foo.c: In function 'main':
foo.c:24:8: warning: implicit declaration of function 'getsecond' [-Wimplicit-function-declaration]
  ret = getsecond(a, length);
        ^~~~~~~~~
/tmp/ccnBNHC9.o: In function `main':
foo.c:(.text.startup+0x69): undefined reference to `getsecond'
collect2: error: ld returned 1 exit status

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