From 4dfdcb760ef18e0d3e6f67eaeb36e936c1048552 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Wed, 15 Apr 2026 05:26:57 +0300
Subject: [PATCH] cgen: fix weird behavior on iterating an array (fixes #26874)

---
 vlib/v/gen/c/cgen.v                           |  3 +++
 .../loops/for_in_mut_mutable_app_field_test.v | 25 +++++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index 524f4a130..e2b56a4e6 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -5467,6 +5467,9 @@ fn (mut g Gen) expr(node_ ast.Expr) {
 						}
 					}
 				}
+				if node.right.is_auto_deref_var() && node.op !in [.amp, .mul, .arrow] {
+					g.write('*')
+				}
 				if tmp_var == '' {
 					g.expr(node.right)
 				} else {
diff --git a/vlib/v/tests/loops/for_in_mut_mutable_app_field_test.v b/vlib/v/tests/loops/for_in_mut_mutable_app_field_test.v
index 0c8800e82..21194db0a 100644
--- a/vlib/v/tests/loops/for_in_mut_mutable_app_field_test.v
+++ b/vlib/v/tests/loops/for_in_mut_mutable_app_field_test.v
@@ -18,3 +18,28 @@ fn test_for_in_struct_with_mutable_array_field_indexed_several_times_in_the_loop
 	}
 	assert app.index[x][y] == Item{[555, 555, 555]}
 }
+
+struct Registers {
+mut:
+	registers [4]bool
+}
+
+fn (mut r Registers) allocate_register() int {
+	for i, mut available in r.registers {
+		if !available {
+			available = true
+			return i
+		}
+	}
+	panic('No available register')
+}
+
+fn test_for_in_struct_with_mutable_fixed_array_field() {
+	mut regs := Registers{}
+	assert regs.allocate_register() == 0
+	assert regs.allocate_register() == 1
+	assert regs.registers[0]
+	assert regs.registers[1]
+	assert !regs.registers[2]
+	assert !regs.registers[3]
+}
-- 
2.39.5