Boost :: linker error option with gcc

Question

I'm a little tired trying to figure out why the following will not compile:

#include <iostream> #include <array> #include <boost/variant.hpp> #include <forward_list> typedef unsigned long long very_long; typedef boost::variant< int, std::string > variants_type; typedef std::array< variants_type, 5 > row_type; typedef std::forward_list<row_type> rows_holder_type; int main() { rows_holder_type rows; row_type row_data; row_data[0] = 0; row_data[1] = 0; row_data[2] = 0; row_data[3] = 0; row_data[4] = 0; rows.push_front(row_data); } 

This is the compiler error I get:

/usr/include/testing/test_code.o||In function 'std::array<boost::variant<int, std::basic_string<char, std::char_traits<char>, std::allocator<char> >, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_>, 5ul>::array(std::array<boost::variant<int, std::basic_string<char, std::char_traits<char>, std::allocator<char> >, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_>, 5ul> const&)' 'std::array<boost::variant<int, std::basic_string<char, std::char_traits<char>, std::allocator<char> >, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_>, 5ul>::array(std::array<boost::variant<int, std::basic_string<char, std::char_traits<char>, std::allocator<char> >, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_>, 5ul> const&)' : |
. Store.cpp :( text._ZNSt5arrayIN5boost7variantIiSsNS0_6detail7variant5void_ES4_S4_S4_S4_S4_S4_S4_S4_S4_S4_S4_S4_S4_S4_S4_S4_S4_EELm5EEC2ERKS6 _ [_ ZNSt5arrayIN5boost7variantIiSsNS0_6detail7variant5void_ES4_S4_S4_S4_S4_S4_S4_S4_S4_S4_S4_S4_S4_S4_S4_S4_S4_EELm5EEC5ERKS6 _] + 0x31) || undefined reference 'boost::variant<int, std::basic_string<char, std::char_traits<char>, std::allocator<char> >, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_>::variant(boost::variant<int, std::basic_string<char, std::char_traits<char>, std::allocator<char> >, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_> const&)' 'boost::variant<int, std::basic_string<char, std::char_traits<char>, std::allocator<char> >, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_>::variant(boost::variant<int, std::basic_string<char, std::char_traits<char>, std::allocator<char> >, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_, boost::detail::variant::void_> const&)' |
|| === Assembly completed: 1 error, 0 warnings === |

If I replace:

 typedef boost::variant< int, std::string > variants_type; 

with:

 typedef boost::any variants_type; 

The code compiles, but I do not want to use boost :: any for performance reasons.

Answer 1

I checked your code with MSVC and gcc 4.7.0. MSVC compiles and binds the code in order (of course with #include <string> ), but gcc gives a linker error on the last line rows.push_front(row_data); . If you comment on this line, gcc accepts the code. I see no reason why gcc gives a linker error and concludes that it is an error with gcc. One way to bypass gcc would be to change std::array to std::vector .

(From the error message, I assume that you are using Code :: Blocks with gcc)

I removed the extra code, and the following example still gives the linker error:

 #include <boost/variant.hpp> #include <array> int main() { std::array<boost::variant<int, double>, 5> row_type1; std::array<boost::variant<int, double>, 5> row_type2 = row_type1; } 

Answer 2

You are missing #include <string> ; except that your code is ok.