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• pointer-to-pointer of derived class in multiple inheritance

  - by Abdul jalil

  i have 3 classes A,B and C. C is derived from A and B. i get pointer to pointer of class C and cast to A** , and B ** , the variable that hold the the B** has the address of A** in my example B ** BdoublePtr hold the address of A** .i am using the following code #include "conio.h" #include "stdio.h" #include "string.h" class A{ public: A() { strA=new char[30]; strcpy(strA,"class A"); } char *strA; }; class B { public: B() { strB=new char[30]; strcpy(strB,"class B"); } char *strB; }; class C :public A, public B { public: C() { strC=new char[30]; strcpy(strC,"class C"); } char *strC; }; int main(void) { C* ptrC=new C(); A * Aptr=(A*)ptrC; printf("\n class A value : %s",Aptr-strA); B * Bptr=(B*)ptrC; printf("\n class B value :%s",Bptr-strB); printf("\n\nnow with double pointer "); A ** AdoublePtr=(A **)&ptrC; Aptr=AdoublePtr; printf("\n class A value : %s",Aptr-strA); B * BdoublePtr=(B **)&ptrC; Bptr=*BdoublePtr; printf("\n class B value : %s",Bptr-strB); getch(); return 0; }

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• C++, function pointer to the template function pointer

  - by Ian

  I am having a pointer to the common static method class MyClass { private: static double ( *pfunction ) ( const Object *, const Object *); ... }; pointing to the static method class SomeClass { public: static double getA ( const Object *o1, const Object *o2); ... }; Initialization: double ( *MyClass::pfunction ) ( const Object *o1, const Object *o2 ) = &SomeClass::getA; I would like to convert this pointer to the static template function pointer: template <class T> static T ( *pfunction ) ( const Object <T> *, const Object <T> *); //Compile error where: class SomeClass { public: template <class T> static double getA ( const Object <T> *o1, const Object <T> *o2); ... }; But there is some error... Thanks for your help...

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• pointer to a pointer in a linked list

  - by user1596497

  I'm trying to set a linked list head through pointer to a pointer. I can see inside the function that the address of the head pointer is changing but as i return to the main progran it becomes NULL again. can someone tell me what I'm doing wrong ?? #include <stdio.h> #include <stdlib.h> typedef void(*fun_t)(int); typedef struct timer_t { int time; fun_t func; struct timer_t *next; }TIMER_T; void add_timer(int sec, fun_t func, TIMER_T *head); void run_timers(TIMER_T **head); void timer_func(int); int main(void) { TIMER_T *head = NULL; int time = 1; fun_t func = timer_func; while (time < 1000) { printf("\nCalling add_timer(time=%d, func=0x%x, head=0x%x)\n", time, func, &head); add_timer(time, func, head); time *= 2; } run_timers(&head); return 0; } void add_timer(int sec, fun_t func, TIMER_T *head) { TIMER_T ** ppScan=&head; TIMER_T *new_timer = NULL; new_timer = (TIMER_T*)malloc(sizeof(TIMER_T)); new_timer->time = sec; new_timer->func = func; new_timer->next = NULL; while((*ppScan != NULL) && (((**ppScan).time)<sec)) ppScan = &(*ppScan)->next; new_timer->next = *ppScan; *ppScan = new_timer; }

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• Can't save data for a member in a data form

  - by RahulS

  Implied sharing is an old thing everyone knows the reasons and solutions of that, still little theory about that: With Essbase implied sharing, some members are shared even if you do not explicitly set them as shared. These members are implied shared members. When an implied share relationship is created, each implied member assumes the other member’s value. Essbase assumes (or implies) a shared member relationship in these situations: 1. A parent has only one child 2. A parent has only one child that consolidates to the parent In a Planning form that contains members with an implied sharing relationship, when a value is added for the parent, the child assumes the same value after the form is saved. Likewise, if a value is added for the child, the parent usually assumes the same value after a form is saved.For example, when a calculation script or load rule populates an implied share member, the other implied share member assumes the value of the member populated by the calculation script or load rule. The last value calculated or imported takes precedence. The result is the same whether you refer to the parent or the child as a variable in a calculation script. For more information have a look at: http://docs.oracle.com/cd/E17236_01/epm.1112/hp_admin_11122/ch14s11.html Now the issue which we are going to talk about is We loose data on save even when the parent is dynamic calc and has a single child. A dynamic calc parent to a single child:  If we design the form with following selection: In the data form we will find parent below the member and this is by design whenever you make a selection using commands to select all the member below parent, always children will appear before the parent: Lets try to enter data, Save it Now, try to change the way we selected members Here we go: Now the question again why this behavior: 1. Data from Planning data form passes to Essbase row by row, 2. Because in data form the child member appears before the parent, 3. First, data goes to Essbase for child (SingleStoreChild), 4. Then when Planning passes the data for parent there was #Missing or No data,  5. Over writes the data to #missing. PS: As we know that dynamic calc members are calculated on the fly they are not allocated with any memory in the Essbase, here the parent was dynamic calc and it was pointing to same memory as child in the background, when Planning was passing data to Essbase for second row it has updated the child with missing data.(Little confusing, let me know if you need more explanation) 6. As one of the solutions just change the order of appearance of parent and child. Cheers..!!! Rahul S. https://www.facebook.com/pages/HyperionPlanning/117320818374228

