destruction

问题 Is the destruction of automatic objects (objects created on the stack) guaranteed to be executed not before they go out of scope? To clarify: #include <iostream> class A { public: A() { std::cout << "1"; } ~A() { std::cout << "3"; } }; void test123() { A a; std::cout << "2"; } To print "2" , a is not required any more, so theoretically the compiler could try to optimise and destroy a as soon as it is not needed any more. Can I rely on the above function always printing 123 ? 回答1: The

问题 Is the destruction of automatic objects (objects created on the stack) guaranteed to be executed not before they go out of scope? To clarify: #include <iostream> class A { public: A() { std::cout << "1"; } ~A() { std::cout << "3"; } }; void test123() { A a; std::cout << "2"; } To print "2" , a is not required any more, so theoretically the compiler could try to optimise and destroy a as soon as it is not needed any more. Can I rely on the above function always printing 123 ? 回答1: The

问题 Is the destruction of automatic objects (objects created on the stack) guaranteed to be executed not before they go out of scope? To clarify: #include <iostream> class A { public: A() { std::cout << "1"; } ~A() { std::cout << "3"; } }; void test123() { A a; std::cout << "2"; } To print "2" , a is not required any more, so theoretically the compiler could try to optimise and destroy a as soon as it is not needed any more. Can I rely on the above function always printing 123 ? 回答1: The

问题 According to 5.2.2/4 "Function call" in n4640 (8.2.2/4 in n4659) function parameters are created and destroyed in the context of the caller. And implementations are allowed to delay the destruction of function parameters to the end of the enclosing full expression (as an implementation-defined feature). Note that the choice is not unspecified , but rather implementation-defined . ( It is not entirely clear how this agrees with 3.3.3 "Block scope" (6.3.3 in n4659), which seems to imply that

问题 I can not understand why after destructuring assignment, items prop does not equal Gorilla . It will be used after deleting the main prop items: "Piggi" in the origin object options. I do not understand why... 'use strict'; let options = { size: 100, items: "Piggi" } let { title="Menu", items:w="Gorilla", size } = options; let a = title; let b = w; console.log(a + " - " + b); // must be "Menu - Gorilla" 回答1: In the destructuring declaration with initialization here: let { items:w = "Gorilla"

问题 login.aspx if (IsPostBack == false) { //destroy any login information Session["password"] = "false"; Session["login"] = "false"; Session.Abandon(); Session.RemoveAll(); } if (TextBox2.Text == main_password) {//then he is website server admin Session["password"] = "password"; Session["login"] = "true"; Response.Redirect("~/TABLE.aspx"); } table.aspx //checking if website server admin if ("password" == (string)Session["password"]) { link_logout.Enabled = true; }//if ends else {//not authorized

问题 If I have this code: class A { ... }; class B { ... }; void dummy() { A a(...); B b(...); ... } I know that variables a and b will be destroyed in reverse allocation order ( b will be destroyed first, then a ); but can I be sure that the optimizer will never swap the allocation and construction of a and b ? Or I must use volatile to enforce it? 回答1: The only guarantees are that any observable side effects (that is, reads and writes to volatile objects and calls to I/O functions) of the

问题 I know that vector elements destruction order is not defined by C++ standard (see Order of destruction of elements of an std::vector) and I saw that all compilers I checked do this destruction from begin to end - which is quite surprising to me since dynamic and static arrays do it in reverse order, and this reverse order is quite often in C++ world. To be strict: I know that "Container members ... can be constructed and destroyed in any order using for example insert and erase member

问题 As a part of trying to tackle a memory leak in our application, we discovered that for every SkinnableComponent , the skinDestructionPolicy is set to "never" by default. This means that when using static skin parts, the skin is forever detained in memory. Furthermore, the override of a partRemoved() in the host component will never be triggered. Hence, event listeners we add in the partAdded() override are not removed, which effectively causes views and skins to be kept in memory. When doing

问题 Consider a function with the following signature: (defn make-widget [& {:keys [x y] :or {x 10 y 20}}] ...) What is the best way to pass a map to the function, e.g.: (make-widget {:x 100}) or (make-widget {:y 200 :x 0}) What I have currently thought of is via vec , flatten and apply e.g.: (apply make-widget (flatten (vec ({:x 100})) I strongly believe there is a better way to do this. Can you please consider one? 回答1: I can't think of a more elegant way, either, though it seems to me to that