Re: error loading cxx local model in isis: undefined symbol

Hi Thomas,

if you have declared your XSPEC local model function prototypes as "C++ 
style", i.e. using RealArray&s instead of Real*s, then you won't be able 
to use them even if the "extern C" linkage problem is fixed, since the 
function explicitly includes C++ objects in the interface to isis. I 
solved this problem by writing a wrapper function and then using the 
wrapper to create an isis alias function for each of my local models, 
e.g. myLocalModel (C++ inputs)-> myLocalModel_isis (C inputs). If this 
is useful to you, let me know and I will send you the source code for 
the wrapper.

Cheers,

Maurice


On 11/14/13 3:45 PM, John Houck wrote:
> On Wed, Nov 13, 2013 at 15:07 -0500, Thomas Dauser wrote:
>> Dear isis-users,
>>
>> did anyone experience problems including a cxx local model in isis?
>>
>> Here is my problem: I compile it once with xspec:
>>
>> initpackage fun_test lmodel.dat .
>>
>> While I can load (and evaluate) it in xspec without errors:
>>
>> XSPEC12>lmod fun_test .
>> Model package fun_test successfully loaded.
>>
>> however, for the same model library (without any recompiling), isis
>> complains with
>>
>> isis> load_xspec_local_models (".");
>> Loading ././libfun_test.so
>> Error loading symbol C_test for model fun
>> Link error: ././libfun_test.so: undefined symbol: C_test
>>
>> And isis is somehow right, as C_test is not defined ("nm -D
>> libfun_test.so | grep C_test" does not give a result).
> Since isis is (usually compiled as) a C program and not a C++
> program, your model must export a "C" linkage symbol for isis
> to link to.
>
> What output does this produce?:
>     nm libfun_test.so
>
> The C++ symbols are usually "mangled" containing embedded
> interface that describes the subroutine interface.
> Probably your library contains only a C++ interface.
>
> To provide a C-linkage symbol, your C++ interface must
> provide an interface declared as extern "C" (and that also
> follows the Xspec interface naming conventions).
>
> Thanks,
> -John
>
>> What am I missing here? Is there a difference, how I need to treat
>> xspec and isis local models? I know that the "C_" has to be included
>> in the lmodel.dat file to tell xspec/isis that this is C/C++ code
>> and not fortran.
>>
>> I have the latest isis version 1.6.2-27 and heasoft 6.14 installed.
>>
>> Thanks for your help.
>>
>> Cheers,
>> Thomas
>>
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