foo.c: In function 'main':
foo.c:19:48: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   19 |           if (year % 400 == 0 || year % 4 == 0 && year % 100 != 0)
      |                                  ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~
foo.c:21:11: warning: this 'else' clause does not guard... [-Wmisleading-indentation]
   21 |           else
      |           ^~~~
foo.c:22:25: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'else'
   22 |               day = 28; break;
      |                         ^~~~~
foo.c:25:5: warning: 'day' may be used uninitialized [-Wmaybe-uninitialized]
   25 |     printf("%d", day);
      |     ^~~~~~~~~~~~~~~~~
foo.c:4:22: note: 'day' was declared here
    4 |     int year, month, day;
      |                      ^~~

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