inline linker instructions in cpp with ?

I understand that there is a possibility to give instructions to the linker inline in the code.

and is used for example here: https://github.com/tbenthompson/cppimport

My question is:

• Under what circumstances do these linker options have to be commented out? Using gcc they don't appear to have any effect anymore when they are commented out.
• I couldn't get any of them to work in visual c++. Is that expected?