[Rd] forcing the use of the c++ linker with c++ and fortran sources

Prof Brian Ripley ripley at stats.ox.ac.uk
Sat Jan 10 08:49:48 CET 2009

You are correct: there is no reason to assume that the F90 compiler 
can link C++ nor that the C++ compiler can link F90, and in general 
they cannot.  Quite a few systems have a different vendor's F9x 
compiler (including say g95 vs gcc3 and SunPro F9x vs gcc4).

Even in a pure gcc4 scenario, each of F9x and C++ needs additional 
libaries and R does not know what they are (it only does for F77). 
So if linking by g++ works for you, it is fortuitous and not portable.

I suspect adding -lstdc++ will work for you, which you can do via 
PKG_LIBS in a Makevars file.

Bottom line: you are asking to do something known not to be portable. 
You can use a Makefile to have complete freedom, but please don't 
distribute such a package without a configure script to check out all 
the assumptions.

On Fri, 9 Jan 2009, Steve Guerrero wrote:

> Sorry I was a little stingy with details.
> I'm building a very simple package on linux with R 2.7.1

Still no details of compilers etc.

> no configure script or homemade makefiles.
> my src directory has two files:
> src/foo.cpp
> src/bar.f90
> I run "R CMD install myproject " which runs fine, no errors, and produces a 
> shared library
> i.e.:
> gfortran -fdefault-real-8 -ffixed-form -fpic -g -O2 -c  GLMnet.f90 -o bar.f90
> g++ (all the right flags) -fpic  -g -O2 -c foo.cpp -o foo.o
> and the link step:
> gfortran -shared -L/usr/local/lib64 -o myproject.so baro foo.o 
> -L/apps/R/R-2.7.1/x86_64-linux-2.6/lib64/R/lib -lR
> The build goes fine, the problem is when I load the library I get this error:
> library(myproject)
> Error in dyn.load(file, DLLpath = DLLpath, ...) :
>  unable to load shared library myproject.so
>  undefined symbol: __gxx_personality_v0
> Error: package/namespace load failed for 'myproject'
> If I manually run the link step with g++ instead of gfortran, the library 
> loads fine, everything works.
> I need to tell the R build process to not link with gfortran but to link with 
> g++ in my mixed c++ and fortran scenario.  A little digging into the R SHLIB 
> build script suggests that I probably can't override it without cooking up my 
> Makefiles
> Here's an excerpt from the R SHLIB script:
> makeargs="SHLIB=\"${shlib}\""
> if ${with_f9x}; then
>    makeargs="SHLIB_LDFLAGS='\$(SHLIB_FCLDFLAGS)' ${makeargs}"
>    makeargs="SHLIB_LD='\$(SHLIB_FCLD)' ${makeargs}"
> else
>  if ${with_cxx}; then
>    makeargs="SHLIB_LDFLAGS='\$(SHLIB_CXXLDFLAGS)' ${makeargs}"
>    makeargs="SHLIB_LD='\$(SHLIB_CXXLD)' ${makeargs}"
>  fi
>  if ${with_f77}; then
>    if ${with_objc}; then
>      shlib_libadd="\$(OBJC_LIBS) ${shlib_libadd}"
>    fi
>    if test -z "${shlib_libadd}"; then
>      makeargs="${makeargs} SHLIB_LIBADD='\$(FLIBS)'"
>    else
>      makeargs="${makeargs} SHLIB_LIBADD='\$(FLIBS) ${shlib_libadd}'"
>    fi
>  else
>    if ${with_objc}; then
>      makeargs="${makeargs} SHLIB_LIBADD='\$(OBJC_LIBS)'"
>    fi
>  fi
> fi
> This logic seems to suggest that if there are fortran95 sources, the LD 
> command will be SHLIB_FCLD...with no apparent way to override it.
> Am I mistaken?
> Thanks,
> -sg
> Duncan Murdoch wrote:
>> On 09/01/2009 4:04 PM, Steve Guerrero wrote:
>>> I'm trying to build a package which has both gfortran and c++ code.
>>> In my installation of R, the R CMD INSTALL process compiles each c++ and 
>>> gfortran code with the correct compiler, but performs the link step with 
>>> "gfortran" and this creates undefined symbols at load time.
>> You should offer more details:  what platform are you working on? What 
>> version of R? Do you have a simple example that people could try, and see 
>> the errors?
>> Duncan Murdoch
>>> How does one override/force the use of a different command in the link 
>>> step?  Is there an appropriate entry in Makevars that will do the trick?
>>> Thanks,
>>> -sg
>>> ______________________________________________
>>> R-devel at r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-devel
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel

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 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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