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• Registry entry using VC++, Data corrupting

  - by sijith

  Hi I want to set system time to registry, i did like this. But some null characters only getting there. when i am giving LPCTSTR data = TEXT("24/3/2010\0"); LONG setRes = RegSetValueEx (hkey, value, 0, REG_SZ, (LPBYTE)data, 100)); thsi is sucessfully adding into registry How to trace the issue IF possible please check my code include include include void Regkey::create_Registry() { HKEY hkey; DWORD dwDisposition,lpData; SYSTEMTIME time; GetLocalTime( &time ); int hour = time.wHour; if (hour 12) hour -= 12; char szData[20]; sprintf (szData, "%02d/%02d/%04d", time.wDay, time.wMonth, time.wYear); if(RegCreateKeyEx(HKEY_LOCAL_MACHINE, TEXT("Software\Sijith\Test"), 0, NULL, 0, 0, NULL, &hkey, &dwDisposition)== ERROR_SUCCESS) { LPCTSTR sk = TEXT("Software\Sijith\Test"); LONG openRes = RegOpenKeyEx(HKEY_LOCAL_MACHINE, sk, 0, KEY_ALL_ACCESS , &hkey); LPCTSTR value = TEXT("CheckSoftwareKey"); LONG setRes = RegSetValueEx (hkey, value, 0, REG_SZ, (CONST BYTE *)szData, sizeof(TCHAR) * (_tcslen(szData) + 1)); RegCloseKey(hkey); } } output value name: CheckSoftwareKey valueData: ?????

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• Image insert problem php sqlserver

  - by Termedi

  Hi I can not save image inside a sql server 2000 database. datatype is image here is the code: // Image Upload <?php include('config.php'); if(is_uploaded_file($_FILES['userfile']['tmp_name'])) { $fileName = $_FILES['userfile']['name']; $tmpName = $_FILES['userfile']['tmp_name']; $fileSize = $_FILES['userfile']['size']; $fileType = $_FILES['userfile']['type']; $size = filesize($tmpName); set_magic_quotes_runtime(0);//to desactive the default escape spacials caracters made by PHP in the externes files $img_binaire = base64_encode(fread(fopen(str_replace("'","''",$tmpName), "r"), $size)); $query = "INSERT INTO test_image (image_name, image_content, image_size) ". "VALUES ('{$fileName}','{$img_binaire}', '{$size}')"; odbc_exec($conn, $query) or die('Error, query failed'); echo "<br>File $fileName uploaded<br>"; echo "<br>File Size: $fileSize <br>"; } ?> // Image Show <?php include('config.php'); $sql = "select * from test_image where id =2"; $rsl = odbc_exec($conn, $sql); $image_info = odbc_fetch_array($rsl); //$count = sizeof($image_info['image_content']); //header('Accept-Ranges: bytes'); //header('Content-Length: '.$image_info['image_size']); //header("Content-length: 17397"); header('Content-Type: image/jpeg'); echo base64_decode($image_info['image_content']); //echo bindec($image_info['image_content']); ?> Error: Warning: odbc_exec() [function.odbc-exec]: SQL error: [Microsoft][ODBC SQL Server Driver][SQL Server]Operand type clash: text is incompatible with image, SQL state 22005 in SQLExecDirect in C:\xampp\htdocs\test\upload.php on line 25 Error, query failed

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• Hi I am facing a fragmentation error while executing this code? Can someone explain why?

  - by aks

  #include<stdio.h> struct table { char *ipAddress; char *domainName; struct table *next; }; struct table *head = NULL; void add_rec(); void show_rec(); int main() { add_rec(); show_rec(); return 0; } void add_rec() { struct table * temp = head; struct table * temp1 = (struct table *)malloc(sizeof(struct table)); if(!temp1) printf("\n Unable to allocate memory \n"); printf("Enter the ip address you want \n"); scanf("%s",temp1->ipAddress); printf("\nEnter the domain name you want \n"); scanf("%s",temp1->domainName); if(!temp) { head = temp; } else { while(temp->next!=NULL) temp = temp->next; temp->next = temp1; } } void show_rec() { struct table * temp = head; if(!temp) printf("\n No entry exists \n"); while(temp!=NULL) { printf("ipAddress = %s\t domainName = %s\n",temp->ipAddress,temp->domainName); temp = temp->next; } } When i execute this code and enters the IP address for the first node, i am facing fragmentation error. The code crashed. Can someone enlighten?

