On Sat, 2002-08-31 at 18:45, Steven W McDougall wrote: Good write-up.
> I tested this theory by hacking mem_allocate() to enforce a minimum > round-up to an 8-type boundary. > > /* Round up to requested alignment */ > if (align_1<7) align_1 = 7; /* <<<==== HACK */ > size = (size + align_1) & ~align_1; > > This keeps top 8-byte aligned. The bus error went away, and > t/pmc/perlhash_1.pbc produced the correct output. > > > I don't know how this thing is supposed to work, so I don't know how > to fix it. Logically, there are a few possibilities. > > 1. Fix gcc on IRIX64 to permit assignment of unions with arbitrary > alignment. > > 2. Add a parameter to mem_alloc() (or use align_1) to control the > alignment of the allocated block. > > 3. Require all callers of mem_alloc() to pass an align_1 parameter > big enough to meet the alignment requirements of the platform. > (Seems like the Wrong Thing.) IIRC, the impetus for rounding up memory allocations was to preserve alignment efficiently, which would imply that the amount of rounding should be a compile-time configure issue. That is a potential space-waster on 64-bit platforms that are storing many smaller items, but it's probably the thing to do anyway because: a) you're going to really slow things down by having to determine if the new thing you're allocating can fit on the tail of a previous allocation, and b) you're going to be wasting some of that space anyway in order to align to the stricter requirements, even when you need to. -- Bryan C. Warnock bwarnock@(gtemail.net|raba.com)
