foo.cc: In function 'int main()':
foo.cc:9:17: error: 't' was not declared in this scope
    9 |                 t=a,a=b,b=t;
      |                 ^
foo.cc:13:17: error: 't' was not declared in this scope
   13 |                 t=a,a=c,c=t;
      |                 ^
foo.cc:17:17: error: 't' was not declared in this scope
   17 |                 t=b,b=c,c=t;
      |                 ^
foo.cc:5:19: warning: unused variable 'd' [-Wunused-variable]
    5 |         int a,b,c,d;
      |                   ^

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