foo.cc: In function 'int main()':
foo.cc:8:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
    8 |  freopen("b.in","r",stdin);
      |  ~~~~~~~^~~~~~~~~~~~~~~~~~
foo.cc:9:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
    9 |  freopen("b.out","w",stdout);
      |  ~~~~~~~^~~~~~~~~~~~~~~~~~~~

Found 10 testcases.