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• c# wrapper for a c DLL

  - by Without me Its just Aweso

  I'm attempting to write a wrapper so that my C# application can use a DLL written in C. Here is a method defintion that i'm trying to wrap: void methodA(const uint32_t *data); //c header declaration The issue I'm having is trying to figure out how to give a equivalent pointer from c#. In c# I want it to operate on a: UInt32 data[] //my c# object i want to be able to pass in but how do I give an equivalent pointer in my wrapper? I have tried ref data //my attempt at giving an equivalent pointer to the DLL but that doesnt seem to be working. Using debug statements in the DLL I can see that the values it gets that way are not what I'm attempting to pass in. So my question boils down to have do I properly wrap a c fuction that is using a pointer to reference an array?

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• how to copy char * into a string and visa versa

  - by user295030

  If i pass a char * into a function. I want to then take that char * convert it to a std::string and once I get my result convert it back to char * from a std::string to show the result. I don't know how to do this for conversion ( I am not talking const char * but just char *) I am not sure how to manipulate the value of the pointer I send in. so steps i need to do take in a char * convert it into a string. take the result of that string and put it back in the form of a char * return the result such that the value should be available outside the function and not get destroyed. If possible can i see how it could be done via reference vs a pointer (whose address I pass in by value however I can still modify the value that pointer is pointing to. so even though the copy of the pointer address in the function gets destroyed i still see the changed value outside. thanks!

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• Intel MKL memory management and exceptions

  - by Andrew

  Hello everyone, I am trying out Intel MKL and it appears that they have their own memory management (C-style). They suggest using their MKL_malloc/MKL_free pairs for vectors and matrices and I do not know what is a good way to handle it. One of the reasons for that is that memory-alignment is recommended to be at least 16-byte and with these routines it is specified explicitly. I used to rely on auto_ptr and boost::smart_ptr a lot to forget about memory clean-ups. How can I write an exception-safe program with MKL memory management or should I just use regular auto_ptr's and not bother? Thanks in advance. EDIT http://software.intel.com/sites/products/documentation/hpc/mkl/win/index.htm this link may explain why I brought up the question UPDATE I used an idea from the answer below for allocator. This is what I have now: template <typename T, size_t TALIGN=16, size_t TBLOCK=4> class aligned_allocator : public std::allocator<T> { public: pointer allocate(size_type n, const void *hint) { pointer p = NULL; size_t count = sizeof(T) * n; size_t count_left = count % TBLOCK; if( count_left != 0 ) count += TBLOCK - count_left; if ( !hint ) p = reinterpret_cast<pointer>(MKL_malloc (count,TALIGN)); else p = reinterpret_cast<pointer>(MKL_realloc((void*)hint,count,TALIGN)); return p; } void deallocate(pointer p, size_type n){ MKL_free(p); } }; If anybody has any suggestions, feel free to make it better.

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• Gtk, whether destroying GtkBuilder destroies all the screens and widgets?

  - by PP

  Hi, Question regarding GtkBuilder. When we unref builder pointer does it destroys all the screens/widgets the builder had created? if( builder_ptr ) g_object_unref(G_OBJECT(builder_ptr)); Suppose we have created one screen using Glade/XML with some 2-3 top_level windows in it gtk_builder_add_from_file(builder_ptr, "Test.glade", &error ) and generated GtkBuilder pointer (as above) so after deleting this pointer does it deletes created Windows or do we need to manually delete these windows? Thanks, PP.

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• C# to unmanaged dll data structures interop

  - by Shane Powell

  I have a unmanaged DLL that exposes a function that takes a pointer to a data structure. I have C# code that creates the data structure and calls the dll function without any problem. At the point of the function call to the dll the pointer is correct. My problem is that the DLL keeps the pointer to the structure and uses the data structure pointer at a later point in time. When the DLL comes to use the pointer it has become invalid (I assume the .net runtime has moved the memory somewhere else). What are the possible solutions to this problem? The possible solutions I can think of are: Fix the memory location of the data structure somehow? I don't know how you would do this in C# or even if you can. Allocate memory manually so that I have control over it e.g. using Marshal.AllocHGlobal Change the DLL function contract to copy the structure data (this is what I'm currently doing as a short term change, but I don't want to change the dll at all if I can help it as it's not my code to begin with). Are there any other better solutions?

