[Python-Dev] mingw32 and gc-header weirdness

[Christian Tismer]

On 7/23/09 2:27 PM, Antoine Pitrou wrote:
> Christian Tismer<tismer<at>  stackless.com>  writes:
...

> I'm not sure a double aligned on a 4-byte boundary is "misaligned" on a x86 CPU.

I'm also not sure. Anyway, the result was neither intended nor
expected, I guess.

> Alignment is primarily important to avoid access violations on CPUs and
> datatypes which don't support arbitrary alignment, although it can also be
> useful for performance reasons.

Performance, performance, of course (that's my job, after all :-) )
...

> Of course, it will also make memory consumption a tad bigger for GC-enabled
> objects (but GC-enabled objects are generally not that small anyway).

For that reason, I don't like the addition of the opaque header
too much. If there were an option to make the header explicit,
we would not have to round up the object size to a multiple
of (8, 16), but could arrange embedded doubles as they fit the best.

> (I disagree, however, that we should remove the "long double". After all, we
> also want alignment of PyObjects to allow inclusion of a "long double" in them)

Well, I doubt that a 12 byte long double causes any other
alignment but 4.
-- 
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