Neophyte question re using dyn.load and accessing c functions

I'm have what's probably a trivial &| silly problem trying to access a
c-function in a shared
library ( R 0.64, under redhat linux 5.2).

    R COMPILE rctest.c
    R SHLIB -o libRC.so rctest.o

produce a reasonable looking shared library ('nm libRC.so' shows that
the function 'rctest' is present).

In R, the command

    dyn.load("/fullpathname/libRC.so")

returns without an error.  However, I'm unable to access the function.
E.g.

    is.loaded(symbol.C("rctest"))

yields FALSE.

    .C("rctest",x)

yields "Error in .C("rctest", x) : C/Fortran function not in load table"

Well when this happens to me it's usually because R configured incorrectly
and decided to either prepend (or not) an underscore when it wasn't (or
was) needed. 
Stepping through the code using a symbolic debugger will let you know
what's going on (or you could try recompiling with
HAVE_NO_SYMBOL_UNDERSCORE, set to the correct value for your machine).

robert

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