[Trilinos-Users] [EXTERNAL] Question About Template Specialization in .hpp Files

[Bradley, Andrew Michael]

Hi Corey,

Thanks for the bug report. I believe you are correct. I have recorded the problem in our issue tracker:
    https://github.com/trilinos/Trilinos/issues/782

Andrew

________________________________________
From: Trilinos-Users <trilinos-users-bounces at trilinos.org> on behalf of Corey A. Henderson <cahenderson at wisc.edu>
Sent: Saturday, November 5, 2016 4:30 PM
To: trilinos-users at trilinos.org
Subject: [EXTERNAL] [Trilinos-Users] Question About Template Specialization in .hpp     Files

I recently chased down a linker problem in a code I'm writing, where I
was getting "multiple definition" errors when I added
MueLu_CreateEpetraPreconditioner.hpp. Specifically
CreateEpetraPreconditioner and ReuseEpetraPreconditioner. I was able
to work around it by ensuring I only include this .hpp file from one
compilation unit, but in researching my problem I learned that
template specializations shouldn't be in .hpp files for this very
reason.

EG: http://stackoverflow.com/questions/4445654/multiple-definition-of-template-specialization-when-using-different-objects

So far as I can tell (Trilinos v12.8.1) there is no way to include
this .hpp file in two different compilation units successfully. I did
configure Trilinos with the Trilinos_ENABLE_EXPLICIT_INSTANTIATION
option ON. I'm not sure if that makes a difference.

Should this code (the template specializations) be in a .cpp file and
thus in the libraries? Or am I missing something?

Corey

--
Corey A. Henderson
PhD Candidate and NSF Graduate Fellow
Dept. of Engineering Physics
Univ. of Wisconsin - Madison
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