[R] Odd underflow(?) error

[William Faulk]

I'm still trying to install R on my Irix machine.  Now I have a new 
problem that crops up during the checks.  I've found the root cause, and 
it's that R is returning zero for certain things for reasons I don't 
understand.

2.225073859e-308, entered directly into R, responds "2.225074e-308".
2.225073858e-308 responds "0".

Their negative values respond similarly, so it would appear that 
somewhere in there is the smallest absolute value that that installation 
of R will hold.

On another machine where the checks passed, both responses are correct, 
not just the first one.  The underflow there is significantly lower, 
with much less accuracy, as opposed to what seems to be good accuracy on 
what looks like the broken one.  The values there are:

2.4703282293e-324 gives 4.940656e-324
2.4703282292e-324 gives 0

My first thought was that GMP and/or MPFR weren't working properly, so I 
recompiled GMP, which passed all of its tests, and GCC, making sure to 
imclude support for them.  This made no difference.

Anyone have any ideas, including which one is broken?  Both?

-Bitt