temp - defer mess (holy shit)

_fixtures/rangeoverfunc.go

@@ -146,6 +146,33 @@ func TestPanickyIterator2() {
 	}
 }
 
+func TestPanickyIteratorWithNewDefer() {
+	var result []int
+	defer func() {
+		r := recover()
+		fmt.Println("Recovering ", r)
+	}()
+	for _, x := range OfSliceIndex([]int{100, 200}) {
+		result = append(result, x)
+	Y:
+		// swallows panics and iterates to end BUT `break Y` disables the body, so--> 10, 1, 2
+		for _, y := range VeryBadOfSliceIndex([]int{10, 20}) {
+			defer func() {
+				fmt.Println("y loop defer")
+			}()
+			result = append(result, y)
+
+			// converts early exit into a panic --> 1, 2
+			for k, z := range PanickyOfSliceIndex([]int{1, 2}) { // iterator panics
+				result = append(result, z)
+				if k == 1 {
+					break Y
+				}
+			}
+		}
+	}
+}
+
 func main() {
 	TestTrickyIterAll()
 	TestTrickyIterAll2()
@@ -154,6 +181,7 @@ func main() {
 	TestMultiCont0()
 	TestPanickyIterator1()
 	TestPanickyIterator2()
+	TestPanickyIteratorWithNewDefer()
 }
 
 type Seq[T any] func(yield func(T) bool)

pkg/proc/proc_test.go

@@ -6548,6 +6548,39 @@ func TestRangeOverFuncNext(t *testing.T) {
 				nx(141), // if k == 1
 				nx(142), // break Y
 				nx(128), // defer func()
+				nx(129), // r := recover()
+				nx(130), // fmt.Println
+			})
+		})
+
+		t.Run("TestPanickyIteratorWithNewDefer", func(t *testing.T) {
+			testseq2intl(t, fixture, grp, p, nil, []seqTest{
+				funcBreak(t, "main.TestPanickyIteratorWithNewDefer"),
+				{contContinue, 149},
+				nx(150),
+				nx(151),
+				nx(155), // for _, x := range (x == 100)
+				nx(155),
+				nx(156),
+				nx(157),
+				nx(159), // for _, y := range (y == 10)
+				nx(159),
+				nx(160),
+				nx(163), // result = append(result, y)
+				nx(166), // for k, z := range (k == 0, z == 1)
+				nx(166),
+				nx(167), // result = append(result, z)
+				nx(168), // if k == 1
+				nx(171),
+
+				nx(166), // for k, z := range (k == 0, z == 1)
+				nx(167), // result = append(result, z)
+				nx(168), // if k == 1
+				nx(169), // break Y
+				nx(159),
+				nx(172),
+				nx(160), // defer func()
+				nx(161), // fmt.Println
 			})
 		})
 	})

pkg/proc/stack.go

@@ -631,6 +631,8 @@ type Defer struct {
 	link    *Defer // Next deferred function
 	argSz   int64  // Always 0 in Go >=1.17
 
+	rangefunc []*Defer // See explanation in $GOROOT/src/runtime/panic.go, comment to function runtime.deferrangefunc (this is the equivalent of the rangefunc variable and head fields, combined)
+
 	variable   *Variable
 	Unreadable error
 }
@@ -657,7 +659,7 @@ func (g *G) readDefers(frames []Stackframe) {
 		}
 
 		if frames[i].TopmostDefer == nil {
-			frames[i].TopmostDefer = curdefer
+			frames[i].TopmostDefer = curdefer.topdefer()
 		}
 
 		if frames[i].SystemStack || curdefer.SP >= uint64(frames[i].Regs.CFA) {
@@ -673,13 +675,17 @@ func (g *G) readDefers(frames []Stackframe) {
 			// compared with deferred frames.
 			i++
 		} else {
-			frames[i].Defers = append(frames[i].Defers, curdefer)
+			if len(curdefer.rangefunc) > 0 {
+				frames[i].Defers = append(frames[i].Defers, curdefer.rangefunc...)
+			} else {
+				frames[i].Defers = append(frames[i].Defers, curdefer)
+			}
 			curdefer = curdefer.Next()
 		}
 	}
 }
 
-func (d *Defer) load() {
+func (d *Defer) load(canrecur bool) {
 	v := d.variable // +rtype _defer
 	v.loadValue(LoadConfig{false, 1, 0, 0, -1, 0})
 	if v.Unreadable != nil {
@@ -714,6 +720,33 @@ func (d *Defer) load() {
 	if linkvar.Addr != 0 {
 		d.link = &Defer{variable: linkvar}
 	}
+
+	if canrecur {
+		h := v
+		for _, fieldname := range []string{"head", "u", "value"} {
+			if h == nil {
+				return
+			}
+			h = h.loadFieldNamed(fieldname)
+		}
+		if h != nil {
+			h := h.newVariable("", h.Addr, pointerTo(linkvar.DwarfType, h.bi.Arch), h.mem).maybeDereference()
+			if h.Addr != 0 {
+				hd := &Defer{variable: h}
+				for {
+					hd.load(false)
+					d.rangefunc = append(d.rangefunc, hd)
+					if hd.link == nil {
+						break
+					}
+					if hd.link.SP < hd.SP {
+						hd.link.Unreadable = errSPDecreased
+					}
+					hd = hd.link
+				}
+			}
+		}
+	}
 }
 
 // errSPDecreased is used when (*Defer).Next detects a corrupted linked
@@ -728,13 +761,20 @@ func (d *Defer) Next() *Defer {
 	if d.link == nil {
 		return nil
 	}
-	d.link.load()
+	d.link.load(true)
 	if d.link.SP < d.SP {
 		d.link.Unreadable = errSPDecreased
 	}
 	return d.link
 }
 
+func (d *Defer) topdefer() *Defer {
+	if len(d.rangefunc) > 0 {
+		return d.rangefunc[0]
+	}
+	return d
+}
+
 // EvalScope returns an EvalScope relative to the argument frame of this deferred call.
 // The argument frame of a deferred call is stored in memory immediately
 // after the deferred header.

pkg/proc/target_exec.go

@@ -726,7 +726,7 @@ func next(dbp *Target, stepInto, inlinedStepOut bool) error {
 
 	if !backward && !topframe.Current.Fn.cu.image.Stripped() {
 		fr := topframe
-		if len(rangeFrames) != 0 {
+		if len(rangeFrames) != 0 && !stepInto {
 			fr = rangeFrames[len(rangeFrames)-2]
 		}
 		_, err = setDeferBreakpoint(dbp, text, fr, sameGCond, stepInto)

pkg/proc/variables.go

@@ -494,7 +494,7 @@ func (g *G) Defer() *Defer {
 		return nil
 	}
 	d := &Defer{variable: dvar}
-	d.load()
+	d.load(true)
 	return d
 }