This has been hanging around in my Inbox for a while. I found this
about how the ARM ABI deals with doubles:
VFP is a newer floating point architecture for ARM. With respect to
endianess, the word endianess of doubles is always the same as the
byte endianess of words. This contrast with the older and more common
FPA architecture, which always uses big endian for doubles. In both
architectures, the word endianness of 64-bit ints matches the word
endianess of doubles.
After looking at NSByteOrder.h, it appears we do it correctly, as far
as I can tell, swapping doubles the same ways as 64-bit int. Does
Nikolaus (or anyone) have an actual bug report which shows the
problem? I'm not sure I want to change anything without at least
some one to verify it.
On Feb 6, 2007, at 9:00 AM, Fred Kiefer wrote:
I had an email discussion with Nikolaus Schaller about the code in
NSByteOrder.h which does the byte swapping for GNUstep and he
convinced
me that we may not handle the case of swapping doubles correctly for
certain ARM processors. Here the word order in doubles seems to differ
from the general byte order.
I had a quick search on the web and found
ax_cv_c_float_words_bigendian
(See http://autoconf-archive.cryp.to/ax_c_float_words_bigendian.html).
Is there anybody out there, who understands word/byte order a bit
better
and is able to fix this?
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