https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53769
--- Comment #9 from Florian Weimer <fw at gcc dot gnu.org> --- (In reply to Vincent Lefèvre from comment #8) > (In reply to Florian Weimer from comment #7) > > Furthermore, if I don't misread the standard, the expectation is that if an > > implementation does not support threads, it still recognizes _Thread_local > > and mostly ignores it, > > I suppose that the goal is to be able to compile multithread-aware programs > on platforms that do not support threads. Since there is only one thread, > thread storage duration is equivalent to static storage duration. Exactly. > > so that it is available even if __STDC_NO_THREADS__ > > is not defined. (Which is of course rather dodgy if you need to conform to > > an existing ABI for thread-local variables, so I think the committee made a > > mistake here.) > > The ABI is out of the scope of the standard, so that I don't see any issue > here. The conformance to the existing ABI is something above the standard. But we still have the issue for compilers targeting an ABI which has threads and full thread-local support but which themselves do not support it. They really should not treat _Thread_local as static storage duration because that would either produce object files which fail to link, or silently corrupt programs (which may even work most of the time).
