R help - Jun 2009 - Calling Fortran from C++

Hi,

can anybody point me to a package with C++ code that call Fortran
subroutines?

I am trying to do the same thing but we scarce success.

Error in dyn.load("utils.so") :
  unable to load shared library 'utils.so':
  dlopen(utils.so, 6): Symbol not found: _robcovf
  Referenced from: utils.so
  Expected in: dynamic lookup

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Giura Gauss wrote:
> 
> Hi,
> 
> can anybody point me to a package with C++ code that call Fortran
> subroutines?
> 
> I am trying to do the same thing but we scarce success.
> 
> Error in dyn.load("utils.so") :
>   unable to load shared library 'utils.so':
>   dlopen(utils.so, 6): Symbol not found: _robcovf
>   Referenced from: utils.so
>   Expected in: dynamic lookup
> 
> 
> 
It seems like you have a problem with function names which is a common
obstacle when interfacing C and Fortran. What usually happens is that a
trailing underscore gets added to fortran function names when they are
compiled. For example, consider a fortran subroutine declared as:

subroutine gaussQuad ( a, b, f1, f2 )

Since an underscore usually gets added and Fortran passes variables by
reference, the above subroutine would be seen by C as:

void gaussQuad_( a&, b&, f1&, f2& );

Furthermore, in C++ I think you h$ave to wrap the prototype in an extern
statement:

extern "C" { void gaussQuad_(a&, b&, f1&, f2& ); }

If you are running a unix system, you can check if your fortran function
names are receiving trailing underscores by running the nm utility on your
shared library. Ignore the leading underscores as they are expected by the C
compiler.

-Charlie




-----
Charlie Sharpsteen
Undergraduate
Environmental Resources Engineering
Humboldt State University
-- 
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> From: r-help-bounces@r-project.org
<http://tolstoy.newcastle.edu.au/R/e6/help/09/03/8794.html#16298qlink1>
*> [mailto:r-help-bounces_at_r-project.org] On Behalf Of Thomas Lumley *
*> Sent: Monday, June 01, 2009 9:33 AM *
*> To: cls59 *
*> Cc: r-help_at_r-project.org *
*> Subject: Re: [R] Calling Fortran from C++ *
*> *
*> On Mon, 1 Jun 2009, cls59 wrote: *
*> *
*> > *
*> > *
*> > Giura Gauss wrote: *
*> >> *
*> >> Hi, *
*> >> *
*> >> can anybody point me to a package with C++ code that call Fortran
*
*> >> subroutines? *
*> >> *
*> >> I am trying to do the same thing but we scarce success. *
*> >> *
*> >> Error in dyn.load("utils.so") : *
*> >> unable to load shared library 'utils.so': *
*> >> dlopen(utils.so, 6): Symbol not found: _robcovf *
*> >> Referenced from: utils.so *
*> >> Expected in: dynamic lookup *
*> >> *
*> >> *
*> >> *
*> > *
*> > It seems like you have a problem with function names which *
*> is a common *
*> > obstacle when interfacing C and Fortran. What usually *
*> happens is that a *
*> > trailing underscore gets added to fortran function names *
*> when they are *
*> > compiled. For example, consider a fortran subroutine declared as: *
*> > *
*> > subroutine gaussQuad ( a, b, f1, f2 ) *
*> > *
*> > Since an underscore usually gets added and Fortran passes *
*> variables by *
*> > reference, the above subroutine would be seen by C as: *
*> > *
*> > void gaussQuad_( a&, b&, f1&, f2& ); *
*> > *
*> *
*> Because this varies from compiler to compiler, R provides *
*> macros that do the correct name mangling, so it would be *
*> void F77_CALL(*a, *b, *f1, *f2) *
*> in C (not a&, b&, etc, which are C++ syntax). *
*> *
*> -thomas *
*> *
*> Thomas Lumley Assoc. Professor, Biostatistics *
*> tlumley_at_u.washington.edu University of Washington, Seattle


Thank you all. I should have known about F77_CALL. I think I used once.

However, I have still problems.

robcovf.f constains a fortran subroutine: subroutine robcovf(n, p, nc,
start, len, u, s, v, w)

My C++ file (utils.cc):

extern "C"{
  void robcovf_(const int *n, const int *p, const int *nc,
        const int *start, const int *len,
        double *u, double *s, double *v, double *w);

  void wb(const double* Xdata, const double* Ydata,
        const int* nrow, const int* ncol, const int* nrep,
        const int* clusstart, const int* clussize, const int* nc,
        double* out1, double* out2)
  {

[...]

F77_CALL(robcovf)(nrow, ncol, nc, clusstart, clussize, u, s, v, w);

[other stuff...]
}


I do:

R CMD SHLIB robcovf.f

**R CMD SHLIB utils.cc

They compile just fine, but
> dyn.load('utils.so')
Error in dyn.load("utils.so") :
  unable to load shared library 'utils.so':
  dlopen(utils.so, 6): Symbol not found: _robcovf_
  Referenced from: utils.so
  Expected in: dynamic lookup


Now, I have two underscores!!






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