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  1.  
  2.  
  3. #pragma pack(push, 8)
  4. struct A
  5. {
  6. 	char c, d;
  7. };
  8. #pragma pack(pop)
  9.  
  10.  
  11. struct B
  12. {
  13. 	_Alignas(8) char c;
  14. 	_Alignas(8) char d;
  15. };
  16.  
  17. ///////
  18.  
  19. #pragma pack(push, 1)
  20. struct C
  21. {
  22. 	float c, d;
  23. };
  24. #pragma pack(pop)
  25.  
  26. /* crash, because 
  27.     
  28.     error: ‘_Alignas’ specifiers cannot reduce alignment of ‘c’
  29.     
  30. struct D
  31. {
  32. 	_Alignas(1) float c;
  33. 	_Alignas(1) float d;
  34. };
  35. */
  36.  
  37.  
  38. #include <stdio.h>
  39.  
  40. int main(int argc, char** argv)
  41. {
  42. 	struct A a;
  43. 	struct B b;
  44. 	struct C c;
  45. //	struct D d;
  46. 	printf("size of A = %llu\n", sizeof(a));
  47. 	printf("size of B = %llu\n", sizeof(b));
  48. 	printf("size of C = %llu\n", sizeof(c));
  49. //	printf("size of D = %llu\n", sizeof(d));
  50.  
  51. 	return 0;
  52. }
Success #stdin #stdout 0s 5680KB
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Standard input is empty
stdout
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size of A = 2
size of B = 16
size of C = 8
https://ideone.com/bv6mET
language:
C (gcc 8.3)
created:
2 years ago
visibility:
public

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