Merge pull request #437 from ToyotaResearchInstitute/apojomovsky/turn…

…_simulation_runner_into_shared_library

Fix the simulation_runner to enable switch form STATIC to SHARED

src/backend/CMakeLists.txt

@@ -95,22 +95,14 @@ install(TARGETS automotive_simulator
 # ----------------------------------------
 # Simulator-runner library
 #
-# Right now this can't be made shared - segfaults. For more
-# information, refer to:
-#
-#   https://github.com/ToyotaResearchInstitute/delphyne/issues/341
-#
 include(${PROJECT_SOURCE_DIR}/cmake/Python.cmake)
 
 add_library(simulation_runner
-  STATIC
   interactive_simulation_stats.cc
   simulation_run_stats.cc
   simulation_runner.cc
   system.h
 )
-# Position independent code can disappear once we are able to drop STATIC
-set_property(TARGET simulation_runner PROPERTY POSITION_INDEPENDENT_CODE ON)
 set_target_properties(simulation_runner PROPERTIES OUTPUT_NAME ${PROJECT_NAME}-simulation-runner)
 target_include_directories(
   simulation_runner

src/backend/simulation_runner.cc

@@ -81,10 +81,18 @@ SimulatorRunner::SimulatorRunner(
     ignerr << "Error advertising service [" << kSceneRequestServiceName << "]"
            << std::endl;
   }
-  // Initializes the python machinery so we can invoke a python callback
-  // function on each simulation step.
-  Py_Initialize();
-  PyEval_InitThreads();
+
+  // The get_internals() function initializes the `internals.tstate` for
+  // subsequent `gil_scoped_acquire` calls. If the gil_scoped_acquire is
+  // attempted to be called before having initialized the internals.tstate,
+  // it would end up into a segmentation fault. This initialization should
+  // only occur if the SimulatorRunner class is instantiated from within a
+  // python script, which is checked in the if statement.
+  // In comment below, a similar approach to the one used here is suggested:
+  // https://github.com/pybind/pybind11/issues/1360#issuecomment-385988887
+  if (Py_IsInitialized()) {
+    pybind11::detail::get_internals();
+  }
 
   // Tell the simulator to run steps as fast as possible, as are handling the
   // sleep (if required) between steps.