Re: Re: [Oledb-dev] double precision error with pg linux server, but not with windows pg server

Shachar Shemesh <shachar(at)shemesh(dot)biz> writes:
> As for the ARM architecture, I've pulled my sources, and the answer is
> this: ARM doesn't have one standard floating point format. Different ARM
> architectures will use different formats. Most architectures will
> actually use IEEE, but some will use decimal based and such.

Okay, I spent some time googling this question, and I can't find any
suggestion that any ARM variant uses non-IEEE-compliant float format.
What *is* real clear is that depending on ARM model and a run time (!)
CPU endianness flag, there are three or four different possibilities
for the endianness of the data, including a PDP-endian-like alternative
in which the order of the high and low words is at variance with the
order of bytes within the words. (Pardon me while I go vomit...)

The intent of the FP binary I/O code we have is that for platforms
supporting IEEE-compliant FP formats, the on-the-wire representation
should be uniformly big-endian, same as is true for integers. So
I would concur with a patch that ensures that this is what happens
on the different ARM variants ... though I'll still be interested
to see how you make that happen given the rather poor visibility
into which model and endianness we are running on.

PS: Of course this does not resolve the generic issue of what to do
with platforms that have outright non-IEEE-format floats. But at the
moment I don't see evidence that we need reach that issue for ARM.

PPS: I'm sort of wondering if the PDP-endian business doesn't afflict
int8 too on this platform.

regards, tom lane