Error Definition Of Implicitly-declared Operator
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Definition Of Implicitly Declared Constructor C++
more about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users definition of implicitly-declared destructor Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping error definition of implicitly-declared 'virtual each other. Join them; it only takes a minute: Sign up Can anyone help me understand this error? “definition of implicitly-declared ‘classA::classA()’” up vote 20 down vote favorite 1 Heres the code: #include
Definition Of Implicitly Declared Copy Assignment Operator
std; class classA { protected: void setX(int a); private: int p; }; classA:: classA() { //error here. p = 0; } void classA:: setX(int a) { p = a; } int main() { system("PAUSE"); return EXIT_SUCCESS; } c++ share|improve this question asked Apr 23 '11 at 17:34 darko 61662248 add a comment| 3 Answers 3 active oldest votes up vote 41 down vote accepted You forgot to declare the constructor in the class definition. Declare it
Which Is Of Non-class Type
in public section of the class (if you want clients to create instance using it): class classA { public: classA(); // you forgot this! protected: void setX(int a); private: int p; }; Now you can write its definition outside the class which you've already done. share|improve this answer edited Apr 23 '11 at 17:41 answered Apr 23 '11 at 17:36 Nawaz 203k62447654 Actually, the thing which I know was that the default constructor is provided by the compiler by default. Here you have mentioned that definition of the constructor was missing. But, I was not knowing the 'WHY' we have to provide the default constructor when it is already being provided by the compiler. But, now, I knew that if we are defining the default constructor which is not in accordance with the one provided by the compiler, we will have to define it explicitly. I din't find the 'WHY'. :) –Chaitanya Mar 6 '13 at 9:43 @Chaitanya: The compiler does generate a default constructor for you IF you don't declare (and define) one yourself. In the question, the OP has attempted to define the default constructor outside the class, without declaring it in the class. The code is ill-formed, and the compiler would generate error. Let me know if you understand it now (see the code in the question to completely understand it)
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C++ Destructor
about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss c++ copy constructor Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up c++ compiling error http://stackoverflow.com/questions/5765780/can-anyone-help-me-understand-this-error-definition-of-implicitly-declared-cl related to constructor/destructor definition up vote 16 down vote favorite 4 I'm trying to define the constructor and destructor of my class but I keep getting the error: definition of implicitly-declared 'x::x()' What does it mean? Part of the code: ///Constructor StackInt::StackInt(){ t = (-1); stackArray = new int[20]; }; ///Destructor StackInt::~StackInt(){ delete[] stackArray; } c++ constructor destructor share|improve this question edited Mar 1 '13 http://stackoverflow.com/questions/708008/c-compiling-error-related-to-constructor-destructor-definition at 15:48 Drew Noakes 127k73394489 asked Apr 2 '09 at 1:53 caesar 1 Post your code ! –Uri Apr 2 '09 at 1:54 How are your files structured (*.h, *.cpp)? Which file is that posted code in? –paxdiablo Apr 2 '09 at 2:02 add a comment| 2 Answers 2 active oldest votes up vote 40 down vote In the class declaration (probably in a header file) you need to have something that looks like: class StackInt { public: StackInt(); ~StackInt(); } To let the compiler know you don't want the default compiler-generated versions (since you're providing them). There will probably be more to the declaration than that, but you'll need at least those - and this will get you started. You can see this by using the very simple: class X { public: X(); // <- remove this. }; X::X() {}; int main (void) { X x ; return 0; } Compile that and it works. Then remove the line with the comment marker and compile again. You'll see your problems appear then: class X {}; X::X() {}; int main (void) { X x ; return 0; }
here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site About Us Learn more about Stack http://stackoverflow.com/questions/26667975/why-does-a-class-with-a-user-declared-destructor-have-an-implicitly-defaulted-co Overflow the company Business Learn more about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up Why does a class with a user-declared destructor have an implicitly defaulted constructor? up vote 0 definition of down vote favorite Code: struct A { ~A(){ }; }; A::A(){ }; //error: definition of implicitly declared default constructor int main() { A a; } DEMO Why does the code produces the error? I expected that the program compiles fine. The Standard says N3797::12.8/7 [class.copy]: If the class definition does not explicitly declare a copy constructor, one is declared implicitly. If the class definition declares a move constructor or move assignment definition of implicitly operator, the implicitly declared copy constructor is defined as deleted; otherwise, it is defined as defaulted (8.4). The latter case is deprecated if the class has a user-declared copy assignment operator or a user-declared destructor. It's a bug or my misunderstanding? c++ constructor default-constructor share|improve this question edited May 6 at 16:45 ThomasMcLeod 3,63331343 asked Oct 31 '14 at 5:18 Dmitrii Bundin 5,68062258 You can only provide definitions for functions that you declared yourself... there's no such thing as giving a non-inline body for an implicitly-declared function –M.M Oct 31 '14 at 5:24 @MattMcNabb Yeah, I've understood it from answer. But what's the point to mark such functions as default. They've declared by a compiler already. –Dmitrii Bundin Oct 31 '14 at 5:26 @DmitryFucintv: There is no need (assuming you are not doing anything which causes the function to be deleted). Some people do it because they want to be very explicit about what functions are available in their classes. A lot of people don't approve of implicitly declared functions, and would prefer if every function was required to be explicit. –Benjamin Lindley Oct 31 '14 at 5:29 That's quite a different question to what you just posted. (a) marking it as default mea