Compiling issues with boost - c++

Question

I'm having problems with compiling a program which includes "boost/asio.hpp".
Compiling this program(taken from boost site):
example.cpp:
#include <boost/lambda/lambda.hpp>
#include <iostream>
#include <iterator>
#include <algorithm>
int main()
{
using namespace boost::lambda;
typedef std::istream_iterator<int> in;
std::for_each(
in(std::cin), in(), std::cout << (_1 * 3) << " " );
}
with
c++ -I path/to/boost_1_55_0 example.cpp -o example
works fine.
But when the program includes:
boost/asio.hpp
And I'm trying to compile it with:
g++ -I /usr/local/boost_1_55_0 example.cpp -o example -lboost_system -lboost_thread
an executable is generated ,but I'm getting this error when trying to execute "example":
./example: error while loading shared libraries: libboost_system.so.1.55.0: cannot open shared object file: No such file or directory
The file "libboost_system.so.1.55.0" is located at "/usr/local/lib".
I also tried to compile the program with :
g++ -I /usr/local/boost_1_55_0 -L/usr/local/lib example.cpp -o example -lboost_system -lboost_thread
And got the same error.
How can I fix this?

Answer 1

You need to tell the linker where to find the library it needs. I prefer RPATH for this:
g++ -I /usr/local/boost_1_55_0 -Wl,-rpath=/usr/local/lib example.cpp -o example -lboost_system -lboost_thread
That bakes /usr/local/lib into the executable so ld can find it later. You can see what ld will load by running ldd example after building. I bet right now it says "not found" and after adding RPATH it will find the library.
Another option is to set /usr/local/lib as a system search path in your /etc/ld.so.conf, but that's quite a bit more heavyweight.

Answer 2

set up LD_LIBRARY_PATH as export LD_LIBRARY_PATH= path to boost