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• C++ memory management of reference types

  - by Russel

  Hello, I'm still a fairly novice programmer and I have a question about c++ memory management with refence types. First of all, my understanding of reference types: A pointer is put on the stack and the actual data that the pointer points to is created and placed on the heap. Standard arrays and user defined classes are refence types. Is this correct? Second, my main question is do c and c++'s memory management mechanisms (malloc, free and new, delete) always handle this properly and free the memory that a class or array is pointing to? Does everything still work if those pointers get reassigned somehow to other objects of the same size/type on the heap? What if a class has a pointer member that points to another object? I am assuming that delete/freeing the class object doesn't free what it's member pointer points to, is that correct? Thanks all! -R

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• how to copy char * into a string and vice-versa

  - by user295030

  If i pass a char * into a function. I want to then take that char * convert it to a std::string and once I get my result convert it back to char * from a std::string to show the result. I don't know how to do this for conversion ( I am not talking const char * but just char *) I am not sure how to manipulate the value of the pointer I send in. so steps i need to do take in a char * convert it into a string. take the result of that string and put it back in the form of a char * return the result such that the value should be available outside the function and not get destroyed. If possible can i see how it could be done via reference vs a pointer (whose address I pass in by value however I can still modify the value that pointer is pointing to. so even though the copy of the pointer address in the function gets destroyed i still see the changed value outside. thanks!

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• Wierdness debugging Visual Studio C++ 2008

  - by Jeff Dege

  I have a legacy C++ app, that in its most incarnation we've been building with makefiles and VS2003's command-line tool. I'm trying to get it to build using VS2008 and MsBuild. The build is working OK, but I'm getting errors where I'd never seen errors, before, and stepping through in VS2008's debugger only confuses me. The app links a number of static libraries, which fall into two categories: those that are part of the same application suite, and those that are shared between a number of application suites. Originally, I had a .csproj file for each static library, and two .sln files, one for the application suite (including the suite-specific libraries) and one for the non-suite-specific shared libraries. The shared libraries were included in the link, their projects were not included in the application suite .sln. The application instantiates an object from a class that is defined in one of the shared libraries. The class has a member object of a class that wraps a linked list. The constructor of the linked list class sets its "head" pointer to null. When I run the app, and try to add an element to the linked list, I get an error - the head pointer contains the value 0xCCCCCCCC. So I step through with the debugger. And see weirdness. When the current line in the debugger is in a source file belonging to the static library, the head pointer contains 0x00000000. When I step into the constructor, I can see the pointer being set to that value, and when I'm stepped into any other method of the class, I can see that the head pointer still contains 0x00000000. But when I step out into methods that are defined in the application suite .sln, it contains 0xCCCCCCCC. It's not like it's being overwritten. It changes back and forth depending upon which source file I am currently debugging. So I included the shared library's project in the application suite .sln, and now I see the head pointer containing 0xCCCCCCCC all the time. It looks like the constructor of the linked list class is not being called. So now, I'm entirely confused. Anyone have any ideas?

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• Getting list of all existing vtables.

  - by Patrick

  In my application I have quite some void-pointers (this is because of historical reasons, application was originally written in pure C). In one of my modules I know that the void-pointers points to instances of classes that could inherit from a known base class, but I cannot be 100% sure of it. Therefore, doing a dynamic_cast on the void-pointer might give problems. Possibly, the void-pointer even points to a plain-struct (so no vptr in the struct). I would like to investigate the first 4 bytes of the memory the void-pointer is pointing to, to see if this is the address of the valid vtable. I know this is platform, maybe even compiler-version-specific, but it could help me in moving the application forward, and getting rid of all the void-pointers over a limited time period (let's say 3 years). Is there a way to get a list of all vtables in the application, or a way to check whether a pointer points to a valid vtable, and whether that instance pointing to the vtable inherits from a known base class?

