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  • error: expected constructor, destructor, or type conversion before '(' token

    - by jonathanasdf
    include/TestBullet.h:12: error: expected constructor, destructor, or type conver sion before '(' token I hate C++ error messages... lol ^^ Basically, I'm following what was written in this post to try to create a factory class for bullets so they can be instantiated from a string, which will be parsed from an xml file, because I don't want to have a function with a switch for all of the classes because that looks ugly. Here is my TestBullet.h: #pragma once #include "Bullet.h" #include "BulletFactory.h" class TestBullet : public Bullet { public: void init(BulletData& bulletData); void update(); }; REGISTER_BULLET(TestBullet); <-- line 12 And my BulletFactory.h: #pragma once #include <string> #include <map> #include "Bullet.h" #define REGISTER_BULLET(NAME) BulletFactory::reg<NAME>(#NAME) #define REGISTER_BULLET_ALT(NAME, CLASS) BulletFactory::reg<CLASS>(NAME) template<typename T> Bullet * create() { return new T; } struct BulletFactory { typedef std::map<std::string, Bullet*(*)()> bulletMapType; static bulletMapType map; static Bullet * createInstance(char* s) { std::string str(s); bulletMapType::iterator it = map.find(str); if(it == map.end()) return 0; return it->second(); } template<typename T> static void reg(std::string& s) { map.insert(std::make_pair(s, &create<T>)); } }; Thanks in advance.

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  • compiler warning at C++ template base class

    - by eike
    I get a compiler warning, that I don't understand in that context, when I compile the "Child.cpp" from the following code. (Don't wonder: I stripped off my class declarations to the bare minuum, so the content will not make much sense, but you will see the problem quicker). I get the warning with VS2003 and VS2008 on the highest warning level. The code AbstractClass.h : #include <iostream> template<typename T> class AbstractClass { public: virtual void Cancel(); // { std::cout << "Abstract Cancel" << std::endl; }; virtual void Process() = 0; }; //outside definition. if I comment out this and take the inline //definition like above (currently commented out), I don't get //a compiler warning template<typename T> void AbstractClass<T>::Cancel() { std::cout << "Abstract Cancel" << std::endl; } Child.h : #include "AbstractClass.h" class Child : public AbstractClass<int> { public: virtual void Process(); }; Child.cpp : #include "Child.h" #include <iostream> void Child::Process() { std::cout << "Process" << std::endl; } The warning The class "Child" is derived from "AbstractClass". In "AbstractClass" there's the public method "AbstractClass::Cancel()". If I define the method outside of the class body (like in the code you see), I get the compiler warning... AbstractClass.h(7) : warning C4505: 'AbstractClass::Cancel' : unreferenced local function has been removed with [T=int] ...when I compile "Child.cpp". I do not understand this, because this is a public function and the compiler can't know if I later reference this method or not. And, in the end, I reference this method, because I call it in main.cpp and despite this compiler warning, this method works if I compile and link all files and execute the program: //main.cpp #include <iostream> #include "Child.h" int main() { Child child; child.Cancel(); //works, despite the warning } If I do define the Cancel() function as inline (you see it as out commented code in AbstractClass.h), then I don't get the compiler warning. Of course my program works, but I want to understand this warning or is this just a compiler mistake? Furthermore, if do not implement AbsctractClass as a template class (just for a test purpose in this case) I also don't get the compiler warning...?

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  • Storing member function pointers of derived classes in map

    - by Kiran Mohan
    Hello, I am trying to implement a factory for two classes Circle, Square both of which inherits from Shape. class Shape { public: virtual static Shape * getInstance() = 0; }; class Circle : public Shape { public: static const std::string type; Shape * getInstance() { return new Circle; } }; const std::string Circle::type = "Circle"; class Square : public Shape { public: static const std::string type; Shape * getInstance() { return new Square; } }; const std::string Square::type = "Square"; I want to now create a map with key as shape type (string) and value as a function pointer to getInstance() of the corresponding derived class. Is it possible? Thanks, Kiran

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  • When is a C++ terminate handler the Right Thing(TM)?

    - by Joseph Garvin
    The C++ standard provides the std::set_terminate function which lets you specify what function std::terminate should actually call. std::terminate should only get called in dire circumstances, and sure enough the situations the standard describes for when it's called are dire (e.g. an uncaught exception). When std::terminate does get called the situation seems analagous to being out of memory -- there's not really much you can sensically do. I've read that it can be used to make sure resources are freed -- but for the majority of resources this should be handled automatically by the OS when the process exits (e.g. file handles). Theoretically I can see a case for if say, you needed to send a server a specific message when exiting due to a crash. But the majority of the time the OS handling should be sufficient. When is using a terminate handler the Right Thing(TM)? Update: People interested in what can be done with custom terminate handlers might find this non-portable trick useful.

