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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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  • NULL In a Class Destructor

    - by Hyper-DarkStar
    Simple question; Is it pointless to set a pointer( which allocates heap memory ) to NULL in the destructor? class SampleClass { public: SampleClass( int Init = 0 ) { Value = new int( Init ); } ~SampleClass( void ) { delete Value; Value = NULL; // Is this pointless? } int *Value; }; While on the subject of classes, when should I use the explicit keyword? Thanks.

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  • How can I validate input to the edit control of a cell in a DataGridView?

    - by Stuart Helwig
    It appears that the only way to capture the keypress events within a cell of a DataGridView control, in order to validate user input as they type, is to us the DataGridView controls OnEditControlShowing event, hook up a method to the edit control's (e.Control) keypress event and do some validation. My problem is that I've built a heap of custom DataGridView column classes, with their own custom cell types. These cells have their own custom edit controls (things like DateTimePickers, and Numeric or Currency textboxes.) I want to do some numeric validation for those cells that have Numeric of Currency Textboxes as their edit controls but not all the other cell types. How can I determine, within the DataGridView's "OnEditControlShowing" override, whether or not a particular edit control needs some numeric validation?

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  • Bitmap size exceeds VM budget after second load

    - by jonny
    This is driving me crazy. I have a game which has a bitmap as the background, this is big so I scale it down and this works fine. However when I navigate to another activity and then reload the game screen it crashes on drawing the background. I am calling recycle on all the bitmaps and setting them to null on onDestroy() but this doesn't help. Any ideas and if not how can I debug the memory to see at which step its growing. I looked at getting the heap but nothing of any size is on there really. Thanks.

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  • How does C++ free the memory when a constructor throws an exception and a custom new is used

    - by Joshua
    I see the following constructs: new X will free the memory if X constructor throws. operator new() can be overloaded. The canonical definition of an operator new overload is void *operator new(heap h) and the corrisponding operator delete. The most common operator new overload is pacement new, which is void *operator new(void *p) { return p; } You almost always cannot call delete on the pointer given to placement new. This leads to a single question. How is memory cleaned up when X constructor throws and an overloaded new is used?

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  • OpenGL "out of memory" on glReadPixels()

    - by spurserh
    Hello, I am running into an "out of memory" error from OpenGL on glReadPixels() under low-memory conditions. I am writing a plug-in to a program that has a robust heap mechanism for such situations, but I have no idea whether or how OpenGL could be made to use it for application memory management. The notion that this is even possible came to my attention through this [albeit dated] thread on a similar issue under Mac OS X: http://lists.apple.com/archives/Mac-opengl/2001/Sep/msg00042.html I am using Windows XP, and have seen it on multiple NVidia cards. I am also interested in any work-arounds I might be able to relay to users (the thread mentions "increasing virtual memory"). Thanks, Sean

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  • Where does static variable work in C# page. At Application level or Page Level

    - by Shantanu Gupta
    I had an interview today and every thing was going very good, but then an interviewer asked me a question Where Does Static Variable Work in C#- At Application Level or At Page Level. I was not very much clear about this answer as I only knew that static variables are stored on heap and I didn't knew anything about web related thing about it. Then tried to make me more clear by giving an example that in a page I am using static variable and three users are accessing the page one of the user updates the value of static variable, What value will be visible to remaining two users an old copy or the update will be reflected.

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  • Does writing program using global variables is safer?

    - by ZoZo123
    I was reading about buffer, stack and heap overflows. I read this post as well. my question is like that: if I use only global variables in my code, can I say it prevents all the exploits of overflow? let's say I have this buffers in code declared in the global scope: char buf1[10]; char buf2[100]; If I send buf1 as the buffer to recv(int s, char *buf, int len,int flags); I will overwrite the data segment and may ruin the buf2 content, right? Would I be able to run a code from it because as I know it is not a code segment and data segment is not executable. Can we conclude that using Globals is the safest way?

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  • MySQL temp table issue

    - by AmyD
    Hi folks! I'm trying to use temp tables to speed up my MySQL 4.1.22-standard database and what seems like a simple operation is causing me all kinds of issues. My code is below.... CREATE TEMPORARY TABLE nonDerivativeTransaction_temp (accession_number varchar(30), transactionDateValue date)) TYPE=HEAP; INSERT INTO nonDerivativeTransaction_temp VALUES( SELECT accession_number, transactionDateValue FROM nonDerivativeTransaction WHERE transactionDateValue = "2010-06-15"); SELECT * FROM nonDerivativeTransaction_temp; The original table (nonDerivativeTransaction) has two fields, accession_number (varchar(30)) and transactionDateValue (date). Apparently I am getting an issue with the first two statements but I can't seem to nail down what it is. Any help would be appreciated. Amy D.

