http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45819
Richard Guenther <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |RESOLVED Resolution| |INVALID --- Comment #15 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-07-22 12:25:01 UTC --- struct ehci_regs { char x; unsigned int port_status[0]; } __attribute__ ((packed)); //} __attribute__ ((packed,aligned(__alignof__(int)))); struct ehci_hcd{ struct ehci_regs *regs; }; int ehci_hub_control ( struct ehci_hcd *ehci, int wIndex ) { unsigned int *status_reg = &ehci->regs->port_status[wIndex]; return *(volatile unsigned int *)status_reg; } this one is invalid as well, with or without the aligned attribute. ehci->regs->port_status[wIndex] _is_ unaligned. I don't think there is currently a way to tell GCC that the struct layout of ehci_regs is packed but port_status is properly aligned to the natural alignment of int.