http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56997
--- Comment #1 from Joey Ye <joey.ye at arm dot com> 2013-04-18 08:12:50 UTC --- Quoted from http://gcc.gnu.org/onlinedocs/gcc-4.8.0/gcc/Code-Gen-Options.html#Code-Gen-Options: -fstrict-volatile-bitfields If the target requires strict alignment, and honoring the field type would require violating this alignment, a warning is issued. If the field has packed attribute, the access is done without honoring the field type. If the field doesn't have packed attribute, the access is done honoring the field type. In both cases, GCC assumes that the user knows something about the target hardware that it is unaware of. There are two issues in current behavior: 1. There is no warning when writing to packed fields requiring strict alignment. Although there is a warning when reading it. 2. The write access to packed field still honors the field type.
