Question

This is a puzzle to me:

c++ undefined reference to destructor

That’s the issue, the code is the same as the link, full makefile and errors here. The linked answers did help but only to highlight that I had some headers in a place I did not expect.

makefile

CXX = g++

BIN = .

LIBS = -L.

INCLUDE = -I . -I 

CXXFLAGS = -pipe # -O6

LFLAGS = -lm

GeomTest_OBJS   =   geomTest.o SASAGeometry.o

geomTest_source =   SASAGeometry.cpp SASAGeometry.h sasa_transformMatrix.cpp sasa_transformMatrix.h geomSetup.cpp

SASAGeometry.o  :   SASAGeometry.cpp SASAGeometry.h sasa_transformMatrix.cpp sasa_transformMatrix.h

geomTest.o  :   geomSetup.cpp

geomTest    : $(GeomTest_OBJS) makefile
            $(CXX) -o geomTest.o -o SASAGeometry.o $(LIBS) $(INCLUDE) $(CXXFLAGS) $(geomTest_source) $(LFLAGS)
            $(CXX) $(LIBS) $(INCLUDE) $(CXXFLAGS) -o $(BIN)/geomTest geomTest.o SASAGeometry.o $(LFLAGS) 

clean       : \rm *.o *~ p1

I have both declared and instantiated the destructor AND not (allowing the compiler to do its thing)

error

geomSetup.cpp:(.text+0x5ab): undefined reference to `SASAGeometry::~SASAGeometry()'
geomSetup.cpp:(.text+0x5cd): undefined reference to `SASAGeometry::~SASAGeometry()'

no other errors. (sorry if its preferable to bump seemingly sorted issues rather than link to them, but my effort at that didn’t work)

Thanks in advance!

EDIT:

MAKE SURE TO COMPILE THE CORRECT SOURCE FILES, NOT THE OLD ONES YOU FORGOT TO COPY.

Hi @trojanfoe and @Kerrick SB, both answers made me look at my makefile and realise it was ugly. Here is the revised version. I am still getting the same ‘undefined reference to destructor’ error though:

makefile:

CXX = g++

BIN = .

LIBS = -L.

INCLUDE = -I. 

CXXFLAGS = -pipe # -O6

LDFLAGS = -lm

GeomTest_OBJS       =   sasa_transformMatrix.o SASAGeometry.o geomSetup.o

SASAGeometry.o      :   SASAGeometry.cpp SASAGeometry.h 

sasa_transformMatrix.o  :   sasa_transformMatrix.cpp sasa_transformMatrix.h 

geomSetup.o         :   geomSetup.cpp

geomTest                : $(GeomTest_OBJS)
                    $(CXX) $(CXXFLAGS) $(LDFLAGS) -o $@ $+

clean           : \rm *.o *~ p1

error:

geomSetup.o: In function `main':
geomSetup.cpp:(.text+0x5ab): undefined reference to `SASAGeometry::~SASAGeometry()'
geomSetup.cpp:(.text+0x5cd): undefined reference to `SASAGeometry::~SASAGeometry()'
collect2: ld returned 1 exit status
make: *** [geomTest] Error 1

Why would the linker complain about the destructor and not the constructor or any other methods/functions in the class?

Thanks again!

Answer 1

Your executable output file and your object file geomTest.o have the same name! That’s bound to get you into trouble when the linker overwrites the object file.

Change it to $(CXX) -o geomTest ..., or better even to $(CXX) $@ ... to avoid such problems in the future.

In fact, you are misusing the linker command altogether: you just want to have one single -o option, and the objects are listed directly, without flags:

g++ -o myprog main.o foo.o bar.o

Within the Makefile, do yourself a favour and use magic macros:

myprog: main.o foo.o bar.o
        $(CXX) $(LDFLAGS) -o $@ $+ $(LIBRARIES)

Here -o $@ matches the target name, i.e. -o myprog, and $+ matches all the dependent names, i.e. main.o foo.o bar.o.

The guiding idea behind using variables is that you should never say the same thing more than once if you can help it. So you can have myprog: $(MyObjects) as the rule, but then use $+ in the command line to avoid repetition of MyObjects. This improves locality and maintainability.