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• Declaration, allocation and assignment of an array of pointers to function pointers

  - by manneorama

  Hello Stack Overflow! This is my first post, so please be gentle. I've been playing around with C from time to time in the past. Now I've gotten to the point where I've started a real project (a 2D graphics engine using SDL, but that's irrelevant for the question), to be able to say that I have some real C experience. Yesterday, while working on the event system, I ran into a problem which I couldn't solve. There's this typedef, //the void parameter is really an SDL_Event*. //but that is irrelevant for this question. typedef void (*event_callback)(void); which specifies the signature of a function to be called on engine events. I want to be able to support multiple event_callbacks, so an array of these callbacks would be an idea, but do not want to limit the amount of callbacks, so I need some sort of dynamic allocation. This is where the problem arose. My first attempt went like this: //initial size of callback vector static const int initial_vecsize = 32; //our event callback vector static event_callback* vec = 0; //size static unsigned int vecsize = 0; void register_event_callback(event_callback func) { if (!vec) __engine_allocate_vec(vec); vec[vecsize++] = func; //error here! } static void __engine_allocate_vec(engine_callback* vec) { vec = (engine_callback*) malloc(sizeof(engine_callback*) * initial_vecsize); } First of all, I have omitted some error checking as well as the code that reallocates the callback vector when the number of callbacks exceed the vector size. However, when I run this code, the program crashes as described in the code. I'm guessing segmentation fault but I can't be sure since no output is given. I'm also guessing that the error comes from a somewhat flawed understanding on how to declare and allocate an array of pointers to function pointers. Please Stack Overflow, guide me.

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• Clone existing structs with different alignment in Visual C++

  - by Crend King

  Is there a way to clone an existing struct with different member alignment in Visual C++? Here is the background: I use an 3rd-party library, which uses several structs. To fill up the structs, I pass the address of the struct instances to some functions. Unfortunately, the functions only returns unaligned buffer, so that data of some members are always wrong. /Zp is out of choice, since it breaks the other parts of the program. I know #pragma pack modifies the alignment of the following struct, but I would like to avoid copying the structs into my code, for the definitions in the library might change in the future. Sample code: test.h: struct am_aligned { BYTE data1[10]; ULONG data2; }; test.cpp: #include "test.h" // typedef alignment(1) struct am_aligned am_unaligned; int APIENTRY wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPTSTR lpCmdLine, int nCmdShow) { char buffer[20] = {}; for (int i = 0; i < sizeof(unaligned_struct); i++) { buffer[i] = i; } am_aligned instance = *(am_aligned*) buffer; return 0; } Consider am_aligned is defined in the library header file. am_unaligned is my custom declaration, and only effective in test.cpp. The commented line does not work of course. instance.data2 is 0x0f0e0d0c, while 0x0d0c0b0a is desired. Thanks for help!

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• Problem in using a second call to send() in C

  - by Paulo Victor

  Hello. Right now I'm working in a simple Server that receives from client a code referring to a certain operation. The server receives this data and send back the signal that it's waiting for the proper data. /*Server Side*/ if (codigoOperacao == 0) { printf("A escolha foi 0\n"); int bytesSent = SOCKET_ERROR; char sendBuff[1080] = "0"; /*Here "send" returns an error msgm while trying to send back the signal*/ bytesSent = send(socketEscuta, sendBuff, 1080, 0); if (bytesSent == SOCKET_ERROR) { printf("Erro ao enviar"); return 0; } else { printf("Bytes enviados : %d\n", bytesSent); char structDesmontada[1080] = ""; bytesRecv = recebeMensagem(socketEscuta, structDesmontada); printf("structDesmontada : %s", structDesmontada); } } Following here is the client code responsible for sending the operation code and receiving the signal char sendMsg[1080] = "0"; char recvMsg[1080] = ""; bytesSent = send(socketCliente, sendMsg, sizeof(sendMsg), 0); printf("Enviei o codigo (%d)\n", bytesSent); /*Here the program blocks in a infinite loop since the server never send anything*/ while (bytesRecv == SOCKET_ERROR) { bytesRecv = recv(socketCliente, recvMsg, 1080, 0); if (bytesRecv > 0) { printf("Recebeu\n"); } Why this is happening only in the second attempt to send some data? Because the first call to send() works fine. Hope someone can help!! Thnks

