Cannot find C++ library when linking, error compliling the `boost::program_options` example

Question

I am trying to compile the multiple_sources.cpp to compile on my computer. I am running Xubuntu Lucid Lynx fully updated.

It will compile without issue with g++ -c multiple_sources.cpp but when I try to link and make an exectuable with g++ multiple_sources.o I get:

multiple_sources.cpp:(.text+0x3d): undefined reference to `boost::program_options::options_description::m_default_line_length'
multiple_sources.cpp:(.text+0x87): undefined reference to `boost::program_options::options_description::options_description(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, unsigned int)'
multiple_sources.cpp:(.text+0x15a): undefined reference to `boost::program_options::options_description::add_options()'
multiple_sources.cpp:(.text+0x17b): undefined reference to `boost::program_options::options_description_easy_init::operator()(char const*, char const*)'
multiple_sources.cpp:(.text+0x193): undefined reference to `boost::program_options::options_description_easy_init::operator()(char const*, char const*)'
multiple_sources.cpp:(.text+0x1af): undefined reference to `boost::program_options::options_description_easy_init::operator()(char const*, boost::program_options::value_semantic const*, char const*)'
multiple_sources.cpp:(.text+0x1eb): undefined reference to `boost::program_options::options_description::m_default_line_length'
multiple_sources.cpp:(.text+0x252): undefined reference to `boost::program_options::options_description::options_description(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, unsigned int)'
...

et cetera ad nauseum.

I do have the library installed:

>ls -l /usr/lib/libboost_program_options*
-rw-r--r-- 1 root root 640800 2010-03-31 21:19 /usr/lib/libboost_program_options.a
lrwxrwxrwx 1 root root     26 2010-04-09 00:57 /usr/lib/libboost_program_options-mt.a     -> libboost_program_options.a
lrwxrwxrwx 1 root root     34 2010-04-09 00:57 /usr/lib/libboost_program_options-mt.so -> libboost_program_options.so.1.40.0
lrwxrwxrwx 1 root root     34 2010-04-09 00:57 /usr/lib/libboost_program_options.so -> libboost_program_options.so.1.40.0
-rw-r--r-- 1 root root 289336 2010-03-31 21:19 /usr/lib/libboost_program_options.so.1.40.0

After reading the g++ man page, I have also tried:

• g++ -llibboost_program_options multiple_sources.cpp
• g++ -llibboost_program_options.a multiple_sources.cpp
• g++ -llibboost_program_options.so multiple_sources.cpp
• and all of the above with -L/usr/lib before the -l

They all fail with a variation on:

/usr/bin/ld: cannot find -llibboost_program_options.so
collect2: ld returned 1 exit status

What am I doing wrong?

Answer 1

The -l param is wrong; get rid of the lib pre-fix and use -lboost_program_options.

The linker expects all libraries to begin with lib, and for you to leave that off when specifying the library.

You could also include the full path to the library in the list of files, without -l (e.g. g++ multiple_sources.cpp /usr/lib/libboost_program_options.so), but for system libraries, it's better to follow convention; they aren't always installed in /usr/lib.