Full error message


ld: duplicate symbol Gnuplot::SetLineStyles() in /MyFolder/UnitGnuplotInterface.o and /MyFolder/GnuplotInterfaceMain.o

Cause

IDE: Xcode 3.1.2

Compiler: Gcc 4.0.1

This might happen if you use my Gnuplot Interface. The cause is in the following lines:


//Yes, this #include is non-standard

//But it enables you to compile-and-run

//To do it correctly, add the file 'Gnuplot.cpp' to your project,

//and #include 'Gnuplot.h' instead.

#include "UnitGnuplotInterface.cpp"

Solution

Duplicate symbols occur when you have both added an implementation file (.cpp) to your project and #included it. This way, the implementation file (.cpp) gets compiled twice: once as a module in your project (as it is added to your project) and subsequently as a piece of #included code.

Avoid #including implementation files (.cpp). Prefer #including header files (.h) only. Prefer adding implementation files (.cpp) to your project.

For the Gnuplot Interface problem: follow the hints from the commments:


//#include "UnitGnuplotInterface.cpp" //Already added to project

#include "UnitGnuplotInterface.h"

Acknowledgements

Thanks to Roger Wehage for sending me a complete and detailed email with this problem

Go back to Richel Bilderbeek's C++ page.

Go back to Richel Bilderbeek's homepage.

(C++) Duplicate symbol

Full error message

Cause

Solution

Acknowledgements