On Mon, 13 Jun 2005, Leopold Toetsch via RT wrote:
> Chip Salzenberg wrote:
> > On Mon, Jun 13, 2005 at 07:12:48PM +0200, Leopold Toetsch wrote:
> >
> >>Andy Dougherty (via RT) wrote:
> >>
> >>>... On SPARC, doubles should be aligned on 8-bit boundaries.
> >>>The speculation is that the _num_val part of the UnionVal in the PMC
> >>>ends up unaligned. However, I couldn't follow where that happened, so I
> >>>can't suggest a patch.
> >>
> >>It happends directly in the PMC memory arena. Whenever the PMC size % 8
> >>isn't zero.
Yes, I saw this bit in include/parrot/pobj.h:
/* Parrot Object - base class for all others */
typedef struct pobj_t {
UnionVal u;
Parrot_UInt flags;
#if ! DISABLE_GC_DEBUG
UINTVAL _pobj_version;
#endif /* ! DISABLE_GC_DEBUG */
} pobj_t;
In an optimized compile, sizeof(pobj_t) is 16, and sizeof(PMC) is
24, both of which are nice multiples of 8.
> > That's gotta be a compiler bug. When a structure contains a member
> > that needs N-byte alignment, and sizeof(structure) % N is not zero,
> > the compiler is busted. (Have they never heard of _arrays_?)
>
> The PMC allocation area is a big bunch of memory, where PMC-sized pieces
> are carved out by the memory allocation system. There is no union or
> compiler bug involved. It's caused by the memory allocator and the GC
> system.
That's what I couldn't follow. Where are PMC-sized pieces carved out
that aren't carved out using sizeof(PMC)?
--
Andy Dougherty [EMAIL PROTECTED]
