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  • Cheapest way of binding local variable to closure

    - by mmotorny
    I believe following to be a cheapest way of binding local variable to closure: void ByRValueReference(A&& a) { } std::function<void ()> CreateClosureByRValueReference() { A a; std::function<void ()> f = std::bind(&ByRValueReference, std::move(a)); // !!! return f; } However, it does not compile under Clang 3.1: error: no viable conversion from '__bind<void (*)(A &&), A>' to 'std::function<void ()>' and gcc 4.6.1: /usr/include/c++/4.6/functional:1778:2: error: no match for call to ‘(std::_Bind<void (*(A))(A&&)>) ()’ Am I violating the standard or it's just broken standard libraries?

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  • Can't insert a number into a C++ custom streambuf/ostream

    - by 0xbe5077ed
    I have written a custom std::basic_streambuf and std::basic_ostream because I want an output stream that I can get a JNI string from in a manner similar to how you can call std::ostringstream::str(). These classes are quite simple. namespace myns { class jni_utf16_streambuf : public std::basic_streambuf<char16_t> { JNIEnv * d_env; std::vector<char16_t> d_buf; virtual int_type overflow(int_type); public: jni_utf16_streambuf(JNIEnv *); jstring jstr() const; }; typedef std::basic_ostream<char16_t, std::char_traits<char16_t>> utf16_ostream; class jni_utf16_ostream : public utf16_ostream { jni_utf16_streambuf d_buf; public: jni_utf16_ostream(JNIEnv *); jstring jstr() const; }; // ... } // namespace myns In addition, I have made four overloads of operator<<, all in the same namespace: namespace myns { // ... utf16_ostream& operator<<(utf16_ostream&, jstring) throw(std::bad_cast); utf16_ostream& operator<<(utf16_ostream&, const char *); utf16_ostream& operator<<(utf16_ostream&, const jni_utf16_string_region&); jni_utf16_ostream& operator<<(jni_utf16_ostream&, jstring); // ... } // namespace myns The implementation of jni_utf16_streambuf::overflow(int_type) is trivial. It just doubles the buffer width, puts the requested character, and sets the base, put, and end pointers correctly. It is tested and I am quite sure it works. The jni_utf16_ostream works fine inserting unicode characters. For example, this works fine and results in the stream containing "hello, world": myns::jni_utf16_ostream o(env); o << u"hello, wor" << u'l' << u'd'; My problem is as soon as I try to insert an integer value, the stream's bad bit gets set, for example: myns::jni_utf16_ostream o(env); if (o.badbit()) throw "bad bit before"; // does not throw int32_t x(5); o << x; if (o.badbit()) throw "bad bit after"; // throws :( I don't understand why this is happening! Is there some other method on std::basic_streambuf I need to be implementing????

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  • Making a Wrapper class for ActiveMQ

    - by DarthVader
    I want to make a Wrapper class for ActiveMQ which will have only send and get functions. I want to wrap them in a static class. Users can use this client and send, get messages to the activemq instance. I want this process to be transparent. There are two classes in this link My only handicap is, i need to this in c++ and not sure where to start. I havent used c++ for ages and now not sure how I can create this wrapper class. I m giving it a try as follows: // .h file #include <stdlib.h> #include <iostream> using namespace std; class ActiveMQWrapper { public: static void send(std::string message); static std::string get(); }; // .cpp file #include<string> #include<iostream> #include "ActiveMQWrapper.h" void ActiveMQWrapper::send(std::string message){ std::cout<<message; } std::string ActiveMQWrapper::get(){ return "test"; } // test file #include <string> #include <iostream> #include "ActiveMQWrapper.h" int main() { std::string foo ="test"; ActiveMQWrapper::send(foo); std::cout<<ActiveMQWrapper::get(); return 1; } When I added the following to .h file, hell breaks loose. Do you think I should seperate this impl to a factory and initialize and instance and return to the wrapper above? How do i deal with all the dependencies? private: Connection* connection; Session* session; Destination* destination; MessageProducer* producer; int numMessages; bool useTopic; bool sessionTransacted; std::string brokerURI; and the header files, i get several messages as errors, which complains about the path. How can i get this correct? I eventually want to build a Factory, get an instance and send or get the messages to the queue. is there a code sample i can look into to get this right? essential i want to use the functionality of only this producer and consumer. Edit: I understand there is no such thing as static class in C++ . This is my reference.

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  • Why isn't the compiler smarter in this const function overloading problem?

    - by Frank
    The following code does not compile: #include <iostream> class Foo { std::string s; public: const std::string& GetString() const { return s; } std::string* GetString() { return &s; } }; int main(int argc, char** argv){ Foo foo; const std::string& s = foo.GetString(); // error return 0; } I get the following error: const1.cc:11: error: invalid initialization of reference of type 'const std::string&' from expression of type 'std::string* It does make some sense because foo is not of type const Foo, but just Foo, so the compiler wants to use the non-const function. But still, why can't it recognize that I want to call the const GetString function, by looking at the (type of) variable I assign it to? I found this kind of surprising.

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  • xutility file???

