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#include <iostream>
using namespace std;
 
class Abstract{
	virtual void method () = 0;
public:
	Abstract(int a){};
};
 
int main() {
	Abstract a;
	return 0;
}

prog.cpp: In function ‘int main()’:
prog.cpp:11:11: error: no matching function for call to ‘Abstract::Abstract()’
  Abstract a;
           ^
prog.cpp:11:11: note: candidates are:
prog.cpp:7:2: note: Abstract::Abstract(int)
  Abstract(int a){};
  ^
prog.cpp:7:2: note:   candidate expects 1 argument, 0 provided
prog.cpp:4:7: note: constexpr Abstract::Abstract(const Abstract&)
 class Abstract{
       ^
prog.cpp:4:7: note:   candidate expects 1 argument, 0 provided
prog.cpp:4:7: note: constexpr Abstract::Abstract(Abstract&&)
prog.cpp:4:7: note:   candidate expects 1 argument, 0 provided
prog.cpp:11:11: error: cannot declare variable ‘a’ to be of abstract type ‘Abstract’
  Abstract a;
           ^
prog.cpp:4:7: note:   because the following virtual functions are pure within ‘Abstract’:
 class Abstract{
       ^
prog.cpp:5:15: note: 	virtual void Abstract::method()
  virtual void method () = 0;
               ^

Standard output is empty