/in/foo.c: In function 'main':
/in/foo.c:6:2: warning: implicit declaration of function 'sacnf' [-Wimplicit-function-declaration]
  sacnf("%lf %lf",&r,&h);
  ^~~~~
/tmp/ccKUxcmY.o: In function `main':
foo.c:(.text.startup+0x16): undefined reference to `sacnf'
collect2: error: ld returned 1 exit status