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  • When does invoking a member function on a null instance result in undefined behavior?

    - by GMan
    This question arose in the comments of a now-deleted answer to this other question. Our question was asked in the comments by STingRaySC as: Where exactly do we invoke UB? Is it calling a member function through an invalid pointer? Or is it calling a member function that accesses member data through an invalid pointer? With the answer deleted I figured we might as well make it it's own question. Consider the following code: #include <iostream> struct foo { void bar(void) { std::cout << "gman was here" << std::endl; } void baz(void) { x = 5; } int x; }; int main(void) { foo* f = 0; f->bar(); // (a) f->baz(); // (b) } We expect (b) to crash, because there is no corresponding member x for the null pointer. In practice, (a) doesn't crash because the this pointer is never used. Because (b) dereferences the this pointer (this->x = 5;), and this is null, the program enters undefined behavior. Does (a) result in undefined behavior? What about if both functions are static?

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  • 'strcpy' error and warning

    - by Leejo
    I'm getting a 'strcpy' error and warning for the following lines: _tcscpy(strCommandLine,_T("MyProgram.exe /param1")); _tcscpy(strApplicationName,_T("MyProgram.exe")); Not sure why I'm getting a 'strcpy' error or warning since I'm not using 'strcpy'. The only lines related to this is: LPCTSTR strApplicationName; LPTSTR strCommandLine; _tcscpy(strCommandLine,_T("MyProgram.exe /param1")); //warning is on this line _tcscpy(strApplicationName,_T("MyProgram.exe")); //error is on this line The output is: 1c:\documents and settings\X.X\my documents\sandbox\sample.cpp(52) : warning C4996: 'strcpy': This function or variable may be unsafe. Consider using strcpy_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details. 1 c:\program files\microsoft visual studio 8\vc\include\string.h(74) : see declaration of 'strcpy' 1c:\documents and settings\X.X\my documents\sandbox\sample.cpp(53) : error C2664: 'strcpy' : cannot convert parameter 1 from 'LPCTSTR' to 'char *' 1 Conversion loses qualifiers Any ideas on what this could means? These are my headers: iostream windows.h stdio.h tchar.h winnt.h

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  • Singleton with inheritance, Derived class is not able to get instantiated in parent?

    - by yesraaj
    Below code instantiates a derived singleton object based on environment variable. The compiler errors saying error C2512: 'Dotted' : no appropriate default constructor. I don't understand what the compiler is complaining about. #include <stdlib.h> #include <iostream> #include <string> using namespace std; class Dotted; class Singleton{ public: static Singleton instant(){ if (!instance_) { char * style = getenv("STYLE"); if (!style){ if (strcmp(style,"dotted")==0) { instance_ = new Dotted(); return *instance_; } } else{ instance_ = new Singleton(); return *instance_; } } return *instance_; } void print(){cout<<"Singleton";} ~Singleton(){}; protected: Singleton(){}; private: static Singleton * instance_; Singleton(const Singleton & ); void operator=(const Singleton & ); }; class Dotted:public Singleton{ public: void print(){cout<<"Dotted";} protected: Dotted(); }; Dotted::Dotted():Singleton(){} int main(){ Singleton::instant().print(); cin.get(); }

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  • Codechef practice question help needed - find trailing zeros in a factorial

    - by manugupt1
    I have been working on this for 24 hours now, trying to optimize it. The question is how to find the number of trailing zeroes in factorial of a number in range of 10000000 and 10 million test cases in about 8 secs. The code is as follows: #include<iostream> using namespace std; int count5(int a){ int b=0; for(int i=a;i>0;i=i/5){ if(i%15625==0){ b=b+6; i=i/15625; } if(i%3125==0){ b=b+5; i=i/3125; } if(i%625==0){ b=b+4; i=i/625; } if(i%125==0){ b=b+3; i=i/125; } if(i%25==0){ b=b+2; i=i/25; } if(i%5==0){ b++; } else break; } return b; } int main(){ int l; int n=0; cin>>l; //no of test cases taken as input int *T = new int[l]; for(int i=0;i<l;i++) cin>>T[i]; //nos taken as input for the same no of test cases for(int i=0;i<l;i++){ n=0; for(int j=5;j<=T[i];j=j+5){ n+=count5(j); //no of trailing zeroes calculted } cout<<n<<endl; //no for each trialing zero printed } delete []T; } Please help me by suggesting a new approach, or suggesting some modifications to this one.

