Programatically determine shared libraries in use by running application

Question

Is it possible to (and, if so, how does one) determine the shared libraries of an application that are used by an application at runtime? Basically, can I programmatically obtain the the output of ldd? Preferred C/C++ solution does not just jump to execute ldd on the command-line.

Consider the following: I have a driver application that calls doAction() from a shared library libfoo. I compile the application once and then set LD_LIBRARY_PATH to an appropriate directory containing a libfoo with the doAction() symbol defined. This way, I can have multiple implementations of doAction() in different libfoos but only ever compile an application once.

A real world example would be a professor having a class of students implement doAction(). Instead of compiling a test harness against each student's implementation of doAction(), the students submit a shared library and the professor can simply change LD_LIBRARY_PATH to evaluate each student.

My goal in obtaining the library currently being used is to perform an md5sum on the library at runtime to ensure I'm calling the correct library. In the contrived example, all students would submit the md5sum of their library and the professor could match the running executable + shared library (database lookup, log to file, ...) to the student, to prevent an accident in setting LD_LIBRARY_PATH effecting another student's grade (forgot to change LD_LIBRARY_PATH to David's directory and ran again with Bill's libfoo).

Answer 1

If you're using Linux, you can use the dl_iterate_phdr function:

The dl_iterate_phdr() function allows an application to inquire at run time to find out which shared objects it has loaded.

http://linux.die.net/man/3/dl_iterate_phdr