[R] dyn.load() error: bad external relocation length

[Walton A. Green]

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
> > 
> > ______________________________________________
> > R-help at stat.math.ethz.ch mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
> 

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