/in/foo.c:2:1: warning: return type defaults to 'int' [-Wimplicit-int]
 main()
 ^~~~
/in/foo.c: In function 'main':
/in/foo.c:23:1: warning: implicit declaration of function 'getch' [-Wimplicit-function-declaration]
 getch();
 ^~~~~
/tmp/cceiPGr9.o: In function `main':
foo.c:(.text.startup+0x93): undefined reference to `getch'
collect2: error: ld returned 1 exit status