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  • When do I need to deallocate memory? C++

    - by extintor
    I am using this code inside a class to make a webbrowser control visit a website: void myClass::visitWeb(const char *url) { WCHAR buffer[MAX_LEN]; ZeroMemory(buffer, sizeof(buffer)); MultiByteToWideChar(CP_ACP, MB_ERR_INVALID_CHARS, url, strlen(url), buffer, sizeof(buffer)-1); VARIANT vURL; vURL.vt = VT_BSTR; vURL.bstrVal = SysAllocString(buffer); // webbrowser navigate code... VariantClear(&vURL); } Do I need to do some memory deallocation here?, I see vURL is being deallocated by VariantClear but should I deallocate memory for buffer? I've been told that in another bool I have in the same app I shouldn't deallocate anything because everything clear out when the bool return true/false, but what happens on this void?

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  • Cant free memory.

    - by atch
    In code: int a[3][4] = {1,2,3,4, 5,6,7,8, 9,10,11,12}; template<class T, int row, int col> void invert(T a[row][col]) { T* columns = new T[col]; T* const free_me = columns; for (int i = 0; i < col; ++i) { for (int j = 0; j < row; ++j) { *columns = a[j][i]; ++columns;//SOMETIMES VALUE IS 0 } } delete[] free_me;//I'M GETTING ERROR OF HEAP ABUSE IN THIS LINE } int main(int argc, char* argv[]) { invert<int,3,4>(a); } I've observed that while iterating, value of variable columns equals zero and I think thats the problem. Thanks for your help.

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  • pointer delegate in STL set.

    - by ananth
    hi. Im kinda stuck with using a set with a pointer delegate. my code is as follows: void Graph::addNodes (NodeSet& nodes) { for (NodeSet::iterator pos = nodes.begin(); pos != nodes.end(); ++pos) { addNode(*pos); } } Here NodeSet is defined as: typedef std::set NodeSet; The above piece of code works perfectly on my windows machine, but when i run the same piece of code on a MAC, it gives me the following error: no matching function for call to 'Graph::addNode(const boost::shared_ptr&)' FYI, Node_ptr is of type: typedef boost::shared_ptr Node_ptr; can somebody plz tell me why this is happening?

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  • How to I count key collisions when using boost::unordered_map?

    - by Nikhil
    I have a data structure with 15 unsigned longs, I have defined a hash function using hash_combine as follows: friend std::size_t hash_value(const TUPLE15& given) { std::size_t seed = 0; boost::hash_combine(seed, val1); boost::hash_combine(seed, val2); ... return seed; } I insert a large number of values into a boost::unordered_map but the performance is not good enough. Probably, I could do better with an alternative hashing function. To confirm this, I need to check how many collisions I am getting. How do I do this?

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  • Is there a way to serialize automatically enums as int?

    - by FireAphis
    Hello, Is there a way to serialize enums automatically as int? Every time I define a new enum and write std::stringstream stream; stream << myenum1; stream >> myenum2; the compiler complains that the operators << and are not defined. Do you know a way to tell the compiler to treat enums as plain int's? What makes the problem harder is that, actually, the serialization is inside a template. Something like this: template <typename T> void serialize(const T& value) { std::stringstream stream; stream << value; } So I cannot add any casts :( Maybe I can specialize it somehow? Thank you.

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  • Python extension building with boost

    - by user1544053
    Hey guys I'm fairly new to boost c/c++ library. I downloaded boost library and build the library. I created a very simple python library in c++ using boost interface (actually it is example code given in the documentation). I built it into a dll file. In the documentation it reads that this dll is exposed to python and they just show the import function in python and include the created library. I don't understand how to expose that dll to python and load the library inside in tradition ('import') manner. In case if you wanna look at the code then here it is: #include <boost/python.hpp> char const* greet() { return "hello, world"; } BOOST_PYTHON_MODULE(hello_ext) { using namespace boost::python; def("greet", greet); } Please help I really want to build applications with c/c++ and python. I simply want to use hello_ext as: >>>import hello_ext >>>print hello_ext.greet() Thank you.

