I guess what I don't understand is why struct A isn't POD. A reference to something is basically just a pointer. It has no alignment restrictions that a pointer wouldn't.
-----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Nathan Sidwell Sent: Wednesday, December 07, 2005 8:03 AM To: Steven L. Zook Cc: gcc@gcc.gnu.org Subject: Re: C++ 3.4.5 packed reference warning Steven L. Zook wrote: > When I compile this using gcc rev 3.4.5 (m68k-elf): > > struct A { char B; > unsigned char & C; } __attribute__((packed)); unsigned char > D; A E = { 'F', D }; > > I get: > > testpp.cpp:2: warning: ignoring packed attribute on unpacked non-POD > field `unsigned char&A::C' > > > sizeof( E ) == 6 (B, a byte of pad since m68k uses 16 bit alignment, > and C). > > This construct compiled without warning under 3.3.3 and gave sizeof( E > ) == 5. > > Is this behavior under 3.4.5 (both the warning and the ignoring of the > packed attribute on the reference member) proper (justified, > necessary, good)? It is bad to pack non-pod structs, because of alignment assumptions of member functions thereof. The checking code just checks the non-podness of the type, as non-pod is a well defined term. This could be relaxed. File a bug report if needed. nathan -- Nathan Sidwell :: http://www.codesourcery.com :: CodeSourcery LLC [EMAIL PROTECTED] :: http://www.planetfall.pwp.blueyonder.co.uk
