From c560d58f1e6c575be577ecd0c6f9ad61e2575e8f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Uwe=20Kr=C3=BCger?=
 <45282134+UweKrueger@users.noreply.github.com>
Date: Sat, 7 Aug 2021 13:56:09 +0200
Subject: [PATCH] cgen: use heuristic to detect circular reference  in auto str
 (#11090)

---
 vlib/v/gen/c/auto_str_methods.v  |  3 +++
 vlib/v/tests/str_circular_test.v | 21 +++++++++++++++++++++
 2 files changed, 24 insertions(+)
 create mode 100644 vlib/v/tests/str_circular_test.v

diff --git a/vlib/v/gen/c/auto_str_methods.v b/vlib/v/gen/c/auto_str_methods.v
index fe5f6d1b64..ffec50cf68 100644
--- a/vlib/v/gen/c/auto_str_methods.v
+++ b/vlib/v/gen/c/auto_str_methods.v
@@ -834,6 +834,9 @@ fn (mut g Gen) gen_str_for_struct(info ast.Struct, styp string, str_fn_name stri
 			if field.typ in ast.charptr_types {
 				fn_builder.write_string('tos2((byteptr)$func)')
 			} else {
+				if field.typ.is_ptr() && sym.kind == .struct_ {
+					fn_builder.write_string('(indent_count > 25) ? _SLIT("<probably circular>") : ')
+				}
 				fn_builder.write_string(func)
 			}
 		}
diff --git a/vlib/v/tests/str_circular_test.v b/vlib/v/tests/str_circular_test.v
new file mode 100644
index 0000000000..7479937b2b
--- /dev/null
+++ b/vlib/v/tests/str_circular_test.v
@@ -0,0 +1,21 @@
+[heap]
+struct Aa {
+mut:
+	bs []Bb
+}
+
+struct Bb {
+mut:
+	a &Aa
+}
+
+fn test_circular() {
+	mut b := Bb{
+		a: &Aa{
+			bs: []Bb{cap: 1}
+		}
+	}
+	b.a.bs << b
+	s := b.str()
+	assert s.len < 3500
+}