Search Results

Search found 53294 results on 2132 pages for 'null pointers etc'.

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

Page 75/2132 | < Previous Page | 71 72 73 74 75 76 77 78 79 80 81 82  | Next Page >

  • Passing an array of an array of char to a function

    - by L.A. Rabida
    In my program, I may need to load a large file, but not always. So I have defined: char** largefilecontents; string fileName="large.txt"; When I need to load the file, the program calles this function: bool isitok=LoadLargeFile(fileName,largefilecontents); And the function is: bool LoadLargeFile(string &filename, char ** &lines) { if (lines) delete [] lines; ifstream largeFile; #ifdef LINUX largeFile.open(filename.c_str()); #endif #ifdef WINDOWS largeFile.open(filename.c_str(),ios::binary); #endif if (!largeFile.is_open()) return false; lines=new char *[10000]; if (!lines) return false; largeFile.clear(); largeFile.seekg(ios::beg); for (int i=0; i>-1; i++) { string line=""; getline(largeFile,line); if (largeFile.tellg()==-1) break; //when end of file is reached, tellg returns -1 lines[i]=new char[line.length()]; lines[i]=const_cast<char*>(line.c_str()); cout << lines[i] << endl; //debug output } return true; } When I view the debug output of this function, "cout << lines[i] << endl;", it is fine. But when I then check this in the main program like this, it is all messed up: for (i=0; i<10000; i++) cout << largefilecontents[i] << endl; So within the function LoadLargeFile(), the results are fine, but without LoadLargeFile(), the results are all messed up. My guess is that the char ** &lines part of the function isn't right, but I do not know what this should be. Could someone help me? Thank you in advance!

    Read the article

  • How to return a copy of the data in C++

    - by Josh Curren
    I am trying to return a new copy of the data in a C++ Template class. The following code is getting this error: invalid conversion from ‘int*’ to ‘int’. If I remove the new T then I am not returning a copy of the data but a pointer to it. template<class T> T OrderedList<T>::get( int k ) { Node<T>* n = list; for( int i = 0; i < k; i++ ) { n=n->get_link(); } return new T( n->get_data() ); // This line is getting the error ********** }

    Read the article

  • How to call shared_ptr<boost::signal> from a vector in a loop?

    - by BTR
    I've got a working callback system that uses boost::signal. I'm extending it into a more flexible and efficient callback manager which uses a vector of shared_ptr's to my signals. I've been able to successfully create and add callbacks to the list, but I'm unclear as to how to actually execute the signals. ... // Signal aliases typedef boost::signal<void (float *, int32_t)> Callback; typedef std::shared_ptr<Callback> CallbackRef; // The callback list std::vector<CallbackRef> mCallbacks; // Adds a callback to the list template<typename T> void addCallback(void (T::* callbackFunction)(float * data, int32_t size), T * callbackObject) { CallbackRef mCallback = CallbackRef(new Callback()); mCallback->connect(boost::function<void (float *, int32_t)>(boost::bind(callbackFunction, callbackObject, _1, _2))); mCallbacks.push_back(mCallback); } // Pass the float array and its size to the callbacks void execute(float * data, int32_t size) { // Iterate through the callback list for (vector<CallbackRef>::iterator i = mCallbacks.begin(); i != mCallbacks.end(); ++i) { // What do I do here? // (* i)(data, size); // <-- Dereferencing doesn't work } } ... All of this code works. I'm just not sure how to run the call from within a shared_ptr from with a vector. Any help would be neat-o. Thanks, in advance.

    Read the article

  • 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.

    Read the article

  • How to declare a pointer to a variable as a parameter of a function in C++?

    - by Keand64
    I have a function that takes a pointer to a D3DXVECTOR3, but I have no reason to declare this beforehand. The most logical solution to me was using new: Function( //other parameters, new D3DXVECTOR3(x, y, 0)); but I don't know how I would go about deleting it, beign intitialized in a function. My next thought was to use the & operator, like so: Function( //other parameters, &D3DVECTOR3(x, y, 0)); but I don't know if this is a valid way to go about doing this. (It doesn't get an error, but neither does int *x; x = 50;). So should I use new, &, or some other technique I'm overlooking?

    Read the article

  • Check if a pointer points to allocated memory on the heap.

    - by Ugo
    Ok, I know this question seems to have been asked many times on stackoverflow. but please read Well the answer for any address is "No you can't" but the question here is to know if a pointer points to a piece of memory allocated with malloc/new. Actually I think it could be easily implemented overriding malloc/free and keeping track of allocated memory ranges. Do you know a memory management library providing this specific tool ?

