c++: gcc barfs with "Multiple definition of ...". What am I doing wrong?

map250r · 02-23-2009, 12:20 PM

I'm working on an app, and changed some data member declarations to be static. I also added definitions outside the class. Now gcc barfs with 'multiple definition of ...'

part of uiStuff.h:

Code:

#include "qoccharnesswindow.h"
#include <limits.h>
#include <QObject>
#include <QMenu>
#include <QToolBar>
#include <gp_Pnt.hxx>
#include <TopoDS_Shape.hxx>

class uiStuff : public QObject {
	Q_OBJECT
public:
	uiStuff(QoccHarnessWindow* window);
	uiStuff(){};
	~uiStuff(){};
protected:
	static QoccHarnessWindow* theWindow;
	static std::vector<TopoDS_Shape> selectedShapes;
	static int errors;
};

QoccHarnessWindow* uiStuff::theWindow = 0;
std::vector<TopoDS_Shape> uiStuff::selectedShapes;
int uiStuff::errors = 0;

g++ 4.3.3 output:

Code:

$ make
cd src/ && make -f Makefile                    
make[1]: Entering directory `/opt/cam-occ/trunk/src'
g++  -o ../bin/camocc2 .obj/main.o .obj/qoccapplication.o .obj/qoccdocument.o .obj/qoccharnesswindow.o .obj/qoccinputoutput.o .obj/qoccmakebottle.o .obj/qoccviewercontext.o .obj/qoccviewwidget.o .obj/shapeInfo.o .obj/cam.o .obj/uiStuff.o .obj/aSample.o .obj/shapeOffset.o .obj/gcode2Model.o .obj/moc_qoccapplication.o .obj/moc_qoccdocument.o .obj/moc_qoccharnesswindow.o .obj/moc_qoccinputoutput.o .obj/moc_qoccviewercontext.o .obj/moc_qoccviewwidget.o .obj/moc_shapeInfo.o .obj/moc_cam.o .obj/moc_uiStuff.o .obj/moc_aSample.o .obj/moc_shapeOffset.o .obj/moc_gcode2Model.o    -L/usr/X11R6/lib -L/usr/lib -L/opt/occ63/lib/ -lTKShHealing -lTKOffset -lTKBool -lTKSTEPBase -lTKSTEP -lTKService -lTKV3d -lTKernel -lTKIGES -lPTKernel -lTKSTL -lTKVRML -lTKTopAlgo -lTKBRep -lTKPShape -lTKShapeSchema -lXext -lX11 -lm -lGLU -lGL -lQtGui -lQtCore -lpthread                                 
.obj/cam.o: In function `__static_initialization_and_destruction_0':                                          
/usr/include/c++/4.3/ext/new_allocator.h:76: multiple definition of `uiStuff::errors'                         
.obj/shapeInfo.o:/opt/occ63/inc/Standard_Real.hxx:72: first defined here                                      
.obj/cam.o: In function `__static_initialization_and_destruction_0':                                          
/usr/include/c++/4.3/ext/new_allocator.h:76: multiple definition of `uiStuff::theWindow'                      
.obj/shapeInfo.o:/opt/occ63/inc/gp.lxx:6: first defined here                                                  
.obj/uiStuff.o: In function `__static_initialization_and_destruction_0':                                      
/usr/include/qt4/QtCore/qglobal.h:1423: multiple definition of `uiStuff::theWindow'                           
.obj/shapeInfo.o:/opt/occ63/inc/gp.lxx:6: first defined here                                                  
.obj/uiStuff.o: In function `__static_initialization_and_destruction_0':                                      
/usr/include/qt4/QtCore/qstring.h:386: multiple definition of `uiStuff::errors'                               
.obj/shapeInfo.o:/opt/occ63/inc/Standard_Real.hxx:72: first defined here                                      
.obj/aSample.o: In function `__static_initialization_and_destruction_0':                                      
/usr/include/qt4/QtCore/qatomic_x86_64.h:117: multiple definition of `uiStuff::theWindow'                     
.obj/shapeInfo.o:/opt/occ63/inc/gp.lxx:6: first defined here                                                  
.obj/aSample.o: In function `__static_initialization_and_destruction_0':                                      
/usr/include/qt4/QtCore/qglobal.h:1423: multiple definition of `uiStuff::errors'                              
