Linker errors

~/Projects/CPP/AssisterLib> clang++ prog.cpp -o program -L. -lassister
./libassister.a(assister.o): In function `ArgumentException':
/home/rudy/Projects/CPP/AssisterLib/assister.cpp:29: undefined reference to `vtable for ArgumentException'
/home/rudy/Projects/CPP/AssisterLib/assister.cpp:34: undefined reference to `vtable for ArgumentException'
./libassister.a(assister.o): In function `str2int(std::string const&)':
/home/rudy/Projects/CPP/AssisterLib/assister.cpp:99: undefined reference to `typeinfo for ArgumentException'
/home/rudy/Projects/CPP/AssisterLib/assister.cpp:99: undefined reference to `ArgumentException::~ArgumentException()'
./libassister.a(assister.o): In function `str2double(std::string const&)':
/home/rudy/Projects/CPP/AssisterLib/assister.cpp:107: undefined reference to `typeinfo for ArgumentException'
/home/rudy/Projects/CPP/AssisterLib/assister.cpp:107: undefined reference to `ArgumentException::~ArgumentException()'
./libassister.a(assister.o): In function `GCC_except_table12':
assister.cpp:(.gcc_except_table+0x1bc): undefined reference to `typeinfo for ArgumentException'
./libassister.a(assister.o): In function `GCC_except_table13':
assister.cpp:(.gcc_except_table+0x224): undefined reference to `typeinfo for ArgumentException'
clang: error: linker command failed with exit code 1 (use -v to see invocation)