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  • Just introducing myself to TMPing, and came across a quirk

    - by Justen
    I was just trying to learn the syntax of the beginner things, and how it worked when I was making this short bit of code. The code below works in adding numbers 1 to 499, but if I add 1 to 500, the compiler bugs out giving me: fatal error C1001: An internal error has occurred in the compiler. And I was just wondering why that is. Is there some limit to how much code the compiler can generate or something and it just happened to be a nice round number of 500 for me? #include <iostream> using namespace std; template < int b > struct loop { enum { sum = loop< b - 1 >::sum + b }; }; template <> struct loop< 0 > { enum { sum = 0 }; }; int main() { cout << "Adding the numbers from 1 to 499 = " << loop< 499 >::sum << endl; return 0; }

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  • Can you tell me why this generates time limit exceeded in spoj(Prime Number Generator)

    - by magiix
    #include<iostream> #include<string.h> #include<math.h> using namespace std; bool prime[1000000500]; void generate(long long end) { memset(prime,true,sizeof(prime)); prime[0]=false; prime[1]=false; for(long long i=0;i<=sqrt(end);i++) { if(prime[i]==true) { for(long long y=i*i;y<=end;y+=i) { prime[y]=false; } } } } int main() { int n; long long b,e; scanf("%d",&n); while(n--) { cin>>b>>e; generate(e); for(int i=b;i<e;i++) { if(prime[i]) printf("%d\n",i); } } return 0; } That's my code for spoj prime generator. Altought it generates the same output as another accepted code ..

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  • How do I pass a const reference in C#?

    - by Maciek
    In C++, passing const references is a common practice - for instance : #include <iostream> using namespace std; class X { public : X() {m_x = 0; } X(const int & x) {m_x = x; } X(const X & other) { *this = other; } X & operator = (const X & other) { m_x = other.m_x; return *this; } void print() { cout << m_x << endl; } private : int m_x; }; void main() { X x1(5); X x2(4); X x3(x2); x2 = x1; x1.print(); x2.print(); x3.print(); } This very simple example illustrates how it's done - pretty much. However I've noticed that in C# this doesn't seem to be the case. Do I have to pass const references in C# ? what do I need the "ref" keyword for? Please note that I know and understand what C# reference and value types are.

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  • Object not declared in scope

    - by jay
    I'm using Xcode for C++ on my computer while using Visual Studio at school. The following code worked just fine in Visual Studio, but I'm having this problem when using Xcode. clock c1(2, 3, 30); Everything works just fine, but it keeps giving me this error that says "Expected ';' before 'c1'" Fine, I put the ';' .. but then, it gives me this error: "'c1' was not declared in this scope" Here's the whole header code: #include <iostream> using namespace std; class clock { private: int h; int m; int s; public: clock(int hr, int mn, int sec); }; clock::clock(int hr, int mn, int sec) { h = hr; m = mn; s = sec; } Here's the whole .cpp code: #include "clock.h" int main() { clock c1(2, 3, 30); return 0; } I stripped everything down to where I had the problem. Everything else, as far as I know, is irrelevant since the problem remains the same with just the mentioned above. Thanks in advance!

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  • Two-phase lookup: can I avoid "code bloat"?

