Re: Bug#44654: dpkg: seg faults w/2.3.17; problem traced to sysinfo()

Chris Lawrence (lawrencc@debian.org)
Fri, 10 Sep 1999 07:27:58 -0500

On Sep 10, Alan Cox wrote:
> > I suggest also to put back the comment about the 64byte alignment.
> >
> > --- 2.3.17/include/linux/kernel.h Wed Sep 8 18:18:56 1999
> > +++ kernel.h Fri Sep 10 02:32:45 1999
> > @@ -96,7 +96,8 @@
> > unsigned short procs; /* Number of current processes */
> > unsigned long totalbig; /* Total big memory size */
> > unsigned long freebig; /* Available big memory size */
> > - char _f[22-2*sizeof(long)]; /* Padding: libc5 uses this.. */
> > + char _f[12]; /* Pads structure to 64 bytes
> > + (libc5 uses this..) */
> > };
> >
> > #endif
> >
> > Andrea
>
> That is trivially and obviously wrong. You have to do the sizeof check
> because of 64bit machines

It looks like we need something like:

unsigned short procs;
unsigned short unused;
unsigned long totalbig;
unsigned long freebig;
char _f[22-2*sizeof(long)-sizeof(short)];

This explicitly includes the alignment in the structure, which IMHO is
a good thing. Yes, I know _f[] looks ugly. Oh, well. (I assume
unsigned short is usually 32 bits on a 64-bit platform, so the
alignment will be fixed here... otherwise, damned if I know how to
portably fix the problem.)

Chris

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