https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52991
m.facchin at arduino dot cc changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |m.facchin at arduino dot cc --- Comment #20 from m.facchin at arduino dot cc --- I just hit this bug on dfu-util 0.8 (i686-w64-mingw32 5.3.0) The patch has been available for 3 years now, but if you don't want to apply that patch please apply at least the workaround (reverting to -mno-ms-bitfields as default)