/in/foo.c:12:2: warning: return type defaults to 'int' [-Wimplicit-int]
  main()
  ^~~~
/in/foo.c: In function 'main':
/in/foo.c:20:3: warning: implicit declaration of function 'getcahr' [-Wimplicit-function-declaration]
   getcahr();
   ^~~~~~~
/in/foo.c: In function 'daoxu':
/in/foo.c:10:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^
/tmp/ccq3k5SQ.o: In function `main':
foo.c:(.text.startup+0x5c): undefined reference to `getcahr'
collect2: error: ld returned 1 exit status