From 839a409dd0e4e9481ad286689437467c954f5838 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Fri, 5 Jun 2026 04:02:32 +0300
Subject: [PATCH] cgen: fix heap struct init hoist positions (#27349)

---
 vlib/v/gen/c/struct.v                         | 13 ++--
 .../heap_struct_init_order.c.must_have        |  8 +++
 .../gen/c/testdata/heap_struct_init_order.out |  1 +
 .../gen/c/testdata/heap_struct_init_order.vv  | 68 +++++++++++++++++++
 4 files changed, 83 insertions(+), 7 deletions(-)
 create mode 100644 vlib/v/gen/c/testdata/heap_struct_init_order.c.must_have
 create mode 100644 vlib/v/gen/c/testdata/heap_struct_init_order.out
 create mode 100644 vlib/v/gen/c/testdata/heap_struct_init_order.vv

diff --git a/vlib/v/gen/c/struct.v b/vlib/v/gen/c/struct.v
index e63386407..9a45d0926 100644
--- a/vlib/v/gen/c/struct.v
+++ b/vlib/v/gen/c/struct.v
@@ -555,7 +555,8 @@ fn (mut g Gen) struct_init(node ast.StructInit) {
 fn (mut g Gen) can_use_direct_heap_struct_init(node ast.StructInit, sym ast.TypeSymbol, aligned int, const_msvc_init bool) bool {
 	if g.is_shared || g.inside_cast_in_heap > 0 || g.inside_cinit || g.inside_const
 		|| g.inside_global_decl || aligned != 0 || const_msvc_init || node.typ.has_flag(.option)
-		|| node.has_update_expr || sym.kind != .struct {
+		|| node.has_update_expr || sym.kind != .struct || g.cur_fn == unsafe { nil }
+		|| g.stmt_path_pos.len <= g.inside_ternary {
 		return false
 	}
 	if sym.info !is ast.Struct {
@@ -579,11 +580,8 @@ fn (mut g Gen) can_use_direct_heap_struct_init(node ast.StructInit, sym ast.Type
 }
 
 fn (mut g Gen) direct_heap_struct_init(node ast.StructInit, styp string, info ast.Struct, language ast.Language) {
-	stmt_str := if g.inside_ternary > 0 {
-		g.go_before_ternary().trim_space()
-	} else {
-		g.go_before_last_stmt().trim_space()
-	}
+	stmt_pos_idx := g.stmt_path_pos.len - (1 + g.inside_ternary)
+	stmt_str := g.out.cut_to(g.stmt_path_pos[stmt_pos_idx]).trim_space()
 	g.empty_line = true
 	tmp_var := g.new_tmp_var()
 	if info.is_empty_struct() {
@@ -631,7 +629,8 @@ fn (mut g Gen) direct_heap_struct_init(node ast.StructInit, styp string, info as
 		g.struct_init_ptr_field(tmp_var, resolved_field, language)
 		g.writeln(';')
 	}
-	g.set_current_pos_as_last_stmt_pos()
+	// Keep the cut position current without leaving stale entries for later hoists.
+	g.stmt_path_pos[stmt_pos_idx] = g.out.len
 	g.write2(stmt_str, ' ')
 	g.write(tmp_var)
 }
diff --git a/vlib/v/gen/c/testdata/heap_struct_init_order.c.must_have b/vlib/v/gen/c/testdata/heap_struct_init_order.c.must_have
new file mode 100644
index 000000000..58b5d4470
--- /dev/null
+++ b/vlib/v/gen/c/testdata/heap_struct_init_order.c.must_have
@@ -0,0 +1,8 @@
+builtin___v_malloc(sizeof(main__Issue27329Object) == 0 ? 1 : sizeof(main__Issue27329Object));
+->kind = _const_main__issue_27329_kind_false;
+->kind = _const_main__issue_27329_kind_true;
+->kind = _const_main__issue_27329_kind_len;
+volatile main__Issue27329Object*
+return builtin__new_array_from_c_array(3, 3, sizeof(main__Issue27329Object*)
+->child = _t
+// THE END.
diff --git a/vlib/v/gen/c/testdata/heap_struct_init_order.out b/vlib/v/gen/c/testdata/heap_struct_init_order.out
new file mode 100644
index 000000000..9766475a4
--- /dev/null
+++ b/vlib/v/gen/c/testdata/heap_struct_init_order.out
@@ -0,0 +1 @@
+ok
diff --git a/vlib/v/gen/c/testdata/heap_struct_init_order.vv b/vlib/v/gen/c/testdata/heap_struct_init_order.vv
new file mode 100644
index 000000000..18e02040b
--- /dev/null
+++ b/vlib/v/gen/c/testdata/heap_struct_init_order.vv
@@ -0,0 +1,68 @@
+const issue_27329_kind_false = 0
+const issue_27329_kind_true = 1
+const issue_27329_kind_len = 2
+
+struct Issue27329Object {
+	kind    int
+	ival    int
+	len_val int
+	child   &Issue27329Object
+}
+
+fn (obj &Issue27329Object) truthy() bool {
+	return if obj.kind == issue_27329_kind_true {
+		true
+	} else if obj.kind == issue_27329_kind_len {
+		obj.len_val > 0
+	} else {
+		false
+	}
+}
+
+fn issue_27329_objects() []&Issue27329Object {
+	return [
+		&Issue27329Object{
+			kind:    issue_27329_kind_false
+			ival:    0
+			len_val: 0
+			child:   unsafe { nil }
+		},
+		&Issue27329Object{
+			kind:    issue_27329_kind_true
+			ival:    1
+			len_val: 0
+			child:   unsafe { nil }
+		},
+		&Issue27329Object{
+			kind:    issue_27329_kind_len
+			ival:    2
+			len_val: 3
+			child:   unsafe { nil }
+		},
+	]
+}
+
+fn issue_27329_nested() &Issue27329Object {
+	return &Issue27329Object{
+		kind:    issue_27329_kind_len
+		ival:    7
+		len_val: 1
+		child:   &Issue27329Object{
+			kind:    issue_27329_kind_false
+			ival:    8
+			len_val: 0
+			child:   unsafe { nil }
+		}
+	}
+}
+
+fn main() {
+	objects := issue_27329_objects()
+	nested := issue_27329_nested()
+	assert !objects[0].truthy()
+	assert objects[1].truthy()
+	assert objects[2].truthy()
+	assert nested.truthy()
+	assert !nested.child.truthy()
+	println('ok')
+}
-- 
2.39.5