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  • Constructors for C++ objects

    - by sasquatch
    I have class Person as following : class Person { char* name; int age; }; Now I need to add two contructors. One taking no arguments, that inserts field values to dynamically allocated resources. Second taking (char*, int) arguments initialized by initialization list. Last part is to define a destructor showing information about destroying objects and deallocating dynamically allocated resources. How to perform this task ? That's what I already have : class Person { char* name; int age; public: Person(){ this->name = new *char; this->age = new int; } Person(char* c, int i){ } };

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  • allocator with no template

    - by Merni
    Every stl container take an allocator as a second object, template < class T, class Allocator = allocator<T> > class vector; If you write your own class It is possible to use your own allocator. But is it possible to write your own allocator without using templates? For example, writing this function is not easy if you are not allowed to use templates pointer allocate(size_type n, const_pointer = 0) { void* p = std::malloc(n * sizeof(T)); if (!p) throw std::bad_alloc(); return static_cast<pointer>(p); } Because how could you know the size of T?

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  • Why is address zero used for null pointer?

    - by Joel
    In C (or C++ for that matter), pointers are special if they have the value zero: I am adviced to set pointers to zero after freeing their memory, because it means freeing the pointer again isn't dangerous; when I call malloc it returns a pointer with the value zero if it can't get me memory; I use if (p != 0) all the time to make sure passed pointers are valid etc. But since memory addressing starts at 0, isn't 0 just as a valid address as any other? How can 0 be used for handling null pointers if that is the case? Why isn't a negative number null instead?

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  • Is it possible with dynamic TSQL query ?

    - by eugeneK
    I have very long select query which i need to filter based on some params, i'm trying to avoid having different stored procedures or if statements inside of single stored procedure by using partly dynamic TSQL... I will avoid long select just for example sake select a from b where c=@c or d=@d @c and @d are filter params, only one can filter at the same time but also both filters could be disabled. 0 for each of these means param is disables so i can create nvarchar with where statement in it... How do i integrate in here dynamic query so 'where' can be added to normal query. I cannot add all the query as big nvarchar because there is too many things in it which will require changes ( ie. when's, subqueries, joins)

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  • Application Servers(java) : Should adding RAM to server depend on each domain's -Xmx value?

    - by ring bearer
    We have Glassfish application server running in Linux servers. Each Glassfish installation hosts 3 domains. Each domain has a JVM configuration such as -Xms 1GB and -XmX 2GB. That means if all these three domains are running at max memory, server should be able to allocate total 6GB to the JVMs With that math,each of our server has 8GB RAM (2 GB Buffer) First of all - is this a good approach? I did not think so, because when we analyzed memory utilization on this server over past few months, it was only up to 1GB; Now there are requests to add an additional domain to these servers - does that mean to add additional 2 GB RAM just to be safe or based on trend, continue with whatever memory the server has?

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  • C#. Struct design. Why 16 byte is recommended size?

    - by maxima120
    I read Cwalina book (recommendations on development and design of .NET apps). He says that good designed struct has to be less than 16 bytes in size (for performance purpose). My questions is - why exactly is this? And (more important) can I have larger struct with same efficiency if I run my .NET 3.5 (soon to be .NET 4.0) 64-bit application on i7 under Win7 x64 (is this limitation CPU / OS based)? Just to stress again - I need as efficient struct as it is possible. I try to keep it in stack all the time, the application is heavily multi-threaded and runs on sub-millisecond intervals, the current size of the struct is 64 byte.

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  • Static variables within functions in C++ - allocated even if function doesn't run?

    - by John C
    I've been reading up on C++ on the Internet, and here's one thing that I haven't been quite able to find an answer to. I know that static variables used within functions are akin to globals, and that subsequent invocations of that function will have the static variable retain its value between calls. However, if the function is never claled, does the static variable get allocated? Thanks

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  • How does the CLR (.NET) internally allocate and pass around custom value types (structs)?