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  • Static member object of a class in the same class

    - by Luv
    Suppose we have a class as class Egg { static Egg e; int i; Egg(int ii):i(ii) {} Egg(const Egg &); //Prevents copy-constructor to be called public: static Egg* instance() {return &e} }; Egg Egg::e(47); This code guarantees that we cannot create any object, but could use only the static object. But how could we declare static object of the same class in the class. And also one thing more since e is a static object, and static objects can call only static member functions, so how could the constructor been called here for static object e, also its constructors are private.

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  • string manipulations in C

    - by Vivek27
    Following are some basic questions that I have with respect to strings in C. If string literals are stored in read-only data segment and cannot be changed after initialisation, then what is the difference between the following two initialisations. char *string = "Hello world"; const char *string = "Hello world"; When we dynamically allocate memory for strings, I see the following allocation is capable enough to hold a string of arbitary length.Though this allocation work, I undersand/beleive that it is always good practice to allocate the actual size of actual string rather than the size of data type.Please guide on proper usage of dynamic allocation for strings. char *string = (char *)malloc(sizeof(char));

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  • hierarchical html listbox with mimicking file explorer level folding

    - by collapsar
    hello everybody, i'm looking for a technique to adapt a html listbox to hierarchical content with an unlimited number of levels ( const 1 would be sufficient ). hierarchy levels should be collapsible as in the usual file explorer views. the html listbox behaviour should be preserved / mimicked as comprehensively as possible. do you have a hint on where to find or how to implement this ? jquery solutions are fine. firefox 3.5+, ie 8+, safari 5 must be supported; opera 11, chrome 9 would be nice. as far as i understand the issue, listbox contents are rendered inside their own browser window sporting none of the standard window adornments. a hint on how to obtain a handle on this window in js would be a sufficient starting point, as well as correcting me in case i misconceived the browser behaviour. thanks in advance for your efforts, best regards, carsten

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  • Magick++ in VS2010 - unresolved external symbol

    - by FlashFan
    Hey guys! I'm trying to use ImageMagick Magick++ for a C++ Project in VS2010. I installed the Library from here: klick Then in my Project, I added c:/program files/ImageMagick-6.6.6-Q16/include to the include folders. Then I tried to use Magick++ with this code: #include <Magick++.h> void main(int argc, char ** argv){ InitializeMagick(*argv); } But this does not work! VS2010 returns the following errors: error LNK2001: unresolved external symbol "__declspec(dllimport) void __cdecl Magick::InitializeMagick(char const *)" (__imp_?InitializeMagick@Magick@@YAXPBD@Z) error LNK1120: 1 unresolved externals What am I doing wrong? Thanks very much for your help!

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  • Where does output of print in kernel go?

    - by apoorv020
    I am debugging a driver for linux (specifically ubuntu server 9.04), and there are several printf statements in the code. Where can I view the output of these statements? EDIT1: What i'm trying to do is write to kernel using the proc file-system. The print code is static int proc_fractel_config_write(struct file *file, const char *argbuf, unsigned long count, void *data) { printk(KERN_DEBUG "writing fractel config\n"); ... In kern.log when I see the following message when i try to overwrite the file /proc/net/madwifi/ath1/fractel_config (with varying time of course). [ 8671.924873] proc write [ 8671.924919] Any explainations?

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  • How to use the boost lexical_cast library for just for checking input

    - by Inverse
    I use the boost lexical_cast library for parsing text data into numeric values quite often. In several situations however, I only need to check if values are numeric; I don't actually need or use the conversion. So, I was thinking about writing a simple function to test if a string is a double: template<typename T> bool is_double(const T& s) { try { boost::lexical_cast<double>(s); return true; } catch (...) { return false; } } My question is, are there any optimizing compilers that would drop out the lexical_cast here since I never actually use the value? Is there a better technique to use the lexical_cast library to perform input checking?

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  • How to fill a section within c++ string?

    - by stacker
    Having a string of whitespaces: string *str = new string(); str->resize(width,' '); I'd like to fill length chars at a position. In C it would look like memset(&str[pos],'#', length ); How can i achieve this with c++ string, I tried string& assign( const string& str, size_type index, size_type len ); but this seems to truncat the original string. Is there an easy C++ way to do this? Thanks.

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  • Any way to avoid a filesort when order by is different to where clause?