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• C -- Basic Struct questions

  - by Ryan Yu

  So I'm trying to learn C right now, and I have some basic struct questions I'd like to clear up: Basically, everything centers around this snippet of code: #include <stdio.h> #include <stdlib.h> #define MAX_NAME_LEN 127 typedef struct { char name[MAX_NAME_LEN + 1]; unsigned long sid; } Student; /* return the name of student s */ const char* getName (const Student* s) { // the parameter 's' is a pointer to a Student struct return s->name; // returns the 'name' member of a Student struct } /* set the name of student s If name is too long, cut off characters after the maximum number of characters allowed. */ void setName(Student* s, const char* name) { // 's' is a pointer to a Student struct | 'name' is a pointer to the first element of a char array (repres. a string) s->name = name; } /* return the SID of student s */ unsigned long getStudentID(const Student* s) { // 's' is a pointer to a Student struct return s->sid; } /* set the SID of student s */ void setStudentID(Student* s, unsigned long sid) { // 's' is a pointer to a Student struct | 'sid' is a 'long' representing the desired SID s->sid = sid; } I've commented up the code in an attempt to solidify my understanding of pointers; I hope they're all accurate. So anyway, I have a feeling that setName and setStudentID aren't correct, but I'm not exactly sure why. Can someone explain? Thanks!

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• Decayed multidimensional array return from function

  - by paul simmons

  related to http://stackoverflow.com/questions/2520535/gcc-multi-dim-array-or-double-pointer-for-warning-free-compile , is there a way to return so-called "decayed array pointer" from a function? in summary (suppose 2 dim array) returning int (*a)[5] format rather than int** format? as far as I see, when returned int** pointer is sent to another function waiting (int*)[] parameter, it is not working correctly.

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• Useless variable name in C struct type definition

  - by user1210233

  I'm implementing a linked list in C. Here's a struct that I made, which represents the linked list: typedef struct llist { struct lnode* head; /* Head pointer either points to a node with data or NULL */ struct lnode* tail; /* Tail pointer either points to a node with data or NULL */ unsigned int size; /* Size of the linked list */ } list; Isn't the "llist" basically useless. When a client uses this library and makes a new linked list, he would have the following declaration: list myList; So typing llist just before the opening brace is practically useless, right? The following code basically does the same job: typedef struct { struct lnode* head; /* Head pointer either points to a node with data or NULL */ struct lnode* tail; /* Tail pointer either points to a node with data or NULL */ unsigned int size; /* Size of the linked list */ } list;

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• Could I ever want to access the address zero?

  - by Joel

  The constant 0 is used as the null pointer in C and C++. But as in http://stackoverflow.com/questions/2389251/pointer-to-a-specific-fixed-address there seems to be some possible use of assigning fixed addresses. Is there ever any conceivable need, in any system, for whatever low level task, for accessing the address 0? If there is, how is that solved with 0 being the null pointer and all? If not, what makes it certain that there is not such a need?

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• sending address of a variable declared on the stack?

  - by kobac

  I have a doubt concerning declaring variables, their scope, and if their address could be sent to other functions even if they are declared on the stack? class A{ AA a; void f1(){ B b; aa.f2(&b); } }; class AA{ B* mb; f2(B* b){ mb = b; //... } }; Afterwards, I use my AA::mb pointer in the code. So things I would like to know are following. When the program exits A::f1() function, b variable since declared as a local variable and placed on the stack, can't be used anymore afterwards. What happens with the validity of the AA::mb pointer? It contains the address of the local variable which could not be available anymore, so the pointer isn't valid anymore? If B class is a std::<vector>, and AA::mb is not a pointer anymore to that vector, but a vector collection itself for example. I would like to avoid copying all of it's contents in AA::f2() to a member AA::mb in line mb = b. Which solution would you recommend since I can't assign a pointer to it, because it'll be destroyed when the program exits AA::f2()

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• walking list in KDB/kernel debugger

  - by user291849

  I need to walk a link list in the kernel debugger. How can I determine the head pointer and walk the list? I have a listing and can find the address and location in the code where I check to see if I have a head, so I know the specific code location and address. But not sure how to determine the pointer or how to determine the next element and pointer on the list.

