From 2c063ea19141163d7ea6a167abc355e7b4341ee4 Mon Sep 17 00:00:00 2001
From: Delyan Angelov <delian66@gmail.com>
Date: Tue, 1 Jul 2025 14:13:03 +0300
Subject: [PATCH] cgen,markused: skip `struct none {` in cgen, if `none` is not
 used by V code reachable from `fn main() {` (#24824)

---
 vlib/v/ast/table.v         | 1 +
 vlib/v/gen/c/cgen.v        | 2 +-
 vlib/v/markused/markused.v | 4 ++++
 3 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/vlib/v/ast/table.v b/vlib/v/ast/table.v
index 0d7c2dc85f..55e67b9200 100644
--- a/vlib/v/ast/table.v
+++ b/vlib/v/ast/table.v
@@ -40,6 +40,7 @@ pub mut:
 	used_veb_types   []Type          // veb context types, filled in by checker
 	used_maps        int             // how many times maps were used, filled in by markused
 	used_arrays      int             // how many times arrays were used, filled in by markused
+	used_none        int             // how many times `none` was used, filled in by markused
 	external_types   bool            // true, when external type is used
 	// json             bool            // json is imported
 	debugger       bool            // debugger is used
diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index 3c200e9d41..75425ff731 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -6635,7 +6635,7 @@ fn (mut g Gen) write_types(symbols []&ast.TypeSymbol) {
 		if sym.name.starts_with('C.') {
 			continue
 		}
-		if sym.kind == .none {
+		if sym.kind == .none && (!g.pref.skip_unused || g.table.used_features.used_none > 0) {
 			g.type_definitions.writeln('struct none {')
 			g.type_definitions.writeln('\tEMPTY_STRUCT_DECLARATION;')
 			g.type_definitions.writeln('};')
diff --git a/vlib/v/markused/markused.v b/vlib/v/markused/markused.v
index 4cb9ecec3e..e9067f109a 100644
--- a/vlib/v/markused/markused.v
+++ b/vlib/v/markused/markused.v
@@ -540,6 +540,10 @@ pub fn mark_used(mut table ast.Table, mut pref_ pref.Preferences, ast_files []&a
 		}
 	}
 
+	table.used_features.used_none = walker.used_none
+	if walker.used_none == 0 {
+		walker.used_fns.delete('${int(ast.none_type)}.str')
+	}
 	table.used_features.used_fns = walker.used_fns.move()
 	table.used_features.used_consts = walker.used_consts.move()
 	table.used_features.used_globals = walker.used_globals.move()