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• Pointer initialization

  - by SoulBeaver

  Sorry if this question has been asked before. On my search through SO I didn't find one that asked what I wanted to know. Basically, when I have this: typedef struct node { int data; node *node; } *head; and do node *newItem = new node; I am under the impression that I am declaring and reserving space, but not defining, a pointer to struct node, is that correct? So when I do newItem->data = 100 and newItem->next = 0 I get confused. newItem = 0would declare what exactly? Both data and next? The object as a whole? I'm especially confused when I use typedef. Which part is the macro? I assume node because that's how I call it, but why do I need it? Finally, what happens when I do: node *temp; temp = new node; temp = head->next; head->next = newItem; newItem->next = temp; I mean, head-next is a pointer pointing to object newItem, so I assume not to newItem.data or next themselves. So how can I use an uninitialized pointer that I described above safely like here? is head now not pointing to an uninitialized pointer?

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• c program pointer

  - by sandy101

  Hello , I am trying some programs in c face a problem with this program #include<stdio.h> int main() { int a=9,*x; float b=3.6,*y; char c='a',*z; printf("the value is %d\n",a); printf("the value is %f\n",b); printf("the value is %c\n",c); x=&a; y=&b; z=&c; printf("%u\n",a); printf("%u\n",b); printf("%u\n",c); x++; y++; z++; printf("%u\n",a); printf("%u\n",b); printf("%u\n",c); return 0; } can any one tell me what is the problem with this and i also want to know that when in the above case if the pointer value is incremented then will it over write the previous value address as suppose that the value we got in the above program (without the increment in the pointer value )is 65524 65520 65519 and after the increment the value of the pointer is 65526(as 2 increment for the int ) 65524(as 4 increment for the float ) 65520(as 1 increment for the char variable ) then if in that case will the new pointer address overwrite the content of the previous address and what value be contained at the new address ......plz help

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• What is the use of Pointer to Pointer?

  - by hiral

  Why do we need a double pointer? What are some examples or use cases?

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• commands&creating pointer [closed]

  - by gcc

  input 23 3 4 4 42 n 23 0 9 9 n n n 3 9 9 x //according to input,i should create int pointer arrays. pointer arrays // starting from 1 (that is initial arrays is arrays[1].when program sees n ,it // must be jumb to arrays 2 // the first int input 23 is num_arrays which used in malloc(sizeof(int)*num_arrays expected output: elements of arrays[1] 3 4 5 42 elements of arrays[2] 23 0 9 9 elements of arrays[5] 3 9 9 another input 12 2 3 4 n n 2 3 4 n 12 3 x expected output elements of arrays[1] 2 3 4 elements of arrays[3] 2 3 4 elements of arrays[4] 12 3 specification: x is stopper n is comman to create new pointer array i am new in this site anyone help me how can i write

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• n & x commands&creating pointer&with using malloc [closed]

  - by gcc

  input 23 3 4 4 42 n 23 0 9 9 n n n 3 9 9 x //according to input,i should create int pointer arrays. pointer arrays // starting from 1 (that is initial arrays is arrays[1].when program sees n ,it // must be jumb to arrays 2 // the first int input 23 is num_arrays which used in malloc(sizeof(int)*num_arrays expected output arrays[1] 3 4 5 42 arrays[2] 23 0 9 9 arrays[5] 3 9 9 another input 12 2 3 4 n n 2 3 4 n 12 3 x expected output arrays[1] 2 3 4 arrays[3] 2 3 4 arrays[4] 12 3 x is stopper n is comman to create new pointer array i am new in this site anyone help me how can i write

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• Question on Pointer Arithmetic

  - by pws5068

  Heyy Everybody! I am trying to create a memory management system, so that a user can call myMalloc, a method I created. I have a linked list keeping track of my free memory. My problem is when I am attempting to find the end of a free bit in my linked list. I am attempting to add the size of the memory free in that section (which is in the linked list) to the pointer to the front of the free space, like this. void *tailEnd = previousPlace->head_ptr + ((previousPlace->size+1)*(sizeof(int)); I was hoping that this would give me a pointer to the end of that segment. However, I keep getting the warning: "pointer of type 'void*' used in arithmetic" Is there a better way of doing this? Thanks!