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  • Vim + OmniCppComplete and completing members of class members

    - by Robert S. Barnes
    I've noticed that I can't seem to complete members of class members using OmniCppComplete. For example, given the following files: // foo.h #include <string> class foo { public: void set_str(const std::string &); std::string get_str_reverse( void ); private: std::string str; }; // foo.cpp #include "foo.h" using std::string; string foo::get_str_reverse ( void ) { string temp; temp.assign(str); reverse(temp.begin(), temp.end()); return temp; } /* ----- end of method foo::get_str ----- */ void foo::set_str ( const string &s ) { str.assign(s); } /* ----- end of method foo::set_str ----- */ I've set up tags for stdlibc++ and generated the tags for these two files using: ctags -R --c++-kinds=+pl --fields=+iaS --extra=+q . When I type temp. in the cpp I get a list of string member functions as expected. But if I type str. omnicomplete spits out "Pattern Not Found". I've noticed that the temp. completion only works if I have the using std::string; declaration. How do I get completion to work on my class members?

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  • Possible: Set Operations on Disparate Maps with Same Key Type?

    - by Catskul
    Let's say I have two maps: typedef int Id; std::map<Id, std::string> idToStringMap; std::map<Id, double> idToDoubleMap; And let's say I would like to do a set operation on the keys of the two maps. Is there an easier way to do this than to create a custom "inserter" iterator? such that I could do something like: std::set<Id> resultSet; set_difference( idToStringMap.begin(), idToStringMap.end(), idToDoubleMap.begin(), idToDoubleMap.end(), resultSet.begin() ); My experimentation results imply that it will be necessary to create a custom inserter and perhaps a custom key comparer to do this, but I want for some insight/shortcut before doing so.

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  • 42 passed to TerminateProcess, sometimes GetExitCodeProcess returns 0

    - by Emil
    After I get a handle returned by CreateProcess, I call TerminateProcess, passing 42 for the process exit code. Then, I use WaitForSingleObject for the process to terminate, and finally I call GetExitCodeProcess. None of the function calls report errors. The child process is an infinite loop and does not terminate on its own. The problem is that sometimes GetExitCodeProcess returns 42 for the exit code (as it should) and sometimes it returns 0. Any idea why? #include <string> #include <sstream> #include <iostream> #include <assert.h> #include <windows.h> void check_call( bool result, char const * call ); #define CHECK_CALL(call) check_call(call,#call); int main( int argc, char const * argv[] ) { if( argc>1 ) { assert( !strcmp(argv[1],"inf") ); for(;;) { } } int err=0; for( int i=0; i!=200; ++i ) { STARTUPINFO sinfo; ZeroMemory(&sinfo,sizeof(STARTUPINFO)); sinfo.cb=sizeof(STARTUPINFO); PROCESS_INFORMATION pe; char cmd_line[32768]; strcat(strcpy(cmd_line,argv[0])," inf"); CHECK_CALL((CreateProcess(0,cmd_line,0,0,TRUE,0,0,0,&sinfo,&pe)!=0)); CHECK_CALL((CloseHandle(pe.hThread)!=0)); CHECK_CALL((TerminateProcess(pe.hProcess,42)!=0)); CHECK_CALL((WaitForSingleObject(pe.hProcess,INFINITE)==WAIT_OBJECT_0)); DWORD ec=0; CHECK_CALL((GetExitCodeProcess(pe.hProcess,&ec)!=0)); CHECK_CALL((CloseHandle(pe.hProcess)!=0)); err += (ec!=42); } std::cout << err; return 0; } std::string get_last_error_str( DWORD err ) { std::ostringstream s; s << err; LPVOID lpMsgBuf=0; if( FormatMessageA( FORMAT_MESSAGE_ALLOCATE_BUFFER|FORMAT_MESSAGE_FROM_SYSTEM|FORMAT_MESSAGE_IGNORE_INSERTS, 0, err, MAKELANGID(LANG_NEUTRAL,SUBLANG_DEFAULT), (LPSTR)&lpMsgBuf, 0, 0) ) { assert(lpMsgBuf!=0); std::string msg; try { std::string((LPCSTR)lpMsgBuf).swap(msg); } catch( ... ) { } LocalFree(lpMsgBuf); if( !msg.empty() && msg[msg.size()-1]=='\n' ) msg.resize(msg.size()-1); if( !msg.empty() && msg[msg.size()-1]=='\r' ) msg.resize(msg.size()-1); s << ", \"" << msg << '"'; } return s.str(); } void check_call( bool result, char const * call ) { assert(call && *call); if( !result ) { std::cerr << call << " failed.\nGetLastError:" << get_last_error_str(GetLastError()) << std::endl; exit(2); } }

