[Rd] bug, feature of mistery?

[Giuseppe Ragusa]

I have two machines a linux_amd64_x86 (gentoo_amd64) and a linux_x86. Both run
R-2.1.0. I have a very long program (hopefully will become a package)
that works perfectly on the linux_amd_x64. Great means no error, no
problems and results that, where the analytic solution exists,
coincide with it. I have problem making the code run on the x64 machine. I
am baffled. The same code on the same version of R, different arch,
is behaving differently. 

After hour of debugging, I traced down what is triggering the error on
the x86 machine.

the code snippet is the following similar to:

R>
g <- h(d)

f <- function( lambda )
{
z <- g %*% lambda
sum( psi(z) )
...
}

optim( init.value, f )

R>

The function f() is using lexical scoping to get obtain g. The
function psi() is a call to a wrapper function that call a (.C) C
function doing some simple calculation on z. 

What's the problem? When f() is called, g is there, lambda is there,
but the assignment  z <- g %*% lambda results in a matrix of NaN. This
happens from the second time f() is called, i.e. the first time f() is
called from optim() after the C call has been made. The error is then
that passing a NaN vector to .C results in halted execution. 

If I debug f() during the call to optim, I can without problem assign
z the correct value, but during the execution z is matrix(NaN, nr,
1). 

At this point I can think of the following:

1) the external C code has errors 

It is not a programming error, because when called from console it
   returns the right results. Also, remember, the program work on my
   other machine (the 64 bit);

2) R error (I do not think so)

3) Compiling error
Can be the gcc is messing thing around?

on the 32bit machine
gcc version 3.3.5  (Gentoo Linux 3.3.5-r1, ssp-3.3.2-3, pie-8.7.7.1)

on the 64-bit machine
gcc version 3.4.3 20041125 (Gentoo Linux 3.4.3-r1, ssp-3.4.3-0, pie-8.7.7)

Any help, suggestions, thoughts?

Thank you.

Giuseppe Ragusa