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  • Compatible types and structures in C

    - by Oli Charlesworth
    I have the following code: int main(void) { struct { int x; } a, b; struct { int x; } c; struct { int x; } *p; b = a; /* OK */ c = a; /* Doesn't work */ p = &a; /* Doesn't work */ return 0; } which fails to compile under GCC (3.4.6), with the following error: test.c:8: error: incompatible types in assignment test.c:9: warning: assignment from incompatible pointer type Now, from what I understand (admittedly from the C99 standard), is that a and c should be compatible types, as they fulfill all the criteria in section 6.2.7, paragraph 1. I've tried compiling with std=c99, to no avail. Presumably my interpretation of the standard is wrong?

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  • C++ enumeration

    - by asli
    Hi,my question is about enumeration,my codes are : #include<iostream> using namespace std; int main() { enum bolumler {programcilik,donanim,muhasebe,motor,buro} bolum; bolum = donanim; cout << bolum << endl; bolum += 2; // bolum=motor cout << bolum; return 0; } The output should be 1 3 but according to these codes the error is: error C2676: binary '+=' : 'enum main::bolumler' does not define this operator or a conversion to a type acceptable to the predefined operator Error executing cl.exe. 111.obj - 1 error(s), 0 warning(s) Can you help me ?The other question is what can I do if I want to see the output like that "muhasebe"?

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  • Returning new base class when the parent class shared pointer is the return type

    - by Ben Dol
    Can you have a parent class shared pointer return type of a function and then return a new child class without it being a shared pointer? I'm not sure how shared pointers work in these situations, do they act like a regular pointer? Here is my example: BaseEventPtr Actions::getEvent(const std::string& nodeName) { if(asLowerCaseString(nodeName) == "action") return new ActionEvent(&m_interface); return nullptr; } ActionEvent is the subclass of BaseEvent in this situation. Cheers!

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  • Why is this c++ string concatenation missing a space?

    - by danutenshu
    I am working with c++ strings, and am a beginner at programming. I am expecting: 99 Red Balloons But I am receiving: 99 RedBalloons Why is that? #include <string> #include <iostream> using namespace std; int main() { string text = "9"; string term( "9 "); string info = "Toys"; string color; char hue[4] = {'R','e','d','\0'}; color = hue; info = "Balloons"; text += (term + color + info); cout << endl << text << endl; return 0; }

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  • Makefile to compile both C and Java programs at the same time

    - by user342745
    I have three programs that need to be compiled at the same time, 2 written in C and 1 in java. I had all three working with the Makefile when they were in C, but then switched one of them to java... is there a way to compile all 3 at once with the same makefile? Here is my current Makefile: CC=gcc JC=javac JFLAGS= -g CFLAGS= -Wall -g -std=c99 LDFLAGS= -lm .SUFFIXES: .java .class .java.class: $(JC) $(JFLAGS) $*.java CLASSES = kasiski.java kentry.java ALL= ic ftable kasiski all: $(ALL) ic: ic.o kasiski: $(CLASSES:.java=.class) ftable: ftable.o ic.o: ic.c ic.h ftable.o: ftable.c ftable.h .PHONY: clean clean: rm -rf core* *.class *.o *.gch $(ALL)

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  • Are pointers primitive types in C++?

    - by Space_C0wb0y
    I was wondering about the last constructor for std::string mentioned here. It says: template<class InputIterator> string (InputIterator begin, InputIterator end); If InputIterator is an integral type, behaves as the sixth constructor version (the one right above this) by typecasting begin and end to call it: string(static_cast<size_t>(begin),static_cast<char>(end)); In any other case, the parameters are taken as iterators, and the content is initialized with the values of the elements that go from the element referred by iterator begin to the element right before the one referred by iterator end. So what does that mean if InputIterator is a char * ?

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  • Excess elements in scalar initializer

    - by Wade Williams
    I'm pretty noobish when it comes to C++ STL stuff. After a compiler upgrade, I'm getting: error: Semantic Issue: Excess elements in scalar initializer on the call: Certificate *tempcert; cValType( tempPerson->name, tempcert ); with a typedef of: typedef std::map< string, certificate* >::value_type cValType; I'm not certain what this error is telling me or how to fix it. (Ok, I realize it's telling me excess elements, but it looks like it matches the map prototype to me, so I'm confused.) Suggestions?