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  • C++ destructor seems to be called 'early'

    - by suicideducky
    Please see the "edit" section for the updated information. Sorry for yet another C++ dtor question... However I can't seem to find one exactly like mine as all the others are assigning to STL containers (that will delete objects itself) whereas mine is to an array of pointers. So I have the following code fragment #include<iostream> class Block{ public: int x, y, z; int type; Block(){ x=1; y=2; z=3; type=-1; } }; template <class T> class Octree{ T* children[8]; public: ~Octree(){ for( int i=0; i<8; i++){ std::cout << "del:" << i << std::endl; delete children[i]; } } Octree(){ for( int i=0; i<8; i++ ) children[i] = new T; } // place newchild in array at [i] void set_child(int i, T* newchild){ children[i] = newchild; } // return child at [i] T* get_child(int i){ return children[i]; } // place newchild at [i] and return the old [i] T* swap_child(int i, T* newchild){ T* p = children[i]; children[i] = newchild; return p; } }; int main(){ Octree< Octree<Block> > here; std::cout << "nothing seems to have broken" << std::endl; } Looking through the output I notice that the destructor is being called many times before I think it should (as Octree is still in scope), the end of the output also shows: del:0 del:0 del:1 del:2 del:3 Process returned -1073741819 (0xC0000005) execution time : 1.685 s Press any key to continue. For some reason the destructor is going through the same point in the loop twice (0) and then dying. All of this occures before the "nothing seems to have gone wrong" line which I expected before any dtor was called. Thanks in advance :) EDIT The code I posted has some things removed that I thought were unnecessary but after copying and compiling the code I pasted I no longer get the error. What I removed was other integer attributes of the code. Here is the origional: #include<iostream> class Block{ public: int x, y, z; int type; Block(){ x=1; y=2; z=3; type=-1; } Block(int xx, int yy, int zz, int ty){ x=xx; y=yy; z=zz; type=ty; } Block(int xx, int yy, int zz){ x=xx; y=yy; z=zz; type=0; } }; template <class T> class Octree{ int x, y, z; int size; T* children[8]; public: ~Octree(){ for( int i=0; i<8; i++){ std::cout << "del:" << i << std::endl; delete children[i]; } } Octree(int xx, int yy, int zz, int size){ x=xx; y=yy; z=zz; size=size; for( int i=0; i<8; i++ ) children[i] = new T; } Octree(){ Octree(0, 0, 0, 10); } // place newchild in array at [i] void set_child(int i, T* newchild){ children[i] = newchild; } // return child at [i] T* get_child(int i){ return children[i]; } // place newchild at [i] and return the old [i] T* swap_child(int i, T* newchild){ T* p = children[i]; children[i] = newchild; return p; } }; int main(){ Octree< Octree<Block> > here; std::cout << "nothing seems to have broken" << std::endl; } Also, as for the problems with set_child, get_child and swap_child leading to possible memory leaks this will be solved as a wrapper class will either use get before set or use swap to get the old child and write this out to disk before freeing the memory itself. I am glad that it is not my memory management failing but rather another error. I have not made a copy and/or assignment operator yet as I was just testing the block tree out, I will almost certainly make them all private very soon. This version spits out -1073741819. Thank you all for your suggestions and I apologise for highjacking my own thread :$

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  • Syntax proposition

    - by Knowing me knowing you
    I wonder if syntax as follows would be helpful in your opinion as a code readability improvent and self-commenting of code: std::map<std::string name, std::vector<int> scores> myMap; In this example it clearly says and no other comment is needed, what for we are using myMap variable. Looking forward to your opinions.

