destructor

问题 The compiler generates some class methods like copy constructors, destructors, etc. Is it possible to have gdb break on those methods to, e.g., observe where objects are being copied or destroyed? 回答1: Can gdb break on implicit class methods? Yes, of course, it can. (gdb) break MyClass::MyClass(const MyClass &) // break when copied (gdb) break MyClass::~MyClass() // break when object destroyed as simple as that. These are breakpoints based, NOT on file:line, but on function names. If you've a

问题 When can an object of a class call the destructor of that class, as if it's a regular function? Why can't it call the constructor of the same class, as one of its regular functions? Why does the compiler stops us from doing this? For example: class c { public: void add() ; c(); ~c() ; }; void main() { c objC ; objC.add() ; objC.~c() ; // this line compiles objC.c() ; // compilation error } 回答1: By definition, a constructor is only called once, when the object is created. If you have access to

问题 I'm very confused about using destructors in Qt4 and hope, you guys can help me. When I have a method like this (with "Des" is a class): void Widget::create() { Des *test = new Des; test->show(); } how can I make sure that this widget is going to be deleted after it was closed? And in class "Des" i have this: Des::Des() { QPushButton *push = new QPushButton("neu"); QHBoxLayout *layout = new QHBoxLayout; layout->addWidget(push); setLayout(layout); } where and how do I have to delete *push and

问题 This question may seem trivial, but I hope you won't ignore it. Before destroying a TThread object it is usually necessary to wait until the thread that called the TThread.Execute() method finishes, for only then can we be sure that, for instance, the objects destroyed inside the class's destructor are no longer accessed. Therefore it is necessary to call Terminate to set the Terminated flag that the thread has to check to know whether to exit or not, and then call the WaitFor() method.

问题 I come across the rule (section N3797::12.8/11 [class.copy] ) An implicitly-declared copy/move constructor is an inline public member of its class. A defaulted copy/ move constructor for a class X is defined as deleted (8.4.3) if X has: [...] — any direct or virtual base class or non-static data member of a type with a destructor that is deleted or inaccessible from the defaulted constructor, or [...] But I can't get the point of deleted destructor appearing in a virtual or direct base class

问题 I'm trying to use an union (C++) that has some non-primitive variables, but I'm stuck trying to create the destructor for that class. As I have read, it is not possible to guess what variable of the union is being used so there is no implicit destructor, and as I'm using this union on the stack, the compiler errors that the destructor is deleted. The union is as follows: struct LuaVariant { LuaVariant() : type(VARIANT_NONE) { } LuaVariantType_t type; union { std::string text; Position pos;

问题 Destructors are weird . I was attempting to eliminate the need of using the disposable pattern by using 'smart' reference management, ensuring that the garbage collector could collect objects at the correct time. In one of my destructors I had to wait for an event from another object, which I noticed it didn't. The application simply shut down and the destructor was terminated in middle of execution. I'd expect a destructor is always allowed to finish running, but as the following test

问题 I have a PHP class that creates a PNG image on the fly and sends it to browser. PHP manual says that I need to make sure that imagedestroy function is called at end to release the memory. Now, if I weren't using a class, I would have some code like this: function shutdown_func() { global $img; if ($img) imagedestroy($img); } register_shutdown_function("shutdown_func"); However, I believe that appropriate place for my class would be to place a call to imagedestroy in class' destructor. I

问题 I have been reading a lot of tutorials on C++ class but they miss something that other tutorials include. Can someone please show me how to write and use a very simple C++ class that uses visibility, methods and a simple constructor and destructor? 回答1: Well documented example taken and explained better from Constructors and Destructors in C++: #include <iostream> // for cout and cin class Cat // begin declaration of the class { public: // begin public section Cat(int initialAge); //

问题 I'm working on a threaded telnet server (one thread per connection), and can't figure out how to get rid of valgrind errors. I've narrowed the problem down to WHERE I delete the tcpsocket. I create the QTcpSocket in the run() method of the QThread: void TelnetConnection::run() { tcpSocketPtr = new QTcpSocket(); if (!tcpSocketPtr->setSocketDescriptor(socketDescriptor)) { emit error(tcpSocketPtr->error()); return; } .... } When my app wants to disconnect the client I call: void TelnetConnection