linking cxx shared library

To link a C++ shared library, you need to follow these steps:

1. Compile your C++ code into an object file using the `-c` flag. For example, if your C++ code is in a file called `mylibrary.cpp`, you would run the following command:

`g++ -c -fPIC mylibrary.cpp`

The `-fPIC` flag is necessary to generate Position Independent Code, which is needed for shared libraries.

2. Link the object file into a shared library using the `-shared` flag. For example, if your object file is called `mylibrary.o`, you would run the following command:

`g++ -shared -o libmylibrary.so mylibrary.o`

The `-o` flag specifies the output file name, and the `.so` extension is used for shared libraries on Linux.

3. Include the shared library in your project by specifying the library name and location in your build system. For example, if you are using CMake, you would add the following lines to your `CMakeLists.txt` file:

   add_library(mylibrary SHARED IMPORTED)
   set_target_properties(mylibrary PROPERTIES IMPORTED_LOCATION /path/to/libmylibrary.so)

This tells CMake to import the `mylibrary` shared library and set its location to `/path/to/libmylibrary.so`.

4. Use the functions and classes defined in the shared library in your code by including the appropriate header files and linking against the library. For example, if your library defines a function called `myfunction`, you would include its header file and link against the library like this:

   #include "mylibrary.h"
   ...
   myfunction();

And in your build system, you would specify the library as a dependency:

   target_link_libraries(myprogram mylibrary)