UCS_STATIC_ASSERT memo

[hiroyuki-sato]

#include <stdio.h>

#define UCS_STATIC_ASSERT(_cond) \
     switch(0) {case 0:case (_cond):;}

int main(){
  UCS_STATIC_ASSERT(sizeof(int) == sizeof(char)); // ERROR
  UCS_STATIC_ASSERT(sizeof(int) == sizeof(int));  // OK
}

test.c: In function ‘main’:
test.c:4:24: error: duplicate case value
      switch(0) {case 0:case (_cond):;}
                        ^
test.c:7:3: note: in expansion of macro ‘UCS_STATIC_ASSERT’
   UCS_STATIC_ASSERT(sizeof(int) == sizeof(char));
   ^~~~~~~~~~~~~~~~~
test.c:4:17: note: previously used here
      switch(0) {case 0:case (_cond):;}
                 ^
test.c:7:3: note: in expansion of macro ‘UCS_STATIC_ASSERT’
   UCS_STATIC_ASSERT(sizeof(int) == sizeof(char));
   ^~~~~~~~~~~~~~~~~