SWIG tcl : undefined symbol error for log4cpp wrapper - tcl

Question

I am new in log4cpp and swig wrapper. I am trying to write an interface for simple logging using log4cpp.
I have installed log4cpp and swig in my Ubuntu machine.
log4cpp.cpp:
#include "log4cpp/Category.hh"
#include "log4cpp/Appender.hh"
#include "log4cpp/FileAppender.hh"
#include "log4cpp/OstreamAppender.hh"
#include "log4cpp/Layout.hh"
#include "log4cpp/BasicLayout.hh"
#include "log4cpp/Priority.hh"
#include "log4cpp.h"
void writeLog() {
log4cpp::Appender *appender1 = new log4cpp::OstreamAppender("console", &std::cout);
appender1->setLayout(new log4cpp::BasicLayout());
log4cpp::Appender *appender2 = new log4cpp::FileAppender("default", "program.log");
appender2->setLayout(new log4cpp::BasicLayout());
log4cpp::Category& root = log4cpp::Category::getRoot();
root.setPriority(log4cpp::Priority::WARN);
root.addAppender(appender1);
log4cpp::Category& sub1 = log4cpp::Category::getInstance(std::string("sub1"));
sub1.addAppender(appender2);
// use of functions for logging messages
root.error("root error");
root.info("root info");
sub1.error("sub1 error");
sub1.warn("sub1 warn");
// printf-style for logging variables
root.warn("%d + %d == %s ?", 1, 1, "two");
// use of streams for logging messages
root << log4cpp::Priority::ERROR << "Streamed root error";
root << log4cpp::Priority::INFO << "Streamed root info";
sub1 << log4cpp::Priority::ERROR << "Streamed sub1 error";
sub1 << log4cpp::Priority::WARN << "Streamed sub1 warn";
// or this way:
root.errorStream() << "Another streamed error";
}
log4cpp.h:
void writeLog(void);
log4cpp.i:
%module log4cpp
%{
#include "log4cpp.h"
%}
%inline %{
extern void writeLog(void);
%}
I have done following steps to generate log4cpp.so file:
swig -tcl -c++ log4cpp.i
g++ -c -fPIC log4cpp.cpp log4cpp_wrap.cxx -I/usr/include/tcl8.5
g++ -shared log4cpp.o log4cpp_wrap.o -o log4cpp.so
It generates the log4cpp_wrap.cxx, log4cpp.o, log4cpp_wrap.o and log4cpp.so files without any warning and error.
Whenever I am running the below command in tcl.
load ./log4cpp.so
It generates an undefined symbol error:
% load ./log4cpp.so
couldn't load file "./log4cpp.so": ./log4cpp.so: undefined symbol: _ZN7log4cpp8Appender29AppenderMapStorageInitializerD1Ev
What to do that to remove this error?

Answer 1

You need to link your SWIG shared library to log4cxx like you would with any other C++ application that uses this library. So when you call
g++ -shared log4cpp.o log4cpp_wrap.o -o log4cpp.so
It really needs to be something like this (but adapted to have real library and search path)
g++ -shared log4cpp.o log4cpp_wrap.o -L/path/to/your/install/of/log4cxx -llog4cxx -o log4cpp.so