I don't see any mention of C++ specifically on that page... but is there any reason it's not implemented? It would be very useful, right now I'm stuck using inline assembly to access non-ds segments. Also found this (unanswered) bug report asking about the same thing: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69549 On 27 March 2017 at 12:16, Jonathan Wakely <jwakely.gcc@xxxxxxxxx> wrote: > On 26 March 2017 at 17:04, J.W. Jagersma <jwjagersma@xxxxxxxxx> wrote: > On 26 March 2017 at 05:39, J.W. Jagersma <jwjagersma@xxxxxxxxx> wrote: >>> However I just found that it does compile when it's a .c file, but not >>> as a .cpp file. Is __seg_gs only implemented in C for some reason? > > Yes, that is true according to the docs: > https://gcc.gnu.org/onlinedocs/gcc/Named-Address-Spaces.html