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  • Redoundant code in exception handling

    - by Nicola Leoni
    Hi, I've a recurrent problem, I don't find an elegant solution to avoid the resource cleaning code duplication: resource allocation: try { f() } catch (...) { resource cleaning code; throw; } resource cleaning code; return rc; So, I know I can do a temporary class with cleaning up destructor, but I don't really like it because it breaks the code flow and I need to give the class the reference to the all stack vars to cleanup, the same problem with a function, and I don't figure out how does not exists an elegant solution to this recurring problem.

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  • Test of procedure is fine but when called from a menu gives uninitialized errors. C

    - by Delfic
    The language is portuguese, but I think you get the picture. My main calls only the menu function (the function in comment is the test which works). In the menu i introduce the option 1 which calls the same function. But there's something wrong. If i test it solely on the input: (1/1)x^2 //it reads the polinomyal (2/1) //reads the rational and returns 4 (you can guess what it does, calculates the value of an instace of x over a rational) My polinomyals are linear linked lists with a coeficient (rational) and a degree (int) int main () { menu_interactivo (); // instanciacao (); return 0; } void menu_interactivo(void) { int i; do{ printf("1. Instanciacao de um polinomio com um escalar\n"); printf("2. Multiplicacao de um polinomio por um escalar\n"); printf("3. Soma de dois polinomios\n"); printf("4. Multiplicacao de dois polinomios\n"); printf("5. Divisao de dois polinomios\n"); printf("0. Sair\n"); scanf ("%d", &i); switch (i) { case 0: exit(0); break; case 1: instanciacao (); break; case 2: multiplicacao_esc (); break; case 3: somar_pol (); break; case 4: multiplicacao_pol (); break; case 5: divisao_pol (); break; default:printf("O numero introduzido nao e valido!\n"); } } while (i != 0); } When i call it with the menu, with the same input, it does not stop reading the polinomyal (I know this because it does not ask me for the rational as on the other example) I've run it with valgrind --track-origins=yes returning the following: ==17482== Memcheck, a memory error detector ==17482== Copyright (C) 2002-2009, and GNU GPL'd, by Julian Seward et al. ==17482== Using Valgrind-3.5.0 and LibVEX; rerun with -h for copyright info ==17482== Command: ./teste ==17482== 1. Instanciacao de um polinomio com um escalar 2. Multiplicacao de um polinomio por um escalar 3. Soma de dois polinomios 4. Multiplicacao de dois polinomios 5. Divisao de dois polinomios 0. Sair 1 Introduza um polinomio na forma (n0/d0)x^e0 + (n1/d1)x^e1 + ... + (nk/dk)^ek, com ei > e(i+1): (1/1)x^2 ==17482== Conditional jump or move depends on uninitialised value(s) ==17482== at 0x401126: simplifica_f (fraccoes.c:53) ==17482== by 0x4010CB: le_f (fraccoes.c:30) ==17482== by 0x400CDA: le_pol (polinomios.c:156) ==17482== by 0x400817: instanciacao (t4.c:14) ==17482== by 0x40098C: menu_interactivo (t4.c:68) ==17482== by 0x4009BF: main (t4.c:86) ==17482== Uninitialised value was created by a stack allocation ==17482== at 0x401048: le_f (fraccoes.c:19) ==17482== ==17482== Conditional jump or move depends on uninitialised value(s) ==17482== at 0x400D03: le_pol (polinomios.c:163) ==17482== by 0x400817: instanciacao (t4.c:14) ==17482== by 0x40098C: menu_interactivo (t4.c:68) ==17482== by 0x4009BF: main (t4.c:86) ==17482== Uninitialised value was created by a stack allocation ==17482== at 0x401048: le_f (fraccoes.c:19) ==17482== I will now give you the functions which are called void le_pol (pol *p) { fraccao f; int e; char c; printf ("Introduza um polinomio na forma (n0/d0)x^e0 + (n1/d1)x^e1 + ... + (nk/dk)^ek,\n"); printf("com ei > e(i+1):\n"); *p = NULL; do { le_f (&f); getchar(); getchar(); scanf ("%d", &e); if (f.n != 0) *p = add (*p, f, e); c = getchar (); if (c != '\n') { getchar(); getchar(); } } while (c != '\n'); } void instanciacao (void) { pol p1; fraccao f; le_pol (&p1); printf ("Insira uma fraccao na forma (n/d):\n"); le_f (&f); escreve_f(inst_esc_pol(p1, f)); } void le_f (fraccao *f) { int n, d; getchar (); scanf ("%d", &n); getchar (); scanf ("%d", &d); getchar (); assert (d != 0); *f = simplifica_f(cria_f(n, d)); } simplifica_f simplifies a rational and cria_f creates a rationa given the numerator and the denominator Can someone help me please? Thanks in advance. If you want me to provide some tests, just post it. See ya.