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• java: "downcasting" to new object / opposite of slicing

  - by rhavin

  Sorry, i really dont know how to make a headline for that question; maybe there is a name for what im trying to do that i dont know, but i can explain it with some code: Guess you have a class that unfortunately neither has a copy-constructor nor a public static copy method. class A { private int i; // <- private, cant access String x; // <- even worse: cant access unless in same pkg! /* … other stuff, ctor, etc. … */ public A clone() { A a = new A(); a.i = i; a.x = x; return x; } } Guess further, there is some function that returns an object of that class: public static A someFn(x,y,z); Now the problem: I want to derive from that class to add some functionality. Unfortunately, i neither have a sizeof in java nor a cc or static copy method. So when i do a class B extends A { protected w; public B clone() { /* as usual */ } } then i can clone my B and get a new one, but how can i convert the returned A from someFn() into a B. Is there anyway to do the opposite of slicing in java? if i clone it, it's still an A, and i cant copy it field by field. This is all simple in c++, but how to do this in Java?

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• Is there a good way to copy a Gtk widget?

  - by Jake

  Is there a way, using the Gtk library in C, to clone a Gtk button (for instance), and pack it somewhere else in the app. I know you can't pack the same widget twice. And that this code obviously wouldn't work, but shows what happens when I attempt a shallow copy of the button: GtkButton *a = g_object_new(GTK_TYPE_BUTTON, "label", "o_0", NULL); GtkButton *b = g_memdup(b, sizeof *b); gtk_box_pack_start_defaults(GTK_BOX(vbox), GTK_WIDGET(b)); There is surrounding code which creates a vbox and packs it in a window and runs gtk_main(). This will result in these hard to understand error messages: (main:6044): Gtk-CRITICAL **: gtk_widget_hide: assertion `GTK_IS_WIDGET (widget)' failed (main:6044): Gtk-CRITICAL **: gtk_widget_realize: assertion `GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed ** Gtk:ERROR:/build/buildd/gtk+2.0-2.18.3/gtk/gtkwidget.c:8431:gtk_widget_real_map: assertion failed: (GTK_WIDGET_REALIZED (widget)) Along the same lines, if I were to write my own GObject (not necessarily a Gtk widget), is there a good way to write a copy constructor. Im thinking it should be an interface with optional hooks and based mostly on the properties, handling the class's hierarchy in some way. I'd want to do this: GtkButton *b = copyable_copy(COPYABLE(a)); If GtkButton could use a theoretical copyable interface.

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• How can I render an in-memory UIViewController's view Landscape?

  - by Aaron

  I'm trying to render an in-memory (but not in hierarchy, yet) UIViewController's view into an in-memory image buffer so I can do some interesting transition animations. However, when I render the UIViewController's view into that buffer, it is always rendering as though the controller is in Portrait orientation, no matter the orientation of the rest of the app. How do I clue this controller in? My code in RootViewController looks like this: MyUIViewController* controller = [[MyUIViewController alloc] init]; int width = self.view.frame.size.width; int height = self.view.frame.size.height; int bitmapBytesPerRow = width * 4; unsigned char *offscreenData = calloc(bitmapBytesPerRow * height, sizeof(unsigned char)); CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); CGContextRef offscreenContext = CGBitmapContextCreate(offscreenData, width, height, 8, bitmapBytesPerRow, colorSpace, kCGImageAlphaPremultipliedLast); CGContextTranslateCTM(offscreenContext, 0.0f, height); CGContextScaleCTM(offscreenContext, 1.0f, -1.0f); [(CALayer*)[controller.view layer] renderInContext:offscreenContext]; At that point, the offscreen memory buffers contents are portrait-oriented, even when the window is in landscape orientation. Ideas?

