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  • C++ Inheritance Question

    - by shaz
    I have a base class MessageHandler and 2 derived classes, MessageHandler_CB and MessageHandler_DQ. The derived classes redefine the handleMessage(...) method. MH_DQ processes a message and puts the result in a deque while MH_CB processes the message and then executes a callback function. The base class has a static callback function that I pass along with a this pointer to a library which calls the static callback when a new message is available for processing. My problem comes when I am in the static callback with a void * pointing to either a MH_DQ or a MH_CB. If I cast it to the base class the empty MessageHandler::handleMessage(...) method is called, rather than the version in the appropriate derived class. What is the best way to address this situation from a design perspective and/or what language features might help me to implement a solution to my problem? Thanks in advance!

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  • C++ inheritance doubt

    - by Poiuyt
    Can you explain why this is not allowed, #include <stdio.h> class B { private: int a; public: int a; }; int main() { return 0; } while this is? #include <stdio.h> class A { public: int a; }; class B : public A{ private: int a; }; int main() { return 0; } In both the cases, we have one public and one private variable named a in class B.

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  • c++ Multiple Inheritance - Compiler modifying my pointers

    - by Bob
    If I run the following code, I get different addresses printed. Why? class Base1 { int x; }; class Base2 { int y; }; class Derived : public Base1, public Base2 { }; union U { Base2* b; Derived* d; U(Base2* b2) : b(b) {} }; int main() { Derived* d = new Derived; cout << d << "\n"; cout << U(d).d << "\n"; return 0; } Even more fun is if you repeatedly go in and out of the union the address keeps incrementing by 4, like this int main() { Derived* d = new Derived; cout << d << "\n"; d = U(d).d; cout << d << "\n"; d = U(d).d; cout << d << "\n"; return 0; } If the union is modified like this, then the problem goes away union U { void* v; Base2* b; Derived* d; U(void* v) : v(v) {} }; Also, if either base class is made empty, the problem goes away. Is this a compiler bug? I want it to leave my pointers the hell alone.

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  • Java inheritance question

    - by user247866
    So I have 3 classes. Abstract class A Class B extends class A independent Class C In class D that contains the main method, I create a list of instances of class B List<B> b = method-call();` // the method returns a list of instances of class B Now in class C I have one method that is common to both A and B, and hence I don't want to duplicate it. I want to have one method that takes as input an instance of class A, as follows: public void some-method(LIst<A> a) However, when I do: C c = new C(). c. some-method(b) I get an error that some-method is not applicable for the argument List, instead it's expecting to get List. Is there a good way to fix this problem? Many thanks!

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  • I want to build a Virtual Machine, are there any good references?

    - by Michael Stum
    I'm looking to build a Virtual Machine as a platform independent way to run some game code (essentially scripting). The Virtual Machines that I'm aware of in games are rather old: Infocom's Z-Machine, LucasArts' SCUMM, id Software's Quake 3. As a .net Developer, I'm familiar with the CLR and looked into the CIL Instructions to get an overview of what you actually implement on a VM Level (vs. the language level). I've also dabbled a bit in 6502 Assembler during the last year. The thing is, now that I want¹ to implement one, I need to dig a bit deeper. I know that there are stack based and register based VMs, but I don't really know which one is better at what and if there are more or hybrid approaches. I need to deal with memory management, decide which low level types are part of the VM and need to understand why stuff like ldstr works the way it does. My only reference book (apart from the Z-Machine stuff) is the CLI Annotated Standard, but I wonder if there is a better, more general/fundamental lecture for VMs? Basically something like the Dragon Book, but for VMs? I'm aware of Donald Knuth's Art of Computer Programming which uses a register-based VM, but I'm not sure how applicable that series still is, especially since it's still unfinished? Clarification: The goal is to build a specialized VM. For example, Infocom's Z-Machine contains OpCodes for setting the Background Color or playing a sound. So I need to figure out how much goes into the VM as OpCodes vs. the compiler that takes a script (language TBD) and generates the bytecode from it, but for that I need to understand what I'm really doing. ¹ I know, modern technology would allow me to just interpret a high level scripting language on the fly. But where is the fun in that? :) It's also a bit hard to google because Virtual Machines is nowadays often associated with VMWare-type OS Virtualization...

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  • How To Convert Virtual Machines Between VirtualBox and VMware

    - by Chris Hoffman
    Migrating to another virtual machine program can be intimidating. if you already have your virtual machines set up they way you like them, you don’t necessarily have to install them from scratch – you can migrate your existing virtual machines. VirtualBox and VMware use different virtual machine formats, but each supports the standard Open Virtualization Format. Convert your existing virtual machine to OVF or OVA and you’ll be able to import it into another virtual machine program. Unfortunately, this may not always work perfectly, as VirtualBox and VMware both seem to use slightly different OVA/OVF implementations that aren’t entirely compatible. If this doesn’t work, you may want to reinstall your virtual machine’s guest operating system from scratch. 8 Deadly Commands You Should Never Run on Linux 14 Special Google Searches That Show Instant Answers How To Create a Customized Windows 7 Installation Disc With Integrated Updates

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  • Virtual DVD writer

    - by AngryHacker
    Hi, my laptop does not have a DVD driver at all. But I'd like to convert my video to a DVD format (e.g. Video_TS and Audio_TS). Is there a Virtual DVD writer out there that can pretend to be a DVD+R or DVD-R or DVD-RW drive?

