Why do I get linker errors trying to compile my first CORBA server (using ACE/TAO ORB implementation)?

Question

Trying to implement my very first CORBA server (with ACE/TAO ORB implementation) I use the following makefile:

#compiler                                                                                                                                                      
CC=g++
#compiler options
CPPFLAGS=-Wall -I. -I/usr/include/ -I/usr/include/orbsvcs/
LFLAGS=-L/usr/lib64/ -lACE -lTAO -lTAO_PortableServer -lTAO_DynamicAny -lTAO_CosNotification -lTAO_CosNaming
#source files
SOURCES=$(wildcard *.cpp)
#object files
OBJECTS=$(SOURCES:.cpp=.o)

#executable filename
EXECUTABLE=main
#Special symbols used:
#$^ - is all the dependencies (in this case =$(OBJECTS) )
#$@ - is the result name (in this case =$(EXECUTABLE) )

all: $(EXECUTABLE)

$(EXECUTABLE): $(OBJECTS)
  #$(LINK.o) $^ -o $@
  $(CC) $(LFLAGS) $^ -o $@

%.o: %.c 
  $(CC) $(CPPFLAGS) -c $<

clean:
  - rm -rf $(EXECUTABLE) $(OBJECTS)

and I get the following error on compilation:

g++  -Wall -I. -I/usr/include/ -I/usr/include/orbsvcs/  -c -o cryptC.o cryptC.cpp
g++  -Wall -I. -I/usr/include/ -I/usr/include/orbsvcs/  -c -o cryptS.o cryptS.cpp
g++  -Wall -I. -I/usr/include/ -I/usr/include/orbsvcs/  -c -o main.o main.cpp
In file included from main.cpp:5:
CryptographicImpl.h: In member function ‘virtual char* CryptographicImpl::decrypt(const CaesarAlgorithm::charsequence&, CORBA::ULong, CORBA::ULong)’:
CryptographicImpl.h:49: warning: comparison between signed and unsigned integer expressions
#g++   cryptC.o cryptS.o main.o -o main
g++ -L/usr/lib64/ -lTAO_PortableServer -lTAO_DynamicAny -lACE -lTAO -lTAO_CosNotification -lTAO_CosNaming cryptC.o cryptS.o main.o -o main
cryptC.o: In function `TAO::Objref_Traits<CaesarAlgorithm>::marshal(CaesarAlgorithm*, TAO_OutputCDR&)':
cryptC.cpp:(.text+0x7f): undefined reference to `CORBA::Object::marshal(CORBA::Object*, TAO_OutputCDR&)'

whole compilation log: http://pastebin.com/0KpLXixw

I use ACE (6.2.8) and TAO(2.2.8) from this repo on my CentOS 6.6

Answer 1

The order of the libraries is important, from right to left you should make sure you first specify the base libraries, than the ones that use the base, for example -lTAO_PortableServer -lTAO_AnyTypeCode -lTAO -lACE -ldl -lrt. For more information see also Why does the order in which libraries are linked sometimes cause errors in GCC?.

I would recommend you to compile one of the TAO shipped unit tests and copy from there, or use MPC to generate the makefiles.

Also check TAOX11, the new IDL to C++11 language mapping is way easier to use and we provide free of charge evaluation licenses that you can use for classroom usage.