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  • Memory error, access violation.

    - by Ordo
    Hello! I'm learning C on my own and as a exercise i have written a program but it does not work. The program is splitted into 3 parts. A header file, a main file for executing the program a file to define the functions. I'm not using all the functions yet but that shouldn't be the problem. Here is my header file, nothing special in it. #ifndef EMPLOYEE_H #define EMPLOYEE_H struct Employee { char first[21]; char last[21]; char title[21]; int salary; }; struct Employee* createEmployee(char*, char*, char*, int); // Creates a struct Employee object on the heap. char* getfirstname (struct Employee*); char* getlastname (struct Employee*); char* gettitle (struct Employee*); int getsalary (struct Employee*); void setfirstname (struct Employee*, char*); void setlastname (struct Employee*, char*); void settitle (struct Employee*, char*); void setsalary (struct Employee*, int); void printEmployee(struct Employee*); #endif In this file i define the functions and how they work: #include "7.1.h" #include <stdio.h> #include <stdlib.h> #include <string.h> struct Employee* createEmployee(char* first, char* last, char* title, int salary) // Creates a struct Employee object on the heap. { struct Employee* p = (struct Employee*) malloc(sizeof(struct Employee)); if (p != NULL) { strcpy(p->first, first); strcpy(p->last, last); strcpy(p->title, title); p->salary, salary; } return p; } char* getfirstname (struct Employee* p) { if (p != NULL) return p ? p->first : ""; } char* getlastname (struct Employee* p) { if (p != NULL) return p ? p->last : ""; } char* gettitle (struct Employee* p) { if (p != NULL) return p ? p->title : ""; } int getsalary (struct Employee* p) { if (p != NULL) return p ? p->salary : 0; } void setfirstname (struct Employee* p, char* first) { if (p != NULL) strcpy(p->first, first); } void setlastname (struct Employee* p, char* last) { if (p != NULL) strcpy(p->last, last); } void settitle (struct Employee* p, char* title) { if (p != NULL) strcpy(p->title, title); } void setsalary (struct Employee* p, char* salary) { if (p != NULL) p->salary, salary; } void printEmployee(struct Employee* p) { if (p != NULL) { printf("%s, %s, %s, %d", p->first, p->last, p->salary, p->salary ); } } And the last file is used to executed the program/functions: #include "7.1.h" #include <stdio.h> #include <stdlib.h> int main () { char decision; struct Employee emp; struct Employee* emps[3]; for ( int i = 0; i < 1; i ++) { printf("Please type in the emplooyes data.\nFirstname:"); scanf("%s", emp.first); printf("Lastname:"); scanf("%s", emp.last); printf("Title:"); scanf("%s", emp.title); printf("Salary:"); scanf("%d", &emp.salary); emps[i] = createEmployee(emp.first, emp.last, emp.title, emp.salary); } printf("Do you want to print out your information? (Y/N):"); scanf("%c", &decision); if (decision == 'y' || decision == 'Y') { printEmployee(emps[1]); } } I don't know what the problem is. I 'm always getting the following error message after typing in first, last, title and salary for the first time. The error is written in german. It means: Unhandled exception at 0x102de42e (msvcr100d.dll) in 7.1.exe: 0xC0000005: Access violation when writing to 0xCCCCCCCC position. I could fix the first problem with the hints given below. Now when i want to print out the employee data using the function:printEmployee(emps[1]);, I get the same kind of error with access violation.

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  • Why is std::tr1::shared_ptr<>.reset() so expensive?

    - by Paul Oyster
    Profiling some code that heavily uses shared_ptrs, I discovered that reset() was surprisingly expensive. For example: struct Test { int i; Test() { this->i = 0; } Test(int i) { this->i = i; } } ; ... auto t = make_shared<Test>(1); ... t.reset(somePointerToATestObject); Tracing the reset() in the last line (under VC++ 2010), I discovered that it creates a new reference-counting object. Is there a cheaper way, that reuses the existing ref-count and does not bother the heap?

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  • Is it bad practice to declare an array mid-function...

