https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85348
crillion at tiscali dot it changed: What |Removed |Added ---------------------------------------------------------------------------- Resolution|INVALID |FIXED --- Comment #3 from crillion at tiscali dot it --- the point is that this directive was in a deeply included header of a library I use. It took me some amount of time (I spent some work hours) to isolate the problem which emerges just in the ostringstream creation. I wasn't aware of this behaviour of the generated code before; if the compiler had warned me, I would have resolved more quickly.