Adding gcc-ism's without testing for gcc in configure is a terrible
idea. Please don't do it. The entire universe doesn't use gcc's
non-standard compiler gunk.
The semi-portable way to do this is with a linker map (the way ELF
versioned symbols are done), but even that is difficult to write in a
way that works on a majority of platforms without post-processing the
map file in configure to handle the syntax idiosyncrasies.
Isn't there enough _real_ work to do on the code and build process
without wasting time on this sort of thing?