g++ -shared -fPIC helloworld.cpp -o ./hw, core dumped

Question

I am a newer of linux, I build a hello world as following command:

g++ -shared -fPIC helloworld.cpp -o hw

./hw causes

Segmentation fault (core dumped)

why?

g++ helloworld.cpp -o hw
./hw 

work well.

Answer 1

The first command builds a shared library instead of a executable file. Shared libraries are different from normal executable files. They (usually) cannot be executed directly, but can be used by other programs.