From ac74944d53ae08faa2f35301d5f40fa1f2b4b5a6 Mon Sep 17 00:00:00 2001
From: aarzilli <alessandro.arzilli@gmail.com>
Date: Sat, 18 Aug 2018 12:12:39 +0200
Subject: [PATCH] proc,service,terminal: information about stack trace
 truncation

Add a flag to Stackframe that indicates where the stack frame is the
bottom-most frame of the stack. This allows clients to know whether the
stack trace terminated normally or if it was truncated because the
maximum depth was reached.
Add a truncation message to the 'stack' command.
---
 pkg/proc/stack.go            |  3 +++
 pkg/terminal/command.go      |  6 ++++++
 pkg/terminal/command_test.go | 19 ++++++++++++++++++-
 service/api/types.go         |  2 ++
 service/debugger/debugger.go |  2 ++
 service/rpc2/server.go       |  4 ++--
 6 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/pkg/proc/stack.go b/pkg/proc/stack.go
index 8222aeec..5c7b3f17 100644
--- a/pkg/proc/stack.go
+++ b/pkg/proc/stack.go
@@ -47,6 +47,8 @@ type Stackframe struct {
 	SystemStack bool
 	// Inlined is true if this frame is actually an inlined call.
 	Inlined bool
+	// Bottom is true if this is the bottom of the stack
+	Bottom bool
 
 	// lastpc is a memory address guaranteed to belong to the last instruction
 	// executed in this stack frame.
@@ -339,6 +341,7 @@ func (it *stackIterator) switchStack() bool {
 
 // Frame returns the frame the iterator is pointing at.
 func (it *stackIterator) Frame() Stackframe {
+	it.frame.Bottom = it.atend
 	return it.frame
 }
 
diff --git a/pkg/terminal/command.go b/pkg/terminal/command.go
index 29273654..5350a32a 100644
--- a/pkg/terminal/command.go
+++ b/pkg/terminal/command.go
@@ -1530,6 +1530,8 @@ func digits(n int) int {
 	return int(math.Floor(math.Log10(float64(n)))) + 1
 }
 
+const stacktraceTruncatedMessage = "(truncated)"
+
 func printStack(stack []api.Stackframe, ind string, offsets bool) {
 	if len(stack) == 0 {
 		return
@@ -1582,6 +1584,10 @@ func printStack(stack []api.Stackframe, ind string, offsets bool) {
 			fmt.Println()
 		}
 	}
+
+	if len(stack) > 0 && !stack[len(stack)-1].Bottom {
+		fmt.Printf("%s"+stacktraceTruncatedMessage+"\n", ind)
+	}
 }
 
 func printcontext(t *Term, state *api.DebuggerState) error {
diff --git a/pkg/terminal/command_test.go b/pkg/terminal/command_test.go
index bf8bb8bd..0715e206 100644
--- a/pkg/terminal/command_test.go
+++ b/pkg/terminal/command_test.go
@@ -224,7 +224,7 @@ func TestExecuteFile(t *testing.T) {
 
 func TestIssue354(t *testing.T) {
 	printStack([]api.Stackframe{}, "", false)
-	printStack([]api.Stackframe{{api.Location{PC: 0, File: "irrelevant.go", Line: 10, Function: nil}, nil, nil, 0, 0, nil, ""}}, "", false)
+	printStack([]api.Stackframe{{api.Location{PC: 0, File: "irrelevant.go", Line: 10, Function: nil}, nil, nil, 0, 0, nil, true, ""}}, "", false)
 }
 
 func TestIssue411(t *testing.T) {
@@ -827,3 +827,20 @@ func TestOptimizationCheck(t *testing.T) {
 		})
 	}
 }
+
+func TestTruncateStacktrace(t *testing.T) {
+	withTestTerminal("stacktraceprog", t, func(term *FakeTerminal) {
+		term.MustExec("break main.stacktraceme")
+		term.MustExec("continue")
+		out1 := term.MustExec("stack")
+		t.Logf("untruncated output %q", out1)
+		if strings.Contains(out1, stacktraceTruncatedMessage) {
+			t.Fatalf("stacktrace was truncated")
+		}
+		out2 := term.MustExec("stack 1")
+		t.Logf("truncated output %q", out2)
+		if !strings.Contains(out2, stacktraceTruncatedMessage) {
+			t.Fatalf("stacktrace was not truncated")
+		}
+	})
+}
diff --git a/service/api/types.go b/service/api/types.go
index 61b4c0f3..df047d59 100644
--- a/service/api/types.go
+++ b/service/api/types.go
@@ -131,6 +131,8 @@ type Stackframe struct {
 
 	Defers []Defer
 
+	Bottom bool `json:"Bottom,omitempty"` // Bottom is true if this is the bottom frame of the stack
+
 	Err string
 }
 
diff --git a/service/debugger/debugger.go b/service/debugger/debugger.go
index 2c3a8283..96df5c5b 100644
--- a/service/debugger/debugger.go
+++ b/service/debugger/debugger.go
@@ -932,6 +932,8 @@ func (d *Debugger) convertStacktrace(rawlocs []proc.Stackframe, cfg *proc.LoadCo
 			FramePointerOffset: rawlocs[i].FramePointerOffset(),
 
 			Defers: d.convertDefers(rawlocs[i].Defers),
+
+			Bottom: rawlocs[i].Bottom,
 		}
 		if rawlocs[i].Err != nil {
 			frame.Err = rawlocs[i].Err.Error()
diff --git a/service/rpc2/server.go b/service/rpc2/server.go
index 7822e16c..cde9dbe5 100644
--- a/service/rpc2/server.go
+++ b/service/rpc2/server.go
@@ -172,11 +172,11 @@ func (s *RPCServer) Stacktrace(arg StacktraceIn, out *StacktraceOut) error {
 	if cfg == nil && arg.Full {
 		cfg = &api.LoadConfig{true, 1, 64, 64, -1}
 	}
-	locs, err := s.debugger.Stacktrace(arg.Id, arg.Depth, arg.Defers, api.LoadConfigToProc(cfg))
+	var err error
+	out.Locations, err = s.debugger.Stacktrace(arg.Id, arg.Depth, arg.Defers, api.LoadConfigToProc(cfg))
 	if err != nil {
 		return err
 	}
-	out.Locations = locs
 	return nil
 }