foo.c: In function 'main':
foo.c:10:2: warning: statement with no effect [-Wunused-value]
  for(i;i>0;i=i/10);
  ^~~
foo.c:10:2: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
foo.c:11:6: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'for'
      {
      ^
foo.c:17:10: warning: zero-length gnu_printf format string [-Wformat-zero-length]
   printf("");
          ^~
foo.c:9:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&num);
  ^~~~~~~~~~~~~~~~

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