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  • Problems with delete in destructor

    - by Vera
    Hello, I wrote this code. The constructor works normally, but in the destructor I get "Windows has triggered a breakpoint." How should I correct this? template class CyclicalArray { private: T* mem_ptr; public: CyclicalArray(size_t capacity, const T& default_value) { this->default_value = default_value; this->capacity = capacity; head_index = 0; mem_ptr = ::new T[capacity]; //memory allocating for(T* p = mem_ptr; p < mem_ptr + capacity * sizeof(T); p += sizeof(T)) { ::new (p) T (default_value); //initialization } } ~CyclicalArray() { for(T* p = mem_ptr + sizeof(T); p < mem_ptr + capacity * sizeof(T); p += sizeof(T)) { p->~T(); } delete[] mem_ptr; }

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  • When do I need to deallocate memory?

    - 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); } I call visitWeb from another void function that gets called on the handlemessage() for the app. 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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  • Vbscript - Object Required for DateLastModified

    - by Kenny Bones
    I don't really know what's wrong right here. I'm trying to create a vbscript that basically checks two Folders for their files and compare the DateLastModified attribute of each and then copies the source files to the destination folder if the DateLastModified of the source file is newer than the existing one. I have this code: Dim strSourceFolder, strDestFolder Dim fso, objFolder, colFiles strSourceFolder = "c:\users\user\desktop\Source\" strDestFolder = "c:\users\user\desktop\Dest\" Set fso = CreateObject("Scripting.FileSystemObject") Set objFolder = fso.GetFolder(strSourceFolder) Set colFiles = objFolder.Files For each objFile in colFiles Dim DateModified DateModified = objFile.DateLastModified ReplaceIfNewer objFile, DateModified, strSourceFolder, strDestFolder Next Sub ReplaceIfNewer (sourceFile, DateModified, SourceFolder, DestFolder) Const OVERWRITE_EXISTING = True Dim fso, objFolder, colFiles, sourceFileName, destFileName Dim DestDateModified, objDestFile Set fso = CreateObject("Scripting.FileSystemObject") sourceFileName = fso.GetFileName(sourceFile) destFileName = DestFolder & sourceFileName if fso.FileExists(destFileName) Then objDestFile = fso.GetFile(destFileName) DestDateModified = objDestFile.DateLastModified msgbox "File last modified: " & DateModified msgbox "New file last modified: " & DestDateModified End if End Sub And I get the error: On line 34, Char 3 "Object required: 'objDestFile' But objDestFile IS created?

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  • use callback function to report stack backtrace

    - by user353394
    Assume I have the following: typedef struct { char *name; char binding; int address; } Fn_Symbol //definition of function symbol static Fn_Symbol *fnSymbols; //array of function symbols in a file statc int total; //number of symbol functions in the array and file static void PrintBacktrace(int sigum, siginfo_t * siginfo, void *context) { printf("\nSignal received %d (%s)\n", signum, strsignal(signum)); const int eip_index = 14; void *eip = (void *)((struct ucontext *)context)->uc_mcontext.gregs[eip_index]; printf("Error at [%p] %s (+0x%x), eip, fnName, offset from start); //????? exit(0); } I have this so far, but what is the best way using the fnSymbols static global pointer to identify the function where the error occured and then back trace through the stack to identify each calling function by address, name, and offset?

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  • Strange error: cannot convert from 'int' to 'ios_base::openmode'

    - by Dylan Klomparens
    I am using g++ to compile some code. I wrote the following snippet: bool WriteAccess = true; string Name = "my_file.txt"; ofstream File; ios_base::open_mode Mode = std::ios_base::in | std::ios_base::binary; if(WriteAccess) Mode |= std::ios_base::out | std::ios_base::trunc; File.open(Name.data(), Mode); And I receive these errors... any idea why? Error 1: invalid conversion from ‘int’ to ‘std::_Ios_Openmode’ Error 2: initializing argument 2 of ‘std::basic_filebuf<_CharT, _Traits* std::basic_filebuf<_CharT, _Traits::open(const char*, std::_Ios_Openmode) [with _CharT = char, _Traits = std::char_traits]’ As far as I could tell from a Google search, g++ is actually breaking the C++ standard here. Which I find quite astonishing, since they generally conform very strictly to the standard. Is this the case? Or am I doing something wrong. My reference for the standard: http://www.cplusplus.com/reference/iostream/ofstream/open/

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  • Multiplying complex with constant in C++

    - by Atilla Filiz
    The following code fails to compile #include <iostream> #include <cmath> #include <complex> using namespace std; int main(void) { const double b=3; complex <double> i(0, 1), comp; comp = b*i; comp=3*i; return 0; } with error: no match for ‘operator*’ in ‘3 * i’ What is wrong here, why cannot I multiply with immediate constants?

