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• From the Tips Box: Controlling Xbox Controllers in Windows, Keeping Your Computer Cool in the Summer, and a DIY Book Scanning Rig

  - by Jason Fitzpatrick

  Once a week we round up some great reader tips from the tips box and reader comments, and share the with the rest of you. This week we’re looking at an alternate way to control Xbox controller in Windows, how to keep your computer cool in the summer heat, and how to build a power DIY book scanner. How to Use an Xbox 360 Controller On Your Windows PC Download the Official How-To Geek Trivia App for Windows 8 How to Banish Duplicate Photos with VisiPic

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• Is it possible to setup a DHCP server only for local virtual machines?

  - by thiesdiggity

  I have a quick question. I have a bunch of virtual machines (VMWare Workstation) running on an Ubuntu server and have found that VMWare NAT (DHCP) service is unreliable and slow. I have to use NAT instead of bridging because the server is in a data-center that does not have DHCP and I don't have enough static IP's for all the VMs. Is it possible to setup the host (Ubuntu) to be a DHCP server but only for the local virtual machines? The server has 2 network interfaces, so I'd set eth0 to be a static IP, which connects to the outside world, and eth1 to listen for DHCP. Now, I am thinking if I don't want DHCP to broadcast I would just not connect a cable to eth1 and setup the VM's to use bridging on eth1. That way DHCP would not broadcast through my network but be listening on that interface. Would that setup work?

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• C# - default parameter values from previous parameter

  - by Sagar R. Kothari

  namespace HelloConsole { public class BOX { double height, length, breadth; public BOX() { } // here, I wish to pass 'h' to remaining parameters if not passed // FOLLOWING Gives compilation error. public BOX (double h, double l = h, double b = h) { Console.WriteLine ("Constructor with default parameters"); height = h; length = l; breadth = b; } } } // // BOX a = new BOX(); // default constructor. all okay here. // BOX b = new BOX(10,20,30); // all parameter passed. all okay here. // BOX c = new BOX(10); // Here, I want = length=10, breadth=10,height=10; // BOX d = new BOX(10,20); // Here, I want = length=10, breadth=20,height=10; Question is : 'To achieve above, Is 'constructor overloading' (as follows) is the only option? public BOX(double h) { height = length = breadth = h; } public BOX(double h, double l) { height = breadth = h; length = l; }

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• Using WiX, how do I change a property of a subfolder of a virtual directory?

  - by Joergen Bech

  I have a hierarchy of Directory elements in a WiX script. I also have a component that creates a virtual directory (using IIS:WebVirtualDir), which points to the root of my Directory hierarchy. How do I change a property (e.g. AnonymousAccess) of a subfolder of the virtual directory, e.g. MyVirtualDir <<< this is the virtual directory root MyVirtualDir\MySubFolder <<< this is the subfolder for which I wish to change a property using WebDirProperties Please note that I do not wish to create a new virtual directory for the subfolder. I only wish to change a few security settings. The current script is too big to post here, but take a look at the WiX tutorial: 5.3 Web Directory. Suppose in that example that there was another Directory element named "MySubFolder" nested within the "InstallDir" element. What would then be the next step in order to set properties for "MySubFolder" without turning it into a virtual directory?

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• Microsoft VDI 2012 - VDI Personal collection vs Session-based deployment

  - by Vazgen

  I have a small confusion about the differences between the 2 types of set ups: When deploying using Add Roles and Features the Wizard requests to choose from one of two Deployment Scenarios: Virtual machine-based desktop deployment : Virtual machine-based desktop deployment allows users to connect to virtual desktop collections that include published RemoteApp programs and virtual desktops. Session-based desktop deployment : Session-based desktop deployment allows users to connect to session collections that include published RemoteApp programs and session-based desktops. Although this seems intuitive now, if I continue with "Virtual machine-based desktop deployment" I later have another two options when creating a collection: Pooled virtual desktop collection Personal virtual desktop collection This is where my confusion lies. What is the differences between a Session-based deployment and Virtual machine-based deployment with Personal virtual desktop collections? I'm mostly finding information pertaining to Windows Server 2008 but I know there are some core improvements in VDI 2012 so would someone please comment on that. Thank you

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• Why did Google remove the search box in developer tool from Chrome 22 stable release?

