https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63991
--- Comment #2 from Eric Botcazou <ebotcazou at gcc dot gnu.org> --- It looks like -fpack-struct cannot be used when -fstrict-volatile-bitfields is in effect, i.e. on ARM EABI. As for unaligned volatile fields on strict-alignment targets, they clearly ask for trouble. Simply do not use -fpack-struct.