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• C++: static assert for const variables?

  - by shoosh

  Static asserts are very convenient for checking things in compile time. A simple static assert idiom looks like this: template<bool> struct StaticAssert; template<> struct StaticAssert<true> {}; #define STATIC_ASSERT(condition) do { StaticAssert<condition>(); } while(0) This is good for stuff like STATIC_ASSERT(sizeof(float) == 4) and: #define THIS_LIMIT (1000) ... STATIC_ASSERT(THIS_LIMIT > OTHER_LIMIT); But using #define is not the "C++" way of defining constants. C++ would have you use an anonymous namespace: namespace { const int THIS_LIMIT = 1000; } or even: static const int THIS_LIMIT = 1000; The trouble with this is that with a const int you can't use STATIC_ASSERT() and you must resort to a run-time check which is silly. Is there a way to properly solve this in current C++? I think I've read C++0x has some facility to do this...

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• object / class methods serialized as well?

  - by Mat90

  I know that data members are saved to disk but I was wondering whether object's/class' methods are saved in binary format as well? Because I found some contradictionary info, for example: Ivor Horton: "Class objects contain function members as well as data members, and all the members, both data and functions, have access specifiers; therefore, to record objects in an external file, the information written to the file must contain complete specifications of all the class structures involved." and: Are methods also serialized along with the data members in .NET? Thus: are method's assembly instructions (opcodes and operands) stored to disk as well? Just like a precompiled LIB or DLL? During the DOS ages I used assembly so now and then. As far as I remember from Delphi and the following site (answer by dan04): Are methods also serialized along with the data members in .NET? sizeof(<OBJECT or CLASS>) will give the size of all data members together (no methods/procedures). Also a nice C example is given there with data and members declared in one class/struct but at runtime these methods are separate procedures acting on a struct of data. However, I think that later class/object implementations like Pascal's VMT may be different in memory.

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• C : files manipulation Can't figure out how to simplify this code with files manipulation.

  - by Bon_chan

  Hey guys, I have been working on this code but I can't find out what is wrong. This program does compile and run but it ends up having a fatal error. I have a file called myFile.txt, with the following content : James------ 07.50 Anthony--- 17.00 And here is the code : int main() { int n =2, valueTest=0,count=0; FILE* file = NULL; float temp= 00.00f, average= 00.00f, flTen = 10.00f; float *totalNote = (float*)malloc(n*sizeof(float)); int position = 0; char selectionNote[5+1], nameBuffer[10+1], noteBuffer[5+1]; file = fopen("c:\\myFile.txt","r"); fseek(file,10,SEEK_SET); while(valueTest<2) { fscanf(file,"%5s",&selectionNote); temp = atof(selectionNote); totalNote[position]= temp; position++; valeurTest++; } for(int counter=0;counter<2;counter++) { average += totalNote[counter]; } printf("The total is : %f \n",average); rewind(file); printf("here is the one with less than 10.00 :\n"); while(count<2) { fscanf(file,"%10s",&nameBuffer); fseek(file,10,SEEK_SET); fscanf(file,"%5s",&noteBuffer); temp = atof(noteBuffer); if(temp<flTen) { printf("%s who has %f\n",nameBuffer,temp); } fseek(file,1,SEEK_SET); count++; } fclose(file); } I am pretty new to c and find it more difficult than c# or java. And I woud like to get some suggestions to help me to get better. I think this code could be simplier. Do you think the same ?

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• pthread_exit and/or pthread_join causing Abort and SegFaults.

