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  • Direct boost serialization to char array

    - by scooterman
    Hi all, Boost serialization doc's assert that the way to serialize/deserialize items is using a binary/text archive with a stream on the underlying structure. This works fine if I wan't to use the serialized data as an std::string, but my intention is to convert it directly to a char* buffer. How can I achieve this without creating a temporary string?

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  • Dynamic allocating of const member structures

    - by Willy
    I've got class which is using plain-only-data struct with const variables and I'm not sure, if I'm allocating these structures in a proper way. It looks more or less like: #include <cstdlib> #include <iostream> using std::cout; using std::endl; struct some_const_struct { const int arg1; const int arg2; }; class which_is_using_above_struct { public: some_const_struct* m_member; const some_const_struct* const m_const_member; public: const some_const_struct& get_member() const { return *m_member; } const some_const_struct& get_const_member() const { return *m_const_member; } void set_member(const int a, const int b) { if(m_member != NULL) { delete m_member; m_member = NULL; } m_member = new some_const_struct((some_const_struct){a, b}); } explicit which_is_using_above_struct(const int a, const int b) : m_const_member(new some_const_struct((const some_const_struct){a, b})) { m_member = NULL; } ~which_is_using_above_struct() { if(m_member != NULL) { delete m_member; } if(m_const_member != NULL) { delete m_const_member; } } }; int main() { which_is_using_above_struct c(1, 2); c.set_member(3, 4); cout << "m_member.arg1 = " << c.get_member().arg1 << endl; cout << "m_member.arg2 = " << c.get_member().arg2 << endl; cout << "m_const_member.arg1 = " << c.get_const_member().arg1 << endl; cout << "m_const_member.arg2 = " << c.get_const_member().arg2 << endl; return 0; } I'm just not quite sure if the statement: m_member = new some_const_struct((some_const_struct){a, b}); doesn't produce unnessesary use of some_const_struct's copy constructor, ergo allocating that struct twice. What do you think? And is it reasonable to make that struct's members const? (they're not supposed to change in their lifetime at all)

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  • Better way to write an object generator for an RAII template class?

    - by Dan
    I would like to write an object generator for a templated RAII class -- basically a function template to construct an object using type deduction of parameters so the types don't have to be specified explicitly. The problem I foresee is that the helper function that takes care of type deduction for me is going to return the object by value, which will result in a premature call to the RAII destructor when the copy is made. Perhaps C++0x move semantics could help but that's not an option for me. Anyone seen this problem before and have a good solution? This is what I have: template<typename T, typename U, typename V> class FooAdder { private: typedef OtherThing<T, U, V> Thing; Thing &thing_; int a_; // many other members public: FooAdder(Thing &thing, int a); ~FooAdder(); void foo(T t, U u); void bar(V v); }; The gist is that OtherThing has a horrible interface, and FooAdder is supposed to make it easier to use. The intended use is roughly like this: FooAdder(myThing, 2) .foo(3, 4) .foo(5, 6) .bar(7) .foo(8, 9); The FooAdder constructor initializes some internal data structures. The foo and bar methods populate those data structures. The ~FooAdder dtor wraps things up and calls a method on thing_, taking care of all the nastiness. That would work fine if FooAdder wasn't a template. But since it is, I would need to put the types in, more like this: FooAdder<Abc, Def, Ghi>(myThing, 2) ... That's annoying, because the types can be inferred based on myThing. So I would prefer to create a templated object generator, similar to std::make_pair, that will do the type deduction for me. Something like this: template<typename T, typename U, typename V> FooAdder<T, U, V> AddFoo(Thing &thing, int a) { return FooAdder<T, U, V>(thing, a); } That seems problematic: because it returns by value, the stack temporary object will be destructed, which will cause the RAII dtor to run prematurely. One thought I had was to give FooAdder a copy ctor with move semantics, kinda like std::auto_ptr. But I would like to do this without dynamic memory allocation, so I thought the copy ctor could set a flag within FooAdder indicating the dtor shouldn't do the wrap-up. Like this: FooAdder(FooAdder &rhs) // Note: rhs is not const : thing_(rhs.thing_) , a_(rhs.a_) , // etc... lots of other members, annoying. , moved(false) { rhs.moved = true; } ~FooAdder() { if (!moved) { // do whatever it would have done } } Seems clunky. Anyone got a better way?

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  • Javawebparts Ajaxparts: Using same Axis event multiple times in signle form.

