R help - Apr 1999 - 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"

There must be something I'm leaving out, but after searching the
documentation and
help archive, I'm stuck.  Does the .so have to be in an R package (if
so, where)?

Thanks,

-------------------
Barnet Wagman

wagman at enteract.com
773-645-8369

1361 N. Hoyne
Chicago, IL 60622
--------------------


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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.
> 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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