proc: use DW_AT_trampoline to detect auto-generated code (#3528)

Use the trampoline attribute to detect auto-generated code. This fixes
a bug where stepping into a method of a generic type called through an
interface will take the debugger into an auto-generated wrapper that
does not have a dictionary and using next will step out of the wrapper.

Fixes a bug reported on the #delve channel of the gophers slack server.

_fixtures/genericintoiface.go

@@ -0,0 +1,25 @@
+package main
+
+import "fmt"
+
+type Blah[T any] struct {
+	x T
+}
+
+func (b *Blah[T]) F(y T) {
+	b.x = y
+}
+
+type BlahInt interface {
+	F(int)
+}
+
+func callf(b BlahInt) {
+	b.F(2)
+	fmt.Println(b)
+}
+
+func main() {
+	b := &Blah[int]{10}
+	callf(b)
+}

pkg/proc/proc_test.go

@@ -428,6 +428,7 @@ const (
 	contReverseStep
 	contReverseStepout
 	contContinueToBreakpoint
+	contNothing
 )
 
 type seqTest struct {
@@ -531,6 +532,8 @@ func testseq2Args(wd string, args []string, buildFlags protest.BuildFlags, t *te
 				assertNoError(grp.Continue(), t, "Continue() returned an error")
 				err := p.ClearBreakpoint(bp.Addr)
 				assertNoError(err, t, "ClearBreakpoint() returned an error")
+			case contNothing:
+				// do nothing
 			}
 
 			f, ln = currentLineNumber(p, t)
@@ -552,6 +555,10 @@ func testseq2Args(wd string, args []string, buildFlags protest.BuildFlags, t *te
 				if !strings.HasSuffix(f, v[0]) || (ln != tgtln) {
 					t.Fatalf("Program did not continue to correct next location, expected %s was %s:%d (%#x) (testcase %d)", pos, filepath.Base(f), ln, pc, i)
 				}
+			case func(*proc.Target):
+				pos(p)
+			default:
+				panic(fmt.Errorf("unexpected type %T", pos))
 			}
 		}
 
@@ -6262,3 +6269,37 @@ func TestWaitForAttach(t *testing.T) {
 
 	cmd.Wait()
 }
+
+func TestNextGenericMethodThroughInterface(t *testing.T) {
+	// Tests that autogenerated wrappers for generic methods called through an
+	// interface are skipped.
+
+	varcheck := func(p *proc.Target) {
+		yvar := evalVariable(p, t, "y")
+		yval, _ := constant.Int64Val(yvar.Value)
+		if yval != 2 {
+			t.Errorf("expected 2 got %#v", yvar.Value)
+		}
+	}
+
+	if runtime.GOOS == "linux" && runtime.GOARCH == "386" {
+		testseq2(t, "genericintoiface", "main.callf", []seqTest{
+			{contContinue, 17},
+			{contStep, 18},
+			{contStep, 10},
+			{contNothing, varcheck},
+			{contNext, 11},
+			{contNext, 19},
+		})
+	} else {
+		testseq2(t, "genericintoiface", "main.callf", []seqTest{
+			{contContinue, 17},
+			{contStep, 18},
+			{contStep, 9},
+			{contNext, 10},
+			{contNothing, varcheck},
+			{contNext, 11},
+			{contNext, 19},
+		})
+	}
+}

pkg/proc/target_exec.go

@@ -990,7 +990,7 @@ func allowDuplicateBreakpoint(bp *Breakpoint, err error) (*Breakpoint, error) {
 }
 
 func isAutogenerated(loc Location) bool {
-	return loc.File == "<autogenerated>" && loc.Line == 1
+	return (loc.File == "<autogenerated>" && loc.Line == 1) || (loc.Fn != nil && loc.Fn.trampoline)
 }
 
 func isAutogeneratedOrDeferReturn(loc Location) bool {

pkg/proc/variables.go

@@ -1191,7 +1191,7 @@ func extractVarInfoFromEntry(tgt *Target, bi *BinaryInfo, image *Image, regs op.
 	t, err = resolveParametricType(bi, mem, t, dictAddr)
 	if err != nil {
 		// Log the error, keep going with t, which will be the shape type
-		logflags.DebuggerLogger().Errorf("could not resolve parametric type of %s", n)
+		logflags.DebuggerLogger().Errorf("could not resolve parametric type of %s: %v", n, err)
 	}
 
 	addr, pieces, descr, err := bi.Location(entry, dwarf.AttrLocation, regs.PC(), regs, mem)