Why gcc doesn't recognize -rdynamic option?

Question

I got a gcc compilation error:

gcc-4.9: error: unrecognized command line option '-rdynamic'

and I tested compilation with -rdynamic in some environments. While I used the same version of gcc (4.9.2), in some environments gcc worked well, but others (e.g. Homebrew gcc 4.9.2_1, cygwin 64bit) not. What makes the difference?

Answer 1

-rdynamic passes the flag -export-dynamic to ELF linker, on targets that support it.

Executable formats in OS X and Windows are not ELF, thus the option -rdynamic is not supported building for these operating systems.