    - by Pietro
    Two-phase lookup question: Is there a more synthetic way to write this code, i.e. avoiding all those "using" directives? I tried with "using CBase<T>;", but it is not accepted. #include <iostream> template <typename T> class CBase { protected: int a, b, c, d; // many more... public: CBase() { a = 123; } }; template <typename T> class CDer : public CBase<T> { // using CBase<T>; // error, but this is what I would like using CBase<T>::a; using CBase<T>::b; using CBase<T>::c; //... public: CDer() { std::cout << a; } }; int main() { CDer<int> cd; } In my real code there are many more member variables/functions, and I was wondering if it is possible to write shorter code in some way. Of course, using the CBase::a syntax does not solve the problem... Thank's! gcc 4.1 MacOS X 10.6

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  • Invalid conversion from int to int

    - by FOXMULDERIZE
    #include <iostream> #include<fstream> using namespace std; void showvalues(int,int,int []); void showvalues2(int,int); void sumtotal(int,int); int main() { const int SIZE_A= 9; int arreglo[SIZE_A]; ifstream archivo_de_entrada; archivo_de_entrada.open("numeros.txt"); int count,suma,total,a,b,c,d,e,f; int total1=0; int total2=0; //lee/// for(count =0 ;count < SIZE_A;count++) archivo_de_entrada>>arreglo[count] ; archivo_de_entrada.close(); showvalues(0,3,9); HERE IS THE PROBLEM showvalues2(5,8); sumtotal(total1,total2); system("pause"); return 0; } void showvalues(int a,int b,int v) { //muestra//////////////////////// cout<< "los num son "; for(count = a ;count <= b;count++) total1 = total1 + arreglo[count]; cout <<total1<<" "; cout <<endl; } void showvalues2(int c,int d) { ////////////////////////////// cout<< "los num 2 son "; for(count =5 ;count <=8;count++) total2 = total2 + arreglo[count]; cout <<total2<<" "; cout <<endl; } void sumtotal(int e,int f) { ///////////////////////////////// cout<<"la suma de t1 y t2 es "; total= total1 + total2; cout<<total; cout <<endl; }

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  • Creating and using a static lib in xcode (MacOSX)

    - by Alasdair Morrison
    I am trying to create a static library in xcode and link to that static library from another program. So as a test i have created a BSD static C library project and just added the following code: //Test.h int testFunction(); //Test.cpp #include "Test.h" int testFunction() { return 12; } This compiles fine and create a .a file (libTest.a). Now i want to use it in another program so I create a new xcode project (cocoa application) Have the following code: //main.cpp #include <iostream> #include "Testlib.h" int main (int argc, char * const argv[]) { // insert code here... std::cout << "Result:\n" <<testFunction(); return 0; } //Testlib.h extern int testFunction(); I right clicked on the project - add - existing framework - add other Selected the .a file and it added it into the project view. I always get this linker error: Build TestUselibrary of project TestUselibrary with configuration Debug Ld build/Debug/TestUselibrary normal x86_64 cd /Users/myname/location/TestUselibrary setenv MACOSX_DEPLOYMENT_TARGET 10.6 /Developer/usr/bin/g++-4.2 -arch x86_64 -isysroot /Developer/SDKs/MacOSX10.6.sdk -L/Users/myname/location/TestUselibrary/build/Debug -L/Users/myname/location/TestUselibrary/../Test/build/Debug -F/Users/myname/location/TestUselibrary/build/Debug -filelist /Users/myname/location/TestUselibrary/build/TestUselibrary.build/Debug/TestUselibrary.build/Objects-normal/x86_64/TestUselibrary.LinkFileList -mmacosx-version-min=10.6 -lTest -o /Users/myname/location/TestUselibrary/build/Debug/TestUselibrary Undefined symbols: "testFunction()", referenced from: _main in main.o ld: symbol(s) not found collect2: ld returned 1 exit status I am new to macosx development and fairly new to c++. I am probably missing something fairly obvious, all my experience comes from creating dlls on the windows platform. I really appreciate any help.

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  • PlaySound linker error in C++

    - by logic-unit
    Hello, I'm getting this error: [Linker error] undefined reference to 'PlaySoundA@12' Id returned 1 exit status From this code: // c++ program to generate a random sequence of numbers then play corresponding audio files #include <windows.h> #include <mmsystem.h> #include <iostream> #pragma comment(lib, "winmm.lib") using namespace std; int main() { int i; i = 0; // set the value of i while (i <= 11) // set the loop to run 11 times { int number; number = rand() % 10 + 1; // generate a random number sequence // cycling through the numbers to find the right wav and play it if (number == 0) { PlaySound("0.wav", NULL, SND_FILENAME); // play the random number } else if (number == 1) { PlaySound("1.wav", NULL, SND_FILENAME); // play the random number } //else ifs repeat to 11... i++; // increment i } return 0; } I've tried absolute and relative paths for the wavs, the file size of them is under 1Mb each too. I've read another thread here on the subject: http://stackoverflow.com/questions/1565439/how-to-playsound-in-c As you may well have guessed this is my first C++ program, so my knowledge is limited with where to go next. I've tried pretty much every page Google has on the subject including MSDN usage page. Any ideas? Thanks in advance...