  - by MJewkes

  The following code is a simple thread game, that switches between threads causing the timer to decrease. It works fine for 3 threads, causes and Abort(core dumped) for 4 threads, and causes a seg fault for 5 or more threads. Anyone have any idea why this might be happening? #include <stdio.h> #include <stdlib.h> #include <pthread.h> #include <errno.h> #include <assert.h> int volatile num_of_threads; int volatile time_per_round; int volatile time_left; int volatile turn_id; int volatile thread_running; int volatile can_check; void * player (void * id_in){ int id= (int)id_in; while(1){ if(can_check){ if (time_left<=0){ break; } can_check=0; if(thread_running){ if(turn_id==id-1){ turn_id=random()%num_of_threads; time_left--; } } can_check=1; } } pthread_exit(NULL); } int main(int argc, char *args[]){ int i; int buffer; pthread_t * threads =(pthread_t *)malloc(num_of_threads*sizeof(pthread_t)); thread_running=0; num_of_threads=atoi(args[1]); can_check=0; time_per_round = atoi(args[2]); time_left=time_per_round; srandom(time(NULL)); //Create Threads for (i=0;i<num_of_threads;i++){ do{ buffer=pthread_create(&threads[i],NULL,player,(void *)(i+1)); }while(buffer == EAGAIN); } can_check=1; time_left=time_per_round; turn_id=random()%num_of_threads; thread_running=1; for (i=0;i<num_of_threads;i++){ assert(!pthread_join(threads[i], NULL)); } return 0; }

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• JNI Stream binary data from C++ to Java

  - by Cliff

  I need help passing binary data into Java. I'm trying to use jbytearray but when the data gets into Java it appears corrupt. Can somebody give me a hand? Here's a snip of some example code. First the native C++ side: printf("Building audio array copy\n"); jbyteArray rawAudioCopy = env-NewByteArray(10); jbyte toCopy[10]; printf("Filling audio array copy\n"); char theBytes[10] = {0,1,2,3,4,5,6,7,8,9}; for (int i = 0; i < sizeof(theBytes); i++) { toCopy[i] = theBytes[i]; } env->SetByteArrayRegion(rawAudioCopy,0,10,toCopy); printf("Finding object callback\n"); jmethodID aMethodId = env->GetMethodID(env->GetObjectClass(obj),"handleAudio","([B)V"); if(0==aMethodId) throw MyRuntimeException("Method not found error",99); printf("Invoking the callback\n"); env->CallVoidMethod(obj,aMethodId, &rawAudioCopy); and then the Java callback method: public void handleAudio(byte[] audio){ System.out.println("Audio supplied to Java [" + audio.length + "] bytes"); byte[] expectedAudio = {0,1,2,3,4,5,6,7,8,9}; for (int i = 0; i < audio.length; i++) { if(audio[i]!= expectedAudio[i]) System.err.println("Expected byte " + expectedAudio[i] + " at byte " + i + " but got byte " + audio[i]); else System.out.print('.'); } System.out.println("Audio passed back accordingly!"); } I get the following output when the callback is invoked: library loaded! Audio supplied to Java [-2019659176] bytes Audio passed back accordingly!

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• CUDA - multiple kernels to compute a single value

  - by Roger

  Hey, I'm trying to write a kernel to essentially do the following in C float sum = 0.0; for(int i = 0; i < N; i++){ sum += valueArray[i]*valueArray[i]; } sum += sum / N; At the moment I have this inside my kernel, but it is not giving correct values. int i0 = blockIdx.x * blockDim.x + threadIdx.x; for(int i=i0; i<N; i += blockDim.x*gridDim.x){ *d_sum += d_valueArray[i]*d_valueArray[i]; } *d_sum= __fdividef(*d_sum, N); The code used to call the kernel is kernelName<<<64,128>>>(N, d_valueArray, d_sum); cudaMemcpy(&sum, d_sum, sizeof(float) , cudaMemcpyDeviceToHost); I think that each kernel is calculating a partial sum, but the final divide statement is not taking into account the accumulated value from each of the threads. Every kernel is producing it's own final value for d_sum? Does anyone know how could I go about doing this in an efficient way? Maybe using shared memory between threads? I'm very new to GPU programming. Cheers

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• C when to allocate and free memory - before function call, after function call...etc

  - by Keith P

  I am working with my first straight C project, and it has been a while since I worked on C++ for that matter. So the whole memory management is a bit fuzzy. I have a function that I created that will validate some input. In the simple sample below, it just ignores spaces: int validate_input(const char *input_line, char* out_value){ int ret_val = 0; /*false*/ int length = strlen(input_line); cout << "length = " << length << "\n"; out_value =(char*) malloc(sizeof(char) * length + 1); if (0 != length){ int number_found = 0; for (int x = 0; x < length; x++){ if (input_line[x] != ' '){ /*ignore space*/ /*get the character*/ out_value[number_found] = input_line[x]; number_found++; /*increment counter*/ } } out_value[number_found + 1] = '\0'; ret_val = 1; } return ret_val; } Instead of allocating memory inside the function for out_value, should I do it before I call the function and always expect the caller to allocate memory before passing into the function? As a rule of thumb, should any memory allocated inside of a function be always freed before the function returns?

