https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86513
--- Comment #2 from Csaba Ráduly <csaba_22 at yahoo dot co.uk> --- I don't get this. ostringstream isn't even supposed to have a default constructor, only the openmode, string and openmode, and the move constructor (if I'm reading [ostringstream.cons] in N4659 right).