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• Linked List manipulation, issues retrieving data c++

  - by floatfil

  I'm trying to implement some functions to manipulate a linked list. The implementation is a template typename T and the class is 'List' which includes a 'head' pointer and also a struct: struct Node { // the node in a linked list T* data; // pointer to actual data, operations in T Node* next; // pointer to a Node }; Since it is a template, and 'T' can be any data, how do I go about checking the data of a list to see if it matches the data input into the function? The function is called 'retrieve' and takes two parameters, the data and a pointer: bool retrieve(T target, T*& ptr); // This is the prototype we need to use for the project "bool retrieve : similar to remove, but not removed from list. If there are duplicates in the list, the first one encountered is retrieved. Second parameter is unreliable if return value is false. E.g., " Employee target("duck", "donald"); success = company1.retrieve(target, oneEmployee); if (success) { cout << "Found in list: " << *oneEmployee << endl; } And the function is called like this: company4.retrieve(emp3, oneEmployee) So that when you cout *oneEmployee, you'll get the data of that pointer (in this case the data is of type Employee). (Also, this is assuming all data types have the apropriate overloaded operators) I hope this makes sense so far, but my issue is in comparing the data in the parameter and the data while going through the list. (The data types that we use all include overloads for equality operators, so oneData == twoData is valid) This is what I have so far: template <typename T> bool List<T>::retrieve(T target , T*& ptr) { List<T>::Node* dummyPtr = head; // point dummy pointer to what the list's head points to for(;;) { if (*dummyPtr->data == target) { // EDIT: it now compiles, but it breaks here and I get an Access Violation error. ptr = dummyPtr->data; // set the parameter pointer to the dummy pointer return true; // return true } else { dummyPtr = dummyPtr->next; // else, move to the next data node } } return false; } Here is the implementation for the Employee class: //-------------------------- constructor ----------------------------------- Employee::Employee(string last, string first, int id, int sal) { idNumber = (id >= 0 && id <= MAXID? id : -1); salary = (sal >= 0 ? sal : -1); lastName = last; firstName = first; } //-------------------------- destructor ------------------------------------ // Needed so that memory for strings is properly deallocated Employee::~Employee() { } //---------------------- copy constructor ----------------------------------- Employee::Employee(const Employee& E) { lastName = E.lastName; firstName = E.firstName; idNumber = E.idNumber; salary = E.salary; } //-------------------------- operator= --------------------------------------- Employee& Employee::operator=(const Employee& E) { if (&E != this) { idNumber = E.idNumber; salary = E.salary; lastName = E.lastName; firstName = E.firstName; } return *this; } //----------------------------- setData ------------------------------------ // set data from file bool Employee::setData(ifstream& inFile) { inFile >> lastName >> firstName >> idNumber >> salary; return idNumber >= 0 && idNumber <= MAXID && salary >= 0; } //------------------------------- < ---------------------------------------- // < defined by value of name bool Employee::operator<(const Employee& E) const { return lastName < E.lastName || (lastName == E.lastName && firstName < E.firstName); } //------------------------------- <= ---------------------------------------- // < defined by value of inamedNumber bool Employee::operator<=(const Employee& E) const { return *this < E || *this == E; } //------------------------------- > ---------------------------------------- // > defined by value of name bool Employee::operator>(const Employee& E) const { return lastName > E.lastName || (lastName == E.lastName && firstName > E.firstName); } //------------------------------- >= ---------------------------------------- // < defined by value of name bool Employee::operator>=(const Employee& E) const { return *this > E || *this == E; } //----------------- operator == (equality) ---------------- // if name of calling and passed object are equal, // return true, otherwise false // bool Employee::operator==(const Employee& E) const { return lastName == E.lastName && firstName == E.firstName; } //----------------- operator != (inequality) ---------------- // return opposite value of operator== bool Employee::operator!=(const Employee& E) const { return !(*this == E); } //------------------------------- << --------------------------------------- // display Employee object ostream& operator<<(ostream& output, const Employee& E) { output << setw(4) << E.idNumber << setw(7) << E.salary << " " << E.lastName << " " << E.firstName << endl; return output; } I will include a check for NULL pointer but I just want to get this working and will test it on a list that includes the data I am checking. Thanks to whoever can help and as usual, this is for a course so I don't expect or want the answer, but any tips as to what might be going wrong will help immensely!