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• Question about member function pointers in a heirarchy

  - by Jesse Beder

  I'm using a library that defines an interface: template<class desttype> void connect(desttype* pclass, void (desttype::*pmemfun)()); and I have a small heirarchy class base { void foo(); }; class derived: public base { ... }; In a member function of derived, I want to call connect(this, &derived::foo); but it seems that &derived::foo is actually a member function pointer of base; gcc spits out error: no matching function for call to ‘connect(derived* const&, void (base::* const&)())’ I can get around this by explicitly casting this to base *; but why can't the compiler match the call with desttype = base (since derived * can be implicitly cast to base *)? Also, why is &derived::foo not a member function pointer of derived?

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• "Initializing" the pointer in the separate function in C

  - by pechenie

  I need to do a simple thing, which I used to do many times in Java, but I'm stuck in C (pure C, not C++). The situation looks like this: int *a; void initArray( int *arr ) { arr = malloc( sizeof( int ) * SIZE ); } int main() { initArray( a ); // a is NULL here! what to do?! return 0; } I have some "initializing" function, which SHOULD assign a given pointer to some allocated data (doesn't matter). How should I give a pointer to a function in order to this pointer will be modified, and then can be used further in the code (after that function call returns)? Thanx for help.

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• C++ inheritance and member function pointers

  - by smh

  In C++, can member function pointers be used to point to derived (or even base) class members? EDIT: Perhaps an example will help. Suppose we have a hierarchy of three classes X, Y, Z in order of inheritance. Y therefore has a base class X and a derived class Z. Now we can define a member function pointer p for class Y. This is written as: void (Y::*p)(); (For simplicity, I'll assume we're only interested in functions with the signature void f() ) This pointer p can now be used to point to member functions of class Y. This question (two questions, really) is then: Can p be used to point to a function in the derived class Z? Can p be used to point to a function in the base class X?

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• cannot override a concrete member without a third member that's overridden by both

  - by huynhjl

  What does the following error message mean? cannot override a concrete member without a third member that's overridden by both (this rule is designed to prevent ``accidental overrides''); I was trying to do stackable trait modifications. It's a little bit after the fact since I already have a hierarchy in place and I'm trying to modify the behavior without having to rewrite a lot of code. I have a base class called AbstractProcessor that defines an abstract method sort of like this: class AbstractProcessor { def onPush(i:Info): Unit } I have a couple existing traits, to implement different onPush behaviors. trait Pass1 { def onPush(i:Info): Unit = { ... } } trait Pass2 { def onPush(i:Info): Unit = { ... } } So that allows me to use new AbstractProcessor with Pass1 or new AbstractProcessor with Pass2. Now I would like to do some processing before and after the onPush call in Pass1 and Pass2 while minimizing code changes to AbstractProcessor and Pass1 and Pass2. I thought of creating a trait that does something like this: trait Custom extends AbstractProcessor { abstract override def onPush(i:Info): Unit = { // do stuff before super.onPush(i) // do stuff after } And using it with new AbstractProcessor with Pass1 with Custom and I got that error message.

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• Passing NSArray Pointer Rather Than A Pointer To a Specific Type

  - by mattmccomb

  I've just written a piece of code to display a UIActionSheet within my app. Whilst looking at the code to initialise my UIActionSheet something struck me as a little strange. The initialisation function has the following signature... initWithTitle:(NSString *)title delegate:(id UIActionSheetDelegate)delegate cancelButtonTitle:(NSString *)cancelButtonTitle destructiveButtonTitle:(NSString *)destructiveButtonTitle otherButtonTitles:(NSString *)otherButtonTitles As you can see the otherButtonTitles parameter is a pointer to a String. In my code I set it as follows... otherButtonTitles: @"Title", @"Date", nil Although this compiles fine I don't really understand how it works. My reading of the statement is that I have created an inline array containing two elements (Title and Date). How come this then compiles? I'm passing a NSArray* in place of a NSString*. I know from a little of understanding of C++ that an array is really a pointer to the first element. So is this inline array that I'm creating a C array as opposed to a NSArray? What I'm hoping to achieve is to be able to pass a static NSArray* used elsewhere in my class to the otherButtonTitles parameter. But passing the NSArray* object directly doesn't work.

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• Normal pointer vs Auto pointer (std::auto_ptr)

  - by AKN

  Code snippet (normal pointer) int *pi = new int; int i = 90; pi = &i; int k = *pi + 10; cout<<k<<endl; delete pi; [Output: 100] Code snippet (auto pointer) Case 1: std::auto_ptr<int> pi(new int); int i = 90; pi = &i; int k = *pi + 10; //Throws unhandled exception error at this point while debugging. cout<<k<<endl; //delete pi; (It deletes by itself when goes out of scope. So explicit 'delete' call not required) Case 2: std::auto_ptr<int> pi(new int); int i = 90; *pi = 90; int k = *pi + 10; cout<<k<<endl; [Output: 100] Can someone please tell why it failed to work for case 1?

