destructor

问题 I came across this in chapter 10, Thinking in C++ vol.1 by Bruce Eckel. Destructors for static objects (that is, all objects with static storage, not just local static objects as in the example above) are called when main( ) exits or when the Standard C library function exit( ) is explicitly called. In most implementations, main( ) just calls exit( ) when it terminates. This means that it can be dangerous to call exit( ) inside a destructor because you can end up with infinite recursion I

问题 I have this class: class Test { private $test = 'ok'; public function doTest() { echo $this->test; } public function __destruct() { $this->test = 'not ok'; } } and the following test case: $test = new Test; $test->__destruct(); // I wish this would throw a Fatal Error or something... $test->doTest(); // prints "not ok" What I want to accomplish is to prevent __destruct() from being called manually, so that doTest() will never print "not ok". I tried setting the destructor's visibility to

问题 I want to design a class in C++ called Entity. That entity has a pointer to a member of Vector3D which is the position of the entity in 3D space. The constructor allows a pointer of type Vector3D to be passed to the constructor, such that the Vector3D instance is instantiated outside of the class. Because there is a pointer to a dynamically allocated object, the copy constructor and assignment operator must be overloaded to deep copy the vector. However, because the vector can be passed in

问题 // Foo.h class Foo { public: Foo(); ~Foo(); void exec(); }; // Foo.cpp Foo::~Foo() { // Statements A exit(0); } //main.cpp int main() { Foo foo; foo.exec(); // Statements B return 0; } So why both Statements A and B get executed? And is the destructor called when we reach return 0? I have seen variants where void exec(); is int exec(); and the main function ends with return foo.exec(); does this calls the destructor? Because I want to have an object that takes control of the code flow from

问题 Here is the code. What interests me is new_data. Why delete[] new_data crashes program? How to fix it? There is a lot going on inside functions and anyway I am writing it to post this post as I am getting: "It looks like your post is mostly code; please add some more details." error, so sorry for the spam but I have such problem with a lot of lines of code so SO asks me to describe my problem with many words. char * new_data; ... new_data = new char[end_file-beg_file+20000000]; string i_str;

问题 Let's say I have two classes: class Container(): def __init__(self, name): self.name = name class Data(): def __init__(self): self._containers = [] def add_container(self,name): self._containers.append(name) setattr(self, name, Container(name)) Now let's say myData = Data() myData.add_container('contA') Now, if I do del myData.contA it of course doesn't remove name from myData._containers . So how would I write a destructor in Container so it deletes the attribute but also removes name from

问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: Can a local variable’s memory be accessed outside its scope? Code: #include <iostream> using namespace std; class B{ public: int b; B():b(1){} ~B(){cout << "Destructor ~B() " << endl;} }; class A{ public: B ob; A()try{throw 4;} catch(...){cout << "Catched in A() handler : ob.b= " << ob.b<<endl;} }; int main()try{ A t; } catch(...){cout << "CATCHED in Main" << endl;} Output: Destructor ~B() Catched in A() handler

问题 Suppose that I have the following code: void foo() { { myclass object; object.do_something(); } cout<<"hello"<<endl; } Is ~myclass() guaranteed to be called by the time the local scope is exited , or might it be called at a later time (such as when the function returns)? 回答1: Yes, it is guaranteed: [class.dtor] Destructors are invoked implicitly for ... a constructed object with automatic storage duration when the block in which the object is created exits. 来源： https://stackoverflow.com

问题 I am trying to write a code that uses opencv Mat objects it goes something like this Mat img; vector<Mat> images; for (i = 1; i < 5; i++) { img.create(h,w,type) // h,w and type are given correctly // input an image from somewhere to img correctly. images.push_back(img); img.release() } for (i = 1; i < 5; i++) images[i].release(); I however still seem to have memory leakage can anyone tell me why it is so? I thought that if the refcount of a mat object = 0 then the memory should be

问题 My friend told me C++ allows us to call a member function even if the instance is destroyed from memory. So I write the code below to verify it, but why the value of a can be extracted even after the object was destroyed? I thought there would be a segment fault. #include <iostream> class Foo{ public: Foo(int a = 0){ std::cout << "created" << std::endl; this->a = a; } ~Foo(){ std::cout << "destroyed" << std::endl; } Foo *f(){ std::cout << "a=" << a << std::endl; return this; } private: int a;