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  • Add every value in stack

    - by rezivor
    I am trying to figure out a method that will add every value in a stack. The goal is to use that value to determine if all the values in the stack are even. I have written to code to do this template <class Object> bool Stack<Object>::objectIsEven( Object value ) const { bool answer = false; if (value % 2 == 0) answer = true; return( answer ); } However, I am stumped on how to add all of the stack's values in a separate method

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  • Why does SQLite not bring back any results from my database

    - by tigermain
    This is my first SQLite based iPhone app and I am trying to get it to read a menu hierarchy from my database. The database appears to be registered fine as the compiled statement doesnt error (tried putting in valid table name to test) but for some reason sqlite3_step(compiledStmt) doesnt ever equal SQLITE_ROW as if to suggest there is no data in there; which there is. sqlite3 *database; menu = [[NSMutableArray alloc] init]; if (sqlite3_open([databasePath UTF8String], &database) == SQLITE_OK) { const char *sqlStmt = "SELECT * FROM Menu"; sqlite3_stmt *compiledStmt; if (sqlite3_prepare_v2(database, sqlStmt, -1, &compiledStmt, NULL) == SQLITE_OK) { while (sqlite3_step(compiledStmt) == SQLITE_ROW) { NSString *aTitle = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStmt, 1)]; MenuItem *menuItem = [[MenuItem alloc] init]; menuItem.title = aTitle; [menu addObject:menuItem]; [menuItem release]; } } else { NSLog(@"There is an error with the SQL Statement"); } sqlite3_finalize(compiledStmt); } sqlite3_close(database);

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  • Is there a standard literal constant that I can use instead of "utf-8" in C# (.Net 3.5)?

    - by Hamish Grubijan
    Hi, I would like to find a better way to do this: XmlNode nodeXML = xmlDoc.AppendChild( xmlDoc.CreateXmlDeclaration( "1.0", "utf-8", String.Empty) ); I do not want to think about "utf-8" vs "UTF-8" vs "UTF8" vs "utf8" as I type code. I would like to make my code less prone to typos. I am sure that some standard library has declatred "utf-8" as a const / readonly string. How can I find it? Also, what about "1.0"? I am assuming that major XML versions have been enumerated somewhere as well. Thanks!

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  • How to 'hide' spurious "declared but never used" warnings?

    - by Roddy
    I'm using the C++Builder compiler which has a minor bug that certain static const items from system header files can cause spurious "xyzzy is declared but never used" warnings. I'm trying to get my code 100% warning free, so want a way of masking these particular warnings (note - but not by simply turning off the warning!) Also, I can't modify the header files. I need a way of 'faking' the use of the items, preferably without even knowing their type. As an example, adding this function to my .cpp modules fixes warnings for these four items, but it seems a bit 'ad-hoc'. Is there a better and preferably self-documenting way of doing this? static int fakeUse() { return OneHour + OneMinute + OneSecond + OneMillisecond; }

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  • For Qt 4.6.x, how to auto-size text to fit in a specified width?

    - by darenchow
    Inside of my QGraphicsRectItem::paint(), I am trying to draw the name of the item within its rect(). However, for each of the different items, they can be of variable width and similarly names can be of variable length. Currently I am starting with a maximum font size, checking if it fits and decrementing it until I find a font size that fits. So far, I haven't been able to find a quick and easy way to do this. Is there a better, or more efficient way to do this? Thanks! void checkFontSize(QPainter *painter, const QString& name) { // check the font size - need a better algorithm... this could take awhile while (painter->fontMetrics().width(name) > rect().width()) { int newsize = painter->font().pointSize() - 1; painter->setFont(QFont(painter->font().family(), newsize)); } }

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  • How to create a string array in matlab?