    - by stakx
    Question: Do all CLR value types, including user-defined structs, live on the evaluation stack exclusively, meaning that they will never need to be reclaimed by the garbage-collector, or are there cases where they are garbage-collected? Background: I have previously asked a question on SO about the impact that a fluent interface has on the runtime performance of a .NET application. I was particuarly worried that creating a large number of very short-lived temporary objects would negatively affect runtime performance through more frequent garbage-collection. Now it has occured to me that if I declared those temporary objects' types as struct (ie. as user-defined value types) instead of class, the garbage collector might not be involved at all if it turns out that all value types live exclusively on the evaluation stack. What I've found out so far: I did a brief experiment to see what the differences are in the CIL generated for user-defined value types and reference types. This is my C# code: struct SomeValueType { public int X; } class SomeReferenceType { public int X; } . . static void TryValueType(SomeValueType vt) { ... } static void TryReferenceType(SomeReferenceType rt) { ... } . . var vt = new SomeValueType { X = 1 }; var rt = new SomeReferenceType { X = 2 }; TryValueType(vt); TryReferenceType(rt); And this is the CIL generated for the last four lines of code: .locals init ( [0] valuetype SomeValueType vt, [1] class SomeReferenceType rt, [2] valuetype SomeValueType <>g__initLocal0, // [3] class SomeReferenceType <>g__initLocal1, // why are these generated? [4] valuetype SomeValueType CS$0$0000 // ) L_0000: ldloca.s CS$0$0000 L_0002: initobj SomeValueType // no newobj required, instance already allocated L_0008: ldloc.s CS$0$0000 L_000a: stloc.2 L_000b: ldloca.s <>g__initLocal0 L_000d: ldc.i4.1 L_000e: stfld int32 SomeValueType::X L_0013: ldloc.2 L_0014: stloc.0 L_0015: newobj instance void SomeReferenceType::.ctor() L_001a: stloc.3 L_001b: ldloc.3 L_001c: ldc.i4.2 L_001d: stfld int32 SomeReferenceType::X L_0022: ldloc.3 L_0023: stloc.1 L_0024: ldloc.0 L_0025: call void Program::TryValueType(valuetype SomeValueType) L_002a: ldloc.1 L_002b: call void Program::TryReferenceType(class SomeReferenceType) What I cannot figure out from this code is this: Where are all those local variables mentioned in the .locals block allocated? How are they allocated? How are they freed? Why are so many anonymous local variables needed and copied to-and-fro only to initialize my two local variables rt and vt?

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  • Filling in uninitialized array in java? (or workaround!)

    - by AlexRamallo
    Hello all, I'm currently in the process of creating an OBJ importer for an opengles android game. I'm relatively new to the language java, so I'm not exactly clear on a few things. I have an array which will hold the number of vertices in the model(along with a few other arrays as well): float vertices[]; The problem is that I don't know how many vertices there are in the model before I read the file using the inputstream given to me. Would I be able to fill it in as I need to like this?: vertices[95] = 5.004f; //vertices was defined like the example above or do I have to initialize it beforehand? if the latter is the case then what would be a good way to find out the number of vertices in the file? Once I read it using inputstreamreader.read() it goes to the next line until it reads the whole file. The only thing I can think of would be to read the whole file, count the number of vertices, then read it AGAIN the fill in the newly initialized array. Is there a way to dynamically allocate the data as is needed?

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  • dojo dynamic right click context menu

    - by levy
    There are tons of different dojo right click context menus in a page slowing down the browser. Some divs have context menus while some others don't. So I just can't have a dynamic global context menu and still be able to fallback to the browser's built in menu in some cases, do I? The non lazy instantiation of the dojo context menus just take too much time. How can I make those context menus dynamic? Preferably being created on demand when the user actually right clicks on them.

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  • Access violation C++ (Deleting items in a vector)

    - by Gio Borje
    I'm trying to remove non-matching results from a memory scanner I'm writing in C++ as practice. When the memory is initially scanned, all results are stored into the _results vector. Later, the _results are scanned again and should erase items that no longer match. The error: Unhandled exception at 0x004016f4 in .exe: 0xC0000005: Access violation reading location 0x0090c000. // Receives data DWORD buffer; for (vector<memblock>::iterator it = MemoryScanner::_results.begin(); it != MemoryScanner::_results.end(); ++it) { // Reads data from an area of memory into buffer ReadProcessMemory(MemoryScanner::_hProc, (LPVOID)(*it).address, &buffer, sizeof(buffer), NULL); if (value != buffer) { MemoryScanner::_results.erase(it); // where the program breaks } }

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  • Dynamic View Creation in Iphone?

    - by adusum
    Hi can any one please tell me how to create Dynamic views in iphone. And I want to know like what is difference between custom views and dynamic views in iphone. Acutally i went throught google but i didn't find any proper answer. And I have one more question is like can we create all the views manually in the coding iteslf like the one we create using a Interface bulder and save it as a .nib. how can it be done?can any one please explain me this. Thanks,

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  • C or C++: how do loaders/wrappers work?