    - by Julian
    I have an incredibly simple query (table type InnoDb) and EXPLAIN says that MySQL must do an extra pass to find out how to retrieve the rows in sorted order. SELECT * FROM `comments` WHERE (commentable_id = 1976) ORDER BY created_at desc LIMIT 0, 5 exact explain output: table select_type type extra possible_keys key key length ref rows comments simple ref using where; using filesort common_lookups common_lookups 5 const 89 commentable_id is indexed. Comments has nothing trick in it, just a content field. The manual suggests that if the order by is different to the where, there is no way filesort can be avoided. http://dev.mysql.com/doc/refman/5.0/en/order-by-optimization.html I also tried order by id as well as it's equivalent but makes no difference, even if I add id as an index (which I understand is not required as id is indexed implicitly in MySQL). thanks in advance for any ideas!

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  • Is there any way to pass an anonymous array as an argument in C++?

    - by Jeremy Friesner
    Hi all, I'd like to be able to declare an array as a function argument in C++, as shown in the example code below (which doesn't compile). Is there any way to do this (other than declaring the array separately beforehand)? #include <stdio.h> static void PrintArray(int arrayLen, const int * array) { for (int i=0; i<arrayLen; i++) printf("%i -> %i\n", i, array[i]); } int main(int, char **) { PrintArray(5, {5,6,7,8,9} ); // doesn't compile return 0; }

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  • C# (ASP.Net) Linking selection values to constants in Codebehind

    - by jasonvogel
    ASPX Code <asp:RadioButtonList ID="rbServer" runat="server" > <asp:ListItem Value=<%=ServerDeveloper%>> Developer </asp:ListItemv <asp:ListItem Value="dev.ahsvendor.com"> dev.test.com</asp:ListItem> <asp:ListItem Value="staging.ahsvendor.com"> staging.test.com</asp:ListItem> </asp:RadioButtonList> ASPX.CS - Codebehind const string ServerDeveloper = "developer"; ASPX Error: Code blocks are not supported in this context. Question: So what is the correct way to tie an dropdown/radio buttion/... ASPX value to a constant that is shared with the CodeBehind code? I know that I could do rbServer.Add.Item("developer") [from the CodeBehind], but is there a way to achieve it from the Presentation side of things?

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  • C++ cin returns 0 for integer no matter what the user inputs

    - by kevin dappah
    No matter the cin it continues to to output 0 for score. Why is that? I tried returning the "return 0;" but still no go :/ #include "stdafx.h" #include <iostream> using namespace std; // Variables int enemiesKilled; const int KILLS = 150; int score = enemiesKilled * KILLS; int main() { cout << "How many enemies did you kill?" << endl; cin >> enemiesKilled; cout << "Your score: " << score << endl; return 0; }

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  • parsing Two-dimensional array in c

    - by gitter78
    I'm trying to parse an array that looks like the one below: char *arr[][2] = { { "1", "Purple" }, { "2", "Blue" }, { "22", "Red" }, ... }; I was thinking having a loop as: char *func(char *a){ for(i = 0; i<sizeof(arr)/sizeof(arr[0]);i++){ if(strstr(a,arr[i][0])!=NULL) return arr[i][1]; } } char *out; const char *hello = "this is my 2 string"; out = func(hello); In this case, I'm trying to get the second value based on the first one: Purple, Blue Red, etc.. The question is how would go in parsing this and instead of printing out the value, return the value. UPDATE/FIXED: It has been fixed above. Thanks

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  • class which cannot be derived

    - by benjamin button
    I found this code here class Usable; class Usable_lock { friend class Usable; private: Usable_lock() {} Usable_lock(const Usable_lock&) {} }; class Usable : public virtual Usable_lock { // ... public: Usable(); Usable(char*); // ... }; Usable a; class DD : public Usable { }; DD dd; // error: DD::DD() cannot access // Usable_lock::Usable_lock(): private member Could anybody explain me this code?

