From 193d6726c68eb41293083a281f73b75a627b78f9 Mon Sep 17 00:00:00 2001
From: Ryan Fleury <ryan.j.fleury@gmail.com>
Date: Fri, 11 Oct 2024 15:09:08 -0700
Subject: [PATCH] adjust control thread single-step path to be a bit more
 robust to malformed requests

---
 src/ctrl/ctrl_core.c             | 18 ++++++++++------
 src/dbg_engine/dbg_engine_core.c | 37 +++++++++++++++++++-------------
 2 files changed, 33 insertions(+), 22 deletions(-)

diff --git a/src/ctrl/ctrl_core.c b/src/ctrl/ctrl_core.c
index 375a4d98..571f35b5 100644
--- a/src/ctrl/ctrl_core.c
+++ b/src/ctrl/ctrl_core.c
@@ -5533,10 +5533,12 @@ ctrl_thread__single_step(DMN_CtrlCtx *ctrl_ctx, CTRL_Msg *msg)
   }
   
   //- rjf: single step
+  DMN_Handle thread = msg->entity.dmn_handle;
+  B32 thread_is_valid = !dmn_handle_match(thread, dmn_handle_zero());
   DMN_Event *stop_event = 0;
   CTRL_EventCause stop_cause = CTRL_EventCause_Null;
+  if(thread_is_valid)
   {
-    DMN_Handle thread = msg->entity.dmn_handle;
     U64 thread_pre_rip = dmn_rip_from_thread(thread);
     U64 thread_post_rip = thread_pre_rip;
     for(B32 done = 0; done == 0;)
@@ -5570,17 +5572,19 @@ ctrl_thread__single_step(DMN_CtrlCtx *ctrl_ctx, CTRL_Msg *msg)
   }
   
   //- rjf: record stop
-  if(stop_event != 0)
   {
     CTRL_EventList evts = {0};
     CTRL_Event *event = ctrl_event_list_push(scratch.arena, &evts);
     event->kind = CTRL_EventKind_Stopped;
     event->cause = stop_cause;
-    event->entity = ctrl_handle_make(CTRL_MachineID_Local, stop_event->thread);
-    event->parent = ctrl_handle_make(CTRL_MachineID_Local, stop_event->process);
-    event->exception_code = stop_event->code;
-    event->vaddr_rng = r1u64(stop_event->address, stop_event->address);
-    event->rip_vaddr = stop_event->instruction_pointer;
+    if(stop_event != 0)
+    {
+      event->entity = ctrl_handle_make(CTRL_MachineID_Local, stop_event->thread);
+      event->parent = ctrl_handle_make(CTRL_MachineID_Local, stop_event->process);
+      event->exception_code = stop_event->code;
+      event->vaddr_rng = r1u64(stop_event->address, stop_event->address);
+      event->rip_vaddr = stop_event->instruction_pointer;
+    }
     ctrl_c2u_push_events(&evts);
   }
   
diff --git a/src/dbg_engine/dbg_engine_core.c b/src/dbg_engine/dbg_engine_core.c
index 725ab11c..dcce7491 100644
--- a/src/dbg_engine/dbg_engine_core.c
+++ b/src/dbg_engine/dbg_engine_core.c
@@ -2148,23 +2148,26 @@ d_tick(Arena *arena, D_TargetArray *targets, D_BreakpointArray *breakpoints, D_P
         {
           B32 good_to_run = 0;
           CTRL_EntityList threads = ctrl_entity_list_from_kind(d_state->ctrl_entity_store, CTRL_EntityKind_Thread);
-          for(CTRL_EntityNode *n = threads.first; n != 0; n = n->next)
+          if(threads.count > 0)
           {
-            if(!n->v->is_frozen)
+            for(CTRL_EntityNode *n = threads.first; n != 0; n = n->next)
             {
-              good_to_run = 1;
-              break;
+              if(!n->v->is_frozen)
+              {
+                good_to_run = 1;
+                break;
+              }
+            }
+            if(good_to_run)
+            {
+              need_run = 1;
+              run_kind = D_RunKind_Run;
+              run_thread = &ctrl_entity_nil;
+            }
+            else
+            {
+              log_user_error(str8_lit("Cannot run with all threads frozen."));
             }
-          }
-          if(good_to_run)
-          {
-            need_run = 1;
-            run_kind = D_RunKind_Run;
-            run_thread = &ctrl_entity_nil;
-          }
-          else
-          {
-            log_user_error(str8_lit("Cannot run with all threads frozen."));
           }
         }break;
         case D_CmdKind_StepIntoInst:
@@ -2174,7 +2177,11 @@ d_tick(Arena *arena, D_TargetArray *targets, D_BreakpointArray *breakpoints, D_P
         case D_CmdKind_StepOut:
         {
           CTRL_Entity *thread = ctrl_entity_from_handle(d_state->ctrl_entity_store, params->thread);
-          if(d_ctrl_targets_running())
+          if(thread == &ctrl_entity_nil)
+          {
+            log_user_error(str8_lit("Must have a selected thread to step."));
+          }
+          else if(d_ctrl_targets_running())
           {
             if(d_ctrl_last_run_kind() == D_RunKind_Run)
             {