  - by Bruce

  In previous version of Chrome, there's the search box in developer tool, on the right top when I open it, just as shown below. (Sorry I can't upload image cuz' I don't have enough reputation for now.) http://i.minus.com/iklSx2vi0uzFB.JPG But, after I upgraded to the first release of Chrome 22 yesterday, that search box was gone, as shown below. http://i.minus.com/ibxXt9wnBekR7E.JPG It is such a useful search box that I rely on all the time, to search for something, or to validate an xpath. So does Google just 'hide' it somewhere else? Or do they really remove it? Anyone know why they made such changes?

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• Use Internet Explorer 6 and 7 in Virtual Box.

  - by Sharon

  Hello. I am trying to install the vhds (virtual hard drive image) of IE6 on XP and IE 7 on XP packs available from Microsoft on Virtual Box. Virtual Box will only mount CD/DVD's and/or ISO's. How do I get it to use the Microsoft files? I need this to test web pages in IE6/IE7s. I am running Windows 7 Home Premium. Is there a way to do this, or another way that will allow me to load XP/IE6 and XP/IE7 in Virtualbox Edit: Ok I got it to work but it says XP must be updated in 3 days due to hardware changes. Microsoft said this would be activated til January 1st 2010. Is there a way to bypass that?

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• Best way to use my windows box as a backup?

  - by DFischer

  I put a 1.5 TB HD in my Windows 7 box and my main computer is a MBP. I have a lot of professional files/folders in a FireWire 800 external HD connected to the MBP and I want to use the 1.5 TB HD in my Windows 7 box as a backup for both the HD and MBP. Right now I am just copying files manually to the HD over the network and that's very slow and open to failure (not rsync'd.) Anyone suggest some appropriate solutions? Should I just figure out how to setup RSync on the windows box or is there a better alternative? Thanks!

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• Best way to use my windows box as a backup?

  - by user29336

  I put a 1.5 TB HD in my Windows 7 box and my main computer is a MBP. I have a lot of professional files/folders in a FireWire 800 external HD connected to the MBP and I want to use the 1.5 TB HD in my Windows 7 box as a backup for both the HD and MBP. Right now I am just copying files manually to the HD over the network and that's very slow and open to failure (not rsync'd.) Anyone suggest some appropriate solutions? Should I just figure out how to setup RSync on the windows box or is there a better alternative? Thanks!

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• Watch TV/recorded shows from my Comcast cable box on my Mac?

  - by IVR Avenger

  Hi, all. I've got a MacBook that's about three years old (it's the first generation that had a dual core CPU), running Leopard. I've got a Comcast DVR/HD Cable box. Is there something that I can install in between these devices that will let me watch TV from the Cable box on the Mac's display? The Cable box is in one room, but my tush and the Mac are in the other (fixing code on another machine that can't be part of the equation). Any ideas? Thanks! IVR Avenger

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• What's up with LDoms: Part 1 - Introduction & Basic Concepts

