1 files changed, 27 insertions, 0 deletions
diff --git a/internal/sexp/fuzz_test.go b/internal/sexp/fuzz_test.go
new file mode 100644
index 0000000..01d436b
--- /dev/null
+++ b/internal/sexp/fuzz_test.go
@@ -0,0 +1,27 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package sexp
+
+import "testing"
+
+// FuzzParse checks that Parse never panics and that every node it returns
+// spans valid bytes, with lists pointing at their own parentheses.
+func FuzzParse(f *testing.F) {
+	for _, s := range []string{`(a "b" (c))`, `"\"`, `(((`, `)`, "; x\n(y)", `("ł" x)`, "\xff", `"\\"`} {
+		f.Add([]byte(s))
+	}
+	f.Fuzz(func(t *testing.T, src []byte) {
+		nodes, err := Parse("f", src)
+		if err != nil {
+			return
+		}
+		walk(nodes, func(n *Node) {
+			if n.Pos.Offset < 0 || n.End.Offset > len(src) || n.Pos.Offset >= n.End.Offset {
+				t.Fatalf("bad span %d..%d in %q", n.Pos.Offset, n.End.Offset, src)
+			}
+			if n.Kind == List && (src[n.Pos.Offset] != '(' || src[n.End.Offset-1] != ')') {
+				t.Fatalf("list %d..%d does not span its parens in %q", n.Pos.Offset, n.End.Offset, src)
+			}
+		})
+	})
+}