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  • overloaded stream insetion operator with a vector

    - by julz666
    hi, i'm trying to write an overloaded stream insertion operator for a class who's only member is a vector. i dont really know what i'm doing. (lets make that clear) it's a vector of "Points" which is a struct containing two doubles. i figure what i want is to insert user input (a bunch of doubles) into a stream that i then send to a modifier method? i keep working off other stream insertion examples such as... std::ostream& operator<< (std::ostream& o, Fred const& fred) { return o << fred.i_; } but when i try a similar..... istream & operator >> (istream &inStream, Polygon &vertStr) { inStream >> ws; inStream >> vertStr.vertices; return inStream; } i get an error "no match for operator etc etc. if i leave off the .vertices it compiles but i figure it's not right? (vertices is the name of my vector ) and even if it is right, i dont actually know what syntax to use in my driver to use it? also not %100 on what my modifier method needs to look like. here's my Polygon class //header #ifndef POLYGON_H #define POLYGON_H #include "Segment.h" #include <vector> class Polygon { friend std::istream & operator >> (std::istream &inStream, Polygon &vertStr); public: //Constructor Polygon(const Point &theVerts); //Default Constructor Polygon(); //Copy Constructor Polygon(const Polygon &polyCopy); //Accessor/Modifier methods inline std::vector<Point> getVector() const {return vertices;} //Return number of Vector elements inline int sizeOfVect() const {return (int) vertices.capacity();} //add Point elements to vector inline void setVertices(const Point &theVerts){vertices.push_back (theVerts);} private: std::vector<Point> vertices; }; #endif //Body using namespace std; #include "Polygon.h" // Constructor Polygon::Polygon(const Point &theVerts) { vertices.push_back (theVerts); } //Copy Constructor Polygon::Polygon(const Polygon &polyCopy) { vertices = polyCopy.vertices; } //Default Constructor Polygon::Polygon(){} istream & operator >> (istream &inStream, Polygon &vertStr) { inStream >> ws; inStream >> vertStr; return inStream; } any help greatly appreciated, sorry to be so vague, a lecturer has just kind of given us a brief example of stream insertion then left us on our own thanks. oh i realise there are probably many other problems that need fixing

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  • Float compile-time calculation not happening?

    - by Klaim
    A little test program: #include <iostream> const float TEST_FLOAT = 1/60; const float TEST_A = 1; const float TEST_B = 60; const float TEST_C = TEST_A / TEST_B; int main() { std::cout << TEST_FLOAT << std::endl; std::cout << TEST_C << std::endl; std::cin.ignore(); return 0; } Result : 0 0.0166667 Tested on Visual Studio 2008 & 2010. I worked on other compilers that, if I remember well, made the first result like the second result. Now my memory could be wrong, but shouldn't TEST_FLOAT have the same value than TEST_C? If not, why? Is TEST_C value resolved at compile time or at runtime? I always assumed the former but now that I see those results I have some doubts...

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  • stl::map insert segmentation fault

    - by Jakub Czaplicki
    Why does this code stop with the segmentation fault : class MapFile { public: /* ... */ std::map <unsigned int, unsigned int> inToOut; }; bool SwitchMapFile::LoadMapFile( const wxString& fileName ) { /* ... */ inToOut.insert( std::make_pair(spmPort,fibreId) ); } but this one works fine : class MapFile { public: /* ... */ }; bool MapFile::LoadMapFile( const wxString& fileName ) { /* ... */ std::map <unsigned int, unsigned int> inToOut; inToOut.insert( std::make_pair(input,output) ); } ?

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  • Can anyone explain why my crypto++ decrypted file 16 bytes short?