  - by Stefan Hinker

  LDoms - the correct name is Oracle VM Server for SPARC - have been around for quite a while now.  But to my surprise, I get more and more requests to explain how they work or to give advise on how to make good use of them.  This made me think that writing up a few articles discussing the different features would be a good idea.  Now - I don't intend to rewrite the LDoms Admin Guide or to copy and reformat the (hopefully) well known "Beginners Guide to LDoms" by Tony Shoumack from 2007.  Those documents are very recommendable - especially the Beginners Guide, although based on LDoms 1.0, is still a good place to begin with.  However, LDoms have come a long way since then, and I hope to contribute to their adoption by discussing how they work and what features there are today.  In this and the following posts, I will use the term "LDoms" as a common abbreviation for Oracle VM Server for SPARC, just because it's a lot shorter and easier to type (and presumably, read). So, just to get everyone on the same baseline, lets briefly discuss the basic concepts of virtualization with LDoms.  LDoms make use of a hypervisor as a layer of abstraction between real, physical hardware and virtual hardware.  This virtual hardware is then used to create a number of guest systems which each behave very similar to a system running on bare metal:  Each has its own OBP, each will install its own copy of the Solaris OS and each will see a certain amount of CPU, memory, disk and network resources available to it.  Unlike some other type 1 hypervisors running on x86 hardware, the SPARC hypervisor is embedded in the system firmware and makes use both of supporting functions in the sun4v SPARC instruction set as well as the overall CPU architecture to fulfill its function. The CMT architecture of the supporting CPUs (T1 through T4) provide a large number of cores and threads to the OS.  For example, the current T4 CPU has eight cores, each running 8 threads, for a total of 64 threads per socket.  To the OS, this looks like 64 CPUs.  The SPARC hypervisor, when creating guest systems, simply assigns a certain number of these threads exclusively to one guest, thus avoiding the overhead of having to schedule OS threads to CPUs, as do typical x86 hypervisors.  The hypervisor only assigns CPUs and then steps aside.  It is not involved in the actual work being dispatched from the OS to the CPU, all it does is maintain isolation between different guests. Likewise, memory is assigned exclusively to individual guests.  Here,  the hypervisor provides generic mappings between the physical hardware addresses and the guest's views on memory.  Again, the hypervisor is not involved in the actual memory access, it only maintains isolation between guests. During the inital setup of a system with LDoms, you start with one special domain, called the Control Domain.  Initially, this domain owns all the hardware available in the system, including all CPUs, all RAM and all IO resources.  If you'd be running the system un-virtualized, this would be what you'd be working with.  To allow for guests, you first resize this initial domain (also called a primary domain in LDoms speak), assigning it a small amount of CPU and memory.  This frees up most of the available CPU and memory resources for guest domains.  IO is a little more complex, but very straightforward.  When LDoms 1.0 first came out, the only way to provide IO to guest systems was to create virtual disk and network services and attach guests to these services.  In the meantime, several different ways to connect guest domains to IO have been developed, the most recent one being SR-IOV support for network devices released in version 2.2 of Oracle VM Server for SPARC. I will cover these more advanced features in detail later.  For now, lets have a short look at the initial way IO was virtualized in LDoms: For virtualized IO, you create two services, one "Virtual Disk Service" or vds, and one "Virtual Switch" or vswitch.  You can, of course, also create more of these, but that's more advanced than I want to cover in this introduction.  These IO services now connect real, physical IO resources like a disk LUN or a networt port to the virtual devices that are assigned to guest domains.  For disk IO, the normal case would be to connect a physical LUN (or some other storage option that I'll discuss later) to one specific guest.  That guest would be assigned a virtual disk, which would appear to be just like a real LUN to the guest, while the IO is actually routed through the virtual disk service down to the physical device.  For network, the vswitch acts very much like a real, physical ethernet switch - you connect one physical port to it for outside connectivity and define one or more connections per guest, just like you would plug cables between a real switch and a real system. For completeness, there is another service that provides console access to guest domains which mimics the behavior of serial terminal servers. The connections between the virtual devices on the guest's side and the virtual IO services in the primary domain are created by the hypervisor.  It uses so called "Logical Domain Channels" or LDCs to create point-to-point connections between all of these devices and services.  These LDCs work very similar to high speed serial connections and are configured automatically whenever the Control Domain adds or removes virtual IO. To see all this in action, now lets look at a first example.  I will start with a newly installed machine and configure the control domain so that it's ready to create guest systems. In a first step, after we've installed the software, let's start the virtual console service and downsize the primary domain.  root@sun # ldm list NAME STATE FLAGS CONS VCPU MEMORY UTIL UPTIME primary active -n-c-- UART 512 261632M 0.3% 2d 13h 58m root@sun # ldm add-vconscon port-range=5000-5100 \ primary-console primary root@sun # svcadm enable vntsd root@sun # svcs vntsd STATE STIME FMRI online 9:53:21 svc:/ldoms/vntsd:default root@sun # ldm set-vcpu 16 primary root@sun # ldm set-mau 1 primary root@sun # ldm start-reconf primary root@sun # ldm set-memory 7680m primary root@sun # ldm add-config initial root@sun # shutdown -y -g0 -i6 So what have I done: I've defined a range of ports (5000-5100) for the virtual network terminal service and then started that service.  The vnts will later provide console connections to guest systems, very much like serial NTS's do in the physical world. Next, I assigned 16 vCPUs (on this platform, a T3-4, that's two cores) to the primary domain, freeing the rest up for future guest systems.  I also assigned one MAU to this domain.  A MAU is a crypto unit in the T3 CPU.  These need to be explicitly assigned to domains, just like CPU or memory.  (This is no longer the case with T4 systems, where crypto is always available everywhere.) Before I reassigned the memory, I started what's called a "delayed reconfiguration" session.  That avoids actually doing the change right away, which would take a considerable amount of time in this case.  Instead, I'll need to reboot once I'm all done.  I've assigned 7680MB of RAM to the primary.  That's 8GB less the 512MB which the hypervisor uses for it's own private purposes.  You can, depending on your needs, work with less.  I'll spend a dedicated article on sizing, discussing the pros and cons in detail. Finally, just before the reboot, I saved my work on the ILOM, to make this configuration available after a powercycle of the box.  (It'll always be available after a simple reboot, but the ILOM needs to know the configuration of the hypervisor after a power-cycle, before the primary domain is booted.) Now, lets create a first disk service and a first virtual switch which is connected to the physical network device igb2. We will later use these to connect virtual disks and virtual network ports of our guest systems to real world storage and network. root@sun # ldm add-vds primary-vds root@sun # ldm add-vswitch net-dev=igb2 switch-primary primary You are free to choose whatever names you like for the virtual disk service and the virtual switch.  I strongly recommend that you choose names that make sense to you and describe the function of each service in the context of your implementation.  For the vswitch, for example, you could choose names like "admin-vswitch" or "production-network" etc. This already concludes the configuration of the control domain.  We've freed up considerable amounts of CPU and RAM for guest systems and created the necessary infrastructure - console, vts and vswitch - so that guests systems can actually interact with the outside world.  The system is now ready to create guests, which I'll describe in the next section. For further reading, here are some recommendable links: The LDoms 2.2 Admin Guide The "Beginners Guide to LDoms" The LDoms Information Center on MOS LDoms on OTN

