http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57440
--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> --- You didn't answer the question about which mingw compiler you are using, the standard mingw gcc does not support std::async.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57440
--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> --- You didn't answer the question about which mingw compiler you are using, the standard mingw gcc does not support std::async.