    - by Bloodboiler
    I'm using Javawebparts Ajaxparts and would like to use one axis event multiple times in a form. Problem is that std:InnerHTML responseHandler takes its target html tag id in axis-config.xml so it seems impossible to reuse the definition when only thing that should change is the target tag id. Is there a way to set responseHandler parameters on the the page where it is used (in asix:event tag or someting)?

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  • gcc check if file is main (#if __BASE_FILE__ == __FILE__)

    - by Marcin Raczkowski
    Hello. In ruby there's very common idiom to check if current file is "main" file: if __FILE__ == $0 # do something here (usually run unit tests) end I'd like to do something similar in C after reading gcc documentation I've figured that it should work like this: #if __FILE__ == __BASE_FILE__ // Do stuff #endif the only problem is after I try this: $ gcc src/bitmap_index.c -std=c99 -lm && ./a.out src/bitmap_index.c:173:1: error: token ""src/bitmap_index.c"" is not valid in preprocessor expressions Am I using #if wrong?

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  • C++: Trouble with tr1::bind (C2065)

    - by Rosarch
    I'm getting a compiler error with bind: using namespace std; bool odp(int arg1, int arg2); // ... find_if(vec.begin(), vec.end(), tr1::bind(odp, iValue, _1)); // C2065 My goal is to curry odp(), so its first argument is iValue, and apply that function in find_if. The error: C2065: '_1' : undeclared identifier. What am I doing wrong?

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  • Get name mangling when I try to use exceptions [CodeBlocks, C++]

    - by Beetroot
    I am trying to use exceptions for the first time but even though it is quite a simple example I just cannot get it to compile, I have looked at several examples and tried coding it in many, many different ways but I am still not even sure exactly where the problem is because I get namemangling when I introduce the catch/try/throw anyway here is my code hopefully it is something really stupid :) #include "Surface.h" #include "SDL_Image.h" using namespace std; SDL_Surface* surface::Load(string fileName){ SDL_Surface* loadedSurface = IMG_Load(fileName.c_str()); if(loadedSurface == 0) throw 0; //Convert surface to same format as display loadedSurface = SDL_DisplayFormatAlpha(loadedSurface); return loadedSurface; } #include "GameState.h" #include "Surface.h" #include<iostream> using namespace std; GameState::GameState(string fileName){ try{ stateWallpaper_ = surface::Load(fileName); } catch(int& e){ cerr << "Could not load " << fileName << endl; } } Thanks in advance for any help! EDIT: Sorry I forgot to post the error message: It is In function `ZN14GameStateIntroC1Ev':| -undefined reference to `__gxx_personality_sj0'| -undefined reference to `_Unwind_SjLj_Register'| -undefined reference to `_Unwind_SjLj_Unregister'| In function `ZN14GameStateIntroC1Ev':| undefined reference to `_Unwind_SjLj_Resume'| In function `ZN14GameStateIntroC2Ev':| -undefined reference to `__gxx_personality_sj0'| -undefined reference to `_Unwind_SjLj_Register'| -undefined reference to `_Unwind_SjLj_Unregister'| obj\Release\GameStateIntro.o||In function `ZN14GameStateIntroC2Ev':| C:\Program Files (x86)\CodeBlocks\MinGW\bin\..\lib\gcc\mingw32\3.4.5\..\..\..\..\include\c++\3.4.5\ext\new_allocator.h|69|undefined reference to `_Unwind_SjLj_Resume'| C:\MinGW\lib\libSDLmain.a(SDL_win32_main.o)||In function `redirect_output':| \Users\slouken\release\SDL\SDL-1.2.15\.\src\main\win32\SDL_win32_main.c|219|undefined reference to `SDL_strlcpy'| \Users\slouken\release\SDL\SDL-1.2.15\.\src\main\win32\SDL_win32_main.c|220|undefined reference to `SDL_strlcat'| \Users\slouken\release\SDL\SDL-1.2.15\.\src\main\win32\SDL_win32_main.c|243|undefined reference to `SDL_strlcpy'| \Users\slouken\release\SDL\SDL-1.2.15\.\src\main\win32\SDL_win32_main.c|244|undefined reference to `SDL_strlcat'| C:\MinGW\lib\libSDLmain.a(SDL_win32_main.o)||In function `console_main':| \Users\slouken\release\SDL\SDL-1.2.15\.\src\main\win32\SDL_win32_main.c|296|undefined reference to `SDL_strlcpy'| \Users\slouken\release\SDL\SDL-1.2.15\.\src\main\win32\SDL_win32_main.c|301|undefined reference to `SDL_GetError'| \Users\slouken\release\SDL\SDL-1.2.15\.\src\main\win32\SDL_win32_main.c|312|undefined reference to `SDL_SetModuleHandle'| C:\MinGW\lib\libSDLmain.a(SDL_win32_main.o)||In function `WinMain@16':| \Users\slouken\release\SDL\SDL-1.2.15\.\src\main\win32\SDL_win32_main.c|354|undefined reference to `SDL_getenv'| \Users\slouken\release\SDL\SDL-1.2.15\.\src\main\win32\SDL_win32_main.c|386|undefined reference to `SDL_strlcpy'| C:\MinGW\lib\libSDLmain.a(SDL_win32_main.o)||In function `cleanup':| \Users\slouken\release\SDL\SDL-1.2.15\.\src\main\win32\SDL_win32_main.c|158|undefined reference to `SDL_Quit'| **

