diff --git a/_demo/setjmp/setjmp.go b/_demo/setjmp/setjmp.go
new file mode 100644
index 00000000..b8508de5
--- /dev/null
+++ b/_demo/setjmp/setjmp.go
@@ -0,0 +1,16 @@
+package main
+
+import (
+	"github.com/goplus/llgo/c/setjmp"
+)
+
+func main() {
+	var jb setjmp.SigjmpBuf
+	switch ret := setjmp.Sigsetjmp(&jb, 0); ret {
+	case 0:
+		println("Hello, setjmp!")
+		setjmp.Siglongjmp(&jb, 1)
+	default:
+		println("exception:", ret)
+	}
+}
diff --git a/c/setjmp/setjmp.go b/c/setjmp/setjmp.go
new file mode 100644
index 00000000..89c6745a
--- /dev/null
+++ b/c/setjmp/setjmp.go
@@ -0,0 +1,53 @@
+/*
+ * Copyright (c) 2024 The GoPlus Authors (goplus.org). All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package setjmp
+
+// #include <setjmp.h>
+import "C"
+
+import (
+	_ "unsafe"
+
+	"github.com/goplus/llgo/c"
+)
+
+const (
+	LLGoPackage = "decl"
+)
+
+type (
+	JmpBuf    = C.jmp_buf
+	SigjmpBuf = C.sigjmp_buf
+)
+
+// -----------------------------------------------------------------------------
+
+//go:linkname Setjmp C.setjmp
+func Setjmp(env *JmpBuf) c.Int
+
+//go:linkname Longjmp C.longjmp
+func Longjmp(env *JmpBuf, val c.Int)
+
+// -----------------------------------------------------------------------------
+
+//go:linkname Sigsetjmp C.sigsetjmp
+func Sigsetjmp(env *SigjmpBuf, savemask c.Int) c.Int
+
+//go:linkname Siglongjmp C.siglongjmp
+func Siglongjmp(env *SigjmpBuf, val c.Int)
+
+// -----------------------------------------------------------------------------
diff --git a/cl/blocks/block.go b/cl/blocks/block.go
index 21960751..4f220339 100644
--- a/cl/blocks/block.go
+++ b/cl/blocks/block.go
@@ -74,7 +74,7 @@ func findLoop(states []*blockState, path []int, from, iblk int) []int {
 			}
 			return path
 		}
-		if ret := findLoop(states, path, from, succ); ret != nil {
+		if ret := findLoop(states, path, from, succ); len(ret) > 0 {
 			return ret
 		}
 	}