segfault happens when I serialize nested class in apache module - serialization

Question

Serializing simple class "A" in Apache module done without error but when I tried to serialize my complex object like "X" which has a member, type of "A", I got segfault in Apache module. ( this doesn't happen to a executable console application )
------------------------- here is my code : ---------------------
class A {
private:
friend class boost::serialization::access; // to enable boost "access" class to call private "serialize" method of class "A"
template<class ArchT>
void serialize(ArchT &ar, unsigned int version) { // method for both serializing and deserializing
ar & memA; // (de)serialize member "memA"
}
std::string memA; // sample member
public:
A(){}
A(std::string pmemA) :
memA(pmemA) {
}
std::string GetMemA()
{
return memA;
}
};
class X {
private:
friend class boost::serialization::access;
template<class ArchT>
void serialize(ArchT &ar, unsigned int version) {
ar & memX;
ar & a;
}
std::string memX;
A a;
public:
X(std::string pmemX, A pa) :
memX(pmemX), a(pa) {
}
X(){}
};
-------------------
string st=GetRandomFileName();
ofstream out(st.c_str());
boost::archive::text_oarchive out_r(out);
A a("Amem");
X x("Xmem", a);
out_r << x; // not works
out_r << a; // works!
------------------- here is stack trace from gdb for apache ----------------
boost::serialization::typeid_system::extended_type_info_typeid_0::is_less_than(boost::serialization::extended_type_info const&) const () from /tmp/libIRSProWebApacheModule.so
2 0xb7223c61 in std::_Rb_tree