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  • From Java Object class to C++

    - by Rui
    Hi, I'm relative new to C++ and my background is in Java. I have to port some code from Java to C++ and some doubts came up relative to the Object Java's class. So, if I want to port this: void Algorithm::setInputParameter(std::string name, Object object) { ..... } I believe I should use void* type or templates right? I don't know what's the "standard" procedure to accomplish it. Thanks

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  • avoiding enums as interface identifiers c++ OOP

    - by AlasdairC
    Hi I'm working on a plugin framework using dynamic loaded shared libraries which is based on Eclipse's (and probally other's) extension-point model. All plugins share similar properties (name, id, version etc) and each plugin could in theory satisfy any extension-point. The actual plugin (ie Dll) handling is managed by another library, all I am doing really is managing collections of interfaces for the application. I started by using an enum PluginType to distinguish the different interfaces, but I have quickly realised that using template functions made the code far cleaner and would leave the grunt work up to the compiler, rather than forcing me to use lots of switch {...} statements. The only issue is where I need to specify like functionality for class members - most obvious example is the default plugin which provides a particular interface. A Settings class handles all settings, including the default plugin for an interface. ie Skin newSkin = settings.GetDefault<ISkin>(); How do I store the default ISkin in a container without resorting to some other means of identifying the interface? As I mentioned above, I currently use a std::map<PluginType, IPlugin> Settings::defaults member to achieve this (where IPlugin is an abstract base class which all plugins derive from. I can then dynamic_cast to the desired interface when required, but this really smells of bad design to me and introduces more harm than good I think. would welcome any tips edit: here's an example of the current use of default plugins typedef boost::shared_ptr<ISkin> Skin; typedef boost::shared_ptr<IPlugin> Plugin; enum PluginType { skin, ..., ... } class Settings { public: void SetDefault(const PluginType type, boost::shared_ptr<IPlugin> plugin) { m_default[type] = plugin; } boost::shared_ptr<IPlugin> GetDefault(const PluginType type) { return m_default[type]; } private: std::map<PluginType, boost::shared_ptr<IPlugin> m_default; }; SkinManager::Initialize() { Plugin thedefault = g_settings.GetDefault(skinplugin); Skin defaultskin = boost::dynamic_pointer_cast<ISkin>(theskin); defaultskin->Initialize(); } I would much rather call the getdefault as the following, with automatic casting to the derived class. However I need to specialize for every class type. template<> Skin Settings::GetDefault<ISkin>() { return boost::dynamic_pointer_cast<ISkin>(m_default(skin)); }

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  • How to handle main option with Getopt

    - by Jérôme
    I want to handle a feature which seems to me almost natural with programs, and I don't know how to handle it with Getopt perl package (no matter Std ot Long). I would like something like: ./perlscript <main option> [some options like -h or --output-file some_name] Options will be handled with - or --, but I want to be able to let the user give me the main and needed option without dashes. Is Getopt able to do that, or do I have to handle it by hand?

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  • Flexible array member in C-structure

    - by Arpan
    Quoting from the C-std section 6.7.2.1, struct s { int n; double d[]; }; This is a valid structure declaration. I am looking for some practical use of this kind of syntax. To be precise, how is this construct any more or less powerful than keeping a double* as the 2nd element? Or is this another case of 'you-can-do-it-in-multiple-ways'? Arpan

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  • How to push_back without operator=() for const members?

    - by WilliamKF
    How to push_back() to a C++ std::vector without using operator=() for which the default definition violates having const members? struct Item { Item(int value) : _value(value) { } const int _value; } vector<Item> items; items.push_back(Item(3)); I'd like to keep the _value const since it should not change after the object is constructed, so the question is how do I initialize my vector with elements without invoking operator=()?

