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  • A pointer member variable having different values

    - by Rohan Prabhu
    Ok, to begin with, this is my code: HyperSprite::HyperSprite() { _view = 0; } void HyperSprite::publish(QGraphicsView* view) { _view = view; } void HyperSprite::getKFrame() { if(_view != 0) { qDebug()<<(void*)_view; } } Now, if I call HyperSprite::getKFrame() from within main(), I get the output: 0xbf8ffb84 I have a TCP server, which requires this QGraphicsView* variable. So whenever a new connection is made, HyperSprite::getKFrame() is called. However, whenever I make a connection to my server, this is the output: 0x1e425ff I honestly don't understand this. Shouldn't the value of a member remain same throughout? Why is the pointer value changing? As is obvious, whenever I try to use the _view pointer to access any of its members, a Segmentation Fault occurs. I tried using QSharedPointer, but it also results in the same problem. The data of the QSharedPointer automatically changes. Why is this happening?

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  • char pointer array in c#

    - by james
    consider the following c++ code #include "stdafx.h" #include<iostream> using namespace std; void ping(int,char* d[]); void ping(int a,char *b[]) { int size; size=sizeof(b)/sizeof(int); // total size of array/size of array data type //cout<<size; for(int i=0;i<=size;i++) cout<<"ping "<<a<<b[i]<<endl; } int _tmain(int argc, _TCHAR* argv[]) { void (*funcptr)(int,char* d[]); char* c[]={"a","b"}; funcptr= ping; funcptr(10,c); return 0; } how can i implement the same in c#.. m new to c#. how can i have char pointer array in c#?

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  • how to return C++ pointer in objective-C++

    - by John Smith
    I have the following objective-C++ header with the simple method to return this pointer. @interface MyObj { MyCPPObj * cpp; } -(MyCPPObj *) getObj; I have created the simple method @implementation MyObj -(MyCPPObj *) getObj { return cpp; } Everything seems to work until I actually try to use the object in another file newObj = [createdMyObj getObj]; It complains: error: cannot convert 'objc_object*' to 'MyCPPObje *' in initialization. It seems that the method is return an objective-c object, but I specifically requested a C++ pointer. How can I fix that?

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  • Use of double pointer in linux kernel Hash list implementation

    - by bala1486
    Hi, I am trying to understand Linux Kernel implementation of linked list and hash table. A link to the implementation is here. I understood the linked list implementation. But i am little confused of why double pointers is being used in hlist (**pprev). Link for hlist is here. I understand that hlist is used in implementation of hash table since head of the list requires only one pointer and it saves space. Why cant it be done using single pointer (just *prev like the linked list)? Please help me.

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  • in free(): error: junk pointer, too high to make sense Segmentation fault: 11 (core dumped) gprof

    - by Mayank
    I am trying to profile my application. For this I compiled my code with -pg and -lc_p option, it compiled successfully During run time I am getting the following error. in free(): error: junk pointer, too high to make sense Segmentation fault: 11 (core dumped) Doing GDB gives error as. (gdb) b main Breakpoint 1 at 0x5124d4: (gdb) r warning: Unable to get location for thread creation breakpoint: generic error [New LWP 100085] cacheIp in free(): error: junk pointer, too high to make sense Program received signal SIGSEGV, Segmentation fault. [Switching to LWP 100085] 0x00000000006c3a1f in pthread_sigmask () My application is multi threaded and is a combination of C and C++ code. uname -a FreeBSD 6.3-RELEASE FreeBSD 6.3-RELEASE #0: Wed Jan 16 01:43:02 UTC 2008 [email protected]:/usr/obj/usr/src/sys/SMP amd64 Why is the code crashing. Am I missing something.

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  • C: Cannot declare pointer inside if statement

    - by echedey lorenzo
    Hi, I have a pointer which points to a function. I would like to: if (mode == 0) { const unsigned char *packet = read_serial_packet(src, &len); } else { const unsigned char *packet = read_network_packet(fd, &len); } But I cannot do it because my compiler complains when I first use the pointer later in the code. error: 'packet' undeclared (first use in this function) This is strange. It worked without the if statement, but now I need my program to be able to get data from different sources. Isn't it possible to do this? I think so. If it isn't, is there any other simple way to get what I am trying? Thanks a lot.

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  • C 64-bit Pointer Alignment

    - by DuneBug
    Are pointers on a 64-bit system still 4 byte aligned (similar to a double on a 32 bit system)? Or are they note 8 byte aligned? For example, on a 64-bit system how big is the following data structure: struct a { void* ptr; char myChar; } Would the pointer by 8 byte aligned, causing 7 bytes of padding for the character (total = 8 + 8 = 16)? Or would the pointer be 4 byte aligned (4 bytes + 4 bytes) causing 3 bytes of padding (total = 4 + 4 + 4 = 12)? Thanks, Ryan

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  • declaring a 2D array of pointer objects

    - by Tyler Stennette
    I'm having a tough time figuring out how to instantiate a 2D array of pointer objects. Here is how I'm doing it: Pieces* chessBoard[9][9]; When I want to set it to an actual object pointer, I'm doing the following: chessBoard[1][1] = new Rook(p1Rook); Rook is a class that inherits attributes from the Pieces class and p1Rook is a char variable set to 'R'. This class also implements virtual functions (not pure virtual) from Pieces such as move() or getPiece() that are unique to the particular chess piece. However, when I compile my program, I get the following error: ChessBoard.cpp:69: error: expected type-specifier before ‘Rook’ ChessBoard.cpp:69: error: cannot convert ‘int*’ to ‘Pieces*’ in assignment Can someone please explain what I should change to get rid of this rather annoying persistent error? I would appreciate it.

