[Boost-users] boost::variant as class member - linker error

2 Aug 2008

      I'm new to boost::variant and I can't seem to use it in a class  
because I get linker errors. I can't find any reference to this in the  
archive or the docs so I figure it must be something silly I'm  
missing. Any help appreciated. The compilation command, error, and  
files are shown below.

Thanks,
Kevin Martin

g++ -I $BOOSTINC test.cpp a.cpp
/usr/lib64/gcc-lib/x86_64-suse-linux/3.3.5/../../../../x86_64-suse- 
linux/bin/ld:  
` 
.gnu 
.linkonce 
.t 
._ZN5boost6detail7variant15visitation_implIN4mpl_4int_ILi0EEENS1_20visitation_impl_stepINS_3mpl6l_iterINS7_6l_itemINS3_5long_ILl2EEEiNS9_INSA_ILl1EEESsNS7_5l_endEEEEEEENS8_ISD_EEEENS1_9destroyerEPvNS_7variantIiSsNS1_5void_ESM_SM_SM_SM_SM_SM_SM_SM_SM_SM_SM_SM_SM_SM_SM_SM_SM_E18has_fallback_type_EEEN7Visitor11result_typeEiiRSP_T2_NS3_5bool_ILb0EEET3_PT_PT0_ 
' referenced in section `.rodata' of /tmp/ccZwRSZE.o: defined in  
discarded section  
` 
.gnu 
.linkonce 
.t 
._ZN5boost6detail7variant15visitation_implIN4mpl_4int_ILi0EEENS1_20visitation_impl_stepINS_3mpl6l_iterINS7_6l_itemINS3_5long_ILl2EEEiNS9_INSA_ILl1EEESsNS7_5l_endEEEEEEENS8_ISD_EEEENS1_9destroyerEPvNS_7variantIiSsNS1_5void_ESM_SM_SM_SM_SM_SM_SM_SM_SM_SM_SM_SM_SM_SM_SM_SM_SM_E18has_fallback_type_EEEN7Visitor11result_typeEiiRSP_T2_NS3_5bool_ILb0EEET3_PT_PT0_ 
' of /tmp/ccZwRSZE.o

The files are:

==== a.h ====

#ifndef __A_HEADER__
#define __A_HEADER__

#include <boost/variant.hpp>
#include <string>

class A
{
         boost::variant<int, std::string> a;
public:
         void setToString(const std::string &x);
         void setToInt(int x);
         int which() const;
};

#endif

==== a.cpp ====

#include "a.h"

int
A::which() const
{
     return this->a.which();
}

void
A::setToString(const std::string &x)
{
     this->a = x;
}

void
A::setToInt(int x)
{
     this->a = x;
}

==== test.cpp ====

#include "a.h"
#include <iostream>

int main() {
     A a;

     a.setToString("abc");
     std::cout << a.which() << std::endl;

     a.setToInt(123);
     std::cout << a.which() << std::endl;

     return 0;
}