    - by Tom Williams
    I suspect it might be too much to hope for, but can anyone with experience with crypto++ explain why the "decrypted.out" file created by main() is 16 characters short (which probably not coincidentally is the block size)? I think the issue must be in CryptStreamBuffer::GetNextChar(), but I've been staring at it and the crypto++ documentation for hours. Any other comments about how crummy or naive my std::streambuf implementation are also welcome ;-) And I've just noticed I'm missing some calls to delete so you don't have to tell me about those. Thanks, Tom // Runtime Includes #include <iostream> // Crypto++ Includes #include "aes.h" #include "modes.h" // xxx_Mode< > #include "filters.h" // StringSource and // StreamTransformation #include "files.h" using namespace std; class CryptStreamBuffer: public std::streambuf { public: CryptStreamBuffer(istream& encryptedInput, CryptoPP::StreamTransformation& c); CryptStreamBuffer(ostream& encryptedOutput, CryptoPP::StreamTransformation& c); protected: virtual int_type overflow(int_type ch = traits_type::eof()); virtual int_type uflow(); virtual int_type underflow(); virtual int_type pbackfail(int_type ch); virtual int sync(); private: int GetNextChar(); int m_NextChar; // Buffered character CryptoPP::StreamTransformationFilter* m_StreamTransformationFilter; CryptoPP::FileSource* m_Source; CryptoPP::FileSink* m_Sink; }; // class CryptStreamBuffer CryptStreamBuffer::CryptStreamBuffer(istream& encryptedInput, CryptoPP::StreamTransformation& c) : m_NextChar(traits_type::eof()), m_StreamTransformationFilter(0), m_Source(0), m_Sink(0) { m_StreamTransformationFilter = new CryptoPP::StreamTransformationFilter(c); m_Source = new CryptoPP::FileSource(encryptedInput, false, m_StreamTransformationFilter); } CryptStreamBuffer::CryptStreamBuffer(ostream& encryptedOutput, CryptoPP::StreamTransformation& c) : m_NextChar(traits_type::eof()), m_StreamTransformationFilter(0), m_Source(0), m_Sink(0) { m_Sink = new CryptoPP::FileSink(encryptedOutput); m_StreamTransformationFilter = new CryptoPP::StreamTransformationFilter(c, m_Sink); } CryptStreamBuffer::int_type CryptStreamBuffer::overflow(int_type ch) { return m_StreamTransformationFilter->Put((byte)ch); } CryptStreamBuffer::int_type CryptStreamBuffer::uflow() { int_type result = GetNextChar(); // Reset the buffered character m_NextChar = traits_type::eof(); return result; } CryptStreamBuffer::int_type CryptStreamBuffer::underflow() { return GetNextChar(); } CryptStreamBuffer::int_type CryptStreamBuffer::pbackfail(int_type ch) { return traits_type::eof(); } int CryptStreamBuffer::sync() { if (m_Sink) { m_StreamTransformationFilter->MessageEnd(); } } int CryptStreamBuffer::GetNextChar() { // If we have a buffered character do nothing if (m_NextChar != traits_type::eof()) { return m_NextChar; } // If there are no more bytes currently available then pump the source // *** I SUSPECT THE PROBLEM IS HERE *** if (m_StreamTransformationFilter->MaxRetrievable() == 0) { m_Source->Pump(1024); } // Retrieve the next byte byte nextByte; size_t noBytes = m_StreamTransformationFilter->Get(nextByte); if (0 == noBytes) { return traits_type::eof(); } // Buffer up the next character m_NextChar = nextByte; return m_NextChar; } void InitKey(byte key[]) { key[0] = -62; key[1] = 102; key[2] = 78; key[3] = 75; key[4] = -96; key[5] = 125; key[6] = 66; key[7] = 125; key[8] = -95; key[9] = -66; key[10] = 114; key[11] = 22; key[12] = 48; key[13] = 111; key[14] = -51; key[15] = 112; } void DecryptFile(const char* sourceFileName, const char* destFileName) { ifstream ifs(sourceFileName, ios::in | ios::binary); ofstream ofs(destFileName, ios::out | ios::binary); byte key[CryptoPP::AES::DEFAULT_KEYLENGTH]; InitKey(key); CryptoPP::ECB_Mode<CryptoPP::AES>::Decryption decryptor(key, sizeof(key)); if (ifs) { if (ofs) { CryptStreamBuffer cryptBuf(ifs, decryptor); std::istream decrypt(&cryptBuf); int c; while (EOF != (c = decrypt.get())) { ofs << (char)c; } ofs.flush(); } else { std::cerr << "Failed to open file '" << destFileName << "'." << endl; } } else { std::cerr << "Failed to open file '" << sourceFileName << "'." << endl; } } void EncryptFile(const char* sourceFileName, const char* destFileName) { ifstream ifs(sourceFileName, ios::in | ios::binary); ofstream ofs(destFileName, ios::out | ios::binary); byte key[CryptoPP::AES::DEFAULT_KEYLENGTH]; InitKey(key); CryptoPP::ECB_Mode<CryptoPP::AES>::Encryption encryptor(key, sizeof(key)); if (ifs) { if (ofs) { CryptStreamBuffer cryptBuf(ofs, encryptor); std::ostream encrypt(&cryptBuf); int c; while (EOF != (c = ifs.get())) { encrypt << (char)c; } encrypt.flush(); } else { std::cerr << "Failed to open file '" << destFileName << "'." << endl; } } else { std::cerr << "Failed to open file '" << sourceFileName << "'." << endl; } } int main(int argc, char* argv[]) { EncryptFile(argv[1], "encrypted.out"); DecryptFile("encrypted.out", "decrypted.out"); return 0; }

