[Rcpp-devel] Symbol not found when including an external library

[Dirk Eddelbuettel]

On 4 September 2013 at 21:08, Steve Jaffe wrote:
| The simplest solution is to build nlopt as a shared library and link to
| that. See http://ab-ini tio.mit.edu/wiki/index.php/NLopt_Installation#Shared_libraries

Please see the subsequent posts by Doug -- we already have that.

| (I may be wrong, but I don't think it's always possible to link a static
| library into a shared library regardless of how the static library was build
| (think: PIC) and on all platforms.

If memory serves, you need -fPIC and can just 'glue' the object files into a
static libfoo.a via the ar command. Been there, done that, but don't have an
example handy.

| This is why I say replacing the static library with a shared library is the
| simplest solution -- we know it will work.) 

I fear it is far from that easy as you also need ldd to play along, ie dll
needs to be told where the library is.  

What R does is (AFAICR) not identical because it manages dlopen() itself --
which is why we have libs/foo.so rather than a standard libfoo.so (and also
why Rcpp ships two libraries but I digress).

It is _all_ hairy. The easiest approaches are, in my view,

  -- to rely on a system-wide library

  -- possibly rely on another build (hence Doug's post about other nlopt
     packages) provided they built the library in a way we can use

  -- punt and place all files in src/ which is what I convinced the authors /
     maintainers of phylobase to do -- and then the multi-arch builds "just
     work" as R know how to the The Right Thing (TM)

Very easy to get pulled into a fight against wind mills here. Resist, if you can.

Dirk


-- 
Dirk Eddelbuettel | edd at debian.org | http://dirk.eddelbuettel.com