/in/foo.c: In function 'main':
/in/foo.c:19:15: warning: implicit declaration of function 'FindMaxNeg' [-Wimplicit-function-declaration]
     maxNegA = FindMaxNeg(a, n1);
               ^~~~~~~~~~
/tmp/ccUVDiXe.o: In function `main':
foo.c:(.text.startup+0xa4): undefined reference to `FindMaxNeg'
foo.c:(.text.startup+0xb4): undefined reference to `FindMaxNeg'
collect2: error: ld returned 1 exit status