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  • g++ and c++0x specification support

    - by SepiDev
    although it's been said that the support for c++0x new features in g++ are in experimental mode, many gcc developer claimed that you can use most of the new features in your codes and get the program to work. but when I try to compile this simple program it results in segmentation fault. Why? #include <thread> #include <iostream> void my_thread_func() { std::cout<<"hello"<<std::endl; } int main() { std::thread t(my_thread_func); t.join(); } g++ -std=c++0x -Wall -o run main.cc

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  • Internal class and access to external members.

    - by Knowing me knowing you
    I always thought that internal class has access to all data in its external class but having code: template<class T> class Vector { template<class T> friend std::ostream& operator<<(std::ostream& out, const Vector<T>& obj); private: T** myData_; std::size_t myIndex_; std::size_t mySize_; public: Vector():myData_(nullptr), myIndex_(0), mySize_(0) { } Vector(const Vector<T>& pattern); void insert(const T&); Vector<T> makeUnion(const Vector<T>&)const; Vector<T> makeIntersection(const Vector<T>&)const; class Iterator : public std::iterator<std::bidirectional_iterator_tag,T> { private: T** itData_; public: Iterator()//<<<<<<<<<<<<<------------COMMENT { /*HERE I'M TRYING TO USE ANY MEMBER FROM Vector<T> AND I'M GETTING ERR SAYING: ILLEGAL CALL OF NON-STATIC MEMBER FUNCTION*/} Iterator(T** ty) { itData_ = ty; } Iterator operator++() { return ++itData_; } T operator*() { return *itData_[0]; } bool operator==(const Iterator& obj) { return *itData_ == *obj.itData_; } bool operator!=(const Iterator& obj) { return *itData_ != *obj.itData_; } bool operator<(const Iterator& obj) { return *itData_ < *obj.itData_; } }; typedef Iterator iterator; iterator begin()const { assert(mySize_ > 0); return myData_; } iterator end()const { return myData_ + myIndex_; } }; See line marked as COMMENT. So can I or I can't use members from external class while in internal class? Don't bother about naming, it's not a Vector it's a Set. Thank you.

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  • Unique_ptr compiler errors

    - by Godric Seer
    I am designing and entity-component system for a project, and C++ memory management is giving me a few issues. I just want to make sure my design is legitimate. So to start I have an Entity class which stores a vector of Components: class Entity { private: std::vector<std::unique_ptr<Component> > components; public: Entity() { }; void AddComponent(Component* component) { this -> components.push_back(std::unique_ptr<Component>(component)); } ~Entity(); }; Which if I am not mistaken means that when the destructor is called (even the default, compiler created one), the destructor for the Entity, will call ~components, which will call ~std::unique_ptr for each element in the vector, and lead to the destruction of each Component, which is what I want. The component class has virtual methods, but the important part is its constructor: Component::Component(Entity parent) { parent.addComponent(this) // I am not sure if this would work like I expect // Other things here } As long as passing this to the method works, this also does what I want. My confusion is in the factory. What I want to do is something along the lines of: std::shared_ptr<Entity> createEntity() { std::shared_ptr<Entity> entityPtr(new Entity()); new Component(*parent); // Initialize more, and other types of Components return entityPtr; } Now, I believe that this setup will leave the ownership of the Component in the hands of its Parent Entity, which is what I want. First a small question, do I need to pass the entity into the Component constructor by reference or pointer or something? If I understand C++, it would pass by value, which means it gets copied, and the copied entity would die at the end of the constructor. The second, and main question is that code based on this sample will not compile. The complete error is too large to print here, however I think I know somewhat of what is going on. The compiler's error says I can't delete an incomplete type. My Component class has a purely virtual destructor with an implementation: inline Component::~Component() { }; at the end of the header. However since the whole point is that Component is actually an interface. I know from here that a complete type is required for unique_ptr destruction. The question is, how do I work around this? For reference I am using gcc 4.4.6.

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  • unique_ptr boost equivalent?

