boost::process system leaking file descriptors

Question

It seems like boost::process::system is leaking fds:

Let's say I have this simple code to flush iptables config every 3 seconds (just an example):

#include <boost/process.hpp>
#include <thread>


int main(void)
{
  while(true)
  {
    std::this_thread::sleep_for(std::chrono::seconds(3));
    boost::process::system(boost::process::search_path("iptables"), "-F");
  }
  return 0;
}

If I observe the count of open file descriptors by listing /proc/PID/fd |wc -l, I can see that the count increases by one every 3 seconds. Eventually, when it reaches 1024, the program will abort, because the system call will throw an exception with what() stating that there are too many open files!

How can I avoid this fd leakage? I'm using boost 1.69.

EDIT: Replacing boost::process::system with boost::process::child does not seem to help, the child seems to also leak fds, no matter if it gets detached or not.

EDIT 2: Valgrind log with --track-fds=yes: https://termbin.com/d6ud

Answer 1

The problem seems to be a bug in the specific version (1.69) of boost, and not in the posted code itself. So upgrading boost/patching the bug solves this problem.

The bug report can be found from here: https://github.com/boostorg/process/issues/62