.obj/shapeInfo.o:/opt/occ63/inc/Standard_Real.hxx:72: first defined here                                      
.obj/shapeOffset.o: In function `TopoDS_Mismatch':                                                            
/opt/occ63/inc/Handle_Standard_Transient.hxx:97: multiple definition of `uiStuff::theWindow'                  
.obj/shapeInfo.o:/opt/occ63/inc/gp.lxx:6: first defined here                                                  
.obj/shapeOffset.o: In function `TopoDS_Mismatch':                                                            
/opt/occ63/inc/Handle_Standard_Transient.hxx:95: multiple definition of `uiStuff::errors'                     
.obj/shapeInfo.o:/opt/occ63/inc/Standard_Real.hxx:72: first defined here                                      
.obj/gcode2Model.o: In function `__static_initialization_and_destruction_0':                                  
/usr/include/qt4/QtCore/qatomic_x86_64.h:129: multiple definition of `uiStuff::theWindow'                     
.obj/shapeInfo.o:/opt/occ63/inc/gp.lxx:6: first defined here                                                  
.obj/gcode2Model.o: In function `__static_initialization_and_destruction_0':                                  
/usr/include/qt4/QtCore/qatomic_x86_64.h:121: multiple definition of `uiStuff::errors'                        
.obj/shapeInfo.o:/opt/occ63/inc/Standard_Real.hxx:72: first defined here                                      
.obj/moc_shapeInfo.o: In function `__static_initialization_and_destruction_0':                                
/opt/cam-occ/trunk/src/.moc/moc_shapeInfo.cpp:75: multiple definition of `uiStuff::selectedShapes'                                                                                                       
.obj/uiStuff.o:/usr/include/qt4/QtCore/qchar.h:370: first defined here                                        
.obj/moc_shapeInfo.o:/opt/cam-occ/trunk/src/.moc/moc_shapeInfo.cpp:48: multiple definition of `uiStuff::theWindow'                                                                                       
.obj/shapeInfo.o:/opt/occ63/inc/gp.lxx:6: first defined here                                                  
.obj/moc_shapeInfo.o: In function `__static_initialization_and_destruction_0':                                
/usr/include/c++/4.3/bits/stl_construct.h:129: multiple definition of `uiStuff::errors'                       
.obj/shapeInfo.o:/opt/occ63/inc/Standard_Real.hxx:72: first defined here                                      
.obj/moc_uiStuff.o: In function `__static_initialization_and_destruction_0':                                  
/usr/include/qt4/QtCore/qstring.h:670: multiple definition of `uiStuff::selectedShapes'                       
.obj/uiStuff.o:/usr/include/qt4/QtCore/qchar.h:370: first defined here                                        
.obj/moc_uiStuff.o:/usr/include/qt4/QtCore/qglobal.h:1423: multiple definition of `uiStuff::theWindow'        
.obj/shapeInfo.o:/opt/occ63/inc/gp.lxx:6: first defined here                                                  
.obj/moc_uiStuff.o: In function `__static_initialization_and_destruction_0':                                  
/usr/include/c++/4.3/bits/stl_construct.h:129: multiple definition of `uiStuff::errors'                       
.obj/shapeInfo.o:/opt/occ63/inc/Standard_Real.hxx:72: first defined here                                      
.obj/moc_aSample.o: In function `__static_initialization_and_destruction_0':                                  
/opt/cam-occ/trunk/src/.moc/moc_aSample.cpp:70: multiple definition of `uiStuff::selectedShapes'                                                                                                         
