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  1. // Safe swap integer. (1.00)
  2.  
  3. #include <limits.h>
  4. #include <stdio.h>
  5.  
  6. void swapint(int *a, int *b)
  7. {
  8.     int t = *a; *a = *b; *b = t; // preferred
  9. }
  10.  
  11. void swapint_xor(int *a, int *b)
  12. {
  13.     if (a != b)
  14.     {
  15.         *a ^= *b; *b ^= *a; *a ^= *b;
  16.     }
  17. }
  18.  
  19. void swapint_add(int *a, int *b)
  20. {
  21.     if (a != b)
  22.     {
  23.         __builtin_add_overflow(*a, *b, a);
  24.         __builtin_sub_overflow(*a, *b, b);
  25.         __builtin_sub_overflow(*a, *b, a);
  26.     }
  27. }
  28.  
  29. int main(void)
  30. {
  31.     typedef void (*swap_type)(int *, int *);
  32.  
  33.     swap_type fs[] = {
  34.         swapint,
  35.         swapint_xor,
  36.         swapint_add,
  37.         0
  38.     };
  39.  
  40.     for (swap_type *f = fs; *f; f++)
  41.     {
  42.         int a = 1;
  43.         int b = INT_MAX;
  44.         (*f)(&a, &b);
  45.         printf("f(a,b): a = %d, b = %d; ", a, b);
  46.         (*f)(&a, &a);
  47.         printf("f(a,a): a = %d\n", a);
  48.     }
  49.     return 0;
  50. }
Success #stdin #stdout 0s 5304KB
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stdin
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Standard input is empty
stdout
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f(a,b): a = 2147483647, b = 1; f(a,a): a = 2147483647
f(a,b): a = 2147483647, b = 1; f(a,a): a = 2147483647
f(a,b): a = 2147483647, b = 1; f(a,a): a = 2147483647
https://ideone.com/E64wez
language:
C (gcc 8.3)
created:
4 hours ago
visibility:
public

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