Re: [Boost-users] dynamic link error: boost::program_options::arg not found

Subject: Re: [Boost-users] dynamic link error: boost::program_options::arg not found
From: Sebastian Hauer (sebastian.hauer_at_[hidden])
Date: 2008-09-17 13:21:41

Hello Ovanes,
thanks for the reply.  I fixed it.
I eventually found your posting and tried your suggestion attributing
boost::program_options::arg with an additional __declspec(selectany)
but either I did something wrong or things are different with msvc-8.0
it did not work for me.

Instead I went down a different path and got rid of the global arg
variable altogether.  Since nothing seems to write into it and the
value is always copied it seemed like a reasonable thing to do
considering it causes so much grief with the linking.

Once this was fixed I got another linker error:

error LNK2001: unresolved external symbol "public: static unsigned int
const boost::program_options::options_description::m_default_line_length"
(?m_default_line_length_at_options_description_at_program_options_at_boost@@2IB)

I found the solution to that one from this posting from Evert at
http://archives.free.net.ph/message/20080815.085344.d72efb54.en.html .
Once I changed the declaration of the class static const
m_default_line_length to:
 BOOST_STATIC_CONSTANT (unsigned, m_default_line_length = 80);

With these two changes in place all compiled and linked without a problem.
Below I've inlined the patch of my changes against the original
boost_1_36_0 source as reference for other people running into this
issue.  If these changes seem like a good idea to others perhaps they
could be included with the next boost release.

Regards,
Sebastian

diff -ru -x '*~'
boost_1_36_0_src_orig/boost/program_options/detail/value_semantic.hpp
boost_1_36_0_src/boost/program_options/detail/value_semantic.hpp
--- boost_1_36_0_src_orig/boost/program_options/detail/value_semantic.hpp	2007-11-25
13:07:19.000000000 -0500
+++ boost_1_36_0_src/boost/program_options/detail/value_semantic.hpp	2008-09-17
12:36:20.447677200 -0400
@@ -10,12 +10,11 @@

 namespace boost { namespace program_options {

-    extern BOOST_PROGRAM_OPTIONS_DECL std::string arg;
-
     template<class T, class charT>
     std::string
     typed_value<T, charT>::name() const
     {
+        static std::string arg("arg");
         if (!m_implicit_value.empty() && !m_implicit_value_as_text.empty()) {
             std::string msg = "[=arg(=" + m_implicit_value_as_text + ")]";
             if (!m_default_value.empty() && !m_default_value_as_text.empty())
diff -ru -x '*~'
boost_1_36_0_src_orig/boost/program_options/options_description.hpp
boost_1_36_0_src/boost/program_options/options_description.hpp
--- boost_1_36_0_src_orig/boost/program_options/options_description.hpp	2007-11-25
13:07:19.000000000 -0500
+++ boost_1_36_0_src/boost/program_options/options_description.hpp	2008-09-17
12:35:37.306223900 -0400
@@ -155,8 +155,8 @@
     */
     class BOOST_PROGRAM_OPTIONS_DECL options_description {
     public:
-        static const unsigned m_default_line_length;
-
+        BOOST_STATIC_CONSTANT (unsigned, m_default_line_length = 80);
+
         /** Creates the instance. */
         options_description(unsigned line_length = m_default_line_length);
         /** Creates the instance. The 'caption' parameter gives the name of
diff -ru -x '*~'
boost_1_36_0_src_orig/libs/program_options/src/options_description.cpp
boost_1_36_0_src/libs/program_options/src/options_description.cpp
--- boost_1_36_0_src_orig/libs/program_options/src/options_description.cpp	2007-11-25
13:38:02.000000000 -0500
+++ boost_1_36_0_src/libs/program_options/src/options_description.cpp	2008-09-17
13:07:03.748692900 -0400
@@ -201,8 +201,6 @@
         return *this;
     }

-    const unsigned options_description::m_default_line_length = 80;
-
     options_description::options_description(unsigned line_length)
     : m_line_length(line_length)
     {}
diff -ru -x '*~'
boost_1_36_0_src_orig/libs/program_options/src/value_semantic.cpp
boost_1_36_0_src/libs/program_options/src/value_semantic.cpp
--- boost_1_36_0_src_orig/libs/program_options/src/value_semantic.cpp	2007-11-25
13:38:02.000000000 -0500
+++ boost_1_36_0_src/libs/program_options/src/value_semantic.cpp	2008-09-17
12:40:16.983468600 -0400
@@ -64,12 +64,10 @@
     }
 #endif

-    BOOST_PROGRAM_OPTIONS_DECL std::string arg("arg");
-
     std::string
     untyped_value::name() const
     {
-        return arg;
+        return "arg";
     }

     unsigned