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  • Virtual Box state not saving upon restart/reset/shutdown - reverting to an earlier state

    - by user638756
    Every time I restart/shut down my VM in VirtualBox (image is Ubuntu 10.02), whenever I start it back up, it reverts to the state it was in after I installed Guest Additions. This is extremely frustrating as every time I make progress on a project, whenever it restarts (mostly from crashing), I have to redo mostly everything. Is this a known problem with Guest Additions or with Virtual Box in general, and if so is there some solution?

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  • VMWare ESXi virtual machine can contact the gateway but not the DNS server

    - by Nathan Palmer
    I am having a bit of a strange issue. I have a VMWare ESXi server with two virtual machines running on it. They are running just fine and can communicate on the network without a problem. I am now trying to add a third. I am installing Ubuntu 8.04 Server. I assign it a static IP address and it's a fresh installation. Once installed I can ping the gateway but I cannot ping the DNS server. It's on the same network with the other two VMs which are communicating just fine. I have tried to reinstall the operating system but it still fails to connect. Here is /etc/network/interfaces auto eth0 iface eth0 inet static address 192.168.1.23 netmask 255.255.255.0 network 192.168.1.0 broadcast 192.168.1.255 gateway 192.168.1.1 dns-nameservers 208.67.222.222 #opendns dns-search mydomain.com Here is route Destination | Gateway | Genmask | Flags | Metric | Ref | Use | Iface localnet | * | 255.255.255.0 | U | 0 | 0 | 0 | eth0 default | 192.168.1.1 | 0.0.0.0 | UG | 100 | 0 | 0 | eth0 Since I'm running this behind a FortiGate this is what the sniff command gives me when I try to ping 208.67.222.222 arp who-has 192.168.1.1 tell 192.168.1.23 arp reply 192.168.1.1 is-at MAC 192.168.1.23 -> 208.67.222.222: icmp: echo request 192.168.1.23 -> 208.67.222.222: icmp: echo request 192.168.1.23 -> 208.67.222.222: icmp: echo request 192.168.1.23 -> 208.67.222.222: icmp: echo request 192.168.1.23 -> 208.67.222.222: icmp: echo request As you can see it looks like I never get a response. One interesting thing I notice is the arp reply's MAC doesn't look right. I have cleared the FortiGate's ARP cache though and checked the entry and it seems correct. The MAC it lists is the one for the router. However if I ping from a different virtual machine that is also Ubuntu 8.04 with a nearly identical configuration I get this. 192.168.1.22 -> 208.67.222.222: icmp: echo request 208.67.222.222 -> 192.168.1.22: icmp: echo reply 192.168.1.22 -> 208.67.222.222: icmp: echo request 208.67.222.222 -> 192.168.1.22: icmp: echo reply 192.168.1.22 -> 208.67.222.222: icmp: echo request 208.67.222.222 -> 192.168.1.22: icmp: echo reply So, what could I be missing? Thanks.

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  • Using Windows XP Mode Virtual Machine on a Domain

    - by DavidStein
    I've followed the instructions and installed and configured the Windows Virtual PC XP Mode. I've added it as a machine on the network and can log into it and use network resources. In the process I removed the saved credentials, which are just a default local login to the VM. I need to know how to set this so that the VM auto logs in with the domain account credentials used to log into the physical computer. Google hasn't helped me find the answer.

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  • Using Windows XP Mode Virtual Machine on a Domain

    - by DavidStein
    I've followed the instructions and installed and configured the Windows Virtual PC XP Mode. I've added it as a machine on the network and can log into it and use network resources. In the process I removed the saved credentials, which are just a default local login to the VM. I need to know how to set this so that the VM auto logs in with the domain account credentials used to log into the physical computer. Google hasn't helped me find the answer.

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  • Connect to host computer from Virtual PC 2007

    - by Vegard Larsen
    I am having trouble using my guest (Windows XP SP3) to communicate over TCP/IP to the host computer (Windows 7) using Virtual PC 2007. I have WAMPServer running on my host, and want to be able to access the websites on there from my guest OS. What do I do to make this work? What is the IP address of the host computer when using Shared Networking? As far as I can tell "Internal Networking" won't work, because that only allows communication between the guests, not between a guest and the host.

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  • Access denied on virtual machine

    - by newbie
    I have a friend on the same network as me hosting a virtual machine using vmware server.The guest OS is Windows 7 and Windows Server 2003.He granted me administrative priveleges for the machine but when i try to add a user to that VM it says access denied. Moreover when i try to start the VM remotely using the command vmrun -T server -h https://computer-name.domain.com:8333/sdk -u domain/user -p passwd start "[standard] Win2k3Client1/Win2k3Client1.vmx" This shows unsufficient priveleges on host operating system but i am able to login with same username password on VMWare Web Access

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  • Virtual PC with Multi Monitors

    - by user41013
    Hi I have recently intalled Virtual PC and was wondering if it possible to make use of both of my monitors with it. I have managed to get a pseudo multi screen effect by connecting using Remote Desktop connection, but this isn't really what i wanted. Is this possible? Thanks

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  • Virtual PC with Multi Monitors

    - by user34710
    Hi I have recently intalled Virtual PC and was wondering if it possible to make use of both of my monitors with it. I have managed to get a pseudo multi screen effect by connecting using Remote Desktop connection, but this isn't really what i wanted. Is this possible? Thanks

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  • Virtual Box between differnt PCs

    - by Jim
    I am using Virtual Box machine (as .vdi) on external HDD drive so I can move it between different pcs. On each PC I have created new VM machine, attached that vdi and it seems working well. However, I've noticed that during my last transfer the latest installed applications were not saved on the .vdi, which made me to loose 1 day of work. I don't remember of doing any snapshots which I could merge. Can someone give me a hint how to handle this efficiently in feature?

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