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 (eg 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 .