    - by Maximus
    In C, which would be more proper... void MyFunction() { int* array; int size; //do a bunch of stuff size = 10; array = (int*)(sizeof(int)*size); //do more stuff... //no longer need array... free(array); } Or is something like this okay? void MyFunction() { int size; //do a bunch of stuff size = 10; array[size]; //do more stuff... } The malloc uses the heap instead of the stack, so I suppose if you know size is going to be very large you'd want to malloc... but if you're quite certain size will be small enough, would the second method be reasonable?

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  • Saving object state on Java without using external memory

    - by TryHarder
    Good day. I know that in order to save object state in Java I should use serialization. But in every single topic about serialization states that I must save my object somewhere (disk, network). My problem is that I'm not allowed to do so. I need a way to save and recover object state without writing it on "external" memory. Maybe to save it on heap or stack... Please don't offer to clone it, I'm not allowed to do so as well. Thanks.

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  • Per Process Memory Calculation Alogrithm in Linux (say kernel 2.6 and above)

    - by Vaibhav Singh
    How do you calculate the linux process's Acutal Memory Usage and Not Virtual Memory Usage through the information supplied by /proc//smaps or maps or status or stat. To be more precise I need the heap usage only. I need to do this on an PowerPc based embedded system and hence I do not have utilities like exmap, valgrind etc. I understand the concepts of shared/non shared memory. I have read through the other topics given in this forum about the same but they talk more using the tools mentioned. What I need is the native way of calculation done by the same tools so that I may write a shell script for the same.

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  • How to research unmanaged memory leaks in .NET?

    - by Brandon
    I have a WCF service running over MSMQ. Memory gradually increases over time, indicating that there is some sort of memory leak. I ran the service locally and monitored some counters using PerfMon. Total CLR memory managed heap bytes remains relatively constant, while the process' private bytes increases over time. This leads me to believe that there is some sort of unmanaged memory leak. Assuming that unmanaged memory leak is the issue, how do I address the issue? Are there any tools I could use to give me hints as to what is causing the unmanaged memory leak? Also, all my service is doing is reading from the transactional queue and writing to a database, all as part of a DTC transaction (handled under the hood by requiring a transaction on the service contract). I am not doing anything explicitly with COM or DllImports. Thanks in advance!

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  • Optimizing Code

    - by Claudiu
    You are given a heap of code in your favorite language which combines to form a rather complicated application. It runs rather slowly, and your boss has asked you to optimize it. What are the steps you follow to most efficiently optimize the code? What strategies have you found to be unsuccessful when optimizing code? Re-writes: At what point do you decide to stop optimizing and say "This is as fast as it'll get without a complete re-write." In what cases would you advocate a simple complete re-write anyway? How would you go about designing it?

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  • Intercommunication between Java Chat Servers

    - by Pravingate
    I have a application in which I am using socket programming , having this(image) scenario. Where number of clients will try to connect Broadcast server. Now here I am managing load through LVS(Load balancer). so as a example shown in image, suppose 200 clients will wish to login for broadcast they will be distributed as 100 users on server 1 and another 100 users on server 2.clients will get connected to servers using TCP connection. Now I am maintaining user information on server side in arraylist which will be stored in heap memory,Now the problem is if client wish to broadcast to all logged in users, but that particular client is logged in server 1. and so client will not be able to broadcast another 100 users from server 2. Because both ther servers are unaware about each others state. please suggest to solve this scenario by whatever means you want.

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  • C++ Singleton design pattern

    - by Artem Barger
    Recently I've bumped into a realization/implementation of the Singleton design pattern for C++. It has looked like this (I have adopted it from the real life example): // a lot of methods are omitted here class Singleton { public: static Singleton* getInstance( ); ~Singleton( ); private: Singleton( ); static Singleton* instance; }; From this declaration I can deduce that the instance field is initiated on the heap. That means there is a memory allocation. What is completely unclear for me is when exactly the memory is going to be deallocated? Or is there a bug and memory leak? It seems like there is a problem in the implementation. My main question is, how do I implement it in the right way?

