foo.c:3:6: warning: return type of ‘main’ is not ‘int’ [-Wmain]
    3 | void main()
      |      ^~~~
foo.c: In function ‘main’:
foo.c:15:33: warning: this ‘for’ clause does not guard... [-Wmisleading-indentation]
   15 |                                 for(i=2;i<=sqrt(b);i++)
      |                                 ^~~
foo.c:22:41: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the ‘for’
   22 |                                         if(t==0)
      |                                         ^~