cgen: fix array fixed with default init

vlib/v/gen/c/cgen.v

@@ -5777,31 +5777,40 @@ fn (mut g Gen) return_stmt(node ast.Return) {
 				g.expr_with_opt(node.exprs[0], node.types[0], g.fn_decl.return_type)
 			} else {
 				if fn_return_is_fixed_array && !node.types[0].has_option_or_result() {
-					g.writeln('{0};')
 					if node.exprs[0] is ast.Ident {
+						g.writeln('{0};')
 						typ := if expr0.is_auto_deref_var() {
 							node.types[0].deref()
 						} else {
 							node.types[0]
 						}
-						g.write('memcpy(${tmpvar}.ret_arr, ${g.expr_string(node.exprs[0])}, sizeof(${g.typ(typ)})) /*ret*/')
+						g.write('memcpy(${tmpvar}.ret_arr, ${g.expr_string(node.exprs[0])}, sizeof(${g.typ(typ)}))')
 					} else if node.exprs[0] in [ast.ArrayInit, ast.StructInit] {
 						if node.exprs[0] is ast.ArrayInit && node.exprs[0].is_fixed
 							&& node.exprs[0].has_init {
-							g.write('memcpy(${tmpvar}.ret_arr, ')
-							g.expr_with_cast(node.exprs[0], node.types[0], g.fn_decl.return_type)
-							g.write(', sizeof(${g.typ(node.types[0])})) /*ret*/')
+							if (node.exprs[0] as ast.ArrayInit).init_expr.is_literal() {
+								g.write('{.ret_arr=')
+								g.expr_with_cast(node.exprs[0], node.types[0], g.fn_decl.return_type)
+								g.writeln('};')
+							} else {
+								g.writeln('{0};')
+								g.write('memcpy(${tmpvar}.ret_arr, ')
+								g.expr_with_cast(node.exprs[0], node.types[0], g.fn_decl.return_type)
+								g.write(', sizeof(${g.typ(node.types[0])}))')
+							}
 						} else {
+							g.writeln('{0};')
 							tmpvar2 := g.new_tmp_var()
 							g.write('${g.typ(node.types[0])} ${tmpvar2} = ')
 							g.expr_with_cast(node.exprs[0], node.types[0], g.fn_decl.return_type)
 							g.writeln(';')
-							g.write('memcpy(${tmpvar}.ret_arr, ${tmpvar2}, sizeof(${g.typ(node.types[0])})) /*ret*/')
+							g.write('memcpy(${tmpvar}.ret_arr, ${tmpvar2}, sizeof(${g.typ(node.types[0])}))')
 						}
 					} else {
+						g.writeln('{0};')
 						g.write('memcpy(${tmpvar}.ret_arr, ')
 						g.expr_with_cast(node.exprs[0], node.types[0], g.fn_decl.return_type)
-						g.write(', sizeof(${g.typ(node.types[0])})) /*ret*/')
+						g.write(', sizeof(${g.typ(node.types[0])}))')
 					}
 				} else {
 					g.expr_with_cast(node.exprs[0], node.types[0], g.fn_decl.return_type)

vlib/v/tests/array_init_fixed_test.v

@@ -0,0 +1,26 @@
+module main
+
+pub const n = 7
+pub const nsq = n * n
+
+pub fn empty_board(with_init bool) [nsq]u8 {
+	if with_init {
+		a := [nsq]u8{init: 0}
+		dump(a)
+		return [nsq]u8{init: 0}
+	} else {
+		a := [nsq]u8{}
+		dump(a)
+		return [nsq]u8{}
+	}
+}
+
+fn test_with_init() {
+	a := dump(empty_board(true))
+	assert a.len == 49
+}
+
+fn test_without_init() {
+	a := dump(empty_board(false))
+	assert a.len == 49
+}