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  1. #include <iostream>
  2. #include <functional>
  3. #include <memory>
  4. #include <string>
  5.  
  6. using namespace std;
  7.  
  8. struct library
  9. {
  10. 	library()
  11. 	{
  12. 		cout << "creating library\n";
  13. 	}
  14. 	~library()
  15. 	{
  16. 		cout << "destroying library\n";
  17. 	}
  18. };
  19.  
  20. template<typename Signature>
  21. class library_function
  22. {
  23. public:
  24.     library_function(
  25.         shared_ptr<library> lib, Signature* library_function)
  26.         :
  27.     m_library(lib),
  28.     m_function(library_function)
  29.    {}
  30.  
  31.     operator Signature*() const { return m_function; }
  32.  
  33. private:
  34.    shared_ptr<library> m_library;
  35.    Signature* m_function;
  36. };
  37.  
  38. void test_lib_func(string s)
  39. {
  40. 	cout << "called test_lib_func(" << s << ")\n";
  41. }
  42.  
  43. int main()
  44. {
  45. 	shared_ptr<library> lib = make_shared<library>();
  46. 	{
  47. 	    library_function<void(string)> functor(lib, test_lib_func);
  48. 	    functor("direct call before reset");
  49. 	    lib.reset();
  50. 	    functor("direct call after reset");
  51. 	    cout << "functor about to go out of scope\n";
  52. 	}
  53.  
  54. 	lib = make_shared<library>();
  55. 	function<void(string)> func =
  56. 	    library_function<void(string)>(lib, test_lib_func);
  57. 	func("std::function call before reset");
  58. 	lib.reset();
  59. 	func("std::function call after reset");
  60. 	return 0;
  61. }
Success #stdin #stdout 0s 3432KB
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stdin
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Standard input is empty
stdout
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creating library
called test_lib_func(direct call before reset)
called test_lib_func(direct call after reset)
functor about to go out of scope
destroying library
creating library
called test_lib_func(std::function call before reset)
called test_lib_func(std::function call after reset)
destroying library
https://ideone.com/BZvuk9
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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