foo.cc: In function 'int main()':
foo.cc:25:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
freopen("mason.in","r",stdin);freopen("mason.out","w",stdout);
~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
foo.cc:25:40: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
freopen("mason.in","r",stdin);freopen("mason.out","w",stdout);
~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
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