pkg/proc: defend better against missing DWARF

pkg/dwarf/godwarf/tree.go

@@ -2,6 +2,7 @@ package godwarf
 
 import (
 	"debug/dwarf"
+	"errors"
 	"fmt"
 	"sort"
 )
@@ -90,6 +91,9 @@ type Tree struct {
 // range of addresses that is not covered by its parent LoadTree will fix
 // the parent entry.
 func LoadTree(off dwarf.Offset, dw *dwarf.Data, staticBase uint64) (*Tree, error) {
+	if dw == nil {
+		return nil, errors.New("unable to load DWARF tree: no DWARF information present")
+	}
 	rdr := dw.Reader()
 	rdr.Seek(off)
 

pkg/proc/eval.go

@@ -371,6 +371,10 @@ func (scope *EvalScope) Locals(flags localsFlags) ([]*Variable, error) {
 		return nil, errors.New("unable to find function context")
 	}
 
+	if scope.image().Stripped() {
+		return nil, errors.New("unable to find locals: no debug information present in binary")
+	}
+
 	trustArgOrder := (flags&localsTrustArgOrder != 0) && scope.BinInfo.Producer() != "" && goversion.ProducerAfterOrEqual(scope.BinInfo.Producer(), 1, 12) && scope.Fn != nil && (scope.PC == scope.Fn.Entry)
 
 	dwarfTree, err := scope.image().getDwarfTree(scope.Fn.offset)

pkg/proc/proc_test.go

@@ -3216,11 +3216,19 @@ func TestDebugStripped(t *testing.T) {
 		assertLineNumber(p, t, 37, "first continue")
 		assertNoError(grp.Next(), t, "Next")
 		assertLineNumber(p, t, 38, "after next")
+
+		// Assert that commands like "args", "locals", etc... will
+		// return an error instead of panic.
+		s, err := proc.ThreadScope(p, p.CurrentThread())
+		assertNoError(err, t, "ThreadScope")
+		_, err = s.Locals(0)
+		if err == nil {
+			t.Error("expected an error to be returned from scope.Locals in stripped binary")
+		}
 	})
 }
 
 func TestDebugStripped2(t *testing.T) {
-	// Currently only implemented for Linux ELF executables.
 	// TODO(derekparker): Add support for PE.
 	skipOn(t, "not working on windows", "windows")
 	skipOn(t, "not working on freebsd", "freebsd")