    - by user574290
    Hi all. I'm trying to use c code with opencv in face detection and counting, but I cannot build the source. I am trying to compile my project and I am having a lot of problems with a line in the xutility file. the error message show that it error with xutility file. Please help me, how to solve this problem? this is my code // Include header files #include "stdafx.h" #include "cv.h" #include "highgui.h" #include <stdio.h> #include <stdlib.h> #include <string.h> #include <assert.h> #include <math.h> #include <float.h> #include <limits.h> #include <time.h> #include <ctype.h> #include <iostream> #include <fstream> #include <vector> using namespace std; #ifdef _EiC #define WIN32 #endif int countfaces=0; int numFaces = 0; int k=0 ; int list=0; char filelist[512][512]; int timeCount = 0; static CvMemStorage* storage = 0; static CvHaarClassifierCascade* cascade = 0; void detect_and_draw( IplImage* image ); void WriteInDB(); int found_face(IplImage* img,CvPoint pt1,CvPoint pt2); int load_DB(char * filename); const char* cascade_name = "C:\\Program Files\\OpenCV\\OpenCV2.1\\data\\haarcascades\\haarcascade_frontalface_alt_tree.xml"; // BEGIN NEW CODE #define WRITEVIDEO char* outputVideo = "c:\\face_counting1_tracked.avi"; //int faceCount = 0; int posBuffer = 100; int persistDuration = 10; //faces can drop out for 10 frames int timestamp = 0; float sameFaceDistThreshold = 30; //pixel distance CvPoint facePositions[100]; int facePositionsTimestamp[100]; float distance( CvPoint a, CvPoint b ) { float dist = sqrt(float ( (a.x-b.x)*(a.x-b.x) + (a.y-b.y)*(a.y-b.y) ) ); return dist; } void expirePositions() { for (int i = 0; i < posBuffer; i++) { if (facePositionsTimestamp[i] <= (timestamp - persistDuration)) //if a tracked pos is older than three frames { facePositions[i] = cvPoint(999,999); } } } void updateCounter(CvPoint center) { bool newFace = true; for(int i = 0; i < posBuffer; i++) { if (distance(center, facePositions[i]) < sameFaceDistThreshold) { facePositions[i] = center; facePositionsTimestamp[i] = timestamp; newFace = false; break; } } if(newFace) { //push out oldest tracker for(int i = 1; i < posBuffer; i++) { facePositions[i] = facePositions[i - 1]; } //put new tracked position on top of stack facePositions[0] = center; facePositionsTimestamp[0] = timestamp; countfaces++; } } void drawCounter(IplImage* image) { // Create Font char buffer[5]; CvFont font; cvInitFont(&font, CV_FONT_HERSHEY_SIMPLEX, .5, .5, 0, 1); cvPutText(image, "Faces:", cvPoint(20, 20), &font, CV_RGB(0,255,0)); cvPutText(image, itoa(countfaces, buffer, 10), cvPoint(80, 20), &font, CV_RGB(0,255,0)); } #ifdef WRITEVIDEO CvVideoWriter* videoWriter = cvCreateVideoWriter(outputVideo, -1, 30, cvSize(240, 180)); #endif //END NEW CODE int main( int argc, char** argv ) { CvCapture* capture = 0; IplImage *frame, *frame_copy = 0; int optlen = strlen("--cascade="); const char* input_name; if( argc > 1 && strncmp( argv[1], "--cascade=", optlen ) == 0 ) { cascade_name = argv[1] + optlen; input_name = argc > 2 ? argv[2] : 0; } else { cascade_name = "C:\\Program Files\\OpenCV\\OpenCV2.1\\data\\haarcascades\\haarcascade_frontalface_alt_tree.xml"; input_name = argc > 1 ? argv[1] : 0; } cascade = (CvHaarClassifierCascade*)cvLoad( cascade_name, 0, 0, 0 ); if( !cascade ) { fprintf( stderr, "ERROR: Could not load classifier cascade\n" ); fprintf( stderr, "Usage: facedetect --cascade=\"<cascade_path>\" [filename|camera_index]\n" ); return -1; } storage = cvCreateMemStorage(0); //if( !input_name || (isdigit(input_name[0]) && input_name[1] == '\0') ) // capture = cvCaptureFromCAM( !input_name ? 0 : input_name[0] - '0' ); //else capture = cvCaptureFromAVI( "c:\\face_counting1.avi" ); cvNamedWindow( "result", 1 ); if( capture ) { for(;;) { if( !cvGrabFrame( capture )) break; frame = cvRetrieveFrame( capture ); if( !frame ) break; if( !frame_copy ) frame_copy = cvCreateImage( cvSize(frame->width,frame->height), IPL_DEPTH_8U, frame->nChannels ); if( frame->origin == IPL_ORIGIN_TL ) cvCopy( frame, frame_copy, 0 ); else cvFlip( frame, frame_copy, 0 ); detect_and_draw( frame_copy ); if( cvWaitKey( 30 ) >= 0 ) break; } cvReleaseImage( &frame_copy ); cvReleaseCapture( &capture ); } else { if( !input_name || (isdigit(input_name[0]) && input_name[1] == '\0')) cvNamedWindow( "result", 1 ); const char* filename = input_name ? input_name : (char*)"lena.jpg"; IplImage* image = cvLoadImage( filename, 1 ); if( image ) { detect_and_draw( image ); cvWaitKey(0); cvReleaseImage( &image ); } else { /* assume it is a text file containing the list of the image filenames to be processed - one per line */ FILE* f = fopen( filename, "rt" ); if( f ) { char buf[1000+1]; while( fgets( buf, 1000, f ) ) { int len = (int)strlen(buf); while( len > 0 && isspace(buf[len-1]) ) len--; buf[len] = '\0'; image = cvLoadImage( buf, 1 ); if( image ) { detect_and_draw( image ); cvWaitKey(0); cvReleaseImage( &image ); } } fclose(f); } } } cvDestroyWindow("result"); #ifdef WRITEVIDEO cvReleaseVideoWriter(&videoWriter); #endif return 0; } void detect_and_draw( IplImage* img ) { static CvScalar colors[] = { {{0,0,255}}, {{0,128,255}}, {{0,255,255}}, {{0,255,0}}, {{255,128,0}}, {{255,255,0}}, {{255,0,0}}, {{255,0,255}} }; double scale = 1.3; IplImage* gray = cvCreateImage( cvSize(img->width,img->height), 8, 1 ); IplImage* small_img = cvCreateImage( cvSize( cvRound (img->width/scale), cvRound (img->height/scale)), 8, 1 ); CvPoint pt1, pt2; int i; cvCvtColor( img, gray, CV_BGR2GRAY ); cvResize( gray, small_img, CV_INTER_LINEAR ); cvEqualizeHist( small_img, small_img ); cvClearMemStorage( storage ); if( cascade ) { double t = (double)cvGetTickCount(); CvSeq* faces = cvHaarDetectObjects( small_img, cascade, storage, 1.1, 2, 0/*CV_HAAR_DO_CANNY_PRUNING*/, cvSize(30, 30) ); t = (double)cvGetTickCount() - t; printf( "detection time = %gms\n", t/((double)cvGetTickFrequency()*1000.) ); if (faces) { //To save the detected faces into separate images, here's a quick and dirty code: char filename[6]; for( i = 0; i < (faces ? faces->total : 0); i++ ) { /* CvRect* r = (CvRect*)cvGetSeqElem( faces, i ); CvPoint center; int radius; center.x = cvRound((r->x + r->width*0.5)*scale); center.y = cvRound((r->y + r->height*0.5)*scale); radius = cvRound((r->width + r->height)*0.25*scale); cvCircle( img, center, radius, colors[i%8], 3, 8, 0 );*/ // Create a new rectangle for drawing the face CvRect* r = (CvRect*)cvGetSeqElem( faces, i ); // Find the dimensions