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  • calling resize on std vector of pointers crashed

    - by user11869
    The problem can be reproduced using VS 2013 Express. It crashed when internal vector implementation tried to deallocate the original vector. However, the problem can solved by using 'new' instead of 'malloc'. Anyone can shed some light on this? struct UndirectedGraphNode { int label; vector<UndirectedGraphNode *> neighbors; UndirectedGraphNode(int x) : label(x) {}; }; int main(int argc, char** argv) { UndirectedGraphNode* node1 = (UndirectedGraphNode*)malloc(sizeof(UndirectedGraphNode)); node1->label = 0; node1->neighbors.resize(2); return 0; }

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  • zeroing out memory

    - by robUK
    Hello, gcc 4.4.4 c89 I am just wondering what most c programmers do when they want to zero out memory. For example I have a buffer of 1024 bytes. Sometimes I do this: char buffer[1024] = {0}; Which will zero all bytes. However, should I declare like this and use memset? char buffer[1024]; . . memset(buffer, 0, sizeof(buffer); Is there any real reason you have to zero the memory? What is the worst that can happen by not doing it? Many thanks for any suggestions,

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  • C++ vector and struct problem win32

    - by ~james2432
    I have a structure defined in my header file: struct video { wchar_t* videoName; std::vector<wchar_t*> audio; std::vector<wchar_t*> subs; }; struct ret { std::vector<video*> videos; wchar_t* errMessage; }; struct params{ HWND form; wchar_t* cwd; wchar_t* disk; ret* returnData; }; When I try to add my video structure to a vector of video* I get access violation reading 0xcdcdcdc1 (videoName is @ 0xcdcdcdcd, before I allocate it) //extract of code where problem is video v; v.videoName = (wchar_t*)malloc((wcslen(line)+1)*sizeof(wchar_t)); wcscpy(v.videoName,line); p->returnData->videos.push_back(&v); //error here

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  • C++ dynamic array sizing problem

    - by Peter
    The basic pseudo code looks like this: void myFunction() { int size = 10; int * MyArray; MyArray = new int[size]; cout << size << endl; cout << sizeof(MyArray) << endl; } The first cout returns 10, as expected, while the second cout returns 4. Anyone have an explanation?

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  • WAVEFORMATEX - how to read codecdata at the end??

    - by Roey
    Hi All. I've a WAVEFORMATEX struct with some codecdata at the end of it (10 bytes). I'm using C++. How do I access the data at the end? (this is a purely technical question). I tried : WAVEFORMATEX* wav = (WAVEFORMATEX*)pmt->pbFormat; WORD me = wav->cbSize; wav = wav + sizeof(WAVEFORMATEX); BYTE* arr = new BYTE[me]; memcpy(arr, (BYTE*)wav, me); Didnt work. Thanks Roey

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  • malloc unable to assign memory + doesnt warn

    - by sraddhaj
    char *str=NULL; strsave(s,str,n+1); printf("%s",str-n); when I gdb debug this code I find that the str value is 0x0 which is null and also that my code is not catching this failed memory allocation , it doesnt execute str==NULL perror code ...Any idea void strsave(char *s,char *str,int n) { str=(char *)malloc(sizeof(char)* n); if(str==NULL) perror("failed to allocate memory"); while(*s) { *str++=*s++; } *str='\0'; }

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  • assignment from incompatible pointer type

    - by Hristo
    I have set up the following struct: typedef struct _thread_node_t { pthread_t thread; struct thread_node_t *next; } thread_node_t; ... and then I have defined: // create thread to for incoming connection thread_node_t *thread_node = (thread_node_t*) malloc(sizeof(thread_node_t)); pthread_create(&(thread_node->thread), NULL, client_thread, &csFD); thread_node->next = thread_arr; // assignment from incompatible pointer type thread_arr = thread_node; where thread_arr is thread_node_t *thread_arr = NULL; I don't understand why the compiler is complaining. Maybe I'm misunderstanding something.

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  • How can I get the JSON array data from nsstring or byte in xcode 4.2?

    - by user1471568
    I'm trying to get values from nsdata class and doesn't work. here is my JSON data. { "count": 3, "item": [{ "id": "1", "latitude": "37.556811", "longitude": "126.922015", "imgUrl": "http://175.211.62.15/sample_res/1.jpg", "found": false }, { "id": "3", "latitude": "37.556203", "longitude": "126.922629", "imgUrl": "http://175.211.62.15/sample_res/3.jpg", "found": false }, { "id": "2", "latitude": "37.556985", "longitude": "126.92286", "imgUrl": "http://175.211.62.15/sample_res/2.jpg", "found": false }] } and here is my code -(NSDictionary *)getDataFromItemList { NSData *dataBody = [[NSData alloc] initWithBytes:buffer length:sizeof(buffer)]; NSDictionary *iTem = [[NSDictionary alloc]init]; iTem = [NSJSONSerialization JSONObjectWithData:dataBody options:NSJSONReadingMutableContainers error:nil]; NSLog(@"id = %@",[iTem objectForKey:@"id"]); //for Test output = [[NSString alloc] initWithBytes:buffer length:rangeHeader.length encoding:NSUTF8StringEncoding]; NSLog(@"%@",output); return iTem; } how can I access every value in the JSON? Please help me.