    - by guitar-
    Here's an example of what I mean... User runs LOADER.EXE program LOADER.EXE downloads another EXE but keeps it all in memory without saving it to disk Runs the downloaded EXE just as it would if it were executed from disk, but does it straight from memory I've seen a few applications like this, and I've never seen an example or an explanation of how it works. Does anyone know? Another example is having an encrypted EXE embedded in another one. It gets extracted and decrypted in memory, without ever being saved to disk before it gets executed. I've seen that one used in some applications to prevent piracy.

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  • Help with implementing a function to change size of dynamic array

    - by iRobot
    I'm trying to write a function that will change the size of a dynamic array to a new size. In my header file, I have: Image **images; //pointer to a dynamic array of image pointers int maximum; //size I want to do this by allocating a new array and copying the values over without changing their indices. If there are non-null pointers outside the range newmax, then we cant do this. So heres what I have: There are no compilation or runtime errors. However, I find that the new array isnt getting sized right. When I run the following test case: I should get an index out of bounds error, but instead the system lets it slide. Can anyone see the mistake? I've looked for hours but cant find anything.

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  • c++ link temporary allocations in fuction to custom allocator?

    - by user300713
    Hi, I am currently working on some simple custom allocators in c++ which generally works allready. I also overloaded the new/delete operators to allocate memory from my own allocator. Anyways I came across some scenarios where I don't really know where the memory comes from like this: void myFunc(){ myObj testObj(); ....do something with it } In this case testObj would only be valid inside the function, but where would its memory come from? Is there anyway I could link it to my allocator? Would I have to create to object using new and delete or is there another way? Thanks

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  • The difference between delete and delete [] in C++

    - by Ilya Melamed
    I've written a class that contains two pointers, one is char* color_ and one in vertexesset* vertex_ where vertexesset is a class I created. In the destractor I've written at start delete [] color_; delete [] vertex_; When It came to the destructor it gave me a segmentation fault. Then I changed the destructor to: delete [] color_; delete vertex_; And now it works fine. What is the difference between the two?

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  • .NET DB Query Without Allocations?

    - by Michael Covelli
    I have been given the task of re-writing some libraries written in C# so that there are no allocations once startup is completed. I just got to one project that does some DB queries over an OdbcConnection every 30 seconds. I've always just used .ExecuteReader() which creates an OdbcDataReader. Is there any pattern (like the SocketAsyncEventArgs socket pattern) that lets you re-use your own OdbcDataReader? Or some other clever way to avoid allocations? I haven't bothered to learn LINQ since all the dbs at work are Oracle based and the last I checked, there was no official Linq To Oracle provider. But if there's a way to do this in Linq, I could use one of the third-party ones.

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  • Unpause application in Mac OS X

    - by Xster
    I tried parsing a gigantic XML file and I ended up running out of virtual memory. The OS put all my applications on pause and gave me a screen to shutdown applications to free more space. I killed the XML parsing application and now have tons of space but I can't resume my paused applications anymore. What should I do?

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  • Xen dom0 reports incorrect amount of RAM with dom0_mem set

    - by xen_amnesiac
    I've done a fair bit of searching about this, but have found nothing that answers my question. I have a system with 6GB of RAM which acts as a Xen server. For reference, it runs Ubuntu 12.04. I've set the kernel parameter dom0_mem:512M,max:512M in /etc/default/grub as follows: GRUB_CMDLINE_XEN_DEFAULT="dom0_mem=min:512M,max:512M" I've tried variations of that, with the same result. My question is this: With the above set, the dom0 reports in all applications a RAM amount of 422M. cat /proc/meminfo gives the following: $ cat /proc/meminfo MemTotal: 432472 kB MemFree: 54144 kB Buffers: 17640 kB Cached: 220104 kB SwapCached: 30172 kB Active: 136500 kB Inactive: 167780 kB Active(anon): 6156 kB Inactive(anon): 60516 kB Active(file): 130344 kB Inactive(file): 107264 kB Unevictable: 52 kB Mlocked: 52 kB SwapTotal: 1794044 kB SwapFree: 1682012 kB Dirty: 0 kB Writeback: 0 kB AnonPages: 39572 kB Mapped: 8048 kB Shmem: 136 kB Slab: 44324 kB SReclaimable: 22012 kB SUnreclaim: 22312 kB KernelStack: 1280 kB PageTables: 3840 kB NFS_Unstable: 0 kB Bounce: 0 kB WritebackTmp: 0 kB CommitLimit: 2010280 kB Committed_AS: 329192 kB VmallocTotal: 34359738367 kB VmallocUsed: 313988 kB VmallocChunk: 34359417340 kB HardwareCorrupted: 0 kB AnonHugePages: 0 kB HugePages_Total: 0 HugePages_Free: 0 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB DirectMap4k: 524696 kB DirectMap2M: 0 kB top, htop, free -m, and byobu's RAM monitor all report the same amount. At first I thought this was because of the onboard graphics borrowing some memory, but have now switched to a dedicated GPU and it persists. Is this normal behavior, or has something gone amiss? It's just about 100MB of RAM that's "gone", and I have no idea where it went. I understand that it's normal that not all RAM is available for allocation, but does the system really take an amount relatively high to the amount of RAM available?

