cgen: fix codegen for assigning fixed array on defer var (fix #24300) (#24305)

Author: felipensp

vlib/v/gen/c/assign.v

@@ -938,7 +938,17 @@ fn (mut g Gen) assign_stmt(node_ ast.AssignStmt) {
 							|| gen_or {
 							g.expr_with_opt_or_block(val, val_type, left, var_type, is_option_auto_heap)
 						} else if val is ast.ArrayInit {
-							g.array_init(val, c_name(ident.name))
+							cvar_name := c_name(ident.name)
+							if val.is_fixed && ident.name in g.defer_vars {
+								g.go_before_last_stmt()
+								g.empty_line = true
+								g.write('memcpy(${cvar_name}, ')
+								g.write('(${styp})')
+								g.array_init(val, cvar_name)
+								g.write(', sizeof(${styp}))')
+							} else {
+								g.array_init(val, cvar_name)
+							}
 						} else if val_type.has_flag(.shared_f) {
 							g.expr_with_cast(val, val_type, var_type)
 						} else if val in [ast.MatchExpr, ast.IfExpr]

vlib/v/tests/defer/defer_fixed_array_test.v

@@ -0,0 +1,11 @@
+fn foo() {
+	a := [u8(1), 2, 3]!
+	defer {
+		println('deffered println: ${a}')
+		assert a == [u8(1), 2, 3]!
+	}
+}
+
+fn test_main() {
+	foo()
+}