of the face,and scale it if necessary pt1.x = r->x*scale; pt2.x = (r->x+r->width)*scale; pt1.y = r->y*scale; pt2.y = (r->y+r->height)*scale; // Draw the rectangle in the input image cvRectangle( img, pt1, pt2, CV_RGB(255,0,0), 3, 8, 0 ); CvPoint center; int radius; center.x = cvRound((r->x + r->width*0.5)*scale); center.y = cvRound((r->y + r->height*0.5)*scale); radius = cvRound((r->width + r->height)*0.25*scale); cvCircle( img, center, radius, CV_RGB(255,0,0), 3, 8, 0 ); //update counter updateCounter(center); int y=found_face(img,pt1,pt2); if(y==0) countfaces++; }//end for printf("Number of detected faces: %d\t",countfaces); }//end if //delete old track positions from facePositions array expirePositions(); timestamp++; //draw counter drawCounter(img); #ifdef WRITEVIDEO cvWriteFrame(videoWriter, img); #endif cvShowImage( "result", img ); cvDestroyWindow("Result"); cvReleaseImage( &gray ); cvReleaseImage( &small_img ); }//end if } //end void int found_face(IplImage* img,CvPoint pt1,CvPoint pt2) { /*if (faces) {*/ CvSeq* faces = cvHaarDetectObjects( img, cascade, storage, 1.1, 2, CV_HAAR_DO_CANNY_PRUNING, cvSize(40, 40) ); int i=0; char filename[512]; for( i = 0; i < (faces ? faces->total : 0); i++ ) {//int scale = 1, i=0; //i=iface; //char filename[512]; /* extract the rectanlges only */ // CvRect face_rect = *(CvRect*)cvGetSeqElem( faces, i); CvRect face_rect = *(CvRect*)cvGetSeqElem( faces, i); //IplImage* gray_img = cvCreateImage( cvGetSize(img), IPL_DEPTH_8U, 1 ); IplImage* clone = cvCreateImage (cvSize(img->width, img->height), IPL_DEPTH_8U, img->nChannels ); IplImage* gray = cvCreateImage (cvSize(img->width, img->height), IPL_DEPTH_8U, 1 ); cvCopy (img, clone, 0); cvNamedWindow ("ROI", CV_WINDOW_AUTOSIZE); cvCvtColor( clone, gray, CV_RGB2GRAY ); face_rect.x = pt1.x; face_rect.y = pt1.y; face_rect.width = abs(pt1.x - pt2.x); face_rect.height = abs(pt1.y - pt2.y); cvSetImageROI ( gray, face_rect); //// * rectangle = cvGetImageROI ( clone ); face_rect = cvGetImageROI ( gray ); cvShowImage ("ROI", gray); k++; char *name=0; name=(char*) calloc(512, 1); sprintf(name, "Image%d.pgm", k); cvSaveImage(name, gray); //////////////// for(int j=0;j<512;j++) filelist[list][j]=name[j]; list++; WriteInDB(); //int found=SIFT("result.txt",name); cvResetImageROI( gray ); //return found; return 0; // }//end if }//end for }//end void void WriteInDB() { ofstream myfile; myfile.open ("result.txt"); for(int i=0;i<512;i++) { if(strcmp(filelist[i],"")!=0) myfile << filelist[i]<<"\n"; } myfile.close(); } Error 3 error C4430: missing type specifier - int assumed. Note: C++ does not support default-int Error 8 error C4430: missing type specifier - int assumed. Note: C++ does not support default-int Error 13 error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 9.0\vc\include\xutility 766 Error 18 error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 9.0\vc\include\xutility 768 Error 23 error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\program files\microsoft visual studio 9.0\vc\include\xutility 769 Error 10 error C2868: 'std::iterator_traits<_Iter>::value_type' : illegal syntax for using-declaration; expected qualified-name c:\program files\microsoft visual studio 9.0\vc\include\xutility 765 Error 25 error C2868: 'std::iterator_traits<_Iter>::reference' : illegal syntax for using-declaration; expected qualified-name c:\program files\microsoft visual studio 9.0\vc\include\xutility 769 Error 20 error C2868: 'std::iterator_traits<_Iter>::pointer' : illegal syntax for using-declaration; expected qualified-name c:\program files\microsoft visual studio 9.0\vc\include\xutility 768 Error 5 error C2868: 'std::iterator_traits<_Iter>::iterator_category' : illegal syntax for using-declaration; expected qualified-name c:\program files\microsoft visual studio 9.0\vc\include\xutility 764 Error 15 error C2868: 'std::iterator_traits<_Iter>::difference_type' : illegal syntax for using-declaration; expected qualified-name c:\program files\microsoft visual studio 9.0\vc\include\xutility 766 Error 9 error C2602: 'std::iterator_traits<_Iter>::value_type' is not a member of a base class of 'std::iterator_traits<_Iter>' c:\program files\microsoft visual studio 9.0\vc\include\xutility 765 Error 24 error C2602: 'std::iterator_traits<_Iter>::reference' is not a member of a base class of 'std::iterator_traits<_Iter>' c:\program files\microsoft visual studio 9.0\vc\include\xutility 769 Error 19 error C2602: 'std::iterator_traits<_Iter>::pointer' is not a member of a base class of 'std::iterator_traits<_Iter>' c:\program files\microsoft visual studio 9.0\vc\include\xutility 768 Error 4 error C2602: 'std::iterator_traits<_Iter>::iterator_category' is not a member of a base class of 'std::iterator_traits<_Iter>' c:\program files\microsoft visual studio 9.0\vc\include\xutility 764 Error 14 error C2602: 'std::iterator_traits<_Iter>::difference_type' is not a member of a base class of 'std::iterator_traits<_Iter>' c:\program files\microsoft visual studio 9.0\vc\include\xutility 766 Error 7 error C2146: syntax error : missing ';' before identifier 'value_type' c:\program files\microsoft visual studio 9.0\vc\include\xutility 765 Error 22 error C2146: syntax error : missing ';' before identifier 'reference' c:\program files\microsoft visual studio 9.0\vc\include\xutility 769 Error 17 error C2146: syntax error : missing ';' before identifier 'pointer' c:\program files\microsoft visual studio 9.0\vc\include\xutility 768 Error 2 error C2146: syntax error : missing ';' before identifier 'iterator_category' c:\program files\microsoft visual studio 9.0\vc\include\xutility 764 Error 12 error C2146: syntax error : missing ';' before identifier 'difference_type' c:\program files\microsoft visual studio 9.0\vc\include\xutility 766 Error 6 error C2039: 'value_type' : is not a member of 'CvPoint' c:\program files\microsoft visual studio 9.0\vc\include\xutility 765 Error 21 error C2039: 'reference' : is not a member of 'CvPoint' c:\program files\microsoft visual studio 9.0\vc\include\xutility 769 Error 16 error C2039: 'pointer' : is not a member of 'CvPoint' c:\program files\microsoft visual studio 9.0\vc\include\xutility 768 Error 1 error C2039: 'iterator_category' : is not a member of 'CvPoint' c:\program files\microsoft visual studio 9.0\vc\include\xutility 764 Error 11 error C2039: 'difference_type' : is not a member of 'CvPoint' c:\program files\microsoft visual studio 9.0\vc\include\xutility 766

