From 64343168c6f2d8380bd8bdb0960f90959af8cd33 Mon Sep 17 00:00:00 2001
From: Felipe Pena <felipensp@gmail.com>
Date: Sat, 13 Sep 2025 02:49:09 -0300
Subject: [PATCH] cgen: fix option variadic arg passing (fix #25261) (#25273)

---
 cmd/tools/vast/vast.v                         |  1 +
 vlib/v/ast/ast.v                              |  1 +
 vlib/v/ast/types.v                            |  2 +-
 vlib/v/checker/fn.v                           |  1 +
 vlib/v/gen/c/fn.v                             | 17 +++++++++++++--
 vlib/v/markused/walker.v                      |  3 +++
 .../v/tests/options/option_fn_variadic_test.v | 21 +++++++++++++++++++
 7 files changed, 43 insertions(+), 3 deletions(-)
 create mode 100644 vlib/v/tests/options/option_fn_variadic_test.v

diff --git a/cmd/tools/vast/vast.v b/cmd/tools/vast/vast.v
index 67394cf1f..f74e32529 100644
--- a/cmd/tools/vast/vast.v
+++ b/cmd/tools/vast/vast.v
@@ -1614,6 +1614,7 @@ fn (t Tree) call_expr(node ast.CallExpr) &Node {
 	obj.add_terse('is_ctor_new', t.bool_node(node.is_ctor_new))
 	obj.add_terse('is_return_used', t.bool_node(node.is_return_used))
 	obj.add_terse('is_static_method', t.bool_node(node.is_static_method))
+	obj.add_terse('is_variadic', t.bool_node(node.is_variadic))
 	obj.add('should_be_skipped', t.bool_node(node.should_be_skipped))
 	obj.add_terse('free_receiver', t.bool_node(node.free_receiver))
 	obj.add('scope', t.number_node(int(node.scope)))
diff --git a/vlib/v/ast/ast.v b/vlib/v/ast/ast.v
index b21534929..5c948082a 100644
--- a/vlib/v/ast/ast.v
+++ b/vlib/v/ast/ast.v
@@ -830,6 +830,7 @@ pub mut:
 	is_ctor_new            bool // if JS ctor calls requires `new` before call, marked as `[use_new]` in V
 	is_file_translated     bool // true, when the file it resides in is `@[translated]`
 	is_static_method       bool // it is a static method call
+	is_variadic            bool
 	args                   []CallArg
 	expected_arg_types     []Type
 	comptime_ret_val       bool
diff --git a/vlib/v/ast/types.v b/vlib/v/ast/types.v
index 31dd3896a..0e30e7d59 100644
--- a/vlib/v/ast/types.v
+++ b/vlib/v/ast/types.v
@@ -1617,7 +1617,7 @@ pub fn (t &Table) type_to_str_using_aliases(typ Type, import_aliases map[string]
 	if nr_muls > 0 && !typ.has_flag(.variadic) {
 		res = strings.repeat(`&`, nr_muls) + res
 	}
-	if typ.has_flag(.option) {
+	if typ.has_flag(.option) && res[0] != `?` {
 		res = '?${res}'
 	}
 	if typ.has_flag(.result) {
diff --git a/vlib/v/checker/fn.v b/vlib/v/checker/fn.v
index 0c2b338fa..1c6ebf8f7 100644
--- a/vlib/v/checker/fn.v
+++ b/vlib/v/checker/fn.v
@@ -2907,6 +2907,7 @@ fn (mut c Checker) check_expected_arg_count(mut node ast.CallExpr, f &ast.Fn) !
 		min_required_params--
 	}
 	if f.is_variadic {
+		node.is_variadic = f.is_variadic
 		min_required_params--
 		c.markused_array_method(!c.is_builtin_mod, '')
 	} else {
diff --git a/vlib/v/gen/c/fn.v b/vlib/v/gen/c/fn.v
index c937d3de1..77ddecb61 100644
--- a/vlib/v/gen/c/fn.v
+++ b/vlib/v/gen/c/fn.v
@@ -2398,8 +2398,8 @@ fn (mut g Gen) call_args(node ast.CallExpr) {
 		}
 	}
 	// only v variadic, C variadic args will be appended like normal args
-	is_variadic := expected_types.len > 0 && expected_types.last().has_flag(.variadic)
-		&& node.language == .v
+	is_variadic := node.language == .v && node.is_variadic && expected_types.len > 0
+		&& expected_types.last().has_flag(.variadic)
 	mut already_decomposed := false
 	for i, arg in args {
 		if is_variadic && i == expected_types.len - 1 {
@@ -2568,6 +2568,14 @@ fn (mut g Gen) call_args(node ast.CallExpr) {
 							false)
 					} else {
 						noscan := g.check_noscan(arr_info.elem_type)
+						is_option := arr_info.elem_type.has_flag(.option)
+						tmp_var := if is_option { g.new_tmp_var() } else { '' }
+						base_type := g.base_type(varg_type)
+						tmp := if is_option { g.go_before_last_stmt() } else { '' }
+						if is_option {
+							g.writeln('${g.styp(varg_type)} ${tmp_var};')
+							g.write('builtin___option_ok((${base_type}[]) {')
+						}
 						g.write('builtin__new_array_from_c_array${noscan}(${variadic_count}, ${variadic_count}, sizeof(${elem_type}), _MOV((${elem_type}[${variadic_count}]){')
 						for j in arg_nr .. args.len {
 							g.ref_or_deref_arg(args[j], arr_info.elem_type, node.language,
@@ -2577,6 +2585,11 @@ fn (mut g Gen) call_args(node ast.CallExpr) {
 							}
 						}
 						g.write('}))')
+						if is_option {
+							g.writeln(' }, (${option_name}*)&${tmp_var}, sizeof(${base_type}));')
+							g.write(tmp)
+							g.write(tmp_var)
+						}
 					}
 				}
 			} else {
diff --git a/vlib/v/markused/walker.v b/vlib/v/markused/walker.v
index 4dfc9b69b..57bef1683 100644
--- a/vlib/v/markused/walker.v
+++ b/vlib/v/markused/walker.v
@@ -945,6 +945,9 @@ pub fn (mut w Walker) call_expr(mut node ast.CallExpr) {
 	for arg in node.args {
 		w.expr(arg.expr)
 	}
+	if node.is_variadic && node.expected_arg_types.last().has_flag(.option) {
+		w.used_option++
+	}
 	for concrete_type in node.concrete_types {
 		w.mark_by_type(concrete_type)
 	}
diff --git a/vlib/v/tests/options/option_fn_variadic_test.v b/vlib/v/tests/options/option_fn_variadic_test.v
new file mode 100644
index 000000000..0fb1b4b04
--- /dev/null
+++ b/vlib/v/tests/options/option_fn_variadic_test.v
@@ -0,0 +1,21 @@
+struct Empty {
+}
+
+type Elem = int | Empty
+
+fn new_elems(elems ...?int) []Elem {
+	mut out := []Elem{}
+	for elem in elems {
+		if elem == none {
+			out << Empty{}
+		} else {
+			out << elem
+		}
+	}
+	return out
+}
+
+fn test_main() {
+	elems := new_elems(0, none, 2)
+	assert '${elems}' == '[Elem(0), Elem(Empty{}), Elem(2)]'
+}
-- 
2.39.5