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  • Inline assembler get address of pointer Visual Studio

    - by Joe
    I have a function in VS where I pass a pointer to the function. I then want to store the pointer in a register to further manipulate. How do you do that? I have tried void f(*p) { __asm mov eax, p // try one FAIL __asm mov eax, [p] // try two FAIL __asm mov eax, &p // try three FAIL } Both 1 and 2 are converted to the same code and load the value pointed to. I just want the address. Oddly, option 1 works just fine with integers. void f() { int i = 5; __asm mov eax, i // SUCCESS? }

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  • Inline assembler getaddress of pointer Visual Studio

    - by Joe
    I have a function in VS where I pass a pointer to the function. I then want to store the pointer in a register to further manipulate. How do you do that? I have tried void f(*p) { __asm mov eax, p // try one FAIL __asm mov eax, [p] // try two FAIL __asm mov eax, &p // try three FAIL } Both 1 and 2 are converted to the same code and load the value pointed to. I just want the address. Oddly, option 1 works just fine with integers. void f() { int i = 5; __asm mov eax, i // SUCCESS? }

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  • How to I reference a pointer from a different class

    - by Justagruvn
    Hey team of awesomeness!, (Iphone Objective-C question) First off, I despise singletons with a passion. Though I should probably be trying to use one, I just dont want to. I want to create a data class (that is instantiated only once by a view controller on loading), and then using a different class, message the crap out of that data instance until it is brimming with so much data, it smiles. So, how do i do that? I made a pointer to the instance of the data class when I instantiated it. I'm now over in a separate view controller, action occurs, and I want to update the initial data object. I think I need to reference that object by way of pointer, but I have no idea how to do that. yes I've set properties and getters and setters, which seem to work, but only in the initial view controller class. Peace Love applesauce.

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  • C++ Pointer Issue

    - by Winder
    _stuckVertices is an array of pointers and I would like to update one index of that array without using _stuckVertices[ (row * _cols) + column ] 3 times. The reason it is an array of pointers is because the vast majority of the time the pointer will be NULL. The following code works but I need to dereference a each time I use it: void Cloth::stickPoint(int column, int row) { Anchor **a = &_stuckVertices[ (row * _cols) + column ]; if (!*a) *a = new Anchor(this, column, row); (*a)->stick(); } I originally had it written like this, but the _stuckVertices pointer doesn't get updated: void Cloth::stickPoint(int column, int row) { Anchor *a = _stuckVertices[ (row * _cols) + column ]; if (!a) a = new Anchor(this, column, row); a->stick(); } Is there a way to write Anchor *a = _stuckVertices[ index ] so that a is like an alias into the array that I can update, or is something like the first piece of code how I should do this? Thanks

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  • Why is address zero used for null pointer?

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

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  • Freeing a character pointer returns error

    - by Kraffs
    I'm trying to free a character pointer after having used it but it returns a strange error. The error says: "_CrtDbgREport: String too long or IO Error" The debugger itself returns no errors while compiling. The code currently looks like this: void RespondToUser(SOCKET client, SOCKET server) { char buffer[80]; char *temp = malloc(_scprintf("HTTP/1.1 200 OK\r\n%s\r\nServer: %s\r\nConnection: close\r\n\r\nHi!", buffer, SERVER_NAME)); sprintf(temp, "HTTP/1.1 200 OK\r\n%s\r\nServer: %s\r\nConnection: close\r\n\r\nHi!", buffer, SERVER_NAME); send(client, temp, strlen(temp), 0); closesocket(client); free(temp); ListenToUsers(server); } The problem only occurs when I try to free the temp pointer from the memory and not otherwise. What might be causing this?

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  • Problem with pointer copy in C

    - by Stefano Salati
    I radically re-edited the question to explain better my application, as the xample I made up wasn't correct in many ways as you pointed out: I have one pointer to char and I want to copy it to another pointer and then add a NULL character at the end (in my real application, the first string is a const, so I cannot jsut modify it, that's why I need to copy it). I have this function, "MLSLSerialWriteBurst" which I have to fill with some code adapt to my microcontroller. tMLError MLSLSerialWriteBurst( unsigned char slaveAddr, unsigned char registerAddr, unsigned short length, const unsigned char *data ) { unsigned char *tmp_data; tmp_data = data; *(tmp_data+length) = NULL; // this function takes a tmp_data which is a char* terminated with a NULL character ('\0') if(EEPageWrite2(slaveAddr,registerAddr,tmp_data)==0) return ML_SUCCESS; else return ML_ERROR; } I see there's a problem here: tha fact that I do not initialize tmp_data, but I cannot know it's length.

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  • C pointer initialization and dereferencing, what's wrong here?

    - by randombits
    This should be super simple, but I'm not sure why the compiler is complaining here. #include <stdio.h> #include <stdlib.h> int main(int argc, char *argv[]) { int *n = 5; printf ("n: %d", *n); exit(0); } Getting the following complaints: foo.c: In function ‘main’: foo.c:6: warning: initialization makes pointer from integer without a cast I just want to print the value that the pointer n references. I'm dereferencing it in the printf() statement and I get a segmentation fault. Compiling this with gcc -o foo foo.c.

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  • Null Pointer Exception with an array of bitsets

    - by p0ny
    could someone explain to me why the following results in a Null pointer Exception? And how to set a value for bitarray[0]? BitSet[] bitarray; bitarray= new BitSet[10]; bitarray[0].set(1); Also, why something like this work and not result in a pointer exception? BitSet[] bitarray = new BitSet[10]; BitSet bits = new BitSet(32); bits.set(1); bitarray[0] = bits; Thanks

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