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  • When virtual inheritance IS a good design?

    - by 7vies
    EDIT3: Please be sure to clearly understand what I am asking before answering (there are EDIT2 and lots of comments around). There are (or were) many answers which clearly show misunderstanding of the question (I know that's also my fault, sorry for that) Hi, I've looked over the questions on virtual inheritance (class B: public virtual A {...}) in C++, but did not find an answer to my question. I know that there are some issues with virtual inheritance, but what I'd like to know is in which cases virtual inheritance would be considered a good design. I saw people mentioning interfaces like IUnknown or ISerializable, and also that iostream design is based on virtual inheritance. Would those be good examples of a good use of virtual inheritance, is that just because there is no better alternative, or because virtual inheritance is the proper design in this case? Thanks. EDIT: To clarify, I'm asking about real-life examples, please don't give abstract ones. I know what virtual inheritance is and which inheritance pattern requires it, what I want to know is when it is the good way to do things and not just a consequence of complex inheritance. EDIT2: In other words, I want to know when the diamond hierarchy (which is the reason for virtual inheritance) is a good design

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  • Populate struct values with function argument

    - by adohertyd
    I am working on a program and part of it requires me to create a struct called DETAILS with the fields name, age, and height. I want to populate the record with data using a function argument. When I run my code I get compiler errors. I have put the errors in comment form beside the lines it is returned for but I can't fix them. Really could do with some help here guys thanks so much. Here is my code: #include <cstdlib> #include <iostream> #include <iomanip> using namespace std; const int LEN=100; struct DETAILS { char name[LEN]; int age; double height; }; person fillperson(struct DETAILS, char[LEN], int, double); int main() { struct person David; fillperson(David, "David Greene", 38, 180.0); //deprecated conversion from string constant to char * [-Wwrite-Strings] } person fillperson(struct DETAILS, char[LEN] name, int age, double height) //expected , or ... before 'name' { cin>>David.name>>name; cin>>David.age>>age; cin>>David.height>>height; cout<<"Done"<<endl; }

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  • GDB not breaking on breakpoints set on object creation in C++

    - by Drew
    Hi all, I've got a c++ app, with the following main.cpp: 1: #include <stdio.h> 2: #include "HeatMap.h" 3: #include <iostream> 4: 5: int main (int argc, char * const argv[]) 6: { 7: HeatMap heatMap(); 8: printf("message"); 9: return 0; 10: } Everything compiles without errors, I'm using gdb (GNU gdb 6.3.50-20050815 (Apple version gdb-1346) (Fri Sep 18 20:40:51 UTC 2009)), and compiled the app with gcc (gcc version 4.2.1 (Apple Inc. build 5646) (dot 1)) with the commands "-c -g". When I add breakpoints to lines 7, 8, and 9, and run gdb, I get the following... (gdb) break main.cpp:7 Breakpoint 1 at 0x10000177f: file src/main.cpp, line 8. (gdb) break main.cpp:8 Note: breakpoint 1 also set at pc 0x10000177f. Breakpoint 2 at 0x10000177f: file src/main.cpp, line 8. (gdb) break main.cpp:9 Breakpoint 3 at 0x100001790: file src/main.cpp, line 9. (gdb) run Starting program: /DevProjects/DataManager/build/DataManager Reading symbols for shared libraries ++. done Breakpoint 1, main (argc=1, argv=0x7fff5fbff960) at src/main.cpp:8 8 printf("message"); (gdb) So, why of why, does anyone know, why my app does not break on the breakpoints for the object creation, but does break on the printf line? Drew J. Sonne.