    - by wowus
    Is there some equivalent class for C++1x's std::unique_ptr in the boost libraries? The behavior I'm looking for is being able to have an exception-safe factory function, like so... std::unique_ptr<Base> create_base() { return std::unique_ptr<Base>(new Derived); } void some_other_function() { std::unique_ptr<Base> b = create_base(); // Do some stuff with b that may or may not throw an exception... // Now b is destructed automagically. }

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  • C++ Using a class template argument as a template argument for another type

    - by toefel
    Hey Everyone, I'm having this problem while writing my own HashTable. It all works, but when I try to templatize the thing, it gave me errors. I recreated the problem as follows: THIS CODE WORKS: typedef double Item; class A { public: A() { v.push_back(pair<string, Item>("hey", 5.0)); } void iterate() { for(Iterator iter = v.begin(); iter != v.end(); ++iter) cout << iter->first << ", " << iter->second << endl; } private: vector<pair<string, double> > v; typedef vector< pair<string, double> >::iterator Iterator; }; THIS CODE DOES NOT: template<typename ValueType> class B { public: B(){} void iterate() { for(Iterator iter = v.begin(); iter != v.end(); ++iter) cout << iter->first << ", " << iter->second << endl; } private: vector<pair<string, ValueType> > v; typedef vector< pair<string, ValueType> >::iterator Iterator; }; the error messages: g++ -O0 -g3 -Wall -c -fmessage-length=0 -omain.o ..\main.cpp ..\main.cpp:50: error: type std::vector<std::pair<std::string, ValueType>, std::allocator<std::pair<std::string, ValueType> > >' is not derived from typeB' ..\main.cpp:50: error: ISO C++ forbids declaration of `iterator' with no type ..\main.cpp:50: error: expected `;' before "Iterator" ..\main.cpp: In member function `void B::iterate()': ..\main.cpp:44: error: `Iterator' was not declared in this scope ..\main.cpp:44: error: expected `;' before "iter" ..\main.cpp:44: error: `iter' was not declared in this scope Does anybody know why this is happening? Thanks!

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  • Why do bind1st and bind2nd require constant function objects?

    - by rlbond
    So, I was writing a C++ program which would allow me to take control of the entire world. I was all done writing the final translation unit, but I got an error: error C3848: expression having type 'const `anonymous-namespace'::ElementAccumulator<T,BinaryFunction>' would lose some const-volatile qualifiers in order to call 'void `anonymous-namespace'::ElementAccumulator<T,BinaryFunction>::operator ()(const point::Point &,const int &)' with [ T=SideCounter, BinaryFunction=std::plus<int> ] c:\program files (x86)\microsoft visual studio 9.0\vc\include\functional(324) : while compiling class template member function 'void std::binder2nd<_Fn2>::operator ()(point::Point &) const' with [ _Fn2=`anonymous-namespace'::ElementAccumulator<SideCounter,std::plus<int>> ] c:\users\****\documents\visual studio 2008\projects\TAKE_OVER_THE_WORLD\grid_divider.cpp(361) : see reference to class template instantiation 'std::binder2nd<_Fn2>' being compiled with [ _Fn2=`anonymous-namespace'::ElementAccumulator<SideCounter,std::plus<int>> ] I looked in the specifications of binder2nd and there it was: it took a const AdaptibleBinaryFunction. So, not a big deal, I thought. I just used boost::bind instead, right? Wrong! Now my take-over-the-world program takes too long to compile (bind is used inside a template which is instantiated quite a lot)! At this rate, my nemesis is going to take over the world first! I can't let that happen -- he uses Java! So can someone tell me why this design decision was made? It seems like an odd decision. I guess I'll have to make some of the elements of my class mutable for now...

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  • Sort CMap Key by String Length

    - by Yan Cheng CHEOK
    Previously, I am using STL map to perform the mentioned task. struct ltstr { bool operator()(std::string s1, std::string s2) const { const int l1 = s1.length(); const int l2 = s2.length(); if (l1 == l2) { // In alphabetical order. return s1.compare(s2) < 0; } // From longest length to shortest length. return l1 > l2; } }; std::map<std::string, int, ltstr> m; How can I perform the same task using CMap? // How to make key sorted by string length? CMap<CString, LPCTSTR, int, int> m;

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  • Why does the following not work?

    - by Dony
    Hi, I tried to make the code #1 more terse by changing it to code #2 but it doesn't work as expected. Can anyone please tell me why it doesn't work? Thanks. Code #1 std::ostringstream q0; q0 << "(" << x << "," << y << "," << z << ")"; std::string s = q0.str(); Code #2 double x = 8.9, y = 3.4, z = -4.5; std::string s = static_cast<std::ostringstream &>( std::ostringstream() << "(" << x << "," << y << "," << z << ")").str();

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  • Why is processing a sorted array faster than an unsorted array?

