proc: allow evaluator to reference previous frames (#3534)

Fixes #3515

_fixtures/condframe.go

@@ -0,0 +1,17 @@
+package main
+
+import "fmt"
+
+func callme() {
+	for i := 0; i < 10; i++ {
+		callme2()
+	}
+}
+
+func callme2() {
+	fmt.Println("called again!!")
+}
+
+func main() {
+	callme()
+}

pkg/proc/eval.go

@@ -963,7 +963,19 @@ func (stack *evalStack) executeOp() {
 		stack.push(newConstant(op.Value, scope.Mem))
 
 	case *evalop.PushLocal:
-		vars, err := scope.Locals(0)
+		var vars []*Variable
+		var err error
+		if op.Frame != 0 {
+			var frameScope *EvalScope
+			frameScope, err = ConvertEvalScope(scope.target, scope.g.ID, int(op.Frame), 0)
+			if err != nil {
+				stack.err = err
+				return
+			}
+			vars, err = frameScope.Locals(0)
+		} else {
+			vars, err = scope.Locals(0)
+		}
 		if err != nil {
 			stack.err = err
 			return

pkg/proc/evalop/evalcompile.go

@@ -193,7 +193,7 @@ func (ctx *compileCtx) compileAST(t ast.Expr) error {
 				ctx.pushOp(&PushThreadID{})
 
 			case ctx.HasLocal(x.Name):
-				ctx.pushOp(&PushLocal{x.Name})
+				ctx.pushOp(&PushLocal{Name: x.Name})
 				ctx.pushOp(&Select{node.Sel.Name})
 
 			case ctx.HasGlobal(x.Name, node.Sel.Name):
@@ -203,6 +203,27 @@ func (ctx *compileCtx) compileAST(t ast.Expr) error {
 				return ctx.compileUnary(node.X, &Select{node.Sel.Name})
 			}
 
+		case *ast.CallExpr:
+			ident, ok := x.Fun.(*ast.SelectorExpr)
+			if ok {
+				f, ok := ident.X.(*ast.Ident)
+				if ok && f.Name == "runtime" && ident.Sel.Name == "frame" {
+					switch arg := x.Args[0].(type) {
+					case *ast.BasicLit:
+						fr, err := strconv.ParseInt(arg.Value, 10, 8)
+						if err != nil {
+							return err
+						}
+						// Push local onto the stack to be evaluated in the new frame context.
+						ctx.pushOp(&PushLocal{Name: node.Sel.Name, Frame: fr})
+						return nil
+					default:
+						return fmt.Errorf("expected integer value for frame, got %v", arg)
+					}
+				}
+			}
+			return ctx.compileUnary(node.X, &Select{node.Sel.Name})
+
 		case *ast.BasicLit: // try to accept "package/path".varname syntax for package variables
 			s, err := strconv.Unquote(x.Value)
 			if err != nil {
@@ -271,7 +292,6 @@ func (ctx *compileCtx) compileAST(t ast.Expr) error {
 
 	default:
 		return fmt.Errorf("expression %T not implemented", t)
-
 	}
 	return nil
 }
@@ -392,7 +412,7 @@ func (ctx *compileCtx) compileBuiltinCall(builtin string, args []ast.Expr) error
 func (ctx *compileCtx) compileIdent(node *ast.Ident) error {
 	switch {
 	case ctx.HasLocal(node.Name):
-		ctx.pushOp(&PushLocal{node.Name})
+		ctx.pushOp(&PushLocal{Name: node.Name})
 	case ctx.HasGlobal("", node.Name):
 		ctx.pushOp(&PushPackageVar{"", node.Name})
 	case node.Name == "true" || node.Name == "false":

pkg/proc/evalop/ops.go

@@ -40,6 +40,7 @@ func (*PushConst) depthCheck() (npop, npush int) { return 0, 1 }
 // PushLocal pushes the local variable with the given name on the stack.
 type PushLocal struct {
 	Name  string
+	Frame int64
 }
 
 func (*PushLocal) depthCheck() (npop, npush int) { return 0, 1 }

pkg/proc/native/threads_linux_ppc64le.go

@@ -1,14 +1,13 @@
 package native
 
 import (
-	"fmt"
 	"debug/elf"
+	"fmt"
 	"syscall"
 	"unsafe"
 
 	sys "golang.org/x/sys/unix"
 
-
 	"github.com/go-delve/delve/pkg/proc"
 	"github.com/go-delve/delve/pkg/proc/linutil"
 )
@@ -45,4 +44,3 @@ func (t *nativeThread) restoreRegisters(savedRegs proc.Registers) error {
 	}
 	return restoreRegistersErr
 }
-

pkg/proc/proc_test.go

@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"go/ast"
 	"go/constant"
+	"go/parser"
 	"go/token"
 	"io"
 	"math/rand"
@@ -1770,6 +1771,36 @@ func TestCondBreakpoint(t *testing.T) {
 	})
 }
 
+func TestCondBreakpointWithFrame(t *testing.T) {
+	protest.AllowRecording(t)
+	withTestProcess("condframe", t, func(p *proc.Target, grp *proc.TargetGroup, fixture protest.Fixture) {
+		bp := setFileBreakpoint(p, t, fixture.Source, 12)
+		parsed, err := parser.ParseExpr("runtime.frame(1).i == 3")
+		if err != nil {
+			t.Fatalf("failed to parse expression: %v", err)
+		}
+		bp.UserBreaklet().Cond = parsed
+
+		assertNoError(grp.Continue(), t, "Continue()")
+
+		g := p.SelectedGoroutine()
+		scope, err := proc.ConvertEvalScope(p, g.ID, 1, 0)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		v, err := scope.EvalExpression("i", normalLoadConfig)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		vval, _ := constant.Int64Val(v.Value)
+		if vval != 3 {
+			t.Fatalf("Incorrect value for frame variable: %v", vval)
+		}
+	})
+}
+
 func TestCondBreakpointError(t *testing.T) {
 	protest.AllowRecording(t)
 	withTestProcess("parallel_next", t, func(p *proc.Target, grp *proc.TargetGroup, fixture protest.Fixture) {
@@ -3381,7 +3412,7 @@ func TestCgoStacktrace(t *testing.T) {
 			logStacktrace(t, p, frames)
 
 			m := stacktraceCheck(t, tc, frames)
-			mismatch := (m == nil)
+			mismatch := m == nil
 
 			for i, j := range m {
 				if strings.HasPrefix(tc[i], "C.hellow") {
@@ -5085,7 +5116,7 @@ func TestStepOutPreservesGoroutine(t *testing.T) {
 			}
 			pc := currentPC(p, t)
 			f, l, fn := p.BinInfo().PCToLine(pc)
-			var fnname string = "???"
+			var fnname = "???"
 			if fn != nil {
 				fnname = fn.Name
 			}

pkg/terminal/command_test.go

@@ -1242,6 +1242,19 @@ func TestHitCondBreakpoint(t *testing.T) {
 	})
 }
 
+func TestCondBreakpointWithFrame(t *testing.T) {
+	withTestTerminal("condframe", t, func(term *FakeTerminal) {
+		term.MustExec("break bp1 callme2")
+		term.MustExec("condition bp1 runtime.frame(1).i == 3")
+		term.MustExec("continue")
+		out := term.MustExec("frame 1 print i")
+		t.Logf("%q", out)
+		if !strings.Contains(out, "3\n") {
+			t.Fatalf("wrong value of i")
+		}
+	})
+}
+
 func TestClearCondBreakpoint(t *testing.T) {
 	withTestTerminal("break", t, func(term *FakeTerminal) {
 		term.MustExec("break main.main:4")