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• Static member function pointer to hold non static member function

  - by user1425406

  This has defeated me. I want to have a static class variable which is a pointer to a (non-static) member function. I've tried all sorts of ways, but with no luck (including using typedefs, which just seemed to give me a different set of errors). In the code below I have the static class function pointer funcptr, and I can call it successfully from outside the class, but not from within the member function CallFuncptr - which is what I want to do. Any suggestions? #include <stdio.h> class A { public: static int (A::*funcptr)(); int Four() { return 4;}; int CallFuncptr() { return (this->*funcptr)(); } // doesn't link - undefined reference to `A::funcptr' }; int (A::*funcptr)() = &A::Four; int main() { A fred; printf("four? %d\n", (fred.*funcptr)()); // This works printf("four? %d\n", fred.CallFuncptr()); // But this is the way I want to call it }

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• segmentation fault when using pointer to pointer

  - by user3697730

  I had been trying to use a pointer to pointer in a function,but is seems that I am not doing the memory allocation correctly... My code is: #include<stdio.h> #include<math.h> #include<ctype.h> #include<stdlib.h> #include<string.h> struct list{ int data; struct list *next; }; void abc (struct list **l,struct list **l2) { *l2=NULL; l2=(struct list**)malloc( sizeof(struct list*)); (*l)->data=12; printf("%d",(*l)->data); (*l2)->next=*l2; } int main() { struct list *l,*l2; abc(&l,&l2); system("pause"); return(0); } This code compiles,but I cannot run thw program..I get a segmentation fault..What should I do?Any help would be appreciated!

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• Handles and pointer to object

  - by Tony

  I have a python Interpreter written in C++, the PyRun_String function from the Python API is said to return a handle, however in my code I have it assigned to pointer to a PyObject? PyObject* presult = PyRun_String(code, parse_mode, dict, dict); Is this actually correct? Can you implicitly cast this handle to this object pointer? Should it not be a HANDLE instead?

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• Why subtract null pointer in offsetof()?

  - by Bruce Christensen

  Linux's stddef.h defines offsetof() as: #define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER) whereas the Wikipedia article on offsetof() (http://en.wikipedia.org/wiki/Offsetof) defines it as: #define offsetof(st, m) \ ((size_t) ( (char *)&((st *)(0))->m - (char *)0 )) Why subtract (char *)0 in the Wikipedia version? Is there any case where that would actually make a difference?

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• pointer is always byte aligned

  - by kumar

  Hi, I read something like pointer must be byte-aligned. My understanding in a typical 32bit architecture... all pointers are byte aligned...No ? Please confirm. can there be a pointer which is not byte-aligned ?

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• Get default value of class member ( C# )

  - by Ruben Aster

  Let's assume I have a class ClassWithMember class ClassWithMember { int myIntMember = 10; } How do I get the default value 10 of the myIntMember member by System.Type? I'm currently struggling around with reflections by all I retreive is the default value of int (0) not the classes default member (10)..

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• C++ pointer to objects

  - by Tony

  In C++ do you always have initialize a pointer to an object with the new keyword? Or can you just have this too: MyClass *myclass; myclass->DoSomething(); I thought this was a pointer allocated on the stack instead of the heap, but since objects are normally heap allocated, I think my theory is probably faulty?? Please advice.

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• the "new" operator in c++, pointer question

  - by Crystal

  Dumb question, but whenever you call new, do you always have a pointer? SomeClass *person = new SomeClass(); And is that because you need a pointer to point to that new space of memory that was allocated for the SomeClass variable person? Thanks!

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• The best way to have a pointer to several methods - critique requested

  - by user827992

  I'm starting with a short introduction of what i know from the C language: a pointer is a type that stores an adress or a NULL the * operator reads the left value of the variable on its right and use this value as address and reads the value of the variable at that address the & operator generate a pointer to the variable on its right so i was thinking that in C++ the pointers can work this way too, but i was wrong, to generate a pointer to a static method i have to do this: #include <iostream> class Foo{ public: static void dummy(void){ std::cout << "I'm dummy" << std::endl; }; }; int main(){ void (*p)(); p = Foo::dummy; // step 1 p(); p = &(Foo::dummy); // step 2 p(); p = Foo; // step 3 p->dummy(); return(0); } now i have several questions: why step 1 works why step 2 works too, looks like a "pointer to pointer" for p to me, very different from step 1 why step 3 is the only one that doesn't work and is the only one that makes some sort of sense to me, honestly how can i write an array of pointers or a pointer to pointers structure to store methods ( static or non-static from real objects ) what is the best syntax and coding style for generating a pointer to a method?

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