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• gluNewQuadric() before opengl's initialization

  - by Schrödinger's cat

  Hello, I'm working on a c++ code that uses SDL/opengl. Is this possible to create a pointer to a quadric with 'gluNewQuadric()' before having initialized opengl with 'SDL_SetVideoMode'? The idea is to create a class with a (pointer to a) quadric class member that has to be instantiate before the 'SDL_SetVideoMode' call. This pointer is initialized in the class' constructor with a 'gluNewQuadric()' call.

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• Using `g_object_set_data` for passing user name.

  - by PP

  I am using g_object_set_data to set user name with event_box so in call back i can get it with in event_box pointer. g_object_set_data(G_OBJECT(event_box), "user_name", (gpointer)(user_name) ); but problem is that i am setting user_name which is not an pointer allocated string. It is an local string (not allocated on hip) which gets destroyed. So is it necessary to allocated and then use the pointer, i just want to associate one name with this event_box.

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• Java reference storage question

  - by aab

  In java, when you pass an object to a method as a parameter, it is actually passing a reference, or a pointer, to that object because objects in Java are references. Inside the function, it has a pointer to that object which is a location in memory. I am wondering where this pointer lives in memory? Is a new memory location created once inside the function to hold this reference?

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• how i should create a reference of a object of a class

  - by vishal_niist

  How i get address pointer of a object

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• Make Windows Position Your Dual Monitors Correctly

  - by Mysticgeek

  If you have a dual monitor setup and each monitor is a different size or height, it can be annoying trying to move the mouse pointer between them. Here is a quick tip that will help make the process easier. Align Monitors In our example, we’re using Windows 7, but the process is essentially the same in all versions, but getting to Display Settings is different. In Windows 7 open the Start menu and type display settings into the search box and hit Enter. In Vista right-click the desktop and click Personalize. Then from the Personalize appearance and sounds menu click on Display Settings. In XP right-click on the desktop and select Properties then in Display Properties click the Settings tab. Now here is where you can change the appearance of your monitors. In this example we have a larger 22” LCD and a smaller 19” and it can be annoying getting the mouse pointer from one to another depending where you are on each monitor. So what you want to do is simply move each display around to a particular height so it’s easier to get the pointer over. For example with this setting we know we’ll have no problem moving the pointer to the other screen at the top of each display.   Of course here you can flip your monitors around, change the display resolution, orientation, etc. If you have dual monitors where one might be larger or set up higher than the other, then this is a great way to get them finely tuned. You will have to play around with the settings a bit to settle on what works best for you. Similar Articles Productive Geek Tips GeekNewb: Get to Know These Windows 7 HotkeysDual Monitors: Use a Different Wallpaper on Each DesktopSet Windows as Default OS when Dual Booting UbuntuEasily Set Default OS in a Windows 7 / Vista and XP Dual-boot SetupSet XP as the Default OS in a Windows Vista Dual-Boot Setup TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips DVDFab 6 Revo Uninstaller Pro Registry Mechanic 9 for Windows PC Tools Internet Security Suite 2010 Download Wallpapers From National Geographic Site Spyware Blaster v4.3 Yes, it’s Patch Tuesday Generate Stunning Tag Clouds With Tagxedo Install, Remove and HIDE Fonts in Windows 7 Need Help with Your Home Network?