.obj/uiStuff.o:/usr/include/qt4/QtCore/qchar.h:370: first defined here                                        
.obj/moc_aSample.o:/opt/cam-occ/trunk/src/.moc/moc_aSample.cpp:45: multiple definition of `uiStuff::theWindow'                                                                                           
.obj/shapeInfo.o:/opt/occ63/inc/gp.lxx:6: first defined here                                                  
.obj/moc_aSample.o: In function `__static_initialization_and_destruction_0':
/usr/include/c++/4.3/bits/stl_construct.h:129: multiple definition of `uiStuff::errors'
.obj/shapeInfo.o:/opt/occ63/inc/Standard_Real.hxx:72: first defined here
.obj/moc_shapeOffset.o: In function `__static_initialization_and_destruction_0':
/opt/cam-occ/trunk/src/.moc/moc_shapeOffset.cpp:70: multiple definition of `uiStuff::selectedShapes'
.obj/uiStuff.o:/usr/include/qt4/QtCore/qchar.h:370: first defined here
.obj/moc_shapeOffset.o:/opt/cam-occ/trunk/src/.moc/moc_shapeOffset.cpp:45: multiple definition of `uiStuff::theWindow'
.obj/shapeInfo.o:/opt/occ63/inc/gp.lxx:6: first defined here
.obj/moc_shapeOffset.o: In function `__static_initialization_and_destruction_0':
/usr/include/c++/4.3/bits/stl_construct.h:129: multiple definition of `uiStuff::errors'
.obj/shapeInfo.o:/opt/occ63/inc/Standard_Real.hxx:72: first defined here
.obj/moc_gcode2Model.o: In function `__static_initialization_and_destruction_0':
/opt/cam-occ/trunk/src/.moc/moc_gcode2Model.cpp:70: multiple definition of `uiStuff::selectedShapes'
.obj/uiStuff.o:/usr/include/qt4/QtCore/qchar.h:370: first defined here
.obj/moc_gcode2Model.o:/opt/cam-occ/trunk/src/.moc/moc_gcode2Model.cpp:45: multiple definition of `uiStuff::theWindow'
.obj/shapeInfo.o:/opt/occ63/inc/gp.lxx:6: first defined here
.obj/moc_gcode2Model.o: In function `__static_initialization_and_destruction_0':
/usr/include/c++/4.3/bits/stl_construct.h:129: multiple definition of `uiStuff::errors'
.obj/shapeInfo.o:/opt/occ63/inc/Standard_Real.hxx:72: first defined here
collect2: ld returned 1 exit status
make[1]: *** [../bin/camocc2] Error 1
make[1]: Leaving directory `/opt/cam-occ/trunk/src'
make: *** [sub-src-make_default] Error 2

I have not examined *every* one of the headers where there's a supposed multiple definition, but in the ones I looked at I found nothing.

johnsfine · 02-23-2009, 12:25 PM

Quote:

Originally Posted by map250r

changed some data member declarations to be static. I also added definitions outside the class. Now gcc barfs with 'multiple definition of ...'

You can't have those definitions in multiple compilation units.

You put those definitions outside the class and inside a header, then included that header in multiple .cpp files and that is not permitted.

The usual correct approach is to put the definitions in a .cpp file rather than in a header file.

An alternative (that might be considered more maintainable code) is to wrap the definitions within the header file in some #ifdef and then define that symbol (before including that header) in exactly one compilation unit.

map250r · 02-23-2009, 12:59 PM

Quote:

Originally Posted by johnsfine

You can't have those definitions in multiple compilation units.

You put those definitions outside the class and inside a header, then included that header in multiple .cpp files and that is not permitted.

The usual correct approach is to put the definitions in a .cpp file rather than in a header file.

An alternative (that might be considered more maintainable code) is to wrap the definitions within the header file in some #ifdef and then define that symbol (before including that header) in exactly one compilation unit.

Well I swear I tried that, but this time it worked.

Anyway, thanks.