/in/foo.c: In function 'main':
/in/foo.c:6:12: error: expected '(' before '{' token
    6 |         for{sun=100;sum<1000;sum++};
      |            ^
      |            (
/in/foo.c:6:13: error: 'sun' undeclared (first use in this function); did you mean 'sum'?
    6 |         for{sun=100;sum<1000;sum++};
      |             ^~~
      |             sum
/in/foo.c:6:13: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:6:24: warning: statement with no effect [-Wunused-value]
    6 |         for{sun=100;sum<1000;sum++};
      |                     ~~~^~~~~
/in/foo.c:6:35: error: expected ';' before '}' token
    6 |         for{sun=100;sum<1000;sum++};
      |                                   ^
      |                                   ;