Question

I am using the following structure for a Makefile:

OBJECTS := time.o
PROGRAM := time
CPPFLAGS += -Iusr/include/boost_1_49_0 -Lusr/include/boost_1_49_0/stage/lib
CXXFLAGS := -Wall -ggdb3
LDFLAGS += -lboost_date_time
$(PROGRAM) : $(OBJECTS)
g++ -o time time.cpp

clean :
rm $(PROGRAM) $(OBJECTS)

But when I enter make, it gives me lots of errors – including:

undefined reference to `boost::gregorian::greg_month::as_short_string() const' time.cpp:
(.text._ZN5boost9date_time15month_formatterINS_9gregorian10greg_monthENS0_13simple_formatIcEEcE12format_monthERKS3_RSo[boost::date_time::month_formatter<boost::gregorian::greg_month, boost::date_time::simple_format<char>, char>::format_month(boost::gregorian::greg_month const&, std::basic_ostream<char, std::char_traits<char> >&)]+0x56):
    undefined reference to `boost::gregorian::greg_month::as_long_string() const'
collect2: ld returned 1 exit status

When I use g++ -Wall -Iusr/include/boost_1_49_0 -Lusr/include/boost_1_49_0/stage/lib -o time time.cpp -lboost_date_time, the code compiles fine so something is wrong with my Makefile. Please help. Note: I tried placing the -L <directory> flag in the LDFLAG variable but that didn’t work either.

Answer 1

LDFLAGS is not used in your Makefile – neither directly nor implicit via built-in rules. The following should work:

$(PROGRAM): $(OBJECTS)
    $(CXX) $(LDFLAGS) $(TARGET_ARCH) $^ $(LOADLIBES) $(LDLIBS) -o $@ 

make is a powerful tool. However, it is not trivial to use. If you are not forced to use make, I suggest taking a closer look at alternatives. Personally, I recommend the usage of bjam/boost-build. Here is an example for a simple Jamroot:

project
    : requirements <cflags>-Wall <cflags>-ggdb3
    ;

using gcc ;

lib boost_date_time
    :
    : <search>/usr/include/boost_1_49_0/stage/lib
    :
    : <include>/usr/include/boost_1_49_0
    ;

exe time
    : time.cpp foo.cpp bar.cpp boost_date_time
    ;