    Read the article

  • C++: Question about freeing memory

    - by Martijn Courteaux
    On Learn C++, they wrote this to free memory: int *pnValue = new int; // dynamically allocate an integer *pnValue = 7; // assign 7 to this integer delete pnValue; pnValue = 0; My question is: "Is the last statement needed to free the memory correctly, completly?" I thought that the pointer *pnValue was still on the stack and new doesn't make any sense to the pointer. And if it is on the stack it will be cleaned up when the application leaves the scope (where the pointer is declared in), isn't it?

    Read the article

  • C pointer question, dereferencing crash

    - by skynorth
    Why do this work? int *var; while(scanf("%d", &var) && *var != 0) printf("%d \n", var); While this does not? int *var; while(scanf("%d", &var) && var != 0) printf("%d \n", var); Doesn't * (dereference operator) give you the value pointed by the pointer? So why does *var != 0 crash the program, while var != 0 does not?

    Read the article

  • collect string in loop and printout all the string outside loop

    - by user1508163
    I'm newbie here and there is some question that I want have some lesson from you guys. For example: #include <stdio.h> #include<stdlib.h> #include<ctype.h> void main() { char name[51],selection; do { printf("Enter name: "); fflush(stdin); gets(name); printf("Enter another name?(Y/N)"); scanf("%c",&selection); selection=toupper(selection); }while (selection=='Y'); //I want to printout the entered name here but dunno the coding printf("END\n"); system("pause"); } As I know when the loops perform will overwrite the variable then how I perform a coding that will printout all the name user entered? I have already ask my tutor and he is ask me to use pointer, can anyone guide me in this case?

    Read the article

  • Call c++ function pointer from c#

    - by Sam
    Is it possible to call a c(++) static function pointer like this typedef int (*MyCppFunc)(void* SomeObject); from c#? void CallFromCSharp(MyCppFunc funcptr, IntPtr param) { funcptr(param); } I need to be able to callback from c# into some old c++ classes. C++ is managed, but the classes are not ref classes (yet). So far I got no idea how to call a c++ function pointer from c#, is it possible?

    Read the article

  • How can I return to a string address and then assign it to a new string?

    - by Y_Y
    I have 1 function that I want to return the address of an assigned string to the main function and assign an new string pointer with the same address so that the new string will have the contents of the old string. For example: unknown_datatype function() { char *old = "THE STRING"; return old; } int main() { char *snew = ""; snew = function(); return 0; } *unknown_datatype means I don't know that to put there... *How can I approach this without changing anything in the main() method

    Read the article

  • why no implicit conversion from pointer to reference to const pointer.

    - by user316606
    I'll illustrate my question with code: #include <iostream> void PrintInt(const unsigned char*& ptr) { int data = 0; ::memcpy(&data, ptr, sizeof(data)); // advance the pointer reference. ptr += sizeof(data); std::cout << std::hex << data << " " << std::endl; } int main(int, char**) { unsigned char buffer[] = { 0x11, 0x11, 0x11, 0x11, 0x22, 0x22, 0x22, 0x22, }; /* const */ unsigned char* ptr = buffer; PrintInt(ptr); // error C2664: ... PrintInt(ptr); // error C2664: ... return 0; } When I run this code (in VS2008) I get this: error C2664: 'PrintInt' : cannot convert parameter 1 from 'unsigned char *' to 'const unsigned char *&'. If I uncomment the "const" comment it works fine. However shouldn't pointer implicitly convert into const pointer and then reference be taken? Am I wrong in expecting this to work? Thanks!

    Read the article

  • How do I return the indices of a multidimensional array element in C?

    - by Eddy
    Say I have a 2D array of random boolean ones and zeroes called 'lattice', and I have a 1D array called 'list' which lists the addresses of all the zeroes in the 2D array. This is how the arrays are defined: define n 100 bool lattice[n][n]; bool *list[n*n]; After filling the lattice with ones and zeroes, I store the addresses of the zeroes in list: for(j = 0; j < n; j++) { for(i = 0; i < n; i++) { if(!lattice[i][j]) // if element = 0 { list[site_num] = &lattice[i][j]; // store address of zero site_num++; } } } How do I extract the x,y coordinates of each zero in the array? In other words, is there a way to return the indices of an array element through referring to its address?

    Read the article

  • how do you set a property of a control to an address of a function in xaml?