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• Is there an alternative to Google Code Search?

  - by blunders

  Per the Official Google Blog: Code Search, which was designed to help people search for open source code all over the web, will be shut down along with the Code Search API on January 15, 2012. Google Code Search is now gone, and since that makes it much harder to understand the features it presented, here's my attempt to render them via information I gathered from a cache of the page for the Search Options: The "In Search Box" just notes the syntax to type the command directly in the main search box instead of using the advance search interface. Package (In Search Box: "package:linux-2.6") Language (In Search Box: "lang:c++") (OPTIONS: any language, actionscript, ada, applescript, asp, assembly, autoconf, automake, awk, basic, bat, c, c#, c++, caja, cobol, coldfusion, configure, css, d, eiffel, erlang, fortran, go, haskell, inform, java, java, javascript, jsp, lex, limbo, lisp, lolcode, lua, m4, makefile, maple, mathematica, matlab, messagecatalog, modula2, modula3, objectivec, ocaml, pascal, perl, php, pod, prolog, proto, python, python, r, rebol, ruby, sas, scheme, scilab, sgml, shell, smalltalk, sml, sql, svg, tcl, tex, texinfo, troff, verilog, vhdl, vim, xslt, xul, yacc) File (In Search Box: "file:^.*.java$") Class (In Search Box: "class:HashMap") Function (In Search Box: "function:toString") License (In Search Box: "license:mozilla") (OPTIONS: null/any-license, aladdin/Aladdin-Public-License, artistic/Artistic-License, apache/Apache-License, apple/Apple-Public-Source-License, bsd/BSD-License, cpl/Common-Public-License, epl/Eclipse-Public-License, agpl/GNU-Affero-General-Public-License, gpl/GNU-General-Public-License, lgpl/GNU-Lesser-General-Public-License, disclaimer/Historical-Permission-Notice-and-Disclaimer, ibm/IBM-Public-License, lucent/Lucent-Public-License, mit/MIT-License, mozilla/Mozilla-Public-License, nasa/NASA-Open-Source-Agreement, python/Python-Software-Foundation-License, qpl/Q-Public-License, sleepycat/Sleepycat-License, zope/Zope-Public-License) Case Sensitive (In Search Box: "case:no") (OPTIONS: yes, no) Also of use in understanding the search tool would be the still live FAQs page for Google Code Search. Is there any code search engine that would fully replace Google Code Search's features?