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  • boost timer usage question

    - by stefita
    I have a really simple question, yet I can't find an answer for it. I guess I am missing something in the usage of the boost timer.hpp. Here is my code, that unfortunately gives me an error message: include <boost/timer.hpp> int main() { boost::timer t; } And the error messages are as follows: /usr/include/boost/timer.hpp: In member function ‘double boost::timer::elapsed_max() const’: /usr/include/boost/timer.hpp:59: error: ‘numeric_limits’ is not a member of ‘std’ /usr/include/boost/timer.hpp:59: error: ‘::max’ has not been declared /usr/include/boost/timer.hpp:59: error: expected primary-expression before ‘double’ /usr/include/boost/timer.hpp:59: error: expected `)' before ‘double’ The used library is boost 1.36 (SUSE 11.1). Thanks in advance!

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  • Call a C++ constructor from an Objective C class

    - by syvex
    How can I call a C++ constructor from inside an Objective C class? class CppClass { public: CppClass(int arg1, const std::string& arg2): _arg1(arg1), _arg2(arg2) { } // ... private: int _arg1; std::string _arg2; }; @interface ObjC: NSObject { CppClass _cppClass; } @end @implementation ObjC - (id)init { self = [super init]; if ( self ) { // what is the syntax to call CppClass::CppClass(5, "hello") on _cppClass? } return self; } @end

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  • How can I load a SQLITE database from a buffer with the C API ?

    - by rockeye
    Hello, I am trying to load a database from the memory instead of opening a .sqlite file. I have read the C/C++ API reference but I can not find the proper method. The buffer I am trying to load is simply an sqlite file loaded in memory. I just want to use this buffer (a const char* array) without using the filesystem (I could have saved this buffer in a file, then load the file, but no). First, I create a memory DB : mErrorCode = sqlite3_open_v2(":memory:", &mSqlDatabase, lMode, NULL); This returns SQLITE_OK, then I tried to use the buffer as a statement and call preparev2(MyDB, MyBufferData, MyBufferLength, MyStatement, NULL) but it's not really a statement, and it returns an error. Same result if I call directly exec(MyDB, MyBufferData, NULL, NULL, NULL); I guess there is an appropriate method to achieve this as it might be common to load a DB from a stream or from decrypted data... Thanks.

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  • Calling some functions before main in C

    - by minjang
    I'd like to do some stuffs before main function. I have multiple source files. In each file, there is some work that needs to be done before main. It was no problem in C++, but problematic with C. In C++, this can be done by two ways: Exploiting a constructor of a global class/struct. Calling a function to a global variable For example, static const int __register_dummy_ = __AddRegisterMetaInfo(...); However, in C, either ways is impossible. Obviously, there is no constructor. So, the first option is inherently impossible. I thought that the second option would be possible, but not compiled in C (I tested only with Visual C++. It gives C2099.). C only allows a constant to a non-automatic variable. Is there any way to call some functions before main?

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  • Context Menu event with QGraphicsWidget

    - by onurozcelik
    In my application I subclass QGraphicsWidget In paint I am drawing a line with pen width 4. I reimplemented boundingRect() and shape(). But I can't catch context menu event every time I click right mouse button. What is the problem.(Pen Width ? ) //Sample code for boundingRect() and shape() QRectF boundingRect() const { qreal rectLeft = x1 < x2 ? x1 : x2; qreal rectTop = y1 < y2 ? y1 : y2; qreal rectWidth = (x1 - x2) != 0 ? abs(x1-x2) : 4; qreal rectHeight = (y1 - y2) != 0 ? abs(y1 -y2) : 4; return QRectF(rectLeft,rectTop,rectWidth,rectHeigt); } QPainterPath shape() { QPainterPath path; path.addRect(boundingRect()); return path; }

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  • Any side effect of not using USES_CONVERSION

    - by Yan Cheng CHEOK
    Recently, I have a utilities function of // T2CA #include "ATLCONV.H" std::string Utils::CString2String(const CString& cString) { #if _MSC_VER > 1200 // Convert a TCHAR string to a LPCSTR // construct a std::string using the LPCSTR input CT2CA tmp(cString); std::string strStd (tmp); #else // Deprecated in VC2008. // construct a std::string using the LPCSTR input std::string strStd (T2CA (cString)); #endif return strStd; } I do several simple test it seems work fine. However, when I google around, I see most usage of T2CA in VC6, before they call, they will invoke USES_CONVERSION; Is there any thing I had missed out? Shall I invoke my function by : #else // Deprecated in VC2008. // construct a std::string using the LPCSTR input USES_CONVERSION; std::string strStd (T2CA (cString)); #endif

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