    - by aduric
    I would like to pass a vector of strings from C++ to matlab. I have tried using the functions available such as mxCreateCharMatrixFromStrings but it doesn't give me the correct behavior. So, I have something like this: void mexFunction( int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[]) { vector<string> stringVector; stringVector.push_back("string 1"); stringVector.push_back("string 2"); //etc... The problem is how do I get this vector to the matlab environment? plhs[0] = ??? My goal is to be able to run: >> [strings] = MyFunc(...) >> strings(1) = 'string 1'

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  • Avoiding "variable might not have been initialized"

    - by Mason Wheeler
    I recently ran across a routine that looks something like this: procedure TMyForm.DoSomething(list: TList<TMyObject>; const flag: boolean); var local: integer; begin if flag then //do something else local := ExpensiveFunctionCallThatCalculatesSomething; //do something else for i := 0 to list.Count do if flag then //do something else if list[i].IntValue > local then //WARNING HERE //do something else end; This gives Variable 'local' might not have been initialized even though you can tell by reading the code that you won't hit that line unless the code branch that initializes it has run. Now, I could get rid of this warning by adding a useless local := 0; at the top of the procedure, but I wonder if there might not be a better way to structure this to avoid the issue. Anyone have any ideas?

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  • Inline function and calling cost in C

    - by Eonil
    I'm making a vector/matrix library. (GCC, ARM NEON, iPhone) typedef struct{ float v[4]; } Vector; typedef struct{ Vector v[4]; } Matrix; I passed struct data as pointer to avoid performance degrade from data copying when calling function. So I thought designed function like this: void makeTranslation(const Vector* factor, Matrix* restrict result); But, if function is inline, is there any reason to pass values as pointer for performance? Do those variables copied too? How about register and caches? inline Matrix makeTranslation(Vector factor) __attribute__ ((always_inline)); How do you think about calling costs of each cases?

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  • Is There a Good Pattern for Creating a Unique Id based on a Type?

    - by Michael Kelley
    I have a template that creates a unique identifier for each type it is instanced. Here's a streamlined version of the template: template <typename T> class arType { static const arType Id; // this will be unique for every instantiation of arType<>. } // Address of Id is used for identification. #define PA_TYPE_TAG(T) (&arType<T >::Id) This works when you have an executable made purely of static libraries. Unfortunately we're moving to an executable made up of dlls. Each dlls could potentially have its own copy of Id for a type. One obvious solution is to explicitly instantiate all instances of arType. Unfortunately this is cumbersome, and I'd like to ask if anyone can propose a better solution?

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  • How to load an RSA key from binary data to an RSA structure using the OpenSSL C Library?

    - by Andreas Bonini
    Currently I have my private key saved in a file, private.key, and I use the following function to load it: RSA *r = PEM_read_RSAPrivateKey("private.key", NULL, NULL, NULL); This works perfectly but I'm not happy with the file-based format; I want to save my key in pure binary form (ie, no base64 or similar) in a char* variable and load/save the key from/to it. This way I have much more freedom: I'll be able to store the key directly into the application const char key[] { 0x01, 0x02, ... };, send it over a network socket, etc. Unfortunately though I haven't found a way to do that. The only way to save and load a key I know of reads/saves it to a file directly.

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  • CImg compile problems in Codegear 2009

    - by Seth
    I wish to use the CImg library for image processing in my current project. I am using Codegear C++ Builder 2009. I include CImg.h in the source file and put in the following code: int rows =5; int cols = 5; CImg<double> img(rows,cols); I get the following error: [BCC32 Error] CImg.h(39159): E2285 Could not find a match for 'CImg<unsigned char>::move_to<t>(const CImg<unsigned char>)' Does anyone know if there is a #define I should be using when building in Codegear C++ Builder 2009. Or is it simply not compatible?

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  • Determine if a string contains only alphanumeric characters (or a space)

    - by dreamlax
    I'm learning C++ and I am writing a function that determines whether a string contains only alphanumeric characters and spaces. I suppose I am effectively testing whether it matches the regular expression ^[[:alnum:] ]+$ but without using regular expressions. I have seen a lot of algorithms revolve around iterators, so I tried to find a solution that made use of iterators, and this is what I have: #include <algorithm> static inline bool is_not_alnum_space(char c) { return !(isalpha(c) || isdigit(c) || (c == ' ')); } bool string_is_valid(const std::string &str) { return find_if(str.begin(), str.end(), is_not_alnum_space) == str.end(); } Is there a better solution, or a “more C++” way to do this?

