tests/data/test-diff-filter/test-PR25661-4-v1.c

#include <inttypes.h>

struct S
{
  union
  {
    uint64_t marker[0];
    struct
    {
      uint64_t a;
      uint64_t b;
    };
  };
  uint64_t c;
};

void
func(struct S *s)
{
  s->a = 1;
}