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  • Can't figure out where race condition is occuring

    - by Nik
    I'm using Valgrind --tool=drd to check my application that uses Boost::thread. Basically, the application populates a set of "Book" values with "Kehai" values based on inputs through a socket connection. On a seperate thread, a user can connect and get the books send to them. Its fairly simple, so i figured using a boost::mutex::scoped_lock on the location that serializes the book and the location that clears out the book data should be suffice to prevent any race conditions. Here is the code: void Book::clear() { boost::mutex::scoped_lock lock(dataMutex); for(int i =NUM_KEHAI-1; i >= 0; --i) { bid[i].clear(); ask[i].clear(); } } int Book::copyChangedKehaiToString(char* dst) const { boost::mutex::scoped_lock lock(dataMutex); sprintf(dst, "%-4s%-13s",market.c_str(),meigara.c_str()); int loc = 17; for(int i = 0; i < Book::NUM_KEHAI; ++i) { if(ask[i].changed > 0) { sprintf(dst+loc,"A%i%-21s%-21s%-21s%-8s%-4s",i,ask[i].price.c_str(),ask[i].volume.c_str(),ask[i].number.c_str(),ask[i].postTime.c_str(),ask[i].status.c_str()); loc += 77; } } for(int i = 0; i < Book::NUM_KEHAI; ++i) { if(bid[i].changed > 0) { sprintf(dst+loc,"B%i%-21s%-21s%-21s%-8s%-4s",i,bid[i].price.c_str(),bid[i].volume.c_str(),bid[i].number.c_str(),bid[i].postTime.c_str(),bid[i].status.c_str()); loc += 77; } } return loc; } The clear() function and the copyChangedKehaiToString() function are called in the datagetting thread and data sending thread,respectively. Also, as a note, the class Book: struct Book { private: Book(const Book&); Book& operator=(const Book&); public: static const int NUM_KEHAI=10; struct Kehai; friend struct Book::Kehai; struct Kehai { private: Kehai& operator=(const Kehai&); public: std::string price; std::string volume; std::string number; std::string postTime; std::string status; int changed; Kehai(); void copyFrom(const Kehai& other); Kehai(const Kehai& other); inline void clear() { price.assign(""); volume.assign(""); number.assign(""); postTime.assign(""); status.assign(""); changed = -1; } }; std::vector<Kehai> bid; std::vector<Kehai> ask; tm recTime; mutable boost::mutex dataMutex; Book(); void clear(); int copyChangedKehaiToString(char * dst) const; }; When using valgrind --tool=drd, i get race condition errors such as the one below: ==26330== Conflicting store by thread 1 at 0x0658fbb0 size 4 ==26330== at 0x653AE68: std::string::_M_mutate(unsigned int, unsigned int, unsigned int) (in /usr/lib/libstdc++.so.6.0.8) ==26330== by 0x653AFC9: std::string::_M_replace_safe(unsigned int, unsigned int, char const*, unsigned int) (in /usr/lib/libstdc++.so.6.0.8) ==26330== by 0x653B064: std::string::assign(char const*, unsigned int) (in /usr/lib/libstdc++.so.6.0.8) ==26330== by 0x653B134: std::string::assign(char const*) (in /usr/lib/libstdc++.so.6.0.8) ==26330== by 0x8055D64: Book::Kehai::clear() (Book.h:50) ==26330== by 0x8094A29: Book::clear() (Book.cpp:78) ==26330== by 0x808537E: RealKernel::start() (RealKernel.cpp:86) ==26330== by 0x804D15A: main (main.cpp:164) ==26330== Allocation context: BSS section of /usr/lib/libstdc++.so.6.0.8 ==26330== Other segment start (thread 2) ==26330== at 0x400BB59: pthread_mutex_unlock (drd_pthread_intercepts.c:633) ==26330== by 0xC59565: pthread_mutex_unlock (in /lib/libc-2.5.so) ==26330== by 0x805477C: boost::mutex::unlock() (mutex.hpp:56) ==26330== by 0x80547C9: boost::unique_lock<boost::mutex>::~unique_lock() (locks.hpp:340) ==26330== by 0x80949BA: Book::copyChangedKehaiToString(char*) const (Book.cpp:134) ==26330== by 0x80937EE: BookSerializer::serializeBook(Book const&, std::string const&) (BookSerializer.cpp:41) ==26330== by 0x8092D05: BookSnapshotManager::getSnaphotDataList() (BookSnapshotManager.cpp:72) ==26330== by 0x8088179: SnapshotServer::getDataList() (SnapshotServer.cpp:246) ==26330== by 0x808870F: SnapshotServer::run() (SnapshotServer.cpp:183) ==26330== by 0x808BAF5: boost::_mfi::mf0<void, RealThread>::operator()(RealThread*) const (mem_fn_template.hpp:49) ==26330== by 0x808BB4D: void boost::_bi::list1<boost::_bi::value<RealThread*> >::operator()<boost::_mfi::mf0<void, RealThread>, boost::_bi::list0>(boost::_bi::type<void>, boost::_mfi::mf0<void, RealThread>&, boost::_bi::list0&, int) (bind.hpp:253) ==26330== by 0x808BB90: boost::_bi::bind_t<void, boost::_mfi::mf0<void, RealThread>, boost::_bi::list1<boost::_bi::value<RealThread*> > >::operator()() (bind_template.hpp:20) ==26330== Other segment end (thread 2) ==26330== at 0x400B62A: pthread_mutex_lock (drd_pthread_intercepts.c:580) ==26330== by 0xC59535: pthread_mutex_lock (in /lib/libc-2.5.so) ==26330== by 0x80546B8: boost::mutex::lock() (mutex.hpp:51) ==26330== by 0x805473B: boost::unique_lock<boost::mutex>::lock() (locks.hpp:349) ==26330== by 0x8054769: boost::unique_lock<boost::mutex>::unique_lock(boost::mutex&) (locks.hpp:227) ==26330== by 0x8094711: Book::copyChangedKehaiToString(char*) const (Book.cpp:113) ==26330== by 0x80937EE: BookSerializer::serializeBook(Book const&, std::string const&) (BookSerializer.cpp:41) ==26330== by 0x808870F: SnapshotServer::run() (SnapshotServer.cpp:183) ==26330== by 0x808BAF5: boost::_mfi::mf0<void, RealThread>::operator()(RealThread*) const (mem_fn_template.hpp:49) ==26330== by 0x808BB4D: void boost::_bi::list1<boost::_bi::value<RealThread*> >::operator()<boost::_mfi::mf0<void, RealThread>, boost::_bi::list0>(boost::_bi::type<void>, boost::_mfi::mf0<void, RealThread>&, boost::_bi::list0&, int) (bind.hpp:253) For the life of me, i can't figure out where the race condition is. As far as I can tell, clearing the kehai is done only after having taken the mutex, and the same holds true with copying it to a string. Does anyone have any ideas what could be causing this, or where I should look? Thank you kindly.

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  • Trouble passing a template function as an argument to another function in C++

    - by Darel
    Source of the problem -Accelerated C++, problem 8-5 I've written a small program that examines lines of string input, and tallies the number of times a word appears on a given line. The following code accomplishes this: #include <map> #include <iostream> #include <string> #include <vector> #include <list> #include <cctype> #include <iterator> using std::vector; using std::string; using std::cin; using std::cout; using std::endl; using std::getline; using std::istream; using std::string; using std::list; using std::map; using std::isspace; using std::ostream_iterator; using std::allocator; inline void keep_window_open() { cin.clear(); cout << "Please enter EOF to exit\n"; char ch; cin >> ch; return; } template <class Out> void split(const string& s, Out os) { vector<string> ret; typedef string::size_type string_size; string_size i = 0; // invariant: we have processed characters `['original value of `i', `i)' while (i != s.size()) { // ignore leading blanks // invariant: characters in range `['original `i', current `i)' are all spaces while (i != s.size() && isspace(s[i])) ++i; // find end of next word string_size j = i; // invariant: none of the characters in range `['original `j', current `j)' is a space while (j != s.size() && !isspace(s[j])) ++j; // if we found some nonwhitespace characters if (i != j) { // copy from `s' starting at `i' and taking `j' `\-' `i' chars *os++ = (s.substr(i, j - i)); i = j; } } } // find all the lines that refer to each word in the input map<string, vector<int> > xref(istream& in) // works // now try to pass the template function as an argument to function - what do i put for templated type? //map<string, vector<int> > xref(istream& in, void find_words(vector<string, typedef Out) = split) #LINE 1# { string line; int line_number = 0; map<string, vector<int> > ret; // read the next line while (getline(in, line)) { ++line_number; // break the input line into words vector<string> words; // works // #LINE 2# split(line, back_inserter(words)); // #LINE 3# //find_words(line, back_inserter(words)); // #LINE 4# attempting to use find_words as an argument to function // remember that each word occurs on the current line for (vector<string>::const_iterator it = words.begin(); it != words.end(); ++it) ret[*it].push_back(line_number); } return ret; } int main() { cout << endl << "Enter lines of text, followed by EOF (^Z):" << endl; // call `xref' using `split' by default map<string, vector<int> > ret = xref(cin); // write the results for (map<string, vector<int> >::const_iterator it = ret.begin(); it != ret.end(); ++it) { // write the word cout << it->first << " occurs on line(s): "; // followed by one or more line numbers vector<int>::const_iterator line_it = it->second.begin(); cout << *line_it; // write the first line number ++line_it; // write the rest of the line numbers, if any while (line_it != it->second.end()) { cout << ", " << *line_it; ++line_it; } // write a new line to separate each word from the next cout << endl; } keep_window_open(); return 0; } As you can see, the split function is a template function to handle various types of output iterators as desired. My problem comes when I try to generalize the xref function by passing in the templated split function as an argument. I can't seem to get the type correct. So my question is, can you pass a template function to another function as an argument, and if so, do you have to declare all types before passing it? Or can the compiler infer the types from the way the templated function is used in the body? To demonstrate the errors I get, comment out the existing xref function header, and uncomment the alternate header I'm trying to get working (just below the following commment line.) Also comment the lines tagged LINE 2 and LINE 3 and uncomment LINE 4, which is attempting to use the argument find_words (which defaults to split.) Thanks for any feedback!