    - by GManNickG
    Here is a piece of code that shows some very peculiar performance. For some strange reason, sorting the data miraculously speeds up the code by almost 6x: #include <algorithm> #include <ctime> #include <iostream> int main() { // generate data const unsigned arraySize = 32768; int data[arraySize]; for (unsigned c = 0; c < arraySize; ++c) data[c] = std::rand() % 256; // !!! with this, the next loop runs faster std::sort(data, data + arraySize); // test clock_t start = clock(); long long sum = 0; for (unsigned i = 0; i < 100000; ++i) { // primary loop for (unsigned c = 0; c < arraySize; ++c) { if (data[c] >= 128) sum += data[c]; } } double elapsedTime = static_cast<double>(clock() - start) / CLOCKS_PER_SEC; std::cout << elapsedTime << std::endl; std::cout << "sum = " << sum << std::endl; } Without std::sort(data, data + arraySize);, the code runs in 11.54 seconds. With the sorted data, the code runs in 1.93 seconds. Initially I thought this might be just a language or compiler anomaly. So I tried it Java... import java.util.Arrays; import java.util.Random; public class Main { public static void main(String[] args) { // generate data int arraySize = 32768; int data[] = new int[arraySize]; Random rnd = new Random(0); for (int c = 0; c < arraySize; ++c) data[c] = rnd.nextInt() % 256; // !!! with this, the next loop runs faster Arrays.sort(data); // test long start = System.nanoTime(); long sum = 0; for (int i = 0; i < 100000; ++i) { // primary loop for (int c = 0; c < arraySize; ++c) { if (data[c] >= 128) sum += data[c]; } } System.out.println((System.nanoTime() - start) / 1000000000.0); System.out.println("sum = " + sum); } } with a similar but less extreme result. My first thought was that sorting brings the data into cache, but my next thought was how silly that is because the array was just generated. What is going on? Why is a sorted array faster than an unsorted array? The code is summing up some independent terms, the order should not matter.

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  • Illegal token on right side of ::

    - by Adam Haile
    I have the following template declaration: template <typename T> void IterTable(int& rIdx, std::vector<double>& rVarVector, const std::vector<T>& aTable, const T aValue, T aLowerBound = -(std::numeric_limits<T>::max()), //illegal token on right side of '::' shows here bool aLeftOpen = true) const; Which throws the illegal token error as noted, on the line with "-(std::numeric_limits::max())". I got this code from some old linux source that I'm trying to compile on Windows. Any idea what the issue is?

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  • getline() sets failbit and skips last line

    - by Thanatos
    I'm using std::getline() to enumerate through the lines in a file, and it's mostly working. It's left me curious however - std::getline() is skipping the very last line in my file, but only if it's blank. Using this minimal example: #include <iostream> #include <string> int main() { std::string line; while(std::getline(std::cin, line)) std::cout << "Line: “" << line << "”\n"; return 0; } If I feed it this: Line A Line B Line C I get those lines back at me. But this: Line A Line B Line C [* line is present but blank, ie, the file end is: "...B\nLine C\n" *] (I unfortunately can't have a blank line in SO's little code box thing...) So, first file has three lines ( ["Line A", "Line B", "Line C"] ), second file has four ( ["Line A", "Line B", "Line C", ""] ) This to me seems wrong - I have a four line file, and enumerating it with getline() leaves me with 3. What's really got me scratching my head is that this is exactly what the standard says it should do. (21.3.7.9) Even Python has similar behaviour (but it gives me the newlines too - C++ chops them off.) Is this some weird thing where C++ is expected lines to be terminated, and not separated by '\n', and I'm feeding it differently? Edit Clearly, I need to expand a bit here. I've met up with two philosophies of determining what a "line" in a file is: Lines are terminated by newlines - Dominant in systems such as Linux, and editors like vim. Possible to have a slightly "odd" file by not having a final '\n' (a "noeol" in vim). Impossible to have a blank line at the end of a file. Lines are separated by newlines - Dominant in just about every Windows editor I've ever come across. Every file is valid, and it's possible to have the last line be blank. Of course, YMMV as to what a newline is. I've always treated these as two completely different schools of thought. One earlier point I tried to make was to ask if the C++ standard was explicitly or merely implicitly following the first. (Curiously, where is Mac? terminated or separated?)

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