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  • Method sscanf() ambiguous behavior

    - by Carmen Cojocaru
    I am trying to understand how sscanf() works. I ran some examples from this page: http://docs.roxen.com/pike/7.0/tutorial/strings/sscanf.xml and they don't work on my platform. I can't understand why. For instance: "sscanf("4711bar", "%d%s", a, b);" makes the program exit with an error... Here is one of the examples that work: "sscanf("foo", "f%s", a);". Does anybody know why? Do they work on your platforms? Thank you. This is my code: int main(void){ char *b = (char*)malloc(sizeof(char)*100); int a = 0; sscanf("4711bar", "%d%s", a, b); printf("%d", a); printf("%s", b); }

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  • trying to sort a simple string in c++

    - by every_answer_gets_a_point
    #include "stdio.h" #include "conio.h" #include <iostream> using namespace std; int main (void) { char my_char[] = "happy birthday"; int i; bool j=false; char my_char_temp[1]; do { for (i=0;i<sizeof(my_char)-2;i++) { j=false; if (my_char[i+1] < my_char[i]) { my_char_temp[0]=my_char[i+1]; my_char[i+1] = my_char[i]; my_char[i] = my_char_temp[0]; j=true; } } }while (j); cout << my_char; } what am i doing wrong? im just trying to sort the letters within the char the output i get is completely wrong

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  • Help with memory leak (malloc)

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

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  • What key concepts and nuances in C++ you know?

    - by Narek
    What kind of key points and concepts should a person know from C++ (and from programming in general) to be considered that he/she possesses C++ (and programming, in general) skills good. e.g. //Even if sizeof(T) may not be equal to 1, this code steps over array elements T v[]; for(T *p = v ; *p != 0 ; p++) cout<<*p<<endl; P.S. I hope by exchanging this info we will help each other to know C++ and programing thechnics better by doing explicit our notion that we got from practice.

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  • Increase a recive buffer in UDP socket

    - by unresolved_external
    I'wm writing an app, which transmits video and obviously uses UDP protocol fot this purpose. So I am wondering how can I increase a size of send/recieve buffer, cause currently the maximal size of data, which I can send is 65000 bytes. I already tried to do it in following way: int option = 262144; if(setsockopt(m_SocketHandle,SOL_SOCKET,SO_RCVBUF ,(char*)&option,sizeof(option)) < 0) { printf("setsockopt failed\n"); } But it did not work. So how can I do it?

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  • iOS Development: How can I encapsulate a string in an NSData object?

    - by BeachRunnerJoe
    Hello. I'm building a multiplayer game on the iPhone and I need to send string data to the other players in the game. To do that, I need to encapsulate my NSString* string data in an NSData object somehow. Here's an example of how my code is structured... typedef struct { PACKETTYPE packetType; ??? stringToSend; //<---not sure how to store this } StringPacket; StringPacket msg; msg.packetType = STRING_PACKET; msg.stringToSend = ... // <---not sure what to do here NSData *packet = [NSData dataWithBytes:&msg length:sizeof(StringPacket)]; So my question is, if StringPacket is a struct defined in my header, what type should the stringToSend property be so that I can easily call the dataWithBytes method of NSData to encapsulate the packet data in an NSData object? Thanks for your wisdom!

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  • Access violation C++ (Deleting items in a vector)

    - by Gio Borje
    I'm trying to remove non-matching results from a memory scanner I'm writing in C++ as practice. When the memory is initially scanned, all results are stored into the _results vector. Later, the _results are scanned again and should erase items that no longer match. The error: Unhandled exception at 0x004016f4 in .exe: 0xC0000005: Access violation reading location 0x0090c000. // Receives data DWORD buffer; for (vector<memblock>::iterator it = MemoryScanner::_results.begin(); it != MemoryScanner::_results.end(); ++it) { // Reads data from an area of memory into buffer ReadProcessMemory(MemoryScanner::_hProc, (LPVOID)(*it).address, &buffer, sizeof(buffer), NULL); if (value != buffer) { MemoryScanner::_results.erase(it); // where the program breaks } }

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  • What types of conditions can be used for conditional compilation in C++?

    - by user1002288
    This is an exam question for C++: Which of the following statements accurately describe the condition that can be used for conditional compilation in C++? A. The condition can depend on the value of environment variables. B. The condition can depend on the value of any const variables. C. The condition can depend on the value of program variables. D. The condition can use the sizeof() operator to make decision about compiler-dependent operations based on the size of standard data type. E. The condition must evaluate to either a 0 or 1 during preprocessing. I think the answer is E. Is this correct?

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  • How to algorithmically partion a keyspace?