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  • How to get notified of modification in the memory in Linux

    - by Song Yuan
    In a userspace program in Linux, I get a piece of memory via allocation from the heap, then the pointer is distributed to a lot of other components running in other threads to use. I would like to get notified when the said piece of memory is modified. I can of course develop a custom userspace solution for other components to use when they try to modify the memory. The problem in my case is that these are legacy components and they can write to memory in many occasions. So I'm wondering whether there is a similar API like inotify (get notified when file is changed) or other approaches in order to get notified when a piece of memory is changed. I considered using mmap and inotify, which obviously won't work if the changes are not flushed. Any suggestions are appreciated :-)

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  • c++ classes & lua

    - by anon
    I want to have C++ objects that I can read/write in both C++ & Lua. I have looked at: http://www.lua.org/pil/28.html However, I do not like that solution, since my objects have constructors & destructors (and they are important as I use RAII and these take care of reference counts). What I don't like in the PIL solution is that the object is allocated in Lua's heap. What i want instead, is to create hte C++ object on my own, and just have lua have a way to do get/set on them. Does anyone have a good tutorial/link on this? Tanks!

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  • is this code correct? [closed]

    - by davit-datuashvili
    hi i have poste this code from this title http://stackoverflow.com/questions/2896363/hi-i-have-question-here-is-pseudo-code-about-sift-up-and-sift-down-on-heaps i have following code of siftup on heap is it correct?i have put here because i have changed at old place my question and it became unreadable so i have posted here public class siftup{ public static void main(String[]args){ int p; int n=12; int a[]=new int[]{15,20,12,29,23,17,22,35,40,26,51,19}; int i=n-1; while (i!=0){ if (i==1) break; p=i/2; if (a[p]<=a[i]){ int t=a[p]; a[p]=a[i]; a[i]=t; } i=p; } for (int j=0;j<n;j++){ System.out.println(a[j]); } } } //result is this 15 20 19 29 23 12 22 35 40 26 51 17 is it correct?

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  • Help with memory leak (malloc)

    - by user146780
    I'v followed a tutorial to use OGL tesselaton. In one of the callbacks there is a malloc and it creates a leak every time I render a new frame. void CALLBACK combineCallback(GLdouble coords[3], GLdouble *vertex_data[4], GLfloat weight[4], GLdouble **dataOut) { GLdouble *vertex; vertex = (GLdouble *) malloc(6 * sizeof(GLdouble)); vertex[0] = coords[0]; vertex[1] = coords[1]; vertex[2] = coords[2]; for (int i = 3; i < 6; i++) { vertex[i] = weight[0] * vertex_data[0][i] + weight[1] * vertex_data[0][i] + weight[2] * vertex_data[0][i] + weight[3] * vertex_data[0][i]; } *dataOut = vertex; } I'v tried to free(vertex) but then the polygons did not render. I also tried allocating on the heap then doing delete(vertex) but then the polygon rendered awkwardly. I'm not sure what to do. Thanks

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  • An explanation of memory usage on Windows server 2003

    - by Rich
    Hi, We've been working on a bit of puzzle at work. We have an application service installed on two machines, both running Windows server 2003. These services do exactly the same thing. However once loaded, one of the services uses 200mb less than the other service. We're at a bit of a loss to what might be causing this discrepancy. I was wondering if there was some kind of server setting that would cause an application to use more memory (heap block size) or anything to explain this. If anyone has any ideas on what may be causing this, or how to find out what is causing this I'd be very grateful. Cheers Rich

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  • Memory allocated with malloc does not persist outside function scope?

    - by PM
    Hi, I'm a bit new to C's malloc function, but from what I know it should store the value in the heap, so you can reference it with a pointer from outside the original scope. I created a test program that is supposed to do this but I keep getting the value 0, after running the program. What am I doing wrong? int f1(int * b) { b = malloc(sizeof(int)); *b = 5; } int main() { int * a; f1(a); printf("%d\n", a); return 0; }

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  • Eclipse 3.5 (Cocoa) slowing down irregularly after some time

    - by chris_l
    Hi, I'd like to hear, if anyone else encounters the same problems, and doesn't use Google's GWT (2.0) plugins: Sometimes, my Eclipse 3.5 (Cocoa) slows down after some time of usage (=30 minutes), so that things like maximizing an editor or moving the splitters becomes unbearably slow (reacting only after several seconds). After an Eclipse restart, everything's fine again. I'm not running low on memory (neither free RAM, nor memory available to Eclipse - Heap/Stack/PermGenSpace), and my system specs are not too bad. I know exactly one other person so far, who sees the same problem - but he also uses the GWT plugins. Since these issues appear irregularly, they're hard to track. Before creating an issue on the GWT bug tracker, I'd like to find out, if this also happens for somebody without Google's plugins. Thanks, Chris Edit: I'm running Snow Leopard 10.6.2

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