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  • Achieving forward compatibility with C++11

    - by mcmcc
    I work on a large software application that must run on several platforms. Some of these platforms support some features of C++11 (e.g. MSVS 2010) and some don't support any (e.g. GCC 4.3.x). I see this situation continuing on for several years (my best guess: 3-5 years). Given that, I would like set up a compatibility interface such that (to whatever degree possible) people can write C++11 code that will still compile with older compilers with a minimum of maintenance. Overall, the goal is to minimize #ifdef's as much as reasonably possible while still enabling basic C++11 syntax/features on the platforms that support them, and provide emulation on the platforms that don't. Let's start with std::move(). The most obvious way to achieve compatibility would be to put something like this in a common header file: #if !defined(HAS_STD_MOVE) namespace std { // C++11 emulation template <typename T> inline T& move(T& v) { return v; } template <typename T> inline const T& move(const T& v) { return v; } } #endif // !defined(HAS_STD_MOVE) This allow people to write things like std::vector<Thing> x = std::move(y); ... with impugnity. It does what they want in C++11 and it does the best it can in C++03. When we finally drop the last of the C++03 compilers, this code can remain as is. However, according to the standard, it is illegal to inject new symbols into the std namespace. That's the theory. My question is, practically speaking, is there any harm in doing this as a way of achieving forward compatibility?

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  • Why isn't my lighting working properly? Are my normals messed up?

    - by Radek Slupik
    I'm relatively new to OpenGL and I am trying to draw a 3D model (loaded from a 3ds file using lib3ds) using OpenGL with lighting, but about half of it is drawn in black. I set up the light as such: glEnable(GL_LIGHTING); glShadeModel(GL_SMOOTH); GLfloat ambientColor[] = {0.2f, 0.2f, 0.2f, 1.0f}; glLightModelfv(GL_LIGHT_MODEL_AMBIENT, ambientColor); glEnable(GL_LIGHT0); GLfloat lightColor0[] = {1.0f, 1.0f, 1.0f, 1.0f}; GLfloat lightPos0[] = {4.0f, 0.0f, 8.0f, 0.0f}; glLightfv(GL_LIGHT0, GL_DIFFUSE, lightColor0); glLightfv(GL_LIGHT0, GL_POSITION, lightPos0); The model is in a VBO and drawn using glDrawArrays. The normals are in a separate VBO, and the normals are calculated using lib3ds_mesh_calculate_vertex_normals: std::vector<std::array<float, 3>> normals; for (std::size_t i = 0; i < model->nmeshes; ++i) { auto& mesh = *model->meshes[i]; std::vector<float[3]> vertex_normals(mesh.nfaces * 3); lib3ds_mesh_calculate_vertex_normals(&mesh, vertex_normals.data()); for (std::size_t j = 0; j < mesh.nfaces; ++j) { auto& face = mesh.faces[j]; normals.push_back(make_array(vertex_normals[j])); } } glBindBuffer(GL_ARRAY_BUFFER, normal_vbo_); glBufferData(GL_ARRAY_BUFFER, normals.size() * sizeof(decltype(normals)::value_type), normals.data(), GL_STATIC_DRAW); The problem isn't the vertices; the model is drawn correctly when drawing it as a wireframe. I also fixed the normals in Blender using controlN. What could be the problem? Should I store the normals in a different order?

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  • Is this Ubuntu One DBus signal connection code correct?

    - by Chris Wilson
    This is my first time using DBus so I'm not entirely sure if I'm going about this the right way. I'm attempting to connect the the Ubuntu One DBus service and obtain login credentials for my app, however the slots I've connected to the DBus return signals detailed here never seem to be firing, despite a positive result being returned during the connection. Before I start looking for errors in the details relating to this specific service, could someone please tell me if this code would even work in the first place, or if I'm done something wrong here? int main() { UbuntuOneDBus *u1Dbus = new UbuntuOneDBus; if( u1Dbus->init() ){ qDebug() << "Message queued"; } } UbuntuOneDBus::UbuntuOneDBus() { service = "com.ubuntuone.Credentials"; path = "/credentials"; interface = "com.ubuntuone.CredentialsManagement"; method = "register"; signature = "a{ss} (Dict of {String, String})"; connectReturnSignals(); } bool UbuntuOneDBus::init() { QDBusMessage message = QDBusMessage::createMethodCall( service, path, interface, method ); bool queued = QDBusConnection::sessionBus().send( message ); return queued; } void UbuntuOneDBus::connectReturnSignals() { bool connectionSuccessful = false; connectionSuccessful = QDBusConnection::sessionBus().connect( service, path, interface, "CredentialsFound", "a{ss} (Dict of {String, String})", this, SLOT( credentialsFound() ) ); if( ! connectionSuccessful ) qDebug() << "Connection to DBus::CredentialsFound signal failed"; connectionSuccessful = QDBusConnection::systemBus().connect( service, path, interface, "CredentialsNotFound", "(nothing)", this, SLOT( credentialsNotFound() ) ); if( ! connectionSuccessful ) qDebug() << "Connection to DBus::CredentialsNotFound signal failed"; connectionSuccessful = QDBusConnection::systemBus().connect( service, path, interface, "CredentialsError", "a{ss} (Dict of {String, String})", this, SLOT( credential if( ! connectionSuccessful ) qDebug() << "Connection to DBus::CredentialsError signal failed"; } void UbuntuOneDBus::credentialsFound() { std::cout << "Credentials found" << std::endl; } void UbuntuOneDBus::credentialsNotFound() { std::cout << "Credentials not found" << std::endl; } void UbuntuOneDBus::credentialsError() { std::cout << "Credentials error" << std::endl; }

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  • Does putting types/functions inside namespace make compiler's parsing work easy?