    - by pbhogan
    This is related to consistent hashing and while I conceptually understand what I need to do, I'm having a hard time translating this into code. I'm trying to divide a given keyspace (say, 128 bits) into equal sized partitions. I want the upper bound (highest key) of each partition. Basically, how would I complete this? #define KEYSPACE_BYTE_SIZE 16 #define KEYSPACE_BIT_SIZE (KEYSPACE_BYTE_SIZE * 8) typedef struct _key { char byte[KEYSPACE_BYTE_SIZE]; } key; key * partition_keyspace( int num_partitions ) { key * partitions = malloc( sizeof(key) * num_partitions ); // ... }

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

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

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  • Getting MATLAB variable (string) from C

    - by Hamming
    Hi! I'm writing a small C application that launchs a Matlab script (.m file). I need to exchange some variables and I don't know how to get an array of chars that exists in Matlab. I'm doing something like this: enter code here result = engGetVariable(ep,"X"); if (!result) { printf ("Error..."); exit -1; } int n = mxGetN(result); char *varx = NULL; memcpy(varx, mxGetData(result),n*sizeof(char)); It doesn't work. Does someone know how to get a Matlab string in C? I've read Matlab documentation about engGetVariable() and the provided example but any of this things clarify me.

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  • finding character in string C language

    - by iSight
    Hi, I am searching a character at first occurence in string using the following code. But, it is taking some time when the character is too long or the character that i am searching is at far extend, which makes delay in other operations. How could i tackle with this problem. The code is below here. Note: attrPtr is a char* which holds a reference to a string containing '"' character at far extend. int position = 0; char qolon = '"';//character to search while (*(attrPtr + position++) != qolon); char* attrValue = NULL; attrValue = (char*)malloc(position * sizeof(char)); strncpy(attrValue, attrPtr, position-1);

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  • Using popen() to invoke a shell command?

    - by Anvar
    When running the following code through xcode I get inconsistent behavior. Sometimes it prints the git version correctly, other times it doesn't print anything. The return code from the shell command is always 0 though. Any ideas on why this might be? What am I doing wrong? #define BUFFER_SIZE 256 int main (int argc, const char * argv[]) { FILE *fpipe; char *command="/opt/local/bin/git --version"; char line[BUFFER_SIZE]; if ( !(fpipe = (FILE*)popen(command, "r")) ) { // If fpipe is NULL perror("Problems with pipe"); exit(1); } while ( fgets( line, sizeof(char) * BUFFER_SIZE, fpipe)) { // Inconsistent (happens sometimes) printf("READING LINE"); printf("%s", line); } int status = pclose(fpipe); if (status != 0) { // Never happens printf("Strange error code: %d", status); } return 0; }

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  • how divide herader from binary data

    - by fixo2020
    Hi, I have this code: ofstream dest("test.txt",ios::binary); while (true){ size_t retval = recv (sd, buffer, sizeof(buffer), 0); dest.write(buffer,retval); if(retval <= 0) { delete[] buffer; break;} } Now, the recv() function return 4 bytes each loop right? and buffer contain it, this return all data so, pseudo-header and binary data (image), but I want know how capture only binary data, I know that the end of header are "\n\r" right? but what's are the solution better for make this? I make a function that detect when are "\n\r"? and after how capture binary data? Or, I put all data in memory, and after parse it? but how? I'm desperate :(

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  • need to loop through a PHP array in JavaScript

    - by user296516
    Hi guys, For example I have a PHP array, such as this one <?php $s= array('a','b','c','d','e','f') ; ?> And I need to loop through it in JavaScript, any ideas how do I do that? for ( i=0 ; i < <?php echo sizeof($s) ?> ; i++) { document.write('<?php echo $s [somehow need to get the 'i' value into here] ?>'); } Any suggestions? Thanks!

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  • Checking for an "end of line" in a C-string

    - by Numerator
    I would really love your help with the following problem: I want to get as an input from the user a maximum length of 30 chars string and check whether it contains an end of line. This is what I tried to write so far: int main(void) { int i; char* command = (char*)calloc(31, sizeof(char)); while (0 < 1) { scanf("%s", command); for (i = 0; i <= strlen(command); ++i) { if (command[i] == '\n') printf("here"); } if (strcmp(command, "quit") == 0) break; } The idea is to check whether the command given by the user as input is "legal" - that is of length < 31. when i run this code, it never prints "here" regardless of the length of input.

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  • Macros giving problems with dladdr()

    - by Veger
    I have implemented tracing behavior using the -finstrument-functions option of gcc and this (simplified) code: void __cyg_profile_func_enter(void *this_fn, void *call_site) { Dl_info di; if(dladdr(this_fn, &di)) printf("entered %s\n", (di.dli_sname?di_dli_sname:"<unknown>")); } This works great, except for one thing: macros are processed as well, but the function prints the information of the function which contains the macro. So functions containing macros have their information printed multiple times (which is of course undesired). Is there anything to detect that a macro is being processed? Or is is possible to turn off instrumenting macros at all? PS Same problems occur with sizeof()

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