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  • Pure virtual destructor in interface

    - by ALOR
    Hello all. Here is my problem. I'm making C++ dll, which extensively relies on instance object exports. So i return my actual instances as a pointers to interface through some exported factory method. Interfaces i use are purely virtual, to avoid linking problame. So i need a pure virtual destructor too, and i implemented one (with empty body, as i googled it). All compiles perfectly well, except... I can't see, if the actual destructors are called or not - because when i added some std::cout << "hello destructor"; i never get to see it. I have some explicit "delete obj", that's not the problem. Am i missing something? Is there another way to delete my object through interface?

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  • vector segmentation fault

    - by user1849298
    I have a problem with the segmentation fault. Look: #include<fstream> using namespace std; int main(){ int n,i,vector[10001],vectorcopy[10001]; ifstream in("program.in"); ofstream out("program.out"); in>>n; for(i=1;i<=n;i++){ in>>vector[i]; vectorcopy[i]=vector[i]; } return 0;} And the debugger says: Program recived signal SIGSEGV, Segmentation fault Please, tell me what to do!

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  • How might I assume a "default value" when parsing using boost::spirit?

    - by tJener
    Let's say I have a grammar defined to something like: a b c d where c, and d are optional and default to 14 if not given. Can I get it to automatically return the 14 if the value isn't given? The closest I've come is like the following: qi::rule<Iterator, std::vector<int>(), ascii::space_type> some_rule; some_rule %= >> int_ >> int_ >> -int_ >> -int_; // ... some_other_rule = some_rule[&some_callback_for_int_vectors]; which will then get 0 for the optional values that didn't show up (I believe). I then change consecutive 0s at the end into 14. Not only is this horribly wrong, but its also just not elegant. Is there a better way to do this?

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  • Does C++ have a static polymorphism implementation of interface that does not use vtable?

    - by gilbertc
    Does C++ have a proper implementation of interface that does not use vtable? for example class BaseInterface{ public: virtual void func() const = 0; } class BaseInterfaceImpl:public BaseInterface{ public: void func(){ std::cout<<"called."<<endl; } } BaseInterface* obj = new BaseInterfaceImpl(); obj->func(); the call to func at the last line goes to vtable to find the func ptr of BaseInterfaceImpl::func, but is there any C++ way to do that directly as the BaseInterfaceImpl is not subclassed from any other class besides the pure interface class BaseInterface? Thanks. Gil.

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  • Segfault when calling a method c++

    - by shuttle87
    I am fairly new to c++ and I am a bit stumped by this problem. I am trying to assign a variable from a call to a method in another class but it always segfaults. My code compiles with no warnings and I have checked that all variables are correct in gdb but the function call itself seems to cause a segfault. The code I am using is roughly like the following: class History{ public: bool test_history(); }; bool History::test_history(){ std::cout<<"test"; //this line never gets executed //more code goes in here return true; } class Game{ private: bool some_function(); public: History game_actions_history; bool local_variable; }; bool Game::some_function(){ local_variable = game_actions_history.test_history(); if (local_variable == true){ return true; } else{ return false; } } Any tips or advice is greatly appreciated!

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  • How do i use 'auto' in C++ (C++0x) ?

    - by LoudNPossiblyRight
    What do i have to do to this code to make it compile, it's braking around this line: auto val = what.getObject(); #include<iostream> using namespace std; class CUP{ public: void whatsHappening(){} }; class MUG{ public: void whatsHappening(){} }; class CupThrower{ public: CUP cp; CUP getObject(){ return cp;} }; class MugThrower{ public: MUG mg; MUG getObject(){return mg;} }; template <typename T> void whatsHappening(T what){ auto val = what.getObject(); //DOES NOT COMPILE val.whatsHappening(); } int main(){ CupThrower ct; MugThrower mt; whatsHappening(ct); whatsHappening(mt); return 0; } i am using VS2008 to compile.