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  • Can the JVM recover from an OutOfMemoryError without a restart

    - by askullhead
    Can the JVM recover from an OutOfMemoryError without a restart if it gets a chance to run the GC before more object allocation requests come in? Do the various JVM implementations differ in this aspect? EDIT: My question was about the JVM recovering and not the user program trying to recover by catching the error. In other words if an OOME is thrown in an application server (jboss/websphere/..) do I have to restart it? Or can I let it run if further requests seem to work without a problem. Sorry if that wan't clear.

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  • Redundant code in exception handling

    - by Nicola Leoni
    Hi, I've a recurrent problem, I don't find an elegant solution to avoid the resource cleaning code duplication: resource allocation: try { f() } catch (...) { resource cleaning code; throw; } resource cleaning code; return rc; So, I know I can do a temporary class with cleaning up destructor, but I don't really like it because it breaks the code flow and I need to give the class the reference to the all stack vars to cleanup, the same problem with a function, and I don't figure out how does not exists an elegant solution to this recurring problem.

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  • Growable data structure in MATLAB

    - by rlbond
    I need to create a queue in matlab that holds structs which are very large. I don't know how large this queue will get. Matlab doesn't have linked lists, and I'm worried that repeated allocation and copying is really going to slow down this code which must be run thousands of times. I need some sort of way to use a growable data structure. I've found a couple of entries for linked lists in the matlab help but I can't understand what's going on. Can someone help me with this problem?

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  • Compiler error when casting to function pointer

    - by detly
    I'm writing a bootloader for the PIC32MX, using HiTech's PICC32 compiler (similar to C90). At some point I need to jump to the real main routine, so somewhere in the bootloader I have void (*user_main) (void); user_main = (void (*) (void)) 0x9D003000; user_main(); (Note that in the actual code, the function signature is typedef'd and the address is a macro.) I would rather calculate that (virtual) address from the physical address, and have something like: void (*user_main) (void); user_main = (void (*) (void)) (0x1D003000 | 0x80000000); user_main(); ...but when I try that I get a compiler error: Error #474: ; 0: no psect specified for function variable/argument allocation Have I tripped over some vagarity of C syntax here? This error doesn't reference any particular line, but if I comment out the user_main() call, it goes away. (This might be the compiler removing a redundant code branch, but the HiTech PICC32 isn't particularly smart in Lite mode, so maybe not.)

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  • How can I create a new class instance from a class within a (static) class?

    - by Mervin
    I'm new to Java (have experience with C#), This is what i want to do: public final class MyClass { public class MyRelatedClass { ... } } public class OtherRandomClass { public void DoStuff() { MyRelatedClass data = new MyClass.MyRelatedClass(); } } which gives this error in Eclipse: "No enclosing instance of type BitmapEffects is accessible. Must qualify the allocation with an enclosing instance of type BitmapEffects (e.g. x.new A() where x is an instance of BitmapEffects)." this is possible in C# with static classes , how should it be done here?

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  • What combination of project-management software will meet my just-started project's needs?

    - by taz
    Hello all, I have a got couple of software projects that I want to run with my friends(max 10 persons) privately(at least for now). But I'm kind of lost between software management systems. I am not even sure about the definitions of my needs. Dear all, what is the definition/name of the system/software that meets my needs listed below? Continuous Integration? And please suggest me a good ALL-IN-ONE instance of it: project roadmap/planning project resource(people) allocation project issue&bug tracking project mailing list project forum project wiki source control server source control client repository change notifier client build system(like scons) nightly build automation IDE integration(VS) Note: I tried Redmine and liked it, but found it kind of slow. All-in-one kind ones will be the most appreciated but if your suggestion includes more than 3 softwares, please suggest me the ones that work together painlessly. thanks in advance..

