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  1. #include <iostream>
  2. using namespace std;
  3.  
  4. struct A 
  5. {
  6. 	unsigned int value = 0;
  7. };
  8.  
  9. A get_set(const A* user_a = nullptr)
  10. {
  11. 	static A a = { 31 };
  12. 	// This need to be thread safe
  13. 	// Multiple readers, one writer
  14. 	if(user_a)
  15. 	{
  16. 		// Copy
  17. 		a = *user_a;
  18. 	}
  19. 	return a;
  20. }
  21.  
  22. A default_a() {
  23. 	return get_set();
  24. }
  25.  
  26.  
  27. A switch_a(const A& user_a) {
  28. 	A old_a = get_set();
  29. 	get_set(&user_a);
  30. 	return old_a;
  31. }
  32.  
  33. void set_a(const A& user_a) {
  34. 	get_set(&user_a);
  35. }
  36.  
  37.  
  38. int main() {
  39. 	{
  40. 		A def_a = default_a();
  41. 		cout << def_a.value << endl;
  42. 	}
  43.  
  44. 	{
  45. 		A my_a = { 32 };
  46. 		A old_a = switch_a(my_a);
  47. 		cout << old_a.value << endl;
  48. 		A def_a = default_a();
  49. 		cout << def_a.value << endl;
  50. 	}
  51.  
  52. 	{
  53. 		A my_a = { 33 };
  54. 		set_a(my_a);
  55. 		A def_a = default_a();
  56. 		cout << def_a.value << endl;
  57. 	}
  58.  
  59. 	return 0;
  60. }
Success #stdin #stdout 0s 15232KB
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stdin
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Standard input is empty
stdout
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31
31
32
33
https://ideone.com/iZQwsb
language:
C++14 (gcc 8.3)
created:
5 years ago
visibility:
public

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