    - by iammilind
    Retaining the names inside namespace will make compiler work less stressful!? For example: // test.cpp #include</*iostream,vector,string,map*/> class vec { /* ... */ }; Take 2 scenarios of main(): // scenario-1 using namespace std; // comment this line for scenario-2 int main () { vec obj; } For scenario-1 where using namespace std;, several type names from namespace std will come into global scope. Thus compiler will have to check against vec if any of the type is colliding with it. If it does then generate error. In scenario-2 where there is no using namespace, compiler just have to check vec with std, because that's the only symbol in global scope. I am interested to know that, shouldn't it make the compiler little faster ?

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  • Making an asynchronous Client with boost::asio

    - by tag
    Hello, i'm trying to make an asynchronous Client with boost::asio, i use the daytime asynchronous Server(in the tutorial). However sometimes the Client don't receive the Message, sometimes it do :O I'm sorry if this is too much Code, but i don't know what's wrong :/ Client: #include <iostream> #include <stdio.h> #include <ostream> #include <boost/thread.hpp> #include <boost/bind.hpp> #include <boost/array.hpp> #include <boost/asio.hpp> using namespace std; using boost::asio::ip::tcp; class TCPClient { public: TCPClient(boost::asio::io_service& IO_Service, tcp::resolver::iterator EndPointIter); void Write(); void Close(); private: boost::asio::io_service& m_IOService; tcp::socket m_Socket; boost::array<char, 128> m_Buffer; size_t m_BufLen; private: void OnConnect(const boost::system::error_code& ErrorCode, tcp::resolver::iterator EndPointIter); void OnReceive(const boost::system::error_code& ErrorCode); void DoClose(); }; TCPClient::TCPClient(boost::asio::io_service& IO_Service, tcp::resolver::iterator EndPointIter) : m_IOService(IO_Service), m_Socket(IO_Service) { tcp::endpoint EndPoint = *EndPointIter; m_Socket.async_connect(EndPoint, boost::bind(&TCPClient::OnConnect, this, boost::asio::placeholders::error, ++EndPointIter)); } void TCPClient::Close() { m_IOService.post( boost::bind(&TCPClient::DoClose, this)); } void TCPClient::OnConnect(const boost::system::error_code& ErrorCode, tcp::resolver::iterator EndPointIter) { if (ErrorCode == 0) // Successful connected { m_Socket.async_receive(boost::asio::buffer(m_Buffer.data(), m_BufLen), boost::bind(&TCPClient::OnReceive, this, boost::asio::placeholders::error)); } else if (EndPointIter != tcp::resolver::iterator()) { m_Socket.close(); tcp::endpoint EndPoint = *EndPointIter; m_Socket.async_connect(EndPoint, boost::bind(&TCPClient::OnConnect, this, boost::asio::placeholders::error, ++EndPointIter)); } } void TCPClient::OnReceive(const boost::system::error_code& ErrorCode) { if (ErrorCode == 0) { std::cout << m_Buffer.data() << std::endl; m_Socket.async_receive(boost::asio::buffer(m_Buffer.data(), m_BufLen), boost::bind(&TCPClient::OnReceive, this, boost::asio::placeholders::error)); } else { DoClose(); } } void TCPClient::DoClose() { m_Socket.close(); } int main() { try { boost::asio::io_service IO_Service; tcp::resolver Resolver(IO_Service); tcp::resolver::query Query("127.0.0.1", "daytime"); tcp::resolver::iterator EndPointIterator = Resolver.resolve(Query); TCPClient Client(IO_Service, EndPointIterator); boost::thread ClientThread( boost::bind(&boost::asio::io_service::run, &IO_Service)); std::cout << "Client started." << std::endl; std::string Input; while (Input != "exit") { std::cin >> Input; } Client.Close(); ClientThread.join(); } catch (std::exception& e) { std::cerr << e.what() << std::endl; } } Server: http://www.boost.org/doc/libs/1_39_0/doc/html/boost_asio/tutorial/tutdaytime3/src.html Regards :)

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  • Longest Path in Boost Graph

    - by TheTSPSolver
    Hi, Sorry if this is a very basic questions for some of you but I'm new to C++ (let alone Boost Graph Library) and couldn't figure out this problem. So far I've been able to formulate/gather code to create a graph using the code below. Now I'm trying to figure out the code to find the longest path in this graph. Can someone please help with what would the code be? I was having trouble trying to figure out if/how to traverse through each node and/or edge when trying to find the path? I have to try to return all the nodes and edges in the longest path. Any help will be greatly appreciated. P.S. does anyone know if C++ has organized documentation like Javadoc?? #include <boost/graph/dag_shortest_paths.hpp> #include <boost/graph/adjacency_list.hpp> #include <windows.h> #include <iostream> int main() { using namespace boost; typedef adjacency_list<vecS, vecS, directedS, property<vertex_distance_t, double>, property<edge_weight_t, double> > graph_t; graph_t g(6); enum verts { stationA, stationB, stationC, stationD, stationE, stationF }; char name[] = "rstuvx"; add_edge(stationA, stationB, 5000.23, g); add_edge(stationA, stationC, 3001, g); add_edge(stationA, stationD, 2098.67, g); add_edge(stationA, stationE, 3298.84, g); add_edge(stationB, stationF, 2145, g); add_edge(stationC, stationF, 4290, g); add_edge(stationD, stationF, 2672.78, g); add_edge(stationE, stationF, 11143.876, g); add_edge(stationA, stationF, 1, g); //Display all the vertices typedef property_map<graph_t, vertex_index_t>::type IndexMap; IndexMap index = get(vertex_index, g); std::cout << "vertices(g) = "; typedef graph_traits<graph_t>::vertex_iterator vertex_iter; std::pair<vertex_iter, vertex_iter> vp; for (vp = vertices(g); vp.first != vp.second; ++vp.first) std::cout << index[*vp.first] << " "; std::cout << std::endl; // ... // Display all the edges // ... std::cout << "edges(g) = " << std::endl; graph_traits<graph_t>::edge_iterator ei, ei_end; for (tie(ei, ei_end) = edges(g); ei != ei_end; ++ei) std::cout << "(" << index[source(*ei, g)] << "," << index[target(*ei, g)] << ") \n"; std::cout << std::endl; // ...

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  • push_back of STL list got bad performance?