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  • Designing a frontend/backend architecture

    - by wrp
    What are some good information sources on designing programs with a client/server architecture? This is for development of a desktop application, not a Web service. The only books I have found on client/server apps deal with the case of a thin client connecting to a remote database. Two good examples of what I mean are Mathematica and SuperCollider. I'm looking for platform- and language-agnostic discussion of the issues in developing a frontend/backend system. Especially useful topics would be allocation of responsibilities and options for message passing.

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  • Implementation of APIs on diferent platforms

    - by b-gen-jack-o-neill
    OK, this is basicly just about any non-default OS API running on all different OS. But for my example let´s consider platform Windows, API SDL (Simple DirectMedia Layer). Actually this question came to my mind when I was reading about SDL. Originally, I thought that on Windows (and basicly any other OS) you must use OS API to make certain actions, like wrtiting to screen, creating window and so on, becouse that API knows what kernel calls and system subroutines calls it has to do. But when I read about SDL, I surprised me, becouse, you cannot make computer to do anything more than OS can, since you cannot acess HW directly, only thru OS API, from Console allocation to DirectX. So, my question actually is, how does this not-default-OS APIs work? Do they use (wrap) original system API (like MFC wraps win32 api)? Or, do they actually have direct acess to Windows kernel? Or is there any third, way in between? Thanks.

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  • C++ initializing constants and inheritance

    - by pingvinus
    I want to initialize constant in child-class, instead of base class. And use it to get rid of dynamic memory allocation (I know array sizes already, and there will be a few child-classes with different constants). So I try: class A { public: const int x; A() : x(0) {} A(int x) : x(x) {} void f() { double y[this->x]; } }; class B : A { B() : A(2) {} }; Pretty simple, but compiler says: error C2057: expected constant expression How can I say to compiler, that it is really a constant?

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  • How to implement arrays in an interpreter?

    - by Ray
    I have managed to write several interpreters including Tokenizing Parsing, including more complicated expressions such as ((x+y)*z)/2 Building bytecode from syntax trees Actual bytecode execution What I didn't manage: Implementation of dictionaries/lists/arrays. I always got stuck with getting multiple values into one variable. My value structure (used for all values passed around, including variables) looks like this, for example: class Value { public: ValueType type; int integerValue; string stringValue; } Works fine with integers and strings, but how could I implement arrays? (From now on with array I mean arrays in my experimental language, not in C++) How can I fit the array concept into the Value class above? Is it possible? How should I make arrays able to be passed around just as you could pass around integers and strings in my language, using the class above? Accessing array elements or memory allocation wouldn't be the problem, I just don't know how to store them.

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  • StringBuilder/StringBuffer vs. "+" Operator

    - by matt.seil
    I'm reading "Better, Faster, Lighter Java" (by Bruce Tate and Justin Gehtland) and am familiar with the readability requirements in agile type teams, such as what Robert Martin discusses in his clean coding books. On the team I'm on now, I've been told explicitly not to use the "+" operator because it creates extra (and unnecessary) string objects during runtime. But this article: http://www.ibm.com/developerworks/java/library/j-jtp01274.html Written back in '04 talks about how object allocation is about 10 machine instructions. (essentially free) It also talks about how the GC also helps to reduce costs in this environment. What is the actual performance tradeoffs between using "+," "StringBuilder," or "StringBuffer?" (In my case it is StringBuffer only as we are limited to Java 1.4.2.) StringBuffer to me results in ugly, less readable code, as a couple of examples in Tate's book demonstrates. And StringBuffer is thread-synchronized which seems to have its own costs that outweigh the "danger" in using the "+" operator. Thoughts/Opinions?

