[R] Neophyte question re using dyn.load and accessing c functions
Prof Brian D Ripley
ripley at stats.ox.ac.uk
Sun Apr 25 23:06:39 CEST 1999
On Sun, 25 Apr 1999, Robert Gentleman wrote:
> On Sun, 25 Apr 1999, Barnet Wagman wrote:
> > 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.
Just to point out that tests almost nothing (at present). You can have
a library that loads with unresolvable symbols that will throw you out of
R when you try to use the symbol. About the only think it tests is the
presence of the library file.
> > 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).
You can test if the configuration is right by
If that fails it is the system configuration: if it works it is your
example, about which we will need to know more to help....
(This is such a common system for R it is hard to imagine that
configure did not work, but there is always a first time.)
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272860 (secr)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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