    - by ambog36
    Hi, I have a control that has a "Filter" property that expects a function that defines how the contents of the control should be filtered. so far i am setting the filter in code behind as such: MyControl.Filter = AddressOf Filters.MyFilter In this example MyFilter is a shared function in the Filters class with the following signature: Public Shared Function MyFilter(ByVal obj As Object, ByVal text As String) As Boolean I would like to set this in xaml. I was thinking of setting the Filters.MyFilter as a static resource and setting it that way: ...Filter="{StaticResource myFilter}"/ but i cant set Filters.MyFilter as a static resource. Any ideas on how to achieve this? Thanks,

    Read the article

  • Acessing a struct member, using a pointer to a vector of structs. Error:base operand of '->' has non-pointer type

    - by Matt Munson
    #include <iostream> #include <vector> using namespace std; struct s_Astruct { vector <int> z; }; int main () { vector <s_Astruct> v_a; for(int q=0;q<10;q++) { v_a.push_back(s_Astruct()); for(int w =0;w<5;w++) v_a[q].z.push_back(8); } vector <s_Astruct> * p_v_a = & v_a; cout << p_v_a[0]->z[4]; //error: base operand of '->' has non-pointer type //'__gnu_debug_def::vector<s_Astruct, std::allocator<s_Astruct> >' } There seems to be some issue with this sort of operation that I don't understand. In the code that I'm working on I actually have things like p_class-vector[]-vector[]-int; and I'm getting a similar error.

    Read the article

  • How to guard against memory leaks?

    - by just_wes
    I was recently interviewing for a C++ position, and I was asked how I guard against creating memory leaks. I know I didn't give a satisfactory answer to that question, so I'm throwing it to you guys. What are the best ways to guard against memory leaks? Thanks!

    Read the article

  • Evaluation of (de)reference operators

    - by Micha
    I have an (uncommented...) source file which I'm trying to understand. static const Map *gCurMap; static std::vector<Map> mapVec; then auto e = mapVec.end(); auto i = mapVec.begin(); while(i!=e) { // ... const Map *map = gCurMap = &(*(i++)); // ... } I don't understand what &(*(i++)) does. It does not compile when just using i++, but to me it looks the same, because I'm "incrementing" i, then I'm requesting the value at the given address and then I'm requesting the address of this value?!

    Read the article

  • Pointer mysteriously moves

    - by Armen Ablak
    Hi, I have this code for Node rotation and in a line which is marked something happens and I don't really know what and why :). //Test case 30 \ 16 / 29 RotationRight(node->mParent); //call template<class T> void SplayTree<T>::RotationRight(SplayNode<T> *&node) const { SplayNode<T> *left = node->mLeft; SplayNode<T> *parent = node->mParent; node->mLeft = left->mRight; if(left->HasRight()) left->mRight->mParent = node; left->mRight = node; //node in this line points to 0x00445198 {30} left->mParent = node->mParent; //and in this line it points to 0x00444fb8 {16} (node, not node->mParent) node->mParent = left; node = left; } Well, left-mParent points to node also, so I basically do node = node-mParent. The problem is I can't find a work around - how to unpin in from node and change it's pointing address without changing it's.

    Read the article

  • c Pointer to pointer, or passing list to functions

    - by user361808
    Hi, I am new to c programming. Could anyone please tell me what's wrong with the following program? typedef struct Person_s { int age; char name[40]; } Person_t; int process_list(int *countReturned, Person_t **p_list) { Person_t *rowPtr=0; //the actual program will fethc data from DB int count =1; if(!((*p_list) = (Person_t *) malloc(sizeof(Person_t)))) { return -1; } rowPtr = *p_list; rowPtr[count-1].age =19; strcpy(rowPtr[count-1].name,"Prince Dastan"); *countReturned = count; return 0; } int main(int argc, char *argv[]) { Person_t *tmpPerson=0; Person_t **p_list=0; int *count=0; int i; process_list(count,p_list); tmpPerson = *p_list; for(i=0; i< *count; i++) { printf("Name: %s , age: %d\n",tmpPerson->name,tmpPerson->age); tmpPerson++; } //free(tmpPerson); return 0; }

    Read the article

  • using structures with multidimentional tables

    - by gem
    I have a table of structures and this structures are 2 dimentional table of constants. can you teach me on how to get the values in the table of constants. (note following is just example) typedef struct { unsigned char ** Type1; unsigned char ** Type2; } Formula; typedef struct { Formula tformula[size]; } table; const table Values = { (unsigned char**) &(default_val1), (unsigned char**) &(default_val2) }; const unsigned char default_val1[4][4] = { {0,1,2,3}, {4,5,6,7}, {8,9,0,11}, {12,13,14,15} } const unsigned char default_val2[4][4] = { {15,16,17,13}, {14,15,16,17}, {18,19,10,21}, {22,23,24,25} }

    Read the article

  • Set argument pointer to point to new memory inside a function (without returning it) IN C

    - by user321605
    Hello, Hopefully my title was descriptive enough to attract the right help. I want to write a function that will return 1 thing, and modify a provided pointer in another. My current function declaration is . . . char * afterURL replaceURLS(char * body) What I want to do is copy all of body's data into a new string, and set body to point to this new data. I then want afterURL to point to a location within the new string. My issue is getting the actual pointer that is passed in to this function to point to the new data. Thanks in advance! Rob

    Read the article

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

< Previous Page | 71 72 73 74 75 76 77 78 79 80 81 82  | Next Page >