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  • LLVM Clang 5.0 explicit in copy-initialization error

    - by kevzettler
    I'm trying to compile an open source project on OSX that has only been tested on Linux. $: g++ -v Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1 Apple LLVM version 5.0 (clang-500.2.79) (based on LLVM 3.3svn) Target: x86_64-apple-da I'm trying to compile with the following command line options g++ -MMD -Wall -std=c++0x -stdlib=libc++ -Wno-sign-compare -Wno-unused-variable -ftemplate-depth=1024 -I /usr/local/Cellar/boost/1.55.0/include/boost/ -g -O3 -c level.cpp -o obj-opt/level.o I am seeing several errors that look like this: ./square.h:39:70: error: chosen constructor is explicit in copy-initialization int strength = 0, double flamability = 0, map<SquareType, int> constructions = {}, bool ticking = false); The project states the following are requirements for the Linux setup. How can I confirm I'm making that? gcc-4.8.2 git libboost 1.5+ with libboost-serialize libsfml-dev 2+ (Ubuntu ppa that contains libsfml 2: ) freeglut-dev libglew-dev

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  • What to return as an iterator when there is no container?

    - by DaClown
    I have an inheritance structure of objects with begin() and end() as pure virtual member functions in the base class. From this objects I'm planning to build a composite structure. This inner objects have std::vector member the begin() and end() get their data from. But in a leaf class there is no vector. Now I try to find a return value for begin() and end() in the leaf classes. What would be a good way to do that? The easiest way would be to have a vector member in the leaf classes with no elements in it to fuel begin() and end(), but this just doesn't feel right.

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  • C++ Pointers to functions.

    - by Andy Leman
    using namespace std; int addition (int a, int b) { return (a+b); } int subtraction (int a, int b) { return (a-b); } int operation (int x, int y, int (*functocall)(int,int)) { int g; g = (*functocall)(x,y); return(g); } int main() { int m,n; int (*minus)(int,int) = subtraction; m = operation (7,5,addition); n = operation (20,m,minus); cout << n; return 0; } Can anybody explain this line for me int (*minus)(int,int) = subtraction; Thanks a lot!

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  • Disallow private constructor invocation in friend function

    - by user2907032
    Is there any way to not allow private construction in friend function, In case we do have private constructor with friend function in our class. Only Static method should be responsible for object creation and other than this compiler should flash error message #include <iostream> #include <memory> using namespace std; class a { public: void see () { cout<<"Motimaa"; } static a& getinstance() { static a instance; return instance; } private: a() {}; friend void access(); }; void access () { a obj; obj.see();//still friend function can access } int main() { a::getinstance().see(); access(); return 1; }

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  • Does C++ have a proper implementation of interface that does not use vtable?

    - by gilbertc
    Does C++ have a proper implementation of interface that does not use vtable? for example class BaseInterface{ public: virtual void func() const = 0; } class BaseInterfaceImpl:public BaseInterface{ public: void func(){ std::cout<<"called."<<endl; } } BaseInterface* obj = new BaseInterfaceImpl(); obj->func(); the call to func at the last line goes to vtable to find the func ptr of BaseInterfaceImpl::func, but is there any C++ way to do that directly as the BaseInterfaceImpl is not subclassed from any other class besides the pure interface class BaseInterface? Thanks. Gil.

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  • C++: conjunction of binds?

    - by Helltone
    Suppose the following two functions: #include <iostream> #include <cstdlib> // atoi #include <cstring> // strcmp #include <boost/bind.hpp> bool match1(const char* a, const char* b) { return (strcmp(a, b) == 0); } bool match2(int a, const char* b) { return (atoi(b) == a); } Each of these functions takes two arguments, but can be transformed into a callable object that takes only one argument by using (std/boost)bind. Something along the lines of: boost::bind(match1, "a test"); boost::bind(match2, 42); I want to be able to obtain, from two functions like these that take one argument and return bool, a callable object that takes two arguments and returns the && of the bools. The type of the arguments is arbitrary. Something like an operator&& for functions that return bool.

