cgen: fix option ptr unwrapping (#21415)

Author: felipensp

vlib/v/gen/c/cgen.v

@@ -4901,7 +4901,7 @@ fn (mut g Gen) ident(node ast.Ident) {
 	g.write(g.get_ternary_name(name))
 	if is_auto_heap {
 		g.write('))')
-		if is_option {
+		if is_option && node.or_expr.kind != .absent {
 			g.write('.data')
 		}
 	}
@@ -6992,7 +6992,7 @@ fn (mut g Gen) or_block(var_name string, or_block ast.OrExpr, return_type ast.Ty
 			if g.fn_decl.return_type == ast.void_type {
 				g.writeln('\treturn;')
 			} else {
-				styp := g.typ(g.fn_decl.return_type)
+				styp := g.typ(g.fn_decl.return_type).replace('*', '_ptr')
 				err_obj := g.new_tmp_var()
 				g.writeln('\t${styp} ${err_obj};')
 				g.writeln('\tmemcpy(&${err_obj}, &${cvar_name}, sizeof(_option));')

vlib/v/tests/option_ptr_unwrap_test.v

@@ -0,0 +1,89 @@
+import time
+// 41s.
+
+struct Node[T] {
+mut:
+	data T
+	prev ?&Node[T]
+	next ?&Node[T]
+}
+
+struct LinkedList[T] {
+mut:
+	size usize
+	head ?&Node[T]
+}
+
+fn new_linked_list[T]() &LinkedList[T] {
+	return &LinkedList[T]{}
+}
+
+fn (mut li LinkedList[T]) add[T](data T) {
+	mut node := &Node[T]{data, none, none}
+
+	if li.head == none {
+		li.head = node
+		node.next = node
+		node.prev = node
+	} else {
+		node.next = li.head
+		node.prev = li.head?.prev
+		node.prev?.next = node
+		li.head?.prev = node
+	}
+
+	li.size += 1
+}
+
+fn (mut li LinkedList[T]) pop[T]() ?T {
+	if li.head == none {
+		return none
+	}
+	if li.size == 1 {
+		data := li.head?.data
+		li.head?.next = none
+		li.head?.prev = none
+		li.head = none
+		li.size -= 1
+		return data
+	}
+
+	mut tail := li.head?.prev?
+	mut curr := tail.prev?
+	curr.next = li.head
+	li.head?.prev = curr
+
+	tail.next = none
+	tail.prev = none
+	li.size -= 1
+
+	return tail.data
+}
+
+@[heap]
+struct Integer {
+	value int
+}
+
+fn test_main() {
+	max_itr := 2
+	t := time.now()
+	for itr in 0 .. max_itr {
+		mut list := new_linked_list[&Integer]()
+		println('Itr#${itr} list size: ${list.size}')
+
+		list.add(&Integer{10})
+		println('Itr#${itr} list size: ${list.size}')
+		list.add(&Integer{20})
+		println('Itr#${itr} list size: ${list.size}')
+
+		mut n := list.pop()
+		println('Itr#${itr} list size: ${list.size}, data: ${n?}')
+		n = list.pop()
+		println('Itr#${itr} list size: ${list.size}, data: ${n?}')
+		n = list.pop()
+		println('Itr#${itr} list size: ${list.size}, data: ${n}')
+	}
+	d := time.since(t)
+	println('Bye(time ${d})!')
+}