c++-faq

问题 I learned C# first, and now I'm starting with C++. As I understand, operator new in C++ is not similar to the one in C#. Can you explain the reason of the memory leak in this sample code? class A { ... }; struct B { ... }; A *object1 = new A(); B object2 = *(new B()); 回答1: What is happening When you write T t; you're creating an object of type T with automatic storage duration . It will get cleaned up automatically when it goes out of scope. When you write new T() you're creating an object of

问题 I learned C# first, and now I'm starting with C++. As I understand, operator new in C++ is not similar to the one in C#. Can you explain the reason of the memory leak in this sample code? class A { ... }; struct B { ... }; A *object1 = new A(); B object2 = *(new B()); 回答1: What is happening When you write T t; you're creating an object of type T with automatic storage duration . It will get cleaned up automatically when it goes out of scope. When you write new T() you're creating an object of

问题 Came across a proposal called "rvalue reference for *this" in clang's C++11 status page. I've read quite a bit about rvalue references and understood them, but I don't think I know about this. I also couldn't find much resources on the web using the terms. There's a link to the proposal paper on the page: N2439 (Extending move semantics to *this), but I'm also not getting much examples from there. What is this feature about? 回答1: First, "ref-qualifiers for *this" is a just a "marketing

问题 I have written a simple, working tetris game with each block as an instance of a class singleblock. class SingleBlock { public: SingleBlock(int, int); ~SingleBlock(); int x; int y; SingleBlock *next; }; class MultiBlock { public: MultiBlock(int, int); SingleBlock *c, *d, *e, *f; }; SingleBlock::SingleBlock(int a, int b) { x = a; y = b; } SingleBlock::~SingleBlock() { x = 222; } MultiBlock::MultiBlock(int a, int b) { c = new SingleBlock (a,b); d = c->next = new SingleBlock (a+10,b); e = d-

问题 I have written a simple, working tetris game with each block as an instance of a class singleblock. class SingleBlock { public: SingleBlock(int, int); ~SingleBlock(); int x; int y; SingleBlock *next; }; class MultiBlock { public: MultiBlock(int, int); SingleBlock *c, *d, *e, *f; }; SingleBlock::SingleBlock(int a, int b) { x = a; y = b; } SingleBlock::~SingleBlock() { x = 222; } MultiBlock::MultiBlock(int a, int b) { c = new SingleBlock (a,b); d = c->next = new SingleBlock (a+10,b); e = d-

问题 Why is it not allowed to get non-const reference to a temporary object, which function getx() returns? Clearly, this is prohibited by C++ Standard but I am interested in the purpose of such restriction, not a reference to the standard. struct X { X& ref() { return *this; } }; X getx() { return X();} void g(X & x) {} int f() { const X& x = getx(); // OK X& x = getx(); // error X& x = getx().ref(); // OK g(getx()); //error g(getx().ref()); //OK return 0; } It is clear that the lifetime of the

问题 How does the compilation and linking process work? (Note: This is meant to be an entry to Stack Overflow's C++ FAQ. If you want to critique the idea of providing an FAQ in this form, then the posting on meta that started all this would be the place to do that. Answers to that question are monitored in the C++ chatroom, where the FAQ idea started out in the first place, so your answer is very likely to get read by those who came up with the idea.) 回答1: The compilation of a C++ program involves

问题 What are undefined reference/unresolved external symbol errors? What are common causes and how to fix/prevent them? Feel free to edit/add your own. 回答1: Compiling a C++ program takes place in several steps, as specified by 2.2 (credits to Keith Thompson for the reference): The precedence among the syntax rules of translation is specified by the following phases [see footnote] . Physical source file characters are mapped, in an implementation-defined manner, to the basic source character set

问题 What are undefined reference/unresolved external symbol errors? What are common causes and how to fix/prevent them? Feel free to edit/add your own. 回答1: Compiling a C++ program takes place in several steps, as specified by 2.2 (credits to Keith Thompson for the reference): The precedence among the syntax rules of translation is specified by the following phases [see footnote] . Physical source file characters are mapped, in an implementation-defined manner, to the basic source character set

问题 What are undefined reference/unresolved external symbol errors? What are common causes and how to fix/prevent them? Feel free to edit/add your own. 回答1: Compiling a C++ program takes place in several steps, as specified by 2.2 (credits to Keith Thompson for the reference): The precedence among the syntax rules of translation is specified by the following phases [see footnote] . Physical source file characters are mapped, in an implementation-defined manner, to the basic source character set