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  • Building a world matrix

    - by DeadMG
    When building a world projection matrix from scale, rotate, translate matrices, then the translation matrix must be the last in the process, right? Else you'll be scaling or rotating your translations. Do scale and rotate need to go in a specific order? Right now I've got std::for_each(objects.begin(), objects.end(), [&, this](D3D93DObject* ptr) { D3DXMATRIX WVP; D3DXMATRIX translation, rotationX, rotationY, rotationZ, scale; D3DXMatrixTranslation(&translation, ptr->position.x, ptr->position.y, ptr->position.z); D3DXMatrixRotationX(&rotationX, ptr->rotation.x); D3DXMatrixRotationY(&rotationY, ptr->rotation.y); D3DXMatrixRotationZ(&rotationZ, ptr->rotation.z); D3DXMatrixScaling(&translation, ptr->scale.x, ptr->scale.y, ptr->scale.z); WVP = rotationX * rotationY * rotationZ * scale * translation * ViewProjectionMatrix; });

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  • recv receiving not whole data sometime

    - by milo
    hi all, i have following issue: here is the chunk of code: void get_all_buf(int sock, std::string & inStr) { int n = 1; char c; char temp[1024*1024]; bzero(temp, sizeof(temp)); n = recv(sock, temp, sizeof(temp), 0); inStr = temp; }; but sometimes recv returning not whole data (data length always less then sizeof(temp)), only it's part. write side always sends me whole data (i got it with sniffer). what matter? thx. P.S. i know, good manner suggests me to check n (if (n < 0) perror ("error while receiving data), but it doesn't matter now - it's not reason of my problem. P.S.2 i've forgot - it's blocking socket.

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  • c++ function overloading, making fwrite/fread act like PHP versions

    - by Newbie
    I'm used to the PHP fwrite/fread parameter orders, and i want to make them the same in C++ too. I want it to work with char and string types, and also any data type i put in it (only if length is defined). I am total noob on c++, this is what i made so far: size_t fwrite(FILE *fp, const std::string buf, const size_t len = SIZE_MAX){ if(len == SIZE_MAX){ return fwrite(buf.c_str(), 1, buf.length(), fp); }else{ return fwrite(buf.c_str(), 1, len, fp); } } size_t fwrite(FILE *fp, const void *buf, const size_t len = SIZE_MAX){ if(len == SIZE_MAX){ return fwrite((const char *)buf, 1, strlen((const char *)buf), fp); }else{ return fwrite(buf, 1, len, fp); } } Should this work just fine? And how should this be done if i wanted to do it the absolutely best possible way?

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  • pointer delegate in STL set.

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

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  • problem in reading output of dd command using pipe

    - by Ummar
    I am developing an application, in which I want to redirect the output (progress information) of dd command to my C++ program, but it is not actually getting the output, here is the code FILE * progressInfo = popen("gzip -dc backup/backup.img.gz | pv -ptrbe -i 2 -s 2339876653 | dd of=/dev/sdb","r"); if(!progressInfo) { return -1; } char buf[1024]; while(fgets(buff, sizeof(buff),progressInfo)!=NULL) { std::cout << buff << endl; } but the problem is the progress information is not received in buff, and the output is continuously printed on terminal, and above program halts on while(fgets(buff, sizeof(buff),progressInfo)!=NULL), and as soon as the dd operation is completed, the very next line to loop block is executed. if anyone has any idea why the output is not returned to buff, and its continuously retuned on terminal?

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  • Why do I get corrupt output on my file?

    - by Martin
    I have a simple program which I have compiled in both MinGW and Visual C++ 2008 Express, and both give an output file larger than 88200. When I set s = 0, both programs work as expected. What am I doing wrong? #include <fstream> using namespace std; int main(int argc, char *argv[]) { int i; short s; fstream f; f.open("test.raw", ios_base::out); for(i = 0; i < 44100; i++) { s = i & 0xFFFF; // PROBLEM? f.write(reinterpret_cast<const char *>(&s), sizeof(s)); } f.close(); return 0; }

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