    - by Leon Zhang
    I wrote a simple program to test STL list performance against a simple C list-like data structure. It shows bad performance at "push_back()" line. Any comments on it? $ ./test2 Build the type list : time consumed -> 0.311465 Iterate over all items: time consumed -> 0.00898 Build the simple C List: time consumed -> 0.020275 Iterate over all items: time consumed -> 0.008755 The source code is: #include <stdexcept> #include "high_resolution_timer.hpp" #include <list> #include <algorithm> #include <iostream> #define TESTNUM 1000000 /* The test struct */ struct MyType { int num; }; /* * C++ STL::list Test */ typedef struct MyType* mytype_t; void myfunction(mytype_t t) { } int test_stl_list() { std::list<mytype_t> mylist; util::high_resolution_timer t; /* * Build the type list */ t.restart(); for(int i = 0; i < TESTNUM; i++) { mytype_t aItem = (mytype_t) malloc(sizeof(struct MyType)); if(aItem == NULL) { printf("Error: while malloc\n"); return -1; } aItem->num = i; mylist.push_back(aItem); } std::cout << " Build the type list : time consumed -> " << t.elapsed() << std::endl; /* * Iterate over all item */ t.restart(); std::for_each(mylist.begin(), mylist.end(), myfunction); std::cout << " Iterate over all items: time consumed -> " << t.elapsed() << std::endl; return 0; } /* * a simple C list */ struct MyCList; struct MyCList{ struct MyType m; struct MyCList* p_next; }; int test_simple_c_list() { struct MyCList* p_list_head = NULL; util::high_resolution_timer t; /* * Build it */ t.restart(); struct MyCList* p_new_item = NULL; for(int i = 0; i < TESTNUM; i++) { p_new_item = (struct MyCList*) malloc(sizeof(struct MyCList)); if(p_new_item == NULL) { printf("ERROR : while malloc\n"); return -1; } p_new_item->m.num = i; p_new_item->p_next = p_list_head; p_list_head = p_new_item; } std::cout << " Build the simple C List: time consumed -> " << t.elapsed() << std::endl; /* * Iterate all items */ t.restart(); p_new_item = p_list_head; while(p_new_item->p_next != NULL) { p_new_item = p_new_item->p_next; } std::cout << " Iterate over all items: time consumed -> " << t.elapsed() << std::endl; return 0; } int main(int argc, char** argv) { if(test_stl_list() != 0) { printf("ERROR: error at testcase1\n"); return -1; } if(test_simple_c_list() != 0) { printf("ERROR: error at testcase2\n"); return -1; } return 0; }

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  • Problem with incomplete type while trying to detect existence of a member function

    - by abir
    I was trying to detect existence of a member function for a class where the function tries to use an incomplete type. The typedef is struct foo; typedef std::allocator<foo> foo_alloc; The detection code is struct has_alloc { template<typename U,U x> struct dummy; template<typename U> static char check(dummy<void* (U::*)(std::size_t),&U::allocate>*); template<typename U> static char (&check(...))[2]; const static bool value = (sizeof(check<foo_alloc>(0)) == 1); }; So far I was using incomplete type foo with std::allocator without any error on VS2008. However when I replaced it with nearly an identical implementation as template<typename T> struct allocator { T* allocate(std::size_t n) { return (T*)operator new (sizeof(T)*n); } }; it gives an error saying that as T is incomplete type it has problem instantiating allocator<foo> because allocate uses sizeof. GCC 4.5 with std::allocator also gives the error, so it seems during detection process the class need to be completely instantiated, even when I am not using that function at all. What I was looking for is void* allocate(std::size_t) which is different from T* allocate(std::size_t). My questions are (I have three questions, but as they are correlated , so I thought it is better not to create three separate questions). Why MS std::allocator doesn't check for incomplete type foo while instantiating? Are they following any trick which can be implemented ? Why the compiler need to instantiate allocator<T> to check the existence of the function when sizeof is not used as sfinae mechanism to remove/add allocate in the overload resolutions set? It should be noted that, if I remove the generic implementation of allocate leaving the declaration only, and specialized it for foo afterwards such as struct foo{}; template< struct allocator { foo* allocate(std::size_t n) { return (foo*)operator new (sizeof(foo)*n); } }; after struct has_alloc it compiles in GCC 4.5 while gives error in VS2008 as allocator<T> is already instantiated and explicit specialization for allocator<foo> already defined. Is it legal to use nested types for an std::allocator of incomplete type such as typedef foo_alloc::pointer foo_pointer; ? Though it is practically working for me, I suspect the nested types such as pointer may depend on completeness of type it takes. It will be good to know if there is any possible way to typedef such types as foo_pointer where the type pointer depends on completeness of foo. NOTE : As the code is not copy paste from editor, it may have some syntax error. Will correct it if I find any. Also the codes (such as allocator) are not complete implementation, I simplified and typed only the portion which I think useful for this particular problem.

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  • linking to boost regex in gcc

    - by rboorgapally
    i am trying to compile my program which uses regex on linux. I built the boost library in the libs/regex/build by typing make -fgcc.mak which created a directory gcc which contains the following four files boost_regex-gcc-1_35 boost_regex-gcc-d-1_35 libboost_regex-gcc-1_35.a libboost_regex-gcc-d-1_35.a Now I want to use regex from my program which is in some arbitrary directory. I #included boost/regex.hpp I got the error which stated that regex.hpp is not found. Then I gave the -I option in the g++ compiler. I didn't get that error. But I get the following error undefined reference to `boost::re_detail::perl_matcher<__gnu_cxx::__normal_iterator<char const*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<boost::sub_match<__gnu_cxx::__normal_iterator<char const*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >, boost::regex_traits<char, boost::cpp_regex_traits<char> > >::construct_init(boost::basic_regex<char, boost::regex_traits<char, boost::cpp_regex_traits<char> > > const&, boost::regex_constants::_match_flags)' I googled and found that I need to somehow link one of the above 4 libraries to my program. How can I do it. Which one should I link and why?

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  • Partial template specialization on a class

    - by Jonathan Swinney
    I'm looking for a better way to this. I have a chunk of code that needs to handle several different objects that contain different types. The structure that I have looks like this: class Base { // some generic methods } template <typename T> class TypedBase : public Base { // common code with template specialization private: std::map<int,T> mapContainingSomeDataOfTypeT; } template <> class TypedBase<std::string> : public Base { // common code with template specialization public: void set( std::string ); // functions not needed for other types std::string get(); private: std::map<int,std::string> mapContainingSomeDataOfTypeT; // some data not needed for other types } Now I need to add some additional functionality that only applies to one of the derivative classes. Specifically the std::string derivation, but the type doesn't actually matter. The class is big enough that I would prefer not copy the whole thing simply to specialize a small part of it. I need to add a couple of functions (and accessor and modifier) and modify the body of several of the other functions. Is there a better way to accomplish this?

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  • Why does this cast to Base class in virtual function give a segmentation fault?

    - by dehmann
    I want to print out a derived class using the operator<<. When I print the derived class, I want to first print its base and then its own content. But I ran into some trouble (see segfault below): class Base { public: friend std::ostream& operator<<(std::ostream&, const Base&); virtual void Print(std::ostream& out) const { out << "BASE!"; } }; std::ostream& operator<<(std::ostream& out, const Base& b) { b.Print(out); return out; } class Derived : public Base { public: virtual void Print(std::ostream& out) const { out << "My base: "; //((const Base*)this)->Print(out); // infinite, calls this fct recursively //((Base*)this)->Print(out); // segfault (from infinite loop?) ((Base)*this).Print(out); // OK out << " ... and myself."; } }; int main(int argc, char** argv){ Derived d; std::cout << d; return 0; } Why can't I cast in one of these ways? ((const Base*)this)->Print(out); // infinite, calls this fct recursively ((Base*)this)->Print(out); // segfault (from infinite loop?)

