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  1. #include <iostream>
  2. #include <cstdint>
  3. #include <algorithm>
  4. using namespace std;
  5.  
  6. union structA{
  7.   uint8_t mem[3];
  8.  
  9.   struct{
  10.     unsigned field1 : 8;
  11.     unsigned field2 : 12; 
  12.     unsigned field3 : 4;
  13.   };
  14. };
  15.  
  16. struct structB{
  17.   uint8_t mem[10];
  18. };
  19.  
  20.  
  21. int main() {
  22.  
  23. 	cout << "Infos:"<<endl; 
  24.     cout << "  Alignment constraint of structA: "<<alignof(structA)<<endl;
  25.     cout << "  Alignment constraint of uint8_t: "<<alignof(uint8_t)<<endl;
  26. 	cout << "  Size : "<<sizeof(structA)<<endl;
  27. 	cout << "  Is trivially copyable: "<<is_trivially_copyable<structA>::value<<endl; 
  28.  
  29. 	structA ia;                                         // test object
  30. 	ia.field1 =7; ia.field2=911; ia.field3=5;  
  31.  
  32. 	uint8_t globalMem[128];   
  33. 	fill( globalMem, globalMem +sizeof(globalMem), 0);     
  34.  
  35. 	structA *pa = new (globalMem+10) structA(ia);   // placement new to properly create object
  36.  
  37. 	structA a1 = *reinterpret_cast<structA*>(&globalMem[0]);
  38. 	structA a2 = *reinterpret_cast<structA*>(&globalMem[10]);
  39. 	structB b1 = *reinterpret_cast<structB*>(&globalMem[30]);
  40.  
  41. 	cout <<endl<<"Test:"<<endl;
  42. 	cout << "  original: "<<ia.field1<<" "<<ia.field2<<" "<<ia.field3<<endl; 
  43. 	cout << "  copy:     " <<a2.field1<<" "<<a2.field2<<" "<<a2.field3<<endl; 
  44.  
  45. 	return 0;
  46. }
Success #stdin #stdout 0s 3468KB
comments (?)
stdin 
Standard input is empty
stdout 
Infos:
  Alignment constraint of structA: 4
  Alignment constraint of uint8_t: 1
  Size : 4
  Is trivially copyable: 1

Test:
  original: 7 911 5
  copy:     7 911 5
https://ideone.com/K3PYpT
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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