show function return value after stepping out

fixes #1027 and microsoft/vscode-cpptools#3214
microsoft · Sep 17, 2020 · cd08c1a · cd08c1a
1 parent ec52d60
commit cd08c1a
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Showing 3 changed files with 23 additions and 8 deletions.
diff --git a/src/MIDebugEngine/Engine.Impl/DebuggedProcess.cs b/src/MIDebugEngine/Engine.Impl/DebuggedProcess.cs
@@ -25,7 +25,7 @@ internal class DebuggedProcess : MICore.Debugger
         public AD7Engine Engine { get; private set; }
         public List<string> VariablesToDelete { get; private set; }
         public List<IVariableInformation> ActiveVariables { get; private set; }
-
+        public VariableInformation ReturnValue { get; private set; }
         public SourceLineCache SourceLineCache { get; private set; }
         public ThreadCache ThreadCache { get; private set; }
         public Disassembly Disassembly { get; private set; }
@@ -1053,6 +1053,7 @@ private async Task HandleBreakModeEvent(ResultEventArgs results, BreakRequest br
                     varInfo.Dispose();
                 }
                 this.ActiveVariables.Clear();
+                ReturnValue = null; // already disposed above
             }
 
             ThreadCache.MarkDirty();
@@ -1235,8 +1236,19 @@ private async Task HandleBreakModeEvent(ResultEventArgs results, BreakRequest br
                     }
                 }
             }
-            else if (reason == "end-stepping-range" || reason == "function-finished")
+            // step over/into
+            // NB: unfortunately this event does not provide a return value: https://sourceware.org/bugzilla/show_bug.cgi?id=26354
+            else if (reason == "end-stepping-range")
+                _callback.OnStepComplete(thread);
+            // step out
+            else if (reason == "function-finished")
             {
+                string resultVar = results.Results.TryFindString("gdb-result-var"); // a gdb value history var like "$1"
+                if (!string.IsNullOrEmpty(resultVar))
+                {
+                    ReturnValue = new VariableInformation("$ReturnValue", resultVar, cxt, Engine, (AD7Thread)thread.Client, isParameter: false);
+                    await ReturnValue.Eval();
+                }
                 _callback.OnStepComplete(thread);
             }
             else if (reason == "signal-received")
@@ -1874,6 +1886,9 @@ internal async Task<List<VariableInformation>> GetLocalsAndParameters(AD7Thread
                 variables.Add(vi);
             }
 
+            if (ReturnValue != null && ctx.Level == 0)
+                variables.Add(ReturnValue);
+
             return variables;
         }
 

diff --git a/src/MIDebugEngine/Engine.Impl/Variables.cs b/src/MIDebugEngine/Engine.Impl/Variables.cs
@@ -60,7 +60,7 @@ internal SimpleVariableInformation(string name, bool isParam = false, string val
 
         internal async Task<VariableInformation> CreateMIDebuggerVariable(ThreadContext ctx, AD7Engine engine, AD7Thread thread)
         {
-            VariableInformation vi = new VariableInformation(Name, ctx, engine, thread, IsParameter);
+            VariableInformation vi = new VariableInformation(Name, Name, ctx, engine, thread, IsParameter);
             await vi.Eval();
             return vi;
         }
@@ -73,7 +73,7 @@ public ArgumentList(int level, List<SimpleVariableInformation> args)
         { }
     }
 
-    internal class VariableInformation : IVariableInformation
+    internal sealed class VariableInformation : IVariableInformation
     {
         public string Name { get; private set; }
         public string Value { get; private set; }
@@ -190,12 +190,12 @@ private VariableInformation(ThreadContext ctx, AD7Engine engine, AD7Thread threa
         }
 
         //this constructor is used to create root nodes (local/params)
-        internal VariableInformation(string expr, ThreadContext ctx, AD7Engine engine, AD7Thread thread, bool isParameter = false)
+        internal VariableInformation(string displayName, string expr, ThreadContext ctx, AD7Engine engine, AD7Thread thread, bool isParameter = false)
             : this(ctx, engine, thread)
         {
             // strip off formatting string
             _strippedName = StripFormatSpecifier(expr, out _format);
-            Name = expr;
+            Name = displayName;
             IsParameter = isParameter;
             _parent = null;
             VariableNodeType = NodeType.Root;

diff --git a/src/MIDebugEngine/Natvis.Impl/Natvis.cs b/src/MIDebugEngine/Natvis.Impl/Natvis.cs
@@ -433,7 +433,7 @@ internal IVariableInformation GetVariable(string expr, AD7StackFrame frame)
             if (expr.EndsWith(",viz", StringComparison.Ordinal))
             {
                 expr = expr.Substring(0, expr.Length - 4);
-                variable = new VariableInformation(expr, frame.ThreadContext, frame.Engine, frame.Thread);
+                variable = new VariableInformation(expr, expr, frame.ThreadContext, frame.Engine, frame.Thread);
                 variable.SyncEval();
                 if (!variable.Error)
                 {
@@ -442,7 +442,7 @@ internal IVariableInformation GetVariable(string expr, AD7StackFrame frame)
             }
             else
             {
-                variable = new VariableInformation(expr, frame.ThreadContext, frame.Engine, frame.Thread);
+                variable = new VariableInformation(expr, expr, frame.ThreadContext, frame.Engine, frame.Thread);
             }
             return variable;
         }