C++ linking boost library

Question

First I built the Boost libraries that require building by going to /usr/local/boost_1_49_0/ and running the bootstrap.sh. This went off alright.
Step (1) created all the .so and .a files in /usr/local/boost_1_49_0/stage/lib
I tested linking against a library, say lboost_regex and #include <boost/regex> in my source code. This also went off alright.

Finally trying out the example on asio, I tried:

g++ -I/usr/local/boost_1_49_0 MAIN.cpp -o MAIN -L/usr/local/boost_1_49_0/stage/lib -lboost_thread -lboost_system -lpthread

(4) compiled alright. But when I run the program with ./MAIN, I get the following error:

./MAIN: error while loading shared libraries: libboost_system.so.1.49.0: cannot open shared object file: No such file or directory

Kevin Grant · Accepted Answer · 2012-07-07 04:59:42Z

The -L option only sets a compile-time library search path; if you want a shared library to be found at runtime then its directory must be known at runtime.

One way to set this with g++ is to pass -rpath to the linker, via the compiler; in your case you could say -Wl,-rpath -Wl,/usr/local/boost_1_49_0/stage/lib. (This embeds the directory in the executable.)

Another way is to install the libraries in a place that the linker searches by default (e.g. /usr/local/lib might be such a place, depending on how the system is configured).

Yet another way is to set an environment variable such as LD_LIBRARY_PATH (Linux or Solaris) or DYLD_LIBRARY_PATH (Mac OS X), to tell the linker where to search when launching executables from the shell where the variable is set.

Just a warning about rpath - don't do it if you plan to ship the binaries to anyone else (or to other machines). It can be tricky and painful to track down rpath errors.
That issue can be avoided however by embedding $ORIGIN in the runtime path of the binary. While a $ORIGIN path is still breakable, it at least makes the search path relative to "wherever the binary is" as opposed to a specific location on the system.
@KevinGrant alright, thanks that sorted the issue out. though nothing like hassle free -static flag

Antimony · Accepted Answer · 2012-07-07 04:59:07Z

Are you sure the shared library is in a place where the loader can find it? Either put it in a system wide directory or the same directory as the executable.

Here's a link with more information about the loader.

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