Language: C

#include <stdio.h>

void main(){
  int S[] = 'SUN','MON','TUE','WED','THU','FRI','SAT';
if(S=='SUN')return 7;
  else if(S=='MON')return 6;
  else if(S=='TUE')return 5;
  else if(S=='WED')return 4;
  else if(S=='THU')return 3;
  else if(S=='FRI')return 2;
  else if(S=='SUN')return 7;
  
 return 0;
}

Compiler output:
main.c: In function 'main':
main.c:4:13: warning: multi-character character constant [-Wmultichar]
    4 |   int S[] = 'SUN','MON','TUE','WED','THU','FRI','SAT';
      |             ^~~~~
main.c:4:13: error: invalid initializer
main.c:4:19: warning: multi-character character constant [-Wmultichar]
    4 |   int S[] = 'SUN','MON','TUE','WED','THU','FRI','SAT';
      |                   ^~~~~
main.c:4:19: error: expected identifier or '(' before '\x4d4f4e'
main.c:4:25: warning: multi-character character constant [-Wmultichar]
    4 |   int S[] = 'SUN','MON','TUE','WED','THU','FRI','SAT';
      |                         ^~~~~
main.c:4:31: warning: multi-character character constant [-Wmultichar]
    4 |   int S[] = 'SUN','MON','TUE','WED','THU','FRI','SAT';
      |                               ^~~~~
main.c:4:37: warning: multi-character character constant [-Wmultichar]
    4 |   int S[] = 'SUN','MON','TUE','WED','THU','FRI','SAT';
      |                                     ^~~~~
main.c:4:43: warning: multi-character character constant [-Wmultichar]
    4 |   int S[] = 'SUN','MON','TUE','WED','THU','FRI','SAT';
      |                                           ^~~~~
main.c:4:49: warning: multi-character character constant [-Wmultichar]
    4 |   int S[] = 'SUN','MON','TUE','WED','THU','FRI','SAT';
      |                                                 ^~~~~
main.c:5:7: warning: multi-character character constant [-Wmultichar]
    5 | if(S=='SUN')return 7;
      |       ^~~~~
main.c:5:5: warning: comparison between pointer and integer
    5 | if(S=='SUN')return 7;
      |     ^~
main.c:5:20: error: 'return' with a value, in function returning void [-Wreturn-mismatch]
    5 | if(S=='SUN')return 7;
      |                    ^
main.c:3:6: note: declared here
    3 | void main(){
      |      ^~~~
main.c:6:14: warning: multi-character character constant [-Wmultichar]
    6 |   else if(S=='MON')return 6;
      |              ^~~~~
main.c:6:12: warning: comparison between pointer and integer
    6 |   else if(S=='MON')return 6;
      |            ^~
main.c:6:27: error: 'return' with a value, in function returning void [-Wreturn-mismatch]
    6 |   else if(S=='MON')return 6;
      |                           ^
main.c:3:6: note: declared here
    3 | void main(){
      |      ^~~~
main.c:7:14: warning: multi-character character constant [-Wmultichar]
    7 |   else if(S=='TUE')return 5;
      |              ^~~~~
main.c:7:12: warning: comparison between pointer and integer
    7 |   else if(S=='TUE')return 5;
      |            ^~
main.c:7:27: error: 'return' with a value, in function returning void [-Wreturn-mismatch]
    7 |   else if(S=='TUE')return 5;
      |                           ^
main.c:3:6: note: declared here
    3 | void main(){
      |      ^~~~
main.c:8:14: warning: multi-character character constant [-Wmultichar]
    8 |   else if(S=='WED')return 4;
      |              ^~~~~
main.c:8:12: warning: comparison between pointer and integer
    8 |   else if(S=='WED')return 4;
      |            ^~
main.c:8:27: error: 'return' with a value, in function returning void [-Wreturn-mismatch]
    8 |   else if(S=='WED')return 4;
      |                           ^
main.c:3:6: note: declared here
    3 | void main(){
      |      ^~~~
main.c:9:14: warning: multi-character character constant [-Wmultichar]
    9 |   else if(S=='THU')return 3;
      |              ^~~~~
main.c:9:12: warning: comparison between pointer and integer
    9 |   else if(S=='THU')return 3;
      |            ^~
main.c:9:27: error: 'return' with a value, in function returning void [-Wreturn-mismatch]
    9 |   else if(S=='THU')return 3;
      |                           ^
main.c:3:6: note: declared here
    3 | void main(){
      |      ^~~~
main.c:10:14: warning: multi-character character constant [-Wmultichar]
   10 |   else if(S=='FRI')return 2;
      |              ^~~~~
main.c:10:12: warning: comparison between pointer and integer
   10 |   else if(S=='FRI')return 2;
      |            ^~
main.c:10:27: error: 'return' with a value, in function returning void [-Wreturn-mismatch]
   10 |   else if(S=='FRI')return 2;
      |                           ^
main.c:3:6: note: declared here
    3 | void main(){
      |      ^~~~
main.c:11:14: warning: multi-character character constant [-Wmultichar]
   11 |   else if(S=='SUN')return 7;
      |              ^~~~~
main.c:11:12: warning: comparison between pointer and integer
   11 |   else if(S=='SUN')return 7;
      |            ^~
main.c:11:27: error: 'return' with a value, in function returning void [-Wreturn-mismatch]
   11 |   else if(S=='SUN')return 7;
      |                           ^
main.c:3:6: note: declared here
    3 | void main(){
      |      ^~~~
main.c:13:9: error: 'return' with a value, in function returning void [-Wreturn-mismatch]
   13 |  return 0;
      |         ^
main.c:3:6: note: declared here
    3 | void main(){
      |      ^~~~