Dear Sir or Madam, In Boost 1.64.0, include/boost/process/detail/posix/wait_group.hpp:131:10: warning: unused variable 'start' [-Wunused-variable] auto start = std::chrono::system_clock::now(); ^ /usr/local/include/boost/process/detail/posix/wait_group.hpp:165:10: warning: unused variable 'start' [-Wunused-variable] auto start = std::chrono::system_clock::now(); ^ I believe these two lines should be removed. This appears to be a “copy and paste” issue. The two routines above these lines use the “start” variable to calculate a relative time. However, the later two routines use an absolute time, and the compiler complains as shown above. Removing these two lines should fix the compiler warning and have no adverse effect. Please let me know if this is the wrong place to complain about issues. \W/