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  • Quick question on using the constructer with multiple files.

    - by sil3nt
    Hi there, I have this class header //header for class. #ifndef Container_H #define Container_H #include <iostream> using namespace std; const int DEFAULT=32; class Container{ public: Container(int maxCapacity = DEFAULT); ~Container(); void insert(int item, int index); void erase(int index); int size()const; private: int sizeC; int capacityC; int * elements; }; void info(); #endif and this source file #include "container.h" Container::Container(int maxCapacity = DEFAULT){ int y; } void Container::insert(int item, int index){ int x; } and when i compile this i get the following error message test.cpp:4: error: default argument given for parameter 1 of `Container::Container(int)' container.h:12: error: after previous specification in `Container::Container(int) what have i done wrong here?

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  • Problem Linking Boost Filesystem Library in Microsoft Visual C++

    - by Scott
    Hello. I am having trouble getting my project to link to the Boost (version 1.37.0) Filesystem lib file in Microsoft Visual C++ 2008 Express Edition. The Filesystem library is not a header-only library. I have been following the Getting Started on Windows guide posted on the official boost web page. Here are the steps I have taken: I used bjam to build the complete set of lib files using: bjam --build-dir="C:\Program Files\boost\build-boost" --toolset=msvc --build-type=complete I copied the /libs directory (located in C:\Program Files\boost\build-boost\boost\bin.v2) to C:\Program Files\boost\boost_1_37_0\libs. In Visual C++, under Project Properties Additional Library Directories I added these paths: C:\Program Files\boost\boost_1_37_0\libs C:\Program Files\boost\boost_1_37_0\libs\filesystem\build\msvc-9.0express\debug\link-static\threading-multi I added the second one out of desperation. It is the exact directory where libboost_system-vc90-mt-gd-1_37.lib resides. In Configuration Properties C/C++ General Additional Include Directories I added the following path: C:\Program Files\boost\boost_1_37_0 Then, to put the icing on the cake, under Tools Options VC++ Directories Library files, I added the same directories mentioned in step 3. Despite all this, when I build my project I get the following error: fatal error LNK1104: cannot open file 'libboost_system-vc90-mt-gd-1_37.lib' Additionally, here is the code that I am attempting to compile as well as a screen shot of the aformentioned directory where the (assumedly correct) lib file resides: #include "boost/filesystem.hpp" // includes all needed Boost.Filesystem declarations #include <iostream> // for std::cout using boost::filesystem; // for ease of tutorial presentation; // a namespace alias is preferred practice in real code using namespace std; int main() { cout << "Hello, world!" << endl; return 0; } Can anyone help me out? Let me know if you need to know anything else. As always, thanks in advance.

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  • Common practice for higher-order-polymorphism in scala

    - by raichoo
    Hi, I'm trying to grasp higher-order-polymophism in scala by implementing a very basic interface that describes a monad but I come across a problem that I don't really understand. I implemented the same with C++ and the code looks like this: #include <iostream> template <typename T> class Value { private: T value; public: Value(const T& t) { this->value = t; } T get() { return this->value; } }; template < template <typename> class Container > class Monad { public: template <typename A> Container<A> pure(const A& a); }; template <template <typename> class Container> template <typename A> Container<A> Monad<Container>::pure(const A& a) { return Container<A>(a); } int main() { Monad<Value> m; std::cout << m.pure(1).get() << std::endl; return 0; } When trying to do the same with scala I fail: class Value[T](val value: T) class Monad[Container[T]] { def pure[A](a: A): Container[A] = Container[A](a) } object Main { def main(args: Array[String]): Unit = { val m = new Monad[Value] m.pure(1) } } The compiler complains about: [raichoo@lain:Scala]:434> scalac highorder.scala highorder.scala:5: error: not found: value Container Container[A](a) ^ one error found What am I doing wrong here? There seems to be a fundamental concept I don't seem to understand about scala typeconstructors. Regards, raichoo

