynamic select box refreshDynamicSelectOptions(sel1, sel2, clonedOptions); // Onchange of the main select box: call a generic function to display the related options in the dynamic select box sel1.onchange = function() { refreshDynamicSelectOptions(sel1, sel2, clonedOptions); } } } function refreshDynamicSelectOptions(sel1, sel2, clonedOptions) { // Delete all options of the dynamic select box while (sel2.options.length) { sel2.remove(0); } // Create regular expression objects for "select" and the value of the selected option of the main select box as class names var pattern1 = /( |^)(select)( |$)/; var pattern2 = new RegExp("( |^)(" + sel1.options[sel1.selectedIndex].value + ")( |$)"); // Iterate through all cloned options for (var i = 0; i < clonedOptions.length; i++) { // If the classname of a cloned option either equals "select" or equals the value of the selected option of the main select box if (clonedOptions[i].className.match(pattern1) || clonedOptions[i].className.match(pattern2)) { // Clone the option from the hidden option pool and append it to the dynamic select box sel2.appendChild(clonedOptions[i].cloneNode(true)); } } } Thanks so much for any assistance

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Java reflection appropriateness

- by jsn

This may be a fairly subjective question, but maybe not. My application contains a bunch of forms that are displayed to the user at different times. Each form is a class of its own. Typically the user clicks a button, which launches a new form. I have a convenience function that builds these buttons, you call it like this: buildButton( "button text", new SelectionAdapter() { @Override public void widgetSelected( SelectionEvent e ) { showForm( new TasksForm( args... ) ); } } ); I do this dozens of times, and it's really cumbersome having to make a SelectionAdapter every time. Really all I need for the button to know is what class to instantiate when it's clicked and what arguments to give the constructor, so I built a function that I call like this instead: buildButton( "button text", TasksForm.class, args... ); Where args is an arbitrary list of objects that you could use to instantiate TasksForm normally. It uses reflection to get a constructor from the class, match the argument list, and build an instance when it needs to. Most of the time I don't have to pass any arguments to the constructor at all. The downside is obviously that if I'm passing a bad set of arguments, it can't detect that at compilation time, so if it fails, a dialog is displayed at runtime. But it won't normally fail, and it'll be easy to debug if it does. I think this is much cleaner because I come from languages where the use of function and class literals is pretty common. But if you're a normal Java programmer, would seeing this freak you out, or would you appreciate not having to scan a zillion SelectionAdapters?

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Is locking on the requested object a bad idea?

- by Quick Joe Smith

Most advice on thread safety involves some variation of the following pattern: public class Thing { private static readonly object padlock = new object(); private string stuff, andNonsense; public string Stuff { get { lock (Thing.padlock) { if (this.stuff == null) this.stuff = "Threadsafe!"; } return this.stuff; } } public string AndNonsense { get { lock (Thing.padlock) { if (this.andNonsense == null) this.andNonsense = "Also threadsafe!"; } return this.andNonsense; } } // Rest of class... } In cases where the get operations are expensive and unrelated, a single locking object is unsuitable because a call to Stuff would block all calls to AndNonsense, degrading performance. And rather than create a lock object for each call, wouldn't it be better to acquire the lock on the member itself (assuming it is not something that implements SyncRoot or somesuch for that purpose? For example: public string Stuff { get { lock (this.stuff) { // Pretend that this is a very expensive operation. if (this.stuff == null) this.stuff = "Still threadsafe and good?"; } return this.stuff; } } Strangely, I have never seen this approach recommended or warned against. Am I missing something obvious?

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