Command Line Options Questions
Hi, I have two questions re: the boost command line options library: 1) I am compiling a dynamic library that links to the boost command line options library as a shared library. When I try to unload the dynamic library, I find that it isn’t properly unloaded and the boost library seems to be causing the issue. I did find that things were helped somewhat when I linked to the boost static libraries. However, it still feels unstable. Are there any particular things I should know about in this context in terms of how my makefile should be linking to boost? Or are there other things I should look at. 2) When using program options, I am getting the following error. For some reason this seemed to work with the dynamic libraries (or it may be a coincidence). Am I required to implement the << and >> operators? It had been compiling previously and stopped. After googling this issue there seems to be a lot of confusion. Any help would be greatly appreciated. in file included from /usr/include/boost/any.hpp:27:0, from /usr/include/boost/program_options/value_semantic.hpp:12, from /usr/include/boost/program_options/options_description.hpp:13, from /usr/include/boost/program_options.hpp:15, from /usr/local/src/freeswitch/src/mod/applications/mod_sc_dsp/mod_sc_dsp.cpp:23: /usr/include/boost/lexical_cast.hpp: In instantiation of 'struct boost::detail::deduce_target_char_impl<boost::detail::deduce_character_type_later<dsp_type> >': /usr/include/boost/lexical_cast.hpp:415:89: required from 'struct boost::detail::deduce_target_char<dsp_type>' /usr/include/boost/lexical_cast.hpp:674:92: required from 'struct boost::detail::lexical_cast_stream_traits<std::basic_string<char>, dsp_type>' /usr/include/boost/lexical_cast.hpp:2363:19: required from 'static Target boost::detail::lexical_cast_do_cast<Target, Source>::lexical_cast_impl(const Source&) [with Target = dsp_type; Source = std::basic_string<char>]' /usr/include/boost/lexical_cast.hpp:2543:50: required from 'Target boost::lexical_cast(const Source&) [with Target = dsp_type; Source = std::basic_string<char>]' /usr/include/boost/program_options/detail/value_semantic.hpp:89:38: required from 'void boost::program_options::validate(boost::any&, const std::vector<std::basic_string<charT> >&, T*, long int) [with T = dsp_type; charT = char]' /usr/include/boost/program_options/detail/value_semantic.hpp:170:55: required from 'void boost::program_options::typed_value<T, charT>::xparse(boost::any&, const std::vector<std::basic_string<charT> >&) const [with T = dsp_type; charT = char]' /usr/local/src/freeswitch/src/mod/applications/mod_sc_dsp/mod_sc_dsp.cpp:484:1: required from here /usr/include/boost/lexical_cast.hpp:388:13: error: static assertion failed: Target type is neither std::istream`able nor std::wistream`able BOOST_STATIC_ASSERT_MSG((result_t::value || boost::has_right_shift<std::basic_istream<wchar_t>, T >::value), desc.add_options() ("help", "Generates help message") ("dsp_type", po::value<dsp_type>(¶ms.dsp_type)->required(), “") where dsp_type is this: struct dsp_type { dsp_type() {} dsp_type(std::string const& val): value(val) { } std::string value; }; and I have a validator defined as this: void validate(boost::any& v, std::vector<std::string> const& values, dsp_type* /* target_type */, int) { using namespace boost::program_options; //namespace po = boost::program_options; // Make sure no previous assignment to 'v' was made. validators::check_first_occurrence(v); // Extract the first string from 'values'. If there is more than // one string, it's an error, and exception will be thrown. std::string const& s = validators::get_single_string(values); if (s == "ladspa" || s == "audioweaver" || s == "gstreamer" || s == "lv2") { v = boost::any(dsp_type(s)); } else { throw validation_error(validation_error::invalid_option_value); } } /usr/local/src/freeswitch/build/modmake.rules:214: recipe for target 'mod_sc_dsp.lo' failed make[1]: *** [mod_sc_dsp.lo] Error 1
You have to implement operator<< otherwise the compiler does not know how to print (pipe it into an ostream) dsp_type. You can use Boost.Fusion's I/O feature and BOOST_ADAPT_STRUCT like this
https://github.com/daniel-j-h/argparse-generic/blob/master/example.cc to make your life easier.
On March 6, 2016 5:43:27 PM GMT+01:00, Jon Lederman <jonlederman@gmail.com> wrote:
Hi, I tried like this: std::ostream& operator<<(std::ostream& os, const dsp_type& obj) { // write obj to stream os << obj.value; return os; } std::istream& operator>>(std::istream& is, dsp_type& obj) { // read obj from stream if ( 0 /* T could not be constructed */ ) is.setstate(std::ios::failbit); is >> obj.value; return is; } However now it let’s everything through and doesn’t validate. What is the proper way to do this? -Jon
Take a look at the following docs for the validate function:
http://www.boost.org/doc/libs/1_60_0/doc/html/program_options/howto.html#idm... On 03/07/2016 02:32 PM, Jon Lederman wrote:
On 06-Mar-16 7:43 PM, Jon Lederman wrote:
Jon, could you clarify how you try to unload the dynamic library, for what purpose, and how you determine it's not properly unloaded? If you link to program_options normally, just adding it on linker command line, it will be loaded automatically by the dynamic linker and will remain in memory until your program exits - although if you don't use the library after initial parsing, the unused code pages may be discarded by the operating system. I doubt explicitly unloading, with dlclose, is possible in this case. You possibly can use dlopen to load the library, but I can't see how that would work either, given it's a C++ library with a somewhat wide interface. Thanks, -- Vladimir Prus http://vladimirprus.com
participants (3)
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Daniel Hofmann -
Jon Lederman -
Vladimir Prus