Re: MACH_SEND_MSG_TOO_SMALL is mig breakage (was: Re: current CVS Hurd and glibc (except libthreads)

[Roland McGrath]

I think what's going on is that mig was written to assume that everything
needs to be naturally aligned.  On a 64-bit machine, 64-bit quantities do
need to be aligned to 64 bits.  But on the x86, they don't.  In the Request
structure, the compiler locates the loff_t field misaligned (i.e. only
aligned to 32 bits, which is fine on this machine).  It could well be that
mig has never worked right for 64-bit parameters on 32-bit machines.  The
MK83a version of mig has some changes related to alignment vs the mig code
we have.  A quick inspection doesn't suggest it would do this differently,
but I haven't thought about it a great deal or looked exhaustively at the
differences between the two mig versions.