From caea2daece4cb5f435a61f77ce771496fc8c635a Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Sun, 24 May 2026 15:57:28 +0300
Subject: [PATCH] checker: allow `C.S{}` zero-init for C structs with reference
 fields (fix #27170) (#27228)

---
 vlib/v/checker/struct.v                        |  3 ++-
 vlib/v/tests/c_structs/cstruct.h               | 11 +++++++++++
 .../c_structs/cstruct_ref_zero_init_test.c.v   | 18 ++++++++++++++++++
 3 files changed, 31 insertions(+), 1 deletion(-)
 create mode 100644 vlib/v/tests/c_structs/cstruct_ref_zero_init_test.c.v

diff --git a/vlib/v/checker/struct.v b/vlib/v/checker/struct.v
index aaee12d23..6beb05e83 100644
--- a/vlib/v/checker/struct.v
+++ b/vlib/v/checker/struct.v
@@ -1495,7 +1495,8 @@ fn (mut c Checker) check_uninitialized_struct_fields_and_embeds(node ast.StructI
 		}
 		field_is_option := field.typ.has_flag(.option)
 		if field.typ.is_ptr() && !field.typ.has_flag(.shared_f) && !field_is_option
-			&& !node.has_update_expr && !c.pref.translated && !c.file.is_translated {
+			&& !node.has_update_expr && !c.pref.translated && !c.file.is_translated
+			&& type_sym.language != .c {
 			// Skip this check during generic recheck (concrete instantiation),
 			// because generic code like `T{}` or `Struct[V]{}` cannot provide
 			// initializers for reference fields that only appear after type substitution.
diff --git a/vlib/v/tests/c_structs/cstruct.h b/vlib/v/tests/c_structs/cstruct.h
index 94156494f..6b7ba3532 100644
--- a/vlib/v/tests/c_structs/cstruct.h
+++ b/vlib/v/tests/c_structs/cstruct.h
@@ -33,3 +33,14 @@ typedef struct Bar {
 typedef struct TestAlias {
     int a;
 };
+
+///
+
+typedef struct MyRefStruct MyRefStruct;
+struct MyRefStruct {
+    char* format;
+    char* name;
+    void** children;
+    void (*release)(struct MyRefStruct*);
+    void* private_data;
+};
diff --git a/vlib/v/tests/c_structs/cstruct_ref_zero_init_test.c.v b/vlib/v/tests/c_structs/cstruct_ref_zero_init_test.c.v
new file mode 100644
index 000000000..db04d7ebb
--- /dev/null
+++ b/vlib/v/tests/c_structs/cstruct_ref_zero_init_test.c.v
@@ -0,0 +1,18 @@
+#include "@VMODROOT/cstruct.h"
+
+struct C.MyRefStruct {
+mut:
+	format       &char
+	name         &char
+	children     &voidptr
+	release      fn (&C.MyRefStruct)
+	private_data voidptr
+}
+
+fn test_c_struct_zero_init_with_ref_fields() {
+	s := C.MyRefStruct{}
+	assert s.format == unsafe { nil }
+	assert s.name == unsafe { nil }
+	assert s.children == unsafe { nil }
+	assert s.private_data == unsafe { nil }
+}
-- 
2.39.5