/in/foo.c: In function 'main':
/in/foo.c:16:1: warning: implicit declaration of function 'output' [-Wimplicit-function-declaration]
 output(a,y);
 ^~~~~~
/in/foo.c: In function 'search':
/in/foo.c:7:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^
/tmp/ccp9EAE2.o: In function `main':
foo.c:(.text.startup+0x72): undefined reference to `output'
collect2: error: ld returned 1 exit status