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• SDL beginner: create Rectangle surface filled with color

  - by user3689

  im learning SDL , i like to create Rectangle surface with color that is not image . here is my code that compiles fine but dosnt work : im passing the function this params: SDL_Surface* m_screen = SDL_SetVideoMode(SCREEN_WIDTH,SCREEN_HEIGHT,SCREEN_BPP,SDL_SWSURFACE); SDL_FillRect(m_screen,&m_screen->clip_rect,SDL_MapRGB(m_screen->format,0xFF, 0xFF, 0xFF)); ... Button button(m_screen,0,0,50,50,255,0,0) ... ... Button::Button(SDL_Surface* screen,int x,int y,int w,int h,int R, int G, int B) { SDL_Rect box; SDL_Surface * ButtonSurface; ButtonSurface = NULL ; Uint32 rmask, gmask, bmask, amask; #if SDL_BYTEORDER == SDL_BIG_ENDIAN rmask = 0xff000000; gmask = 0x00ff0000; bmask = 0x0000ff00; amask = 0x000000ff; #else rmask = 0x000000ff; gmask = 0x0000ff00; bmask = 0x00ff0000; amask = 0xff000000; #endif box.x = x; box.y = y; box.w = w; box.h = h; ButtonSurface = SDL_CreateRGBSurface(SDL_SWSURFACE, box.w,box.h, 32, rmask, gmask, bmask, amask); if(ButtonSurface == NULL) { LOG_MSG("Button::Button Button failed"); } SDL_FillRect(screen,&box,SDL_MapRGB ( ButtonSurface->format, R, G, B )); //ut.ApplySurface(0,0,ButtonSurface,screen); SDL_BlitSurface(ButtonSurface,NULL,screen,&box); } what im doing here wrong ?

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• How can I create a rectangular SDL surface filled with a particular color?

  - by user3689

  I'm learning SDL. I'd like to create rectangular surface filled with a flat color (not an image). Below is my code -- it compiles fine, but doesn't work. I'm passing the function these parameters: SDL_Surface* m_screen = SDL_SetVideoMode( SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_BPP, SDL_SWSURFACE ); SDL_FillRect( m_screen, &m_screen->clip_rect, SDL_MapRGB(m_screen->format,0xFF, 0xFF, 0xFF) ); ... Button button(m_screen,0,0,50,50,255,0,0) ... ... Button::Button(SDL_Surface* screen,int x,int y,int w,int h,int R, int G, int B) { SDL_Rect box; SDL_Surface * ButtonSurface; ButtonSurface = NULL ; Uint32 rmask, gmask, bmask, amask; #if SDL_BYTEORDER == SDL_BIG_ENDIAN rmask = 0xff000000; gmask = 0x00ff0000; bmask = 0x0000ff00; amask = 0x000000ff; #else rmask = 0x000000ff; gmask = 0x0000ff00; bmask = 0x00ff0000; amask = 0xff000000; #endif box.x = x; box.y = y; box.w = w; box.h = h; ButtonSurface = SDL_CreateRGBSurface(SDL_SWSURFACE, box.w,box.h, 32, rmask, gmask, bmask, amask); if(ButtonSurface == NULL) { LOG_MSG("Button::Button Button failed"); } SDL_FillRect(screen,&box,SDL_MapRGB ( ButtonSurface->format, R, G, B )); //ut.ApplySurface(0,0,ButtonSurface,screen); SDL_BlitSurface(ButtonSurface,NULL,screen,&box); } What am I doing wrong here?

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• Zero downtime deployment (Tomcat), Nginx or HAProxy, behind hardware LB - how to "starve" old server?

