planning: add default_front_clear_distance gflag to avoid debug confusion.

modules/planning/common/ego_info.cc

@@ -46,7 +46,7 @@ bool EgoInfo::Update(const common::TrajectoryPoint& start_point,
 void EgoInfo::Clear() {
   start_point_.Clear();
   vehicle_state_.Clear();
-  front_clear_distance_ = std::numeric_limits<double>::max();
+  front_clear_distance_ = FLAGS_default_front_clear_distance;
 }
 
 void EgoInfo::CalculateFrontObstacleClearDistance(

modules/planning/common/ego_info.h

@@ -33,6 +33,7 @@
 #include "modules/common/vehicle_state/proto/vehicle_state.pb.h"
 
 #include "modules/planning/common/obstacle.h"
+#include "modules/planning/common/planning_gflags.h"
 #include "modules/planning/reference_line/reference_line.h"
 
 namespace apollo {
@@ -74,7 +75,7 @@ class EgoInfo {
   // ego vehicle state
   common::VehicleState vehicle_state_;
 
-  double front_clear_distance_ = std::numeric_limits<double>::max();
+  double front_clear_distance_ = FLAGS_default_front_clear_distance;
 
   common::VehicleConfig ego_vehicle_config_;
 

modules/planning/common/planning_gflags.cc

@@ -409,3 +409,7 @@ DEFINE_bool(enable_osqp_debug, false,
 DEFINE_bool(export_chart, false, "export chart in planning");
 DEFINE_bool(enable_record_debug, true,
             "True to enable record debug info in chart format");
+
+DEFINE_double(
+    default_front_clear_distance, 300.0,
+    "default front clear distance value in case there is no obstacle around.");

modules/planning/common/planning_gflags.h

@@ -219,3 +219,5 @@ DECLARE_bool(use_osqp_optimizer_for_reference_line);
 DECLARE_bool(enable_osqp_debug);
 DECLARE_bool(export_chart);
 DECLARE_bool(enable_record_debug);
+
+DECLARE_double(default_front_clear_distance);