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• Krita Gemini, 2 fois plus agréable sur un 2 en 1, par Tim Duncan

  Bonjour,Je vous présente cet article intitulé : "Krita Gemini, 2 fois plus agréable sur un 2 en 1" Au fil des années, les ordinateurs ont utilisé une variété de méthodes d'entrée à partir des cartes perforées en passant par des lignes de commande jusqu'à pointer-et-cliquer avec une souris ou d'autres périphériques. Avec l'adoption des écrans tactiles, nous pouvons maintenant pointer-et-cliquer avec une souris, un stylet ou avec les doigts. La plupart d'entre nous ne sommes pas encore...

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• Low coupling and tight cohesion

  - by hidayat

  Of course it depends on the situation. But when a lower lever object or system communicate with an higher level system, should callbacks or events be preferred to keeping a pointer to higher level object? For example, we have a world class that has a member variable vector<monster> monsters. When the monster class is going to communicate with the world class, should I prefer using a callback function then or should I have a pointer to the world class inside the monster class?

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• Memory read/write access efficiency

  - by wolfPack88

  I've heard conflicting information from different sources, and I'm not really sure which one to believe. As such, I'll post what I understand and ask for corrections. Let's say I want to use a 2D matrix. There are three ways that I can do this (at least that I know of). 1: int i; char **matrix; matrix = malloc(50 * sizeof(char *)); for(i = 0; i < 50; i++) matrix[i] = malloc(50); 2: int i; int rowSize = 50; int pointerSize = 50 * sizeof(char *); int dataSize = 50 * 50; char **matrix; matrix = malloc(dataSize + pointerSize); char *pData = matrix + pointerSize - rowSize; for(i = 0; i < 50; i++) { pData += rowSize; matrix[i] = pData; } 3: //instead of accessing matrix[i][j] here, we would access matrix[i * 50 + j] char *matrix = malloc(50 * 50); In terms of memory usage, my understanding is that 3 is the most efficient, 2 is next, and 1 is least efficient, for the reasons below: 3: There is only one pointer and one allocation, and therefore, minimal overhead. 2: Once again, there is only one allocation, but there are now 51 pointers. This means there is 50 * sizeof(char *) more overhead. 1: There are 51 allocations and 51 pointers, causing the most overhead of all options. In terms of performance, once again my understanding is that 3 is the most efficient, 2 is next, and 1 is least efficient. Reasons being: 3: Only one memory access is needed. We will have to do a multiplication and an addition as opposed to two additions (as in the case of a pointer to a pointer), but memory access is slow enough that this doesn't matter. 2: We need two memory accesses; once to get a char *, and then to the appropriate char. Only two additions are performed here (once to get to the correct char * pointer from the original memory location, and once to get to the correct char variable from wherever the char * points to), so multiplication (which is slower than addition) is not required. However, on modern CPUs, multiplication is faster than memory access, so this point is moot. 1: Same issues as 2, but now the memory isn't contiguous. This causes cache misses and extra page table lookups, making it the least efficient of the lot. First and foremost: Is this correct? Second: Is there an option 4 that I am missing that would be even more efficient?

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• Oracle VDI thin client terminal and Synergy

  - by katsumii

  I use my main laptop and old SunRay thin client hardware at my office.I set up Synergy for keyboard/mouse/clipboard sharing and I thought I hit this issue.  Bug #3002 - Mouse Pointer Invisible on Client PC - SynergyRDP and a thin client setup I found this workaround. Turning "Display pointer trails" on somehow made mymouse appear on thin client side.  This may or may not work in different kind of Oracle VDI setup or other vendors' thin client. 

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