Irregular Makefile Behaviour? - c++

Question

I'm compiling a program with 3 source files: main.cpp, DataHandler.cpp and DataHandler.h.
I use a makefile that contains the following code to build:
Makefile
OBJECTS = main.o DataHandler.o
CC = g++
DEBUG = -g
CFLAGS = -c -std=c++11
LFLAGS = -lopendnp3 -lopenpal -lasiodnp3 -lasiopal -lpthread -std=c++11
lvoutstation : $(OBJECTS)
$(CC) $(LFLAGS) $(OBJECTS) -o lvoutstation
main.o : main.cpp DataHandler.h
$(CC) $(CFLAGS) main.cpp
DataHandler.o : DataHandler.cpp DataHandler.h
$(CC) $(CFLAGS) DataHandler.cpp
.PHONY : clean
clean :
rm lvoutstation $(OBJECTS)
It build main.o and DataHandler.o fine, but when it gets to compiling the action executable, it gives linking erros to all my asiodnp3 and opendnp3 namespace function / class calls.
When I run the following command:
g++ -o lvoutstation main.o DataHandler.o -lopendnp3 -lopenpal -lasiodnp3
-lasiopal -lpthread -std=c++11
It works fine..
I don't understand where the linking error comes in?
EDIT
Upon request for the error message:
g++ -lopendnp3 -lopenpal -lasiodnp3 -lasiopal -std=c++11 main.o DataHandler.o -o lvoutstation
main.o: In function `main':
main.cpp:(.text+0x85): undefined reference to `asiodnp3::DNP3Manager::DNP3Manager(unsigned int, openpal::ICryptoProvider*, std::function<void ()>, std::function<void ()>)'
main.cpp:(.text+0xb7): undefined reference to `asiodnp3::DNP3Manager::AddLogSubscriber(openpal::ILogHandler*)'
main.cpp:(.text+0xf0): undefined reference to `opendnp3::ChannelRetry::Default()'
main.cpp:(.text+0x123): undefined reference to `asiodnp3::DNP3Manager::AddTCPServer(char const*, unsigned int, opendnp3::ChannelRetry const&, std::string const&, unsigned short)'
main.cpp:(.text+0x19f): undefined reference to `opendnp3::EventBufferConfig::AllTypes(unsigned short)'
main.cpp:(.text+0x1d6): undefined reference to `opendnp3::DefaultOutstationApplication::Instance()'
main.cpp:(.text+0x2c8): undefined reference to `asiodnp3::DNP3Manager::~DNP3Manager()'
main.o: In function `opendnp3::LinkConfig::LinkConfig(bool, bool)':
main.cpp:(.text._ZN8opendnp310LinkConfigC2Ebb[_ZN8opendnp310LinkConfigC5Ebb]+0x75): undefined reference to `openpal::TimeDuration::Seconds(long)'
main.cpp:(.text._ZN8opendnp310LinkConfigC2Ebb[_ZN8opendnp310LinkConfigC5Ebb]+0x87): undefined reference to `openpal::TimeDuration::Minutes(long)'
main.o: In function `opendnp3::OutstationConfig::OutstationConfig()':
main.cpp:(.text._ZN8opendnp316OutstationConfigC2Ev[_ZN8opendnp316OutstationConfigC5Ev]+0x14): undefined reference to `opendnp3::OutstationParams::OutstationParams()'
main.cpp:(.text._ZN8opendnp316OutstationConfigC2Ev[_ZN8opendnp316OutstationConfigC5Ev]+0x56): undefined reference to `opendnp3::EventBufferConfig::EventBufferConfig(unsigned short, unsigned short, unsigned short, unsigned short, unsigned short, unsigned short, unsigned short, unsigned short)'
main.o: In function `asiodnp3::ConsoleLogger::Instance()':
main.cpp:(.text._ZN8asiodnp313ConsoleLogger8InstanceEv[_ZN8asiodnp313ConsoleLogger8InstanceEv]+0x5): undefined reference to `asiodnp3::ConsoleLogger::instance'
DataHandler.o: In function `DataHandler::ReadMeasurements(asiodnp3::IOutstation*)':
DataHandler.cpp:(.text+0xfe): undefined reference to `asiodnp3::MeasUpdate::MeasUpdate(asiodnp3::IOutstation*)'
DataHandler.cpp:(.text+0x11d): undefined reference to `opendnp3::Analog::Analog(double)'
DataHandler.cpp:(.text+0x137): undefined reference to `asiodnp3::MeasUpdate::Update(opendnp3::Analog const&, unsigned short, opendnp3::EventMode)'
DataHandler.cpp:(.text+0x159): undefined reference to `asiodnp3::MeasUpdate::~MeasUpdate()'
DataHandler.cpp:(.text+0x17b): undefined reference to `asiodnp3::MeasUpdate::~MeasUpdate()'
collect2: error: ld returned 1 exit status
make: *** [lvoutstation] Error 1

Answer 1

The makefile just works as expected. Your action becomes actually different from your command line sample
$(CC) $(LFLAGS) $(OBJECTS) -o lvoutstation
will expand to
g++ -lopendnp3 -lopenpal -lasiodnp3 -lasiopal -lpthread -std=c++11 \
main.o DataHandler.o -o lvoutstation
The order of object files and libraries matters for the linking process.
You can fix the linker errors providing the libraries after the object files:
$(CC) $(OBJECTS) $(LFLAGS) -o lvoutstation