From 992b733e00025defec0fd062820257e068082c51 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Tue, 21 Apr 2026 15:13:08 +0300
Subject: [PATCH] cgen: fix println(struct) unhandled exception 0xc00000fd
 (fixes #19178)

---
 vlib/v/gen/c/auto_str_methods.v               | 17 ++++++++-
 .../string_interpolation_struct_test.v        | 38 +++++++++++++++++++
 2 files changed, 53 insertions(+), 2 deletions(-)

diff --git a/vlib/v/gen/c/auto_str_methods.v b/vlib/v/gen/c/auto_str_methods.v
index 4fce6384e..82dafbe72 100644
--- a/vlib/v/gen/c/auto_str_methods.v
+++ b/vlib/v/gen/c/auto_str_methods.v
@@ -483,8 +483,21 @@ fn (mut g Gen) gen_str_for_interface(info ast.Interface, styp string, typ_str st
 					{_S("${clean_interface_v_type_name}("), ${si_s_code}, {.d_s = ${val}}, 0, 0, 0},
 					{_S(")"), 0, {0}, 0, 0, 0}
 				}))'
-				fn_builder.write_string2('\tif (x._typ == _${styp}_${sub_sym.cname}_index)',
-					' return ${res};\n')
+				if should_use_indent_func(sub_sym.kind) {
+					tmpvar := g.new_tmp_var()
+					fn_builder.writeln('\tif (x._typ == _${styp}_${sub_sym.cname}_index) {')
+					fn_builder.writeln('\t\tif (builtin__isnil(x._object) || builtin__autostr_addr_in_stack(x._object)) {')
+					fn_builder.writeln('\t\t\treturn builtin__isnil(x._object) ? _S("nil") : _S("<circular>");')
+					fn_builder.writeln('\t\t}')
+					fn_builder.writeln('\t\tbuiltin__autostr_addr_push(x._object);')
+					fn_builder.writeln('\t\tstring ${tmpvar} = ${res};')
+					fn_builder.writeln('\t\tbuiltin__autostr_addr_pop();')
+					fn_builder.writeln('\t\treturn ${tmpvar};')
+					fn_builder.writeln('\t}')
+				} else {
+					fn_builder.write_string2('\tif (x._typ == _${styp}_${sub_sym.cname}_index)',
+						' return ${res};\n')
+				}
 			} else {
 				fn_builder.write_string2('\tif (x._typ == _${styp}_${sub_sym.cname}_index)',
 					' return _S("<circular>");\n')
diff --git a/vlib/v/tests/builtin_strings_and_interpolation/string_interpolation_struct_test.v b/vlib/v/tests/builtin_strings_and_interpolation/string_interpolation_struct_test.v
index 2eee2990d..69327d9d1 100644
--- a/vlib/v/tests/builtin_strings_and_interpolation/string_interpolation_struct_test.v
+++ b/vlib/v/tests/builtin_strings_and_interpolation/string_interpolation_struct_test.v
@@ -92,6 +92,44 @@ fn test_cross_reference_field_auto_str() {
 	assert s == '&CrossRefWindow{|    widgets: [CrossRefWidget{|        parent: &CrossRefWindow{|            widgets: [CrossRefWidget{|                parent: &<circular>|            }]|        }|    }]|}'
 }
 
+interface FamilyMember {
+	name string
+	age  u64
+}
+
+struct FamilySelf {
+mut:
+	brothers []&FamilyMember
+	name     string
+	age      u64
+}
+
+struct FamilyBrother {
+mut:
+	brothers []&FamilyMember
+	name     string
+	age      u64
+}
+
+fn test_cross_reference_interface_pointer_array_auto_str() {
+	mut me := &FamilySelf{
+		name: 'Foo'
+		age:  33
+	}
+	mut brother := &FamilyBrother{
+		name: 'Bar'
+		age:  32
+	}
+	me.brothers << brother
+	brother.brothers << me
+	s := '${me}'
+	assert s.contains('&FamilySelf{')
+	assert s.contains('brothers: [&FamilyMember(FamilyBrother{')
+	assert s.contains("name: 'Foo'")
+	assert s.contains("name: 'Bar'")
+	assert s.contains('brothers: [&<circular>]')
+}
+
 struct CircularArray {
 mut:
 	children []CircularArray
-- 
2.39.5