default-constructor

This question already has an answer here: Conditions for automatic generation of default/copy/move ctor and copy/move assignment operator? 3 answers This is just a quick question to understand correctly what happens when you create a class with a constructor like this: class A { public: A() {} }; I know that no default constructor is generated since it is already defined but are copy and assignment constructors generated by the compiler or in other words do i need to declare a private copy constructor and a private assignment operator in order to prevent this from happening? class A { private:

I am working on editing some old C++ code that uses global arrays defined like so: int posLShd[5] = {250, 330, 512, 600, 680}; int posLArm[5] = {760, 635, 512, 320, 265}; int posRShd[5] = {765, 610, 512, 440, 380}; int posRArm[5] = {260, 385, 512, 690, 750}; int posNeck[5] = {615, 565, 512, 465, 415}; int posHead[5] = {655, 565, 512, 420, 370}; I want to make all of these arrays private members of the Robot class defined below. However, the C++ compiler does not let me initialize data members when I declare them. class Robot { private: int posLShd[5]; int posLArm[5]; int posRShd[5]; int

This compiles perfectly fine with the current MSVC compiler: struct Foo { } const foo; However, it fails to compile with the current g++ compiler: error: uninitialized const 'foo' [-fpermissive] note: 'const struct Foo' has no user-provided default constructor If I provide a default constructor myself, it works: struct Foo { Foo() {} } const foo; Is this another case of MSVC being too permissive, or is g++ too strict here? The C++03 Standard: 8.5 [dcl.init] paragraph 9 If no initializer is specified for an object, and the object is of (possibly cv-qualified) non-POD class type (or array

Actually I can not understand that what is the difference between a no-arg constructor and a default constructor. import javax.swing.*; public class Test extends JFrame { public Test() { super(); this.setSize(200,200); this.setVisible(true); } public static void main(Sting[] arg) { Test cFrame = new Test(); } } Does this invoke the default constructor of this class while creating Test object called cFrame? Elliott Frisch The default constructor is a no-args constructor that the Java compiler inserts on your behalf; it contains a default call to super(); (not supper() ) which is the default

The standard and the C++ book say that the default constructor for class type members is called by the implicit generated default constructor, but built-in types are not initialized. However, in this test program I get unexpected results when allocating an object in the heap or when using a temporary object: #include<iostream> struct Container { int n; }; int main() { Container c; std::cout << "[STACK] Num: " << c.n << std::endl; Container *pc = new Container(); std::cout << "[HEAP] Num: " << pc->n << std::endl; delete pc; Container tc = Container(); std::cout << "[TEMP] Num: " << tc.n << std:

When I don't declare a constructor for example, the compiler will provide me with a default constructor that will have no arguments and no definition (body), and thus, will take no action . If I now don't declare a destructor , the compiler will provide me with a default destructor with no defintion (body), and thus, I think no action . So, if I'm finished with an object for example, wouldn't the default destructor reallocate (free) memory used by the object? If it doesn't, why are we getting it? And, maybe the same question applies to the default constructor . If it doesn nothing, why is it

Right now I have a class A that inherits from class B , and B does not have a default constructor. I am trying the create a constructor for A that has the exact same parameters for B 's constructor, but I get: error: no matching function for call to ‘B::B()’ note: candidates are: B::B(int) How would I fix this error? The constructor should look like this: A(int i) : B(i) {} The bit after the colon means, "initialize the B base class sub object of this object using its int constructor, with the value i". I guess that you didn't provide an initializer for B, and hence by default the compiler

In the following code: struct Foo { Foo(int x=0); }; Does the constructor count as a default constructor? C++98 §12.1/5 (emphasis mine) : A default constructor for a class X is a constructor of X that can be called without an argument. If there is no user-declared constructor for class X, a default constructor is implicitly declared. So yes, it does count as a default constructor. See also . 来源： https://stackoverflow.com/questions/11250690/in-c-is-a-constructor-with-only-default-arguments-a-default-constructor