cmd/cgo: avoid endless recursion on recursive type

Fixes #69176

Change-Id: I2e3b2a7cf7699697b957fc69ecf5200ebb137bc3
Reviewed-on: https://go-review.googlesource.com/c/go/+/609975
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Commit-Queue: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

3 files changed, 29 insertions, 2 deletions

diff --git a/src/cmd/cgo/internal/testerrors/errors_test.go b/src/cmd/cgo/internal/testerrors/errors_test.go
index 0780870fe0..941c7eff20 100644
--- a/src/cmd/cgo/internal/testerrors/errors_test.go
+++ b/src/cmd/cgo/internal/testerrors/errors_test.go
@@ -132,6 +132,7 @@ func TestReportsTypeErrors(t *testing.T) {
 		"issue50710.go",
 		"issue67517.go",
 		"issue67707.go",
+		"issue69176.go",
 	} {
 		check(t, file)
 	}
diff --git a/src/cmd/cgo/internal/testerrors/testdata/issue69176.go b/src/cmd/cgo/internal/testerrors/testdata/issue69176.go
new file mode 100644
index 0000000000..e52b1f84c6
--- /dev/null
+++ b/src/cmd/cgo/internal/testerrors/testdata/issue69176.go
@@ -0,0 +1,12 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+import "C"
+
+type T = T // ERROR HERE
+
+//export F
+func F(p *T) {}
diff --git a/src/cmd/cgo/out.go b/src/cmd/cgo/out.go
index 0f58528c59..954c4b70c9 100644
--- a/src/cmd/cgo/out.go
+++ b/src/cmd/cgo/out.go
@@ -1418,9 +1418,18 @@ var goTypes = map[string]*Type{
 
 // Map an ast type to a Type.
 func (p *Package) cgoType(e ast.Expr) *Type {
+	return p.doCgoType(e, make(map[ast.Expr]bool))
+}
+
+// Map an ast type to a Type, avoiding cycles.
+func (p *Package) doCgoType(e ast.Expr, m map[ast.Expr]bool) *Type {
+	if m[e] {
+		fatalf("%s: invalid recursive type", fset.Position(e.Pos()))
+	}
+	m[e] = true
 	switch t := e.(type) {
 	case *ast.StarExpr:
-		x := p.cgoType(t.X)
+		x := p.doCgoType(t.X, m)
 		return &Type{Size: p.PtrSize, Align: p.PtrSize, C: c("%s*", x.C)}
 	case *ast.ArrayType:
 		if t.Len == nil {
@@ -1465,7 +1474,12 @@ func (p *Package) cgoType(e ast.Expr) *Type {
 					continue
 				}
 				if ts.Name.Name == t.Name {
-					return p.cgoType(ts.Type)
+					// Give a better error than the one
+					// above if we detect a recursive type.
+					if m[ts.Type] {
+						fatalf("%s: invalid recursive type: %s refers to itself", fset.Position(e.Pos()), t.Name)
+					}
+					return p.doCgoType(ts.Type, m)
 				}
 			}
 		}