foo.c: In function 'main':
foo.c:5:10: warning: character constant too long for its type
   printf('hello, world');
          ^~~~~~~~~~~~~~
foo.c:5:10: warning: passing argument 1 of 'printf' makes pointer from integer without a cast [-Wint-conversion]
In file included from foo.c:1:0:
C:/mingw32/i686-w64-mingw32/include/stdio.h:380:15: note: expected 'const char * restrict' but argument is of type 'int'
   int __cdecl printf(const char * __restrict__ _Format,...);
               ^~~~~~