  - by alexeypro

  Currently we have the following setup. Hardware Load Balancer (LB) Box A running Tomcat on 8080 (TA) Box B running Tomcat on 8080 (TB) TA and TB are running behind LB. For now it's pretty complicated and manual job to take Box A or Box B out of LB to do the zero downtime deployment. I am thinking to do something like this: Hardware Load Balancer (LB) Box A running Nginx on 8080 (NA) Box A running Tomcat on 8081 (TA1) Box A running Tomcat on 8082 (TA2) Box B running Nginx on 8080 (NB) Box B running Tomcat on 8081 (TB1) Box B running Tomcat on 8082 (TB2) Basically LB will be directing traffic between NA and NB now. On each of Nginx's we'll have TA1, TA2 and TB1, TB2 configured as upstream servers. Once one of the upstreams's healthcheck page is unresponsive (shutdown) the traffic goes to another one (HttpHealthcheckModule module on Nginx). So the deploy process is simple. Say, TA1 is active with version 0.1 of the app. Healthcheck on TA1 is OK. We start TA2 with Healthcheck on it as ERROR. So Nginx is not talking to it. We deploy app version 0.2 to TA2. Make sure it works. Now, we switch the Healthcheck on TA2 to OK, switch Healthcheck to TA1 to ERROR. Nginx will start serving TA2, and will remove TA1 out of rotation. Done! And now same with the other box. While it sounds all cool and nice, how do we "starve" the Nginx? Say we have pending connections, some users on TA1. If we just turn it off, sessions will break (we have cookie-based sessions). Not good. Any way to starve traffic to one of the upstream servers with Nginx? Thanks!

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• VirtualBox guest OS accessing local server on host OS.

  - by Maxim

  Hi, On my Ubuntu HOST I have my local webserver. I installed VirtualBox and Debian as a GUEST. I would like Debian guest to be able to hit my webserver running on my Ubuntu host (for example, I just type http://localhost:8080/ in the browser under Debian). How can this be done? Thanks in advance.

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• How to add a customized box at the bottom left side of wall tab?

  - by Unreality

  Dear all, I have a question about Facebook Page: (NOT user profile page, I mean a facebook page where you can become a fan) How to add a customized box at the bottom left side of wall tab? (I am the page creator/admin) Please don't just give an answer "add the box to the page". Cause I really don't know how. Also, it seems that putting $facebook-api_client-profile_setFBML and $facebook-api_client-profile_setInfo for the application won't provide a way for the page to add the box. Below is an example image that is done by the other. I have circled the box at the image. I would like to know how to do the same to the page that I owned. Many thanks for reading.

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• Linux: page faults and network filesystems

  - by Alex B

  If a Linux system runs out of physical memory, does it drop inactive executable code pages? I assume the answer is yes, since there is no reason to keep them in swap, so they are simply discarded and re-loaded if necessary (as far as I know, that's what FreeBSD does). If the above is true for Linux, my question is, how does it handle executables run from network filesystems (e.g. NFS)? Does it go and fetch executable pages over the network if there is a page fault?

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• How to find out memory layout of your data structure implementation on Linux 64bit machine

  - by ajay

  In this article, http://cacm.acm.org/magazines/2010/7/95061-youre-doing-it-wrong/fulltext the author talks about the memory layouts of 2 data structures - The Binary Heap and the B-Heap and compares how one has better memory layout than the other. http://deliveryimages.acm.org/10.1145/1790000/1785434/figs/f5.jpg http://deliveryimages.acm.org/10.1145/1790000/1785434/figs/f6.jpg I want to get hands on experience on this. I have an implementation of a N-Ary Tree and I want to find out the memory layout of my data structure. What is the best way to come up with a memory layout like the one in the article? Secondly, I think it is easier to identify the memory layout if it is an array based implementation. If the implementation of a Tree uses pointers then what Tools do we have or what kind of approach is required to map it's memory layout? Thanks!

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• How do you differentiate between "box," "machine," "computer" and whatever else?

  - by Corey

  There seems to be a few terms for referring to a computer, especially in the tech world. Different terms seem to be used based on technical expertise. When talking with people with some technical knowledge, I'll refer to it as a machine. When talking to non-technical people (family, friends) I'll call it a computer. On the rare occasion I'm talking about servers, I might call it a box, but even then I'll probably still call it a machine. Is that just me, or do there exist rules already for what to call a computer?

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• Message Box in asp.net not working after publish?

  - by Vibin Jith

  The Message box with ASP.NET(eg:Msgbox ("Updation Successful")) is working properly at the time of development.But after publishing the project in the local IIS the message box is invisible.The message box is not popping out when I run the web application in the local ISS. Can anybody suggest any solution for this?

