https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90740
--- Comment #3 from Valentine <v at vsamko dot com> --- Yep, it uses GCC extension. Interesting observation that it complains about the size of buffer, that looks to be correct as if I change to === char buf[SIZE]; char* pbuf = buf; bar([pbuf, &out...](auto&... column) { (doit(column), ...); }, out...); === then warning goes away. The warning is still erroneous, and shouldn't be there.