dyn.load() error: bad external relocation length

Duncan,

Many thanks: R CMD SHLIB is proably what I was looking for....do you know
where the most extensive documentation for that is located? I looked at
the man page for R and R CMD SHLIP --help, but there wasn't much detail on
how it works. Does it (or can it be configured to) run a makefile? (I have
been compiling the C using a makefile written by someone else: the larger
picture is that we're trying to write R wrappers for a bunch of C
programs---my colleague is modifying the C---so eventually they'll be
put in a package's /src directory, but for now I am just trying to test by
making sure they can be called from R before putting them together in a
package. So far I've just been using system(), which works fine on my
machine, but all the packages I've looked at use .C()/.Call() in
preference to system(), so I assume I should be learning how to use
.C()/.Call()....

Thanks,
Walton

On Sat, 29 Oct 2005, Duncan Temple Lang wrote:

Hi Walton.

.C/.Call are interfaces to _compiled_ C routines in a dynamically
loaded library (DLL or DSO - shared object).  A progra
A program is often created from compiling C code into an executable.
We can call the executable via system, but we cannot access its routines
via .C/.Call.

So, if you have C code, use R CMD SHLIB to compile it into a loadable
libray and use dyn.load() to load it. Putting the code in the src/
directory of a package makes the need to do this less explicit.

But if you want to use system(), again it can be done "portably" in a
package.
Arrange that the package creates and puts the executable in
the package's installed area.  Arrange that the program is
put in, say, inst/bin within the package and then it will be installed
into the bin/ directory of the package. Then you can access it with

    system.file("bin", "myProg", package = "myPackageName")

and you can use that in your call to system().

The down side is that you will have to ensure that the program is built
in a portable way. So if you won the C code, it is almost the same thing
as building a DLL and using .C/.Call.

HTH

   D.



Walton A. Green wrote:

R-helpers,

Is there an easy way to call an external (C) program using .C or .Call
without including the code in a package. I know how to do it using
system(), but that doesn't seem to be a permanent or portable solution.
Initially I tried:

.Call('filepath.to.c.function', arg1)

and got this error:

Error in .Call("filepath.to.c.function", "arg1",  :
	"C" function name not in load table

So read the section on foreign language interfaces in the Writing R
Extensions manual but when I tried:

dyn.load('filepath.to.c.function')

I got:

Error in dyn.load(x, as.logical(local), as.logical(now)) :
	unable to load shared library 'filepath.to.c.function':
  dlopen(filepath.to.c.function, 6): bad external relocation length

Do you need to run R_registerRoutines before dyn.load()? I couldn't find
any mention of this error on the web....

Walton

platform powerpc-apple-darwin7.9.0
arch     powerpc
os       darwin7.9.0
system   powerpc, darwin7.9.0
status
major    2
minor    1.1
year     2005
month    06
day      20
language R

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