multiple definitions of bool boost::polygon::belongs(...) by multiple #include

[Manfred <kuhnkies@…>]

Hello,

my notice:

I encountered a linker problem within the voronoi code of library boost::polygon when using MSVS 2008. There (and I guess on many other compilers) will be multiple definitions of function

bool boost::polygon::belongs(...)

as soon as there is direct or transitive

#include <boost/polygon/voronoi_geometry_type.hpp>

in more than one compile unit (.cpp file). This linker problem will not occur if only one .cpp file #includes this file (see single tutorial file libs/polygon/example/voronoi_visualizer.cpp and e.g. split this file into class related .h/.cpp files).

my explanation:

Seemingly compiling each compile unit like foo.cpp, bar.cpp, etc. produces a definition of

bool boost::polygon::belongs(...)

into its individual .obj-file, namely foo.obj, bar.obj, etc.. Later the linker can not resolve which of the multiple definitions of "belongs", the one in foo.obj or the one in bar.obj, to take when binding the executable.

my suggestion:

I could fix that problem in my local boost code by making "belongs" an inline function.

 file    : boost/polygon/voronoi_geometry_type.hpp 
 line 36 : bool belongs(           // taken from svn-trunk
 altered : inline bool belongs(    // my local modification

Inlining won't create any definition of "belongs" in .obj file(s) at all, hence no multiple definitions. There may be other, better solutions that I don't know of, of course.

Best

Manfred

[Andrii Sydorchuk]

Hi Manfred,

Thank you for the report and suggested fix. The change was pushed to trunk today and will become public in Boost 1.53.

Regards, Andrii