https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85348
--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> --- What warning do you expect? The problem is not specific to ostringstream, so we can't just add a warning when you try to use packing with that particular type. It happens for any code which you link to and don't consistently use the same packing. ostringstream just happens to be instantiated in libstdc++.dll (without the packing pragmas) so you have objects that use a different ABI to the library.