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  • proftpd, dynamic IP, and filezilla: port troubles

    - by Yami
    The basic setup: Two computers, one running proftpd, one attempting to connect via filezilla. Both linux (xubuntu on the server, kubuntu on the client). Both are at the moment behind a router on a residential (read: dynamic IP) connection; the client is a laptop I plan to take away from the home network, so I'll need this to work externally. I have my router set up to allow specific ports forwarded to each machine and, where possible, have plugged in those numbers into proftpd (via gadmin, double-checking the config file) and filezilla. Attempting to connect via active mode using the internal IP works: Status: Connecting to 192.168.1.139:8085... Status: Connection established, waiting for welcome message... Response: 220 Crossroads FTP Command: USER <redacted> Response: 331 Password required for <redacted> Command: PASS ******* Response: 230 Anonymous access granted, restrictions apply Command: OPTS UTF8 ON Response: 200 UTF8 set to on Status: Connected Status: Retrieving directory listing... Command: PWD Response: 257 "/" is the current directory Command: TYPE I Response: 200 Type set to I Command: PORT 192,168,1,52,153,140 Response: 200 PORT command successful Command: LIST Response: 150 Opening ASCII mode data connection for file list Response: 226 Transfer complete Status: Directory listing successful Attempting to connect via the domain name, however, leads to issues; in active mode, the PORT is the last command to be received according to the server's logs, and in passive mode, it's the PASV command. This leads me to believe I'm being redirected to a bad port? Active Sample: Status: Resolving address of <url> Status: Connecting to <ip:port> Status: Connection established, waiting for welcome message... Response: 220 Crossroads FTP Command: USER <redacted> Response: 331 Password required for <redacted> Command: PASS ******* Response: 230 Anonymous access granted, restrictions apply Command: OPTS UTF8 ON Response: 200 UTF8 set to on Status: Connected Status: Retrieving directory listing... Command: PWD Response: 257 "/" is the current directory Command: TYPE I Response: 200 Type set to I Command: PORT 174,111,127,27,153,139 Response: 200 PORT command successful Command: LIST Error: Connection timed out Error: Failed to retrieve directory listing Passive sample: Status: Resolving address of ftp.bonsaiwebdesigns.com Status: Connecting to 174.111.127.27:8085... Status: Connection established, waiting for welcome message... Response: 220 Crossroads FTP Command: USER yamikuronue Response: 331 Password required for yamikuronue Command: PASS ******* Response: 230 Anonymous access granted, restrictions apply Command: OPTS UTF8 ON Response: 200 UTF8 set to on Status: Connected Status: Retrieving directory listing... Command: PWD Response: 257 "/" is the current directory Command: TYPE I Response: 200 Type set to I Command: PASV Response: 227 Entering Passive Mode (64,95,64,197,101,88). Command: LIST Error: Connection timed out Error: Failed to retrieve directory listing In both cases, the log file ends at "PORT" or "PASV" - there's no record of ever receiving a "LIST" command. Just above that I can see the attempt to connect actively via the internal IP, which does indeed include a LIST command. My config file includes "PassivePorts 20001-26999", which are the port forwards I set up for the ftp server, and "Port 8085", which is also forwarded to the same machine. I also have a MasqueradeAddress set up to prevent it from reporting its internal IP, which was an earlier issue I had. I think what I'm asking is, is there another setting someplace I have to change to get this setup to work?

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