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  • C++: Chr() and unichr() equivalent?

    - by alex
    I could have sworn I used a chr() function 40 minutes ago but can't find the file. I know it can go up to 256 so I use this: std::string chars = ""; chars += (char) 42; //etc So that's alright, but I really want to access unicode characters. Can I do (w_char) 512? Or maybe something just like the unichr() function in python, I just can't find a way to access any of those characters.

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  • Vector Troubles in C++

    - by DistortedLojik
    I am currently working on a project that deals with a vector of objects of a People class. The program compiles and runs just fine, but when I use the debugger it dies when trying to do anything with the PersonWrangler object. I currently have 3 different classes, one for the person, a personwrangler which handles all of the people collectively, and a game class that handles the game input and output. Edit: My basic question is to understand why it is dying when it calls outputPeople. Also I would like to understand why my program works exactly as it should unless I use the debugger. The outputPeople function works the way I intended that way. Edit 2: The callstack has 3 bad calls which are: std::vector ::begin(this=0xbaadf00d) std::vector ::size(this=0xbaadf00d) PersonWrangler::outputPeople(this=0xbaadf00d) Relevant code: class Game { public: Game(); void gameLoop(); void menu(); void setStatus(bool inputStatus); bool getStatus(); PersonWrangler* hal; private: bool status; }; which calls outputPeople where it promptly dies from a baadf00d error. void Game::menu() { hal->outputPeople(); } where hal is an object of PersonWrangler type class PersonWrangler { public: PersonWrangler(int inputStartingNum); void outputPeople(); vector<Person*> peopleVector; vector<Person*>::iterator personIterator; int totalPeople; }; and the outputPeople function is defined as void PersonWrangler::outputPeople() { int totalConnections = 0; cout << " Total People:" << peopleVector.size() << endl; for (unsigned int i = 0;i < peopleVector.size();i++) { sort(peopleVector[i]->connectionsVector.begin(),peopleVector[i]->connectionsVector.end()); peopleVector[i]->connectionsVector.erase( unique (peopleVector[i]->connectionsVector.begin(),peopleVector[i]->connectionsVector.end()),peopleVector[i]->connectionsVector.end()); peopleVector[i]->outputPerson(); totalConnections+=peopleVector[i]->connectionsVector.size(); } cout << "Total connections:" << totalConnections/2 << endl; }

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  • Sockets: I/O Error 32

    - by Genesis
    Could someone please explain what an I/O Error 32 refers to in the context of a network socket? I have a multithreaded Socks5 server written using Poco SocketReactors and am getting this error when the server load reaches a certain point. The exception is thrown within my onReadable handlers at the same time across all threads which have connections associated with them. The only other thing I am doing within those threads is std::cout but I am not sure if this is a potential cause.

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  • any stl/boost functors to call operator()

    - by Voivoid
    template <typename T> struct Foo { void operator()(T& t) { t(); } }; Is there any standart or boost functor with the similar implementation? I need it to iterate over container of functors: std::for_each(beginIter, endIter, Foo<Bar>()); Or maybe there are other way to do it?

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  • C/C++ efficient bit array

    - by aaa
    hi. Can you recommend efficient/clean way to manipulate arbitrary length bit array? right now I am using regular int/char bitmask, but those are not very clean when array length is greater than datatype length. std vector<bool> is not available for me. thanks

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  • C++ Class Construction and Member Initialization

    - by anachoret
    The first print shows the member value to be false, and the other two prints show it as true. Why does the first output differ from the last two? #include #include using namespace std; class MyClass { public: bool value; bool stuff; }; class Container { public: vector my_classes; Container() { MyClass c; cout

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  • Do I need to cast the result of strtol to int?

    - by Kristo
    The following code does not give a warning with g++ 4.1.1 and -Wall. int octalStrToInt(const std::string& s) { return strtol(s.c_str(), 0, 8); } I was expecting a warning because strtol returns a long int but my function is only returning a plain int. Might other compilers emit a warning here? Should I cast the return value to int in this case as a good practice?

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  • C++ boost function overloaded template

    - by aaa
    I cannot figure out why this segment gives unresolved overloaded function error (gcc version 4.3.4 (Debian 4.3.4-6)): #include <algorithm> #include <boost/function.hpp> int main { typedef boost::function2<const int&, const int&, const int&> max; max m(static_cast<max>(&std::max<int>)); } can you help me, thanks

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