C上的C编译错误

Question

gcc -c -o fsbench.o fsbench.c -O3 -Wall -Wextra
gcc -o fsbench fsbench.o -O3 -Wall -Wextra -lpthread
Undefined symbols for architecture x86_64:
 "_reposition_offset", referenced from:
  _perf_io in fsbench.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see     invocation)
make: *** [fsbench] Error 1

我无法在mac上编译我的程序。它一直在抛出这个错误。我尝试了几件事，但没有错误地编译它。