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  • Use auto_ptr in VC6 dll cause crash

    - by Yan Cheng CHEOK
    // dll #include <memory> __declspec(dllexport) std::auto_ptr<int> get(); __declspec(dllexport) std::auto_ptr<int> get() { return std::auto_ptr<int>(new int()); } // exe #include <iostream> #include <memory> __declspec(dllimport) std::auto_ptr<int> get(); int main() { { std::auto_ptr<int> x = get(); } std::cout << "done\n"; getchar(); } The following code run perfectly OK under VC9. However, under VC6, I will experience an immediate crash with the following message. Debug Assertion Failed! Program: C:\Projects\use_dynamic_link\Debug\use_dynamic_link.exe File: dbgheap.c Line: 1044 Expression: _CrtIsValidHeapPointer(pUserData) Is it exporting auto_ptr under VC6 is not allowed? It is a known problem that exporting STL collection classes through DLL. http://stackoverflow.com/questions/2451714/access-violation-when-accessing-an-stl-object-through-a-pointer-or-reference-in-a However, I Google around and do not see anything mention for std::auto_ptr. Any workaround?

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  • Using forward declarations for build in datatypes.

    - by bdhar
    I understand that wherever possible we shall use forward declarations instead of includes to speed up the compilation. I have a class Person like this. #pragma once #include <string> class Person { public: Person(std::string name, int age); std::string GetName(void) const; int GetAge(void) const; private: std::string _name; int _age; }; and a class Student like this #pragma once #include <string> class Person; class Student { public: Student(std::string name, int age, int level = 0); Student(const Person& person); std::string GetName(void) const; int GetAge(void) const; int GetLevel(void) const; private: std::string _name; int _age; int _level; }; In Student.h, I have a forward declaration class Person; to use Person in my conversion constructor. Fine. But I have done #include <string> to avoid compilation error while using std::string in the code. How to use forward declaration here to avoid the compilation error? Is it possible? Thanks.

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  • Private member vector of vector dynamic memory allocation

    - by Geoffroy
    Hello, I'm new to C++ (I learned programming with Fortran), and I would like to allocate dynamically the memory for a multidimensional table. This table is a private member variable : class theclass{ public: void setdim(void); private: std::vector < std::vector <int> > thetable; } I would like to set the dimension of thetable with the function setdim(). void theclass::setdim(void){ this->thetable.assign(1000,std::vector <int> (2000)); } I have no problem compiling this program, but as I execute it, I've got a segmentation fault. The strange thing for me is that this piece (see under) of code does exactly what I want, except that it doesn't uses the private member variable of my class : std::vector < std::vector < int > > thetable; thetable.assign(1000,std::vector <int> (2000)); By the way, I have no trouble if thetable is a 1D vector. In theclass : std::vector < int > thetable; and if in setdim : this->thetable.assign(1000,2); So my question is : why is there such a difference with "assign" between thetable and this-thetable for a 2D vector? And how should I do to do what I want? Thank-you for your help, Best regards, -- Geoffroy

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  • Why does C++ not allow multiple types in one auto statement?

    - by Walter
    The 2011 C++ standard introduced the new keyword auto, which can be used for defining variables instead of a type, i.e. auto p=make_pair(1,2.5); // pair<int,double> auto i=std::begin(c), end=std::end(c); // decltype(std::begin(c)) In the second line, i and end are of the same type, referred to as auto. The standard does not allow auto i=std::begin(container), e=std::end(container), x=*i; when x would be of different type. My question: why does the standard not allow this last line? It could be allowed by interpreting auto not as representing some to-be-decuded type, but as indicating that the type of any variable declared auto shall be deduced from its assigned value. Is there any good reason for the C++11 standard to not follow this approach? There is actually a use case for this, namely in the initialisation statement of for loops: for(auto i=std::begin(c), end=std::end(c), x=*i; i!=end; ++i, x+=*i) { ... } when the scope of the variables i, end, and x is limited to the for loop. AFAIK, this cannot be achieved in C++ unless those variables have a common type. Is this correct? (ugly tricks of putting all types inside a struct excluded) There may also be use cases in some variadic template applications.

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  • Inheritance and choose constructor from base class

    - by myle
    My question is rather simple, but I am stuck. How can I choose the desired constructor from base class? // node.h #ifndef NODE_H #define NODE_H #include <vector> // definition of an exception-class class WrongBoundsException { }; class Node { public: ... Node(double, double, std::vector<double>&) throw (WrongBoundsException); ... }; #endif // InternalNode.h #ifndef INTERNALNODE_H #define INTERNALNODE_H #include <vector> #include "Node.h" class InternalNode : public Node { public: // the position of the leftmost child (child left) int left_child; // the position of the parent int parent; InternalNode(double, double, std::vector<double>&, int parent, int left_child) throw (WrongBoundsException); private: int abcd; }; #endif // InternalNode.cpp #include "InternalNode.h" #define UNDEFINED_CHILD -1 #define ROOT -1 // Here is the problem InternalNode::InternalNode(double a, double b, std::vector<double> &v, int par, int lc) throw (WrongBoundsException) : Node(a, b, v), parent(par), left_child(lc) { std::cout << par << std::endl; } I get: $ g++ InternalNode.cpp InternalNode.cpp:16: error: declaration of ‘InternalNode::InternalNode(double, double, std::vector &, int, int) throw (WrongBoundsException)’ throws different exceptions InternalNode.h:17: error: from previous declaration ‘InternalNode::InternalNode(double, double, std::vector &, int, int)’ UPDATE 0: Fixed missing : UPDATE 1: Fixed throw exception

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  • Why does multiple calls to xalloc result in delayed output?

    - by Me myself and I
    When I print the id of a stream in a single expression it prints it backwards. Normally this is what comes out: std::stringstream ss; std::cout << ss.xalloc() << '\n'; std::cout << ss.xalloc() << '\n'; std::cout << ss.xalloc(); Output is: 4 5 6 But when I do it in one expression it prints backwards, why? std::stringstream ss; std::cout << ss.xalloc() << '\n' << ss.xalloc() << '\n' << ss.xalloc(); Output: 6 5 4 I know the order of evaluation is unspecified but then why does the following always result in the correct order: std::cout << 4 << 5 << 6; Can someone explain why xalloc behaves differently? Thanks.

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  • Cannot overload function

    - by anio
    So I've got a templatized class and I want to overload the behavior of a function when I have specific type, say char. For all other types, let them do their own thing. However, c++ won't let me overload the function. Why can't I overload this function? I really really do not want to do template specialization, because then I've got duplicate the entire class. Here is a toy example demonstrating the problem: http://codepad.org/eTgLG932 The same code posted here for your reading pleasure: #include <iostream> #include <cstdlib> #include <string> struct Bar { std::string blah() { return "blah"; } }; template <typename T> struct Foo { public: std::string doX() { return m_getY(my_t); } private: std::string m_getY(char* p_msg) { return std::string(p_msg); } std::string m_getY(T* p_msg) { return p_msg->blah(); } T my_t; }; int main(int, char**) { Foo<char> x; Foo<Bar> y; std::cout << "x " << x.doX() << std::endl; return EXIT_SUCCESS; } Thank you everyone for your suggestions. Two valid solutions have been presented. I can either specialize the doX method, or specialize m_getY() method. At the end of the day I prefer to keep my specializations private rather than public so I'm accepting Krill's answer.

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