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  • C++ initializing constants and inheritance

    - by pingvinus
    I want to initialize constant in child-class, instead of base class. And use it to get rid of dynamic memory allocation (I know array sizes already, and there will be a few child-classes with different constants). So I try: class A { public: const int x; A() : x(0) {} A(int x) : x(x) {} void f() { double y[this->x]; } }; class B : A { B() : A(2) {} }; Pretty simple, but compiler says: error C2057: expected constant expression How can I say to compiler, that it is really a constant?

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  • MinGW screw up with COLORREF and RGB

    - by kjoppy
    I am trying to build a 3rd party open source project using MinGW. One of the dependencies is wxWidgets. When I try to make the project from MSYS I get a compiler error from /MinGW/msys/1.0/local/include/wx-2.8/wx/msw/private.h In function 'COLORREF wxColourToRGB(const wxColour&)': error: cannot convert 'RGB' to 'COLORREF {aka long unsigned in}' in return This is somewhat odd given that, according to Microsoft the RGB macro returns a COLORREF. In fact, looking in H:\MinGW\include I find wingdi.h with the following code #define RGB(r,g,b) ((COLORREF)((BYTE)(r)|((BYTE)(g) << 8)|((BYTE)(b) << 16))) What sort of thing would cause this error? Is there some way I can check to see if COLORREF and RGB are being included from wingdi.h and not somewhere else? Is that even worth checking? Specifications GCC version 4.7.2 wxWidgets version 2.8.12 (I'm new to C++ and MinGW specifically but generally computer and programming literate)

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  • how to open many files simultaneously for reading in c

    - by monkeyking
    I'm trying to port some of my c++ code into c. I have the following construct class reader{ private: FILE *fp; alot_of_data data;//updated by read_until() method public: reader(const char*filename) read_until(some conditional dependent on the contents of the file, and the arg supplied) } Im then instantiating hundreds of these object and iterate over them using several 'read_until()' for each file until allfiles is at eof. I'm failing to see any clever way to do this in c, the only solution I can come up with is making an array of FILE pointers, and do the same with all the private member data from my class. But this seems very messy, can I implement the functionality of my class as a function pointer, or anything better, I think I'm missing a fundamental design pattern? The files are way to big to have all in memory, so reading everything from every file is not feasible Thanks

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  • iPhone OpenGL Template is cheating?

    - by carrots
    XCode's OpenGL template seems to be cheating to solve this "stretched" viewport problem I've been trying to understand for the last 3 hours. In the iphone "OpenGL ES Application" template, the colorful square that bounces up and down on the screen is not really a square at all! ES1Renderer.m (the ES2 file as well) static const GLfloat squareVertices[] = { -0.5f, -0.33f, 0.5f, -0.33f, -0.5f, 0.33f, 0.5f, 0.33f, }; But it comes out looking square on the device/simulator due to the stretching/squashing effect of a non-square viewport. I tried to fix it by fiddling with glFrustumf() but that doesn't seem to change the aspect ratio. I was able to get things looking good (not-stretched) when I fed glViewport() with a 1:1 widht:height.. But this doesn't seem like the answer because it offsets the viewport placement. What's the right way to correct for this stretching and why doesn't XCode do it that way?

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  • Retain cycle on `self` with blocks

    - by Jonathan Sterling
    I'm afraid this question is pretty basic, but I think it's relevant to a lot of Objective-C programmers who are getting into blocks. What I've heard is that since blocks capture local variables referenced within them as const copies, using self within a block can result in a retain cycle, should that block be copied. So, we are supposed to use __block to force the block to deal directly with self instead of having it copied. __block typeof(self) bself = self; [someObject messageWithBlock:^{ [bself doSomething]; }]; instead of just [someObject messageWithBlock:^{ [self doSomething]; }]; What I'd like to know is the following: if this is true, is there a way that I can avoid the ugliness (aside from using GC)?

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  • How to log C++ exception if running outside debugger, otherwise rethrow

    - by Stefan Monov
    I wanna do something like this: int main() { try { runApp(); } catch(std::exception const& ex) { if(runningInDebugger()) throw; // let the IDE show me what went wrong else displayMsgBox("Something went wrong! " + ex.what()); } } Needs to work at least in VS2008 but the more debuggers it supports, the better. I want it to check for a debugger at runtime. I don't want to do "#ifdef NDEBUG", because I prefer not to do release builds at all (can't be bothered). So what should I use as a "runningInDebugger()" check?

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