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• Why does Java's invokevirtual need to resolve the called method's compile-time class?

  - by Chris

  Consider this simple Java class: class MyClass { public void bar(MyClass c) { c.foo(); } } I want to discuss what happens on the line c.foo(). At the bytecode level, the meat of c.foo() will be the invokevirtual opcode, and, according to the documentation for invokevirtual, more or less the following will happen: Look up the foo method defined in compile-time class MyClass. (This involves first resolving MyClass.) Do some checks, including: Verify that c is not an initialization method, and verify that calling MyClass.foo wouldn't violate any protected modifiers. Figure out which method to actually call. In particular, look up c's runtime type. If that type has foo(), call that method and return. If not, look up c's runtime type's superclass; if that type has foo, call that method and return. If not, look up c's runtime type's superclass's superclass; if that type has foo, call that method and return. Etc.. If no suitable method can be found, then error. Step #3 alone seems adequate for figuring out which method to call and verifying that said method has the correct argument/return types. So my question is why step #1 gets performed in the first place. Possible answers seem to be: You don't have enough information to perform step #3 until step #1 is complete. (This seems implausible at first glance, so please explain.) The linking or access modifier checks done in #1 and #2 are essential to prevent certain bad things from happening, and those checks must be performed based on the compile-time type, rather than the run-time type hierarchy. (Please explain.)

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• VS2010 Developer Image

  - by David Ward

  I am about to create a new developer PC image for developing WPF applications using VS2010, WCF, SQL2008 and SharePoint2010. What OS should I opt for? Windows 7? Windows Server 2008 R2? I'd have thought Windows 7 to make sure that I have a similar experience during development as an end user, however I can't install SharePoint on a client OS and so thought about Windows Server 2008 R2 to help with the SharePoint development process. Thoughts?

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• For Loop Question?

  - by NextRev

  I'm programming an app for the iPhone. I'm not very good with loops just yet. How do I shorten this code into a for loop? if(CGRectContainsRect([space1 frame], [box frame])){ space1.image = [UIImage imageNamed:@"box.png"]; } else if(CGRectContainsRect([space2 frame], [box frame])){ space2.image = [UIImage imageNamed:@"box.png"]; } else if(CGRectContainsRect([space3 frame], [box frame])){ space3.image = [UIImage imageNamed:@"box.png"]; } else if(CGRectContainsRect([space4 frame], [box frame])){ space4.image = [UIImage imageNamed:@"box.png"]; } else if(CGRectContainsRect([space5 frame], [box frame])){ space5.image = [UIImage imageNamed:@"box.png"]; }

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• Can you force a crash if a write occurs to a given memory location with finer than page granularity?

  - by Joseph Garvin

  I'm writing a program that for performance reasons uses shared memory (alternatives have been evaluated, and they are not fast enough for my task, so suggestions to not use it will be downvoted). In the shared memory region I am writing many structs of a fixed size. There is one program responsible for writing the structs into shared memory, and many clients that read from it. However, there is one member of each struct that clients need to write to (a reference count, which they will update atomically). All of the other members should be read only to the clients. Because clients need to change that one member, they can't map the shared memory region as read only. But they shouldn't be tinkering with the other members either, and since these programs are written in C++, memory corruption is possible. Ideally, it should be as difficult as possible for one client to crash another. I'm only worried about buggy clients, not malicious ones, so imperfect solutions are allowed. I can try to stop clients from overwriting by declaring the members in the header they use as const, but that won't prevent memory corruption (buffer overflows, bad casts, etc.) from overwriting. I can insert canaries, but then I have to constantly pay the cost of checking them. Instead of storing the reference count member directly, I could store a pointer to the actual data in a separate mapped write only page, while keeping the structs in read only mapped pages. This will work, the OS will force my application to crash if I try to write to the pointed to data, but indirect storage can be undesirable when trying to write lock free algorithms, because needing to follow another level of indirection can change whether something can be done atomically. Is there any way to mark smaller areas of memory such that writing them will cause your app to blow up? Some platforms have hardware watchpoints, and maybe I could activate one of those with inline assembly, but I'd be limited to only 4 at a time on 32-bit x86 and each one could only cover part of the struct because they're limited to 4 bytes. It'd also make my program painful to debug ;)

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