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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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• How do I create an inheritable Semaphore in .NET?

  - by pauldoo

  I am trying to create a Win32 Semaphore object which is inheritable. This means that any child processes I launch may automatically have the right to act on the same Win32 object. My code currently looks as follows: Semaphore semaphore = new Semaphore(0, 10); Process process = Process.Start(pathToExecutable, arguments); But the semaphore object in this code cannot be used by the child process. The code I am writing is a port of come working C++. The old C++ code achieves this by the following: SECURITY_ATTRIBUTES security = {0}; security.nLength = sizeof(security); security.bInheritHandle = TRUE; HANDLE semaphore = CreateSemaphore(&security, 0, LONG_MAX, NULL); Then later when CreateProcess is called the bInheritHandles argument is set to TRUE. (In both the C# and C++ case I am using the same child process (which is C++). It takes the semaphore ID on command line, and uses the value directly in a call to ReleaseSemaphore.) I suspect I need to construct a special SemaphoreSecurity or ProcessStartInfo object, but I haven't figured it out yet.

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• How can I modified the value of a string defined in a struc?

  - by Eric

  Hi, I have the following code in c++: define TAM 4000 define NUMPAGS 512 struct pagina { bitset<12 direccion; char operacion; char permiso; string *dato; int numero; }; void crearPagina(pagina* pag[], int pos, int dir) { pagina * paginas = (pagina*)malloc(sizeof(char) * TAM); paginas - direccion = bitset<12 (dir); paginas - operacion = 'n'; paginas - permiso = 'n'; string **tempDato = &paginas - dato; char *temp = " "; **tempDato = temp; paginas - numero = 0; pag[pos] = paginas; } I want to modify the value of the variable called "string *dato" in the struct pagina but, everytime I want to assing a new value, the compiler throws a segmentation fault. In this case I'm using a pointer to string, but I have also tried with a string. In a few words I want to do the following: pagina - dato = "test"; Any idea? Thanks in advance!!!

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• What happens to class members when malloc is used instead of new?

  - by Felix

  I'm studying for a final exam and I stumbled upon a curious question that was part of the exam our teacher gave last year to some poor souls. The question goes something like this: Is the following program correct, or not? If it is, write down what the program outputs. If it's not, write down why. The program: #include<iostream.h> class cls { int x; public: cls() { x=23; } int get_x(){ return x; } }; int main() { cls *p1, *p2; p1=new cls; p2=(cls*)malloc(sizeof(cls)); int x=p1->get_x()+p2->get_x(); cout<<x; return 0; } My first instinct was to answer with "the program is not correct, as new should be used instead of malloc". However, after compiling the program and seeing it output 23 I realize that that answer might not be correct. The problem is that I was expecting p2->get_x() to return some arbitrary number (whatever happened to be in that spot of the memory when malloc was called). However, it returned 0. I'm not sure whether this is a coincidence or if class members are initialized with 0 when it is malloc-ed. Is this behavior (p2->x being 0 after malloc) the default? Should I have expected this? What would your answer to my teacher's question be? (besides forgetting to #include <stdlib.h> for malloc :P)

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• Structure's with strings and input

  - by Beginnernato

  so i have the following structure and function that add's things to the function - struct scoreentry_node { struct scoreentry_node *next; int score; char* name; } ; typedef struct scoreentry_node *score_entry; score_entry add(int in, char* n, score_entry en) { score_entry r = malloc(sizeof(struct scoreentry_node)); r->score = in; r->name = n; r->next = en; return r; } i have input that take it in the following main file: int score; char name[]; int main(void) { score_entry readin = NULL; while(1) { scanf("%s%d", name, &score); readin = add(score, name, readin); // blah blah I dont know why but when input a name it gets added to readin, but when i input another name all the name's in readin have this new name for example: input: bob 10 readin = 10 bob NULL jill 20 readin = 20 jill 10 jill NULL I dont know why bob disappear's... any reason why it does that ?

