Sorry for the double post. I had to patch Source of the Program Options to solve this issue. Here the organization of the project which produced Linking errors: BoostProgramOptions.LIB (we link against DLL version of LIB) ^ | Lib with PO retriever (static lib) ^ | +------------------------------------------------------------+ | | Lib A Lib B ^ ^ | | +------------------------------------------------------------+ ^ | DLL which links with A & B Lib A & Lib B rely on the same program options reader. Initial problem was as described below. To solve this issue I had to remove the arg definition in the value_semantic.cpp file and initialize it in the header file detail/value_semantic.hpp with MS specific __declspec(selectany) which causes to ignore multiple defined linker symbol. Here the linke in the value_semantic.hpp extern BOOST_PROGRAM_OPTIONS_DECL __declspec(selectany) std::string arg("arg"); I hope you can reproduce this behaviour and apply this patch to next boost destributions. With Kind Regards, Ovanes P.S. I don't know if the entire fix is worth doing it when the arg's value is copied in the source anyway. Just a small example: template std::string typed_value::name() const { if (!m_default_value.empty() && !m_default_value_as_text.empty()) { return arg + " (=" + m_default_value_as_text + ")"; } else { return arg; } } On Wed, Jun 18, 2008 at 3:47 PM, Ovanes Markarian wrote:

Hi *!

We switched the alignment of boost (1.34.0 + VC 7.1) libs to 4 byte, since our project has a restriction of 4byte struct member alignment and we receive a linker error that program_options can no link to a boost::program_options::arg string global.

error LNK2001: unresolved external symbol "class std::basic_string const boost::program_options::arg" (?arg@program_options@boost@@3V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@B)

Making the dumpbin /exports from the boost_program_options....lib I clearly find this symbol as exported one, with the exactly searched signature. Using the default struct member alignment I can link to the program_options lib whithout any problems. Any ideas or suggestions are really welcome!

With Kind Regards, Ovanes