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  • opengl color quadrangle

    - by Tyzak
    hello i try out opengl. i have a programm that creates a black border an white corner (quadrangle). now i want to make the corner of the quadrangle in an different color. i don't know where exactly to write the code, and i don't know much a but color4f, i searcherd on google, but didn't get it. (is there a good description somewhere?) #include <iostream> #include <GL/freeglut.h> void Init() { glColor4f(100,0,0,0); } void RenderScene() //Zeichenfunktion { glLoadIdentity (); glBegin( GL_POLYGON ); glVertex3f( -0.5, -0.5, -0.5 ); glVertex3f( 0.5, -0.5, -0.5 ); glVertex3f( 0.5, 0.5, -0.5 ); glVertex3f( -0.5, 0.5, -0.5 ); glEnd(); glFlush(); } void Reshape(int width,int height) { } void Animate (int value) { std::cout << "value=" << value << std::endl; glutPostRedisplay(); glutTimerFunc(100, Animate, ++value); } int main(int argc, char **argv) { glutInit( &argc, argv ); // GLUT initialisieren glutInitDisplayMode( GLUT_RGB ); // Fenster-Konfiguration glutInitWindowSize( 600, 600 ); glutCreateWindow( "inkrement screen; visual screen" ); // Fenster-Erzeugung glutDisplayFunc( RenderScene ); // Zeichenfunktion bekannt machen glutReshapeFunc( Reshape ); glutTimerFunc( 10, Animate, 0); Init(); glutMainLoop(); return 0; }

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  • Creating and using a static lib in xcode

    - by Alasdair Morrison
    I am trying to create a static library in xcode and link to that static library from another program. So as a test i have created a BSD static C library project and just added the following code: //Test.h int testFunction(); //Test.cpp #include "Test.h" int testFunction() { return 12; } This compiles fine and create a .a file (libTest.a). Now i want to use it in another program so I create a new xcode project (cocoa application) Have the following code: //main.cpp #include <iostream> #include "Testlib.h" int main (int argc, char * const argv[]) { // insert code here... std::cout << "Result:\n" <<testFunction(); return 0; } //Testlib.h extern int testFunction(); I right clicked on the project - add - existing framework - add other Selected the .a file and it added it into the project view. I always get this linker error: Build TestUselibrary of project TestUselibrary with configuration Debug Ld build/Debug/TestUselibrary normal x86_64 cd /Users/myname/location/TestUselibrary setenv MACOSX_DEPLOYMENT_TARGET 10.6 /Developer/usr/bin/g++-4.2 -arch x86_64 -isysroot /Developer/SDKs/MacOSX10.6.sdk -L/Users/myname/location/TestUselibrary/build/Debug -L/Users/myname/location/TestUselibrary/../Test/build/Debug -F/Users/myname/location/TestUselibrary/build/Debug -filelist /Users/myname/location/TestUselibrary/build/TestUselibrary.build/Debug/TestUselibrary.build/Objects-normal/x86_64/TestUselibrary.LinkFileList -mmacosx-version-min=10.6 -lTest -o /Users/myname/location/TestUselibrary/build/Debug/TestUselibrary Undefined symbols: "testFunction()", referenced from: _main in main.o ld: symbol(s) not found collect2: ld returned 1 exit status I am new to macosx development and fairly new to c++. I am probably missing something fairly obvious, all my experience comes from creating dlls on the windows platform. I really appreciate any help.

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  • Why is execution-time method resolution faster than compile-time resolution?

    - by Felix
    At school, we about virtual functions in C++, and how they are resolved (or found, or matched, I don't know what the terminology is -- we're not studying in English) at execution time instead of compile time. The teacher also told us that compile-time resolution is much faster than execution-time (and it would make sense for it to be so). However, a quick experiment would suggest otherwise. I've built this small program: #include <iostream> #include <limits.h> using namespace std; class A { public: void f() { // do nothing } }; class B: public A { public: void f() { // do nothing } }; int main() { unsigned int i; A *a = new B; for (i=0; i < UINT_MAX; i++) a->f(); return 0; } Where I made A::f() once normal, once virtual. Here are my results: [felix@the-machine C]$ time ./normal real 0m25.834s user 0m25.742s sys 0m0.000s [felix@the-machine C]$ time ./virtual real 0m24.630s user 0m24.472s sys 0m0.003s [felix@the-machine C]$ time ./normal real 0m25.860s user 0m25.735s sys 0m0.007s [felix@the-machine C]$ time ./virtual real 0m24.514s user 0m24.475s sys 0m0.000s [felix@the-machine C]$ time ./normal real 0m26.022s user 0m25.795s sys 0m0.013s [felix@the-machine C]$ time ./virtual real 0m24.503s user 0m24.468s sys 0m0.000s There seems to be a steady ~1 second difference in favor of the virtual version. Why is this? Relevant or not: dual-core pentium @ 2.80Ghz, no extra applications running between two tests. Archlinux with gcc 4.5.0. Compiling normally, like: $ g++ test.cpp -o normal Also, -Wall doesn't spit out any warnings, either.

