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  1. // RAII 
  2. #include <iostream>
  3. #include <stdio.h>
  4. #include <stdexcept>
  5.  
  6. using namespace std;
  7.  
  8. void f();
  9.  
  10. // use an object to represent a resource
  11. class File_handle { // belongs in some support library
  12.     FILE* p;
  13. public:
  14. 	File_handle(const char* pp, const char* r) {
  15. 		p = fopen(pp,r);
  16. 		// Commented out for running on Ideone.com
  17.         // if (p==0) throw std::runtime_error("File_error{pp,r}");
  18. 	}
  19.  
  20. 	File_handle(const string& s, const char* r) {
  21.         p = fopen(s.c_str(),r);
  22.         // Commented out for running on Ideone.com
  23.         //if (p==0) throw std::runtime_error("File_error{s,r}");
  24. 	}
  25.  
  26. 	~File_handle() {
  27.         cout << "fclose() called in File_handle" << endl;
  28. 		fclose(p);
  29. 	} // destructor
  30. 	// copy operations
  31. 	// access functions
  32. };
  33.  
  34. struct A
  35. {
  36.     ~A() {
  37.         cout << "~A() called" << endl;
  38.     };
  39. };
  40.  
  41. void good (string s) {
  42.     File_handle fh (s, "r");
  43.     // use fh
  44.     f(); // OOPS!
  45. }
  46.  
  47. void bad(const char* p)
  48. {
  49.     FILE* fh = fopen(p,"r"); // acquire
  50. 	// use f
  51. 	f(); // OOPS!
  52. 	fclose(fh); // release
  53.     cout << "fclose() called" << endl;
  54. }
  55.  
  56. void f()
  57. {
  58. 	A a;
  59. 	throw 42;
  60. }
  61.  
  62. int main() {
  63.  
  64. 	try
  65. 	{
  66.         // Try either of these
  67. 		//f();
  68. 		//bad("c:\\temp\\1.txt");
  69.         //good("c:\\temp\\1.txt");
  70. 	}
  71. 	catch ( ... ) {}
  72.  
  73. 	return 0;
  74. }
Success #stdin #stdout 0s 2892KB
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https://ideone.com/enqHPr
language:
C++ (gcc 8.3)
created:
11 years ago
visibility:
public

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