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  • android java.lang.OutOfMemoryError

    - by xiangdream
    hi, all, when i download large data from website, i got this error information: I/global (20094): Default buffer size used in BufferedInputStream constructor. It would be better to be explicit if an 8k buffer is required. D/dalvikvm(20094): GC freed 6153 objects / 3650840 bytes in 335ms I/dalvikvm-heap(20094): Forcing collection of SoftReferences for 3599051-byte al location D/dalvikvm(20094): GC freed 320 objects / 11400 bytes in 144ms E/dalvikvm-heap(20094): Out of memory on a 3599051-byte allocation. I/dalvikvm(20094): "Thread-9" prio=5 tid=17 RUNNABLE I/dalvikvm(20094): | group="main" sCount=0 dsCount=0 s=0 obj=0x439b9480 I/dalvikvm(20094): | sysTid=25762 nice=0 sched=0/0 handle=4065496 anyone can help me?

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  • Getting exc_bad_access error only when mallocguard is enabled

    - by Nareshkumar
    I have an app for iPhone in development which works properly when the Malloc guard is not enabled. However when i try to enable the malloc guard i get the following error after the app is loaded. #0 0x95f65684 in objc_msgSend () #1 0x30506515 in NSPopAutoreleasePool () #2 0x30901697 in _UIApplicationHandleEvent () #3 0x32046375 in PurpleEventCallback () #4 0x30245560 in CFRunLoopRunSpecific () #5 0x30244628 in CFRunLoopRunInMode () #6 0x308f930d in -[UIApplication _run] () #7 0x309021ee in UIApplicationMain () Now my problem is that i am not able to debug the exact location where its getting the error.. have tried malloc_error_break but didnt work out. Is it that malloc guard enabling auto releases some of the objects based on allocation??

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  • HD Crash SQL server -> DBCC - consistency errors in table 'sysindexes'

    - by Julian de Wit
    Hello A client of mine has had an HD crash an a SQL DB got corrupt : They did not make backups so they have a big problem. When I tried (an ultimate measure) to DBCC-repair I got the following message. Can anybody help me with this ? Server: Msg 8966, Level 16, State 1, Line 1 Could not read and latch page (1:872) with latch type SH. sysindexes failed. Server: Msg 8944, Level 16, State 1, Line 1 Table error: Object ID 2, index ID 0, page (1:872), row 11. Test (columnOffsets->IsComplex (varColumnNumber) && (ColumnId == COLID_HYDRA_TEXTPTR || ColumnId == COLID_INROW_ROOT || ColumnId == COLID_BACKPTR)) failed. Values are 2 and 5. The repair level on the DBCC statement caused this repair to be bypassed. CHECKTABLE found 0 allocation errors and 1 consistency errors in table 'sysindexes' (object ID 2). DBCC execution completed. If DBCC printed error messages, contact your system administrator.

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  • Objective-C: Initializing char with char at index of string.

    - by Mr. McPepperNuts
    unichar myChar = [myString characterAtIndex:0]; [myNSMutableArray addObject:myChar]; I am trying to insert the first char of a string into an array, to create an array of chars. the first line does not give me an error. The second line however, provides the following error: warning: passing argument 1 of 'addObject:' makes pointer from integer without a cast This also crashes the application with a "bad address" error. I thought this error was due to a problem with memory allocation. Can someone shed some light on this.

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  • Suggest changes to make the time a function of input size

    - by KB
    Vector v; int i=0; while(i!=999) { cini; v.push_back(i); } Time taken by this piece of code could vary when the number of inputs vary. Since vector would take amortized time for new allocation. Even for same size the program at different times could take different time. Suggest changes (e.g. use list instead of vector), which makes the time a function of number of inputs.

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  • Ruby: Read large data from stdout and stderr of an external process on Windows

    - by BinaryMuse
    Greetings, all, I need to run a potentially long-running process from Ruby on Windows and subsequently capture and parse the data from the external process's standard output and error. A large amount of data can be sent to each, but I am only necessarily interested in one line at a time (not capturing and storing the whole of the output). After a bit of research, I found that the Open3 class would take care of executing the process and giving me IO objects connected to the process's standard output and error (via popen3). Open3.popen3("external-program.bat") do |stdin, out, err, thread| # Step3.profit() ? end However, I'm not sure how to continually read from both streams without blocking the program. Since calling IO#readlines on out or err when a lot of data has been sent results in a memory allocation error, I'm trying to continuously check both streams for available input, but not having much luck with any of my implementations. Thanks in advance for any advice!

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  • How do you mentally handle going from writing managed to non-managed code?

