Fix build on go1.21

common/buf/ptr.go

@@ -1,4 +1,4 @@
-//go:build !disable_unsafe
+//go:build !disable_unsafe && go1.21
 
 package buf
 
@@ -23,7 +23,7 @@ func init() {
 	if !common.UnsafeBuffer {
 		return
 	}
-	debugVars := *(*[]dbgVar)(unsafe.Pointer(&dbgvars))
+	debugVars := *(*[]*dbgVar)(unsafe.Pointer(&dbgvars))
 	for _, v := range debugVars {
 		if v.name == "invalidptr" {
 			*v.value = 0

common/buf/ptr_go120.go

@@ -0,0 +1,34 @@
+//go:build !disable_unsafe && !go1.21
+
+package buf
+
+import (
+	"unsafe"
+
+	"github.com/sagernet/sing/common"
+)
+
+type dbgVar struct {
+	name  string
+	value *int32
+}
+
+//go:linkname dbgvars runtime.dbgvars
+var dbgvars any
+
+// go.info.runtime.dbgvars: relocation target go.info.[]github.com/sagernet/sing/common/buf.dbgVar not defined
+// var dbgvars []dbgVar
+
+func init() {
+	if !common.UnsafeBuffer {
+		return
+	}
+	debugVars := *(*[]dbgVar)(unsafe.Pointer(&dbgvars))
+	for _, v := range debugVars {
+		if v.name == "invalidptr" {
+			*v.value = 0
+			return
+		}
+	}
+	panic("can't disable invalidptr")
+}