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// cc -o longlong_to_char_array longlong_to_char_array.c
#include <stdio.h>
#include <stdint.h>

int main() {
  uint64_t src = 0x0706050403020100U;
  uint8_t dst[8];

  printf("src: 0x%016llx\n", src);
  ((uint64_t*)dst)[0] = src;
  printf("dst: 0x");
  for(int i=7; i>=0; i--) {
    printf("%02x", dst[i]);
  }
  printf("\n");
  
  return 0;
}