    - by Glenn Sandoval
    ~80% of the code I write is in C#. The other ~20% is in C++. Whenever I have to switch from C# to C++, it takes me quite a while to mentally "shift gears" to thinking in C++. I make simple mistakes using pointers and memory allocation that I would not have made when I was in university. Is this normal? Does anyone else experience something similar and if so, what do you do to cut down on the time this wastes?

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  • Best and safest Java Profiler for production use?

    - by Pete
    I'm looking for a Java Profiler for use in a very high demand production environment, either commercial or free, that meets all of the following requirements: Lightweight integration with code (no recompile with special options, no code hooks, etc). Dropping some profiler specific .jars alongside the application code is ok. Should be able to connect/disconnect to the JVM without restarting the application. When profiling is not active, no impact to performance When profiling is active, negligible impact to performance. Very slight degradation is acceptable. Must do all the 'expected' stuff a profiler does - time spent in each method to find hotspots, object allocation/memory profiling, etc. Essentially I need something that can sit dormant in production when everything is fine without anyone knowing or caring that it is there, but then be able to connect to it hassle (and performance degradation) free to pinpoint the hard to find problems like hotspots and synchronization issues.

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  • Which libraries use the "We Know Where You Live" optimization for std::make_shared?

    - by KnowItAllWannabe
    Over two years ago, Stephan T. Lavavej described a space-saving optimization he implemented in Microsoft's implementation of std::make_shared, and I know from speaking with him that Microsoft has nothing against other library implementations adopting this optimization. If you know for sure whether other libraries (e.g., for Gnu C++, Clang, Intel C++, plus Boost (for boost::make_shared)) have adopted this implementation, please contribute an answer. I don't have ready access to that many make_shared implementations, nor am I wild about digging into the bowels of the ones I have to see if they've implemented the WKWYL optimization, but I'm hoping that SO readers know the answers for some libraries off-hand. I know from looking at the code that as of Boost 1.52, the WKWYL optimization had not been implemented, but Boost is now up to version 1.55. Note that this optimization is different from std::make_shared's ability to avoid a dedicated heap allocation for the reference count used by std::shared_ptr. For a discussion of the difference between WKWYL and that optimication, consult this question.

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  • What is the result of "new int[ 0 ]"? [closed]

    - by ArunSaha
    Possible Duplicates: What does zero-sized array allocation do/mean? C++ new int[0] — will it allocate memory? int * p; p = new int[ 0 ]; What is the expected outcome when new is called for zero number of elements? Is the outcome defined or undefined? Further, is it okay to call delete [] p; on that pointer? What is the intuition/analogy to this situation of pointer to an array of zero elements? Thanks in advance. Regards, Arun

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  • Custom deleters for std::shared_ptrs

    - by Kristian D'Amato
    Is it possible to use a custom deleter after creating a std::shared_ptr without using new? My problem is that object creation is handled by a factory class and its constructors & destructors are protected, which gives a compile error, and I don't want to use new because of its drawbacks. To elaborate: I prefer to create shared pointers like this, which doesn't let you set a custom deleter (I think): auto sp1 = make_shared<Song>(L"The Beatles", L"Im Happy Just to Dance With You"); Or I can create them like this, which does let met set a deleter through an argument: auto sp2(new Song, MyDeleterFunc); But the second one uses new, which AFAIK isn't as efficient as the top sort of allocation. Maybe this is clearer: is it possible to get the benefits of make_shared<> as well as a custom deleter? Would that mean having to write an allocator?

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  • how to get stl map to construct/destruct inserted object only once.

    - by Alberto Toglia
    I have found a very prejudicial fact about stl maps. For some reason I cant get objects being inserted in the map to get constructed/destructed only once. Example: struct MyObject{ MyObject(){ cout << "constructor" << endl; } ~MyObject(){ cout << "destructor" << endl; } }; int main() { std::map<int, MyObject> myObjectsMap; myObjectsMap[0] = MyObject(); return 0; } returns: constructor destructor destructor constructor destructor If I do: typedef std::pair<int, MyObject> MyObjectPair; myObjectsMap.insert( MyObjectPair(0,MyObject())); returns: constructor destructor destructor destructor I'm inserting Objects responsible for their own memory allocation, so when destructed they'll clean themselves up, being destructed several times is causing me some trouble.

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