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• how to remove subsets form given text file

  - by user324887

  i have a problem like this 10 20 30 40 70 20 30 70 30 40 10 20 29 70 80 90 20 30 40 40 45 65 10 20 80 45 65 20 I want to remove all subset transaction from this file. output file should be like follows 10 20 30 40 70 29 70 80 90 20 30 40 40 45 65 10 20 80 Where records like 20 30 70 30 40 10 20 45 65 20 are removed because of they are subset of other records. i AM using set for this but i am not able to create one set for one line can anybody know how to do this please help me here i am sending you my code include include include using namespace std; using namespace std; set s1; int main() { FILE fp = fopen ( "abc.txt", "r" ); if ( fp != NULL ) { char line [ 128 ]; / or other suitable maximum line size */ while ( fgets ( line, sizeof line, fp ) != NULL ) /* read a line */ { istringstream iss(line); do { string sub; iss >> sub; s1.insert(sub); } while (iss); for (set<string>::const_iterator p = s1.begin( );p != s1.end( ); ++p) cout << *p << endl; } } }

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• Pointer arithmetic.

  - by Knowing me knowing you

  Having code: int** a = new int*[2]; a[0] = new int(1); a[1] = new int(2); cout << "a[0] " << a[0] << '\n'; cout << "a[1] " << a[1] << '\n'; cout << "a[2] " << a[2] << '\n'; cout << "a[0] + 1 " << a[0] + 1 << '\n';//WHY THIS ISN'T == a[1] ? cout << "*(a + 1): " << *(a + 1) << '\n'; //WHY THIS IS == a[1] ? cout << "a[0] - a[1] " << static_cast<int>(a[0] - a[1])<< '\n';//WHY THIS IS == 16 not 4? cout << sizeof(int**); Questions are included right next to relevant lines in code.

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• How to store and remove dynamically and automatic variable of generic data type in custum list data

  - by Vineel Kumar Reddy

  Hi I have created a List data structure implementation for generic data type with each node declared as following. struct Node { void *data; .... .... } So each node in my list will have pointer to the actual data(generic could be anything) item that should be stored in the list. I have following signature for adding a node to the list AddNode(struct List *list, void* eledata); the problem is when i want to remove a node i want to free even the data block pointed by *data pointer inside the node structure that is going to be freed. at first freeing of datablock seems to be straight forward free(data) // forget about the syntax..... But if data is pointing to a block created by malloc then the above call is fine....and we can free that block using free function int *x = (int*) malloc(sizeof(int)); *x = 10; AddNode(list,(void*)x); // x can be freed as it was created using malloc what if a node is created as following int x = 10; AddNode(list,(void*)&x); // x cannot be freed as it was not created using malloc Here we cannot call free on variable x!!!! How do i know or implement the functionality for both dynamically allocated variables and static ones....that are passed to my list.... Thanks in advance...

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• How to store an interger value of 4 bytes in a memory of chunk which is malloced as type char

  - by Adi

  Dear all, Hello Guys!! This is my first post in the forum . I am really looking forward to having good fun in this site. My question is : int mem_size = 10; char *start_ptr; if((start_ptr= malloc(mem_size*1024*1024*sizeof(char)))==NULL) {return -1;} I have allocated a chunk of memory of type char and size is say 10 MB (i.e mem_size = 10 ); Now I want to store the size information in the header of the memory chunk, To make myself more clear Lets Say : start_ptr = 0xaf868004 (This is the value I got from my execution, it changes every time) Now I want to put the size information in the start of this pointer.. i.e *start_ptr = mem_size*1024*1024; But I am not able to put this information in the start_ptr. I think the reason is because my ptr is of type char which only takes one byte but I am trying to store int which takes 4 bytes, is the problem . I am not sure how to fix this problem.. I would greatly appreciate your suggestions. Cheers!! Aditya

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