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  • string Comparison

    - by muhammad-aslam
    I want to compare two user input strings, but not able to do so... #include "stdafx.h" #include "iostream" #include "string" using namespace std; int _tmain(int argc, _TCHAR* argv0[]) { string my_string; string my_string2; cout<<"Enter string"<<endl; cin>>my_string; cout<<"Enter 2nd string"<<endl; cin>>my_string2; cout<<my_string<<" "<<my_string2; strcmp(my_string,my_string2); int result; result= strcmp(my_string,my_string2); cout<<result<<endl; return 0; } This error is appearing. Error 1 error C2664: 'strcmp' : cannot convert parameter 1 from 'std::string' to 'const char *' c:\users\asad\documents\visual studio 2008\projects\string\string\string.cpp 23 String

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  • operator<< cannot output std::endl -- Fix?

    - by dehmann
    The following code gives an error when it's supposed to output just std::endl: #include <iostream> #include <sstream> struct MyStream { std::ostream* out_; MyStream(std::ostream* out) : out_(out) {} std::ostream& operator<<(const std::string& s) { (*out_) << s; return *out_; } }; template<class OutputStream> struct Foo { OutputStream* out_; Foo(OutputStream* out) : out_(out) {} void test() { (*out_) << "OK" << std::endl; (*out_) << std::endl; // ERROR } }; int main(int argc, char** argv){ MyStream out(&std::cout); Foo<MyStream> foo(&out); foo.test(); return EXIT_SUCCESS; } The error is: stream1.cpp:19: error: no match for 'operator<<' in '*((Foo<MyStream>*)this)->Foo<MyStream>::out_ << std::endl' stream1.cpp:7: note: candidates are: std::ostream& MyStream::operator<<(const std::string&) So it can output a string (see line above the error), but not just the std::endl, presumably because std::endl is not a string, but the operator<< definition asks for a string. Templating the operator<< didn't help: template<class T> std::ostream& operator<<(const T& s) { ... } How can I make the code work? Thanks!

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  • GLFW - Not drawing square

    - by m00st
    I am using GLFW as GUI for OpenGL projects. I am using my red book and testing code and well the first bit of code doesn't work at all. I want to say this is a GLFW problem because I don't have this problem in JOGL. #include <iostream> #include "GL/glfw.h" #ifndef MAIN #define MAIN #include "GL/gl.h" #include "GL/glu.h" #endif using namespace std; int main() { int running = GL_TRUE; glfwInit(); if( !glfwOpenWindow( 300,300, 0,0,0,0,0,0, GLFW_WINDOW ) ) { glfwTerminate(); return 0; } while( running ) { //GL Code here glClear(GL_COLOR_BUFFER_BIT); glClearColor(0.0, 0.0, 0.0, 0.0); glColor3f(1.0, 1.0, 1.0); glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0); glBegin(GL_POLYGON); glVertex3f(0.25, 0.25, 0.0); glVertex3f(0.75, 0.25, 0.0); glVertex3f(0.75, 0.75, 0.0); glVertex3f(0.25, 0.75, 0.0); glEnd(); glFlush(); glfwSwapBuffers(); // Check if ESC key was pressed or window was closed running = !glfwGetKey( GLFW_KEY_ESC ) && glfwGetWindowParam( GLFW_OPENED ); } glfwTerminate(); return 0; }

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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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