https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79609
--- Comment #1 from roland at gnu dot org ---
Note Clang uses __attribute__((address_space(N))) for this. That automagically
handles the parsing issues in a well-known fashion, and gets C++ support for
free to boot.
Unfortunately they use per-target magic integer values to select among
predefined address spaces, with no symbolic syntax (just documented magic
values). You could e.g. change the __SEG_FS predefine to be the magic number,
so that it's __attribute__((address_space(__SEG_FS))) and macroable-compatible
with Clang. Or you could be more classy and take string values
__attribute__((address_space("fs"))).
