1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 // Verifies that the types and values of static items
12 // are safe. The rules enforced by this module are:
14 // - For each *mutable* static item, it checks that its **type**:
15 // - doesn't have a destructor
16 // - doesn't own an owned pointer
18 // - For each *immutable* static item, it checks that its **value**:
19 // - doesn't own owned, managed pointers
20 // - doesn't contain a struct literal or a call to an enum variant / struct constructor where
21 // - the type of the struct/enum has a dtor
23 // Rules Enforced Elsewhere:
24 // - It's not possible to take the address of a static item with unsafe interior. This is enforced
25 // by borrowck::gather_loans
30 use syntax::codemap::Span;
31 use syntax::visit::Visitor;
33 use syntax::print::pprust;
36 fn safe_type_for_static_mut(cx: &ty::ctxt, e: &ast::Expr) -> Option<String> {
37 let node_ty = ty::node_id_to_type(cx, e.id);
38 let tcontents = ty::type_contents(cx, node_ty);
39 debug!("safe_type_for_static_mut(dtor={}, managed={}, owned={})",
40 tcontents.has_dtor(), tcontents.owns_managed(), tcontents.owns_owned())
42 let suffix = if tcontents.has_dtor() {
44 } else if tcontents.owns_managed() {
46 } else if tcontents.owns_owned() {
52 Some(format!("mutable static items are not allowed to have {}", suffix))
55 struct CheckStaticVisitor<'a, 'tcx: 'a> {
56 tcx: &'a ty::ctxt<'tcx>,
59 pub fn check_crate(tcx: &ty::ctxt, krate: &ast::Crate) {
60 visit::walk_crate(&mut CheckStaticVisitor { tcx: tcx }, krate, false)
63 impl<'a, 'tcx> CheckStaticVisitor<'a, 'tcx> {
64 fn report_error(&self, span: Span, result: Option<String>) -> bool {
68 self.tcx.sess.span_err(span, msg.as_slice());
75 impl<'a, 'tcx> Visitor<bool> for CheckStaticVisitor<'a, 'tcx> {
77 fn visit_item(&mut self, i: &ast::Item, _is_const: bool) {
78 debug!("visit_item(item={})", pprust::item_to_string(i));
80 ast::ItemStatic(_, mutability, ref expr) => {
82 ast::MutImmutable => {
83 self.visit_expr(&**expr, true);
86 let safe = safe_type_for_static_mut(self.tcx, &**expr);
87 self.report_error(expr.span, safe);
91 _ => { visit::walk_item(self, i, false) }
95 /// This method is used to enforce the constraints on
96 /// immutable static items. It walks through the *value*
97 /// of the item walking down the expression and evaluating
98 /// every nested expression. if the expression is not part
99 /// of a static item, this method does nothing but walking
101 fn visit_expr(&mut self, e: &ast::Expr, is_const: bool) {
102 debug!("visit_expr(expr={})", pprust::expr_to_string(e));
105 return visit::walk_expr(self, e, is_const);
109 ast::ExprField(..) | ast::ExprVec(..) |
110 ast::ExprBlock(..) | ast::ExprTup(..) => {
111 visit::walk_expr(self, e, is_const);
113 ast::ExprAddrOf(ast::MutMutable, _) => {
114 span_err!(self.tcx.sess, e.span, E0020,
115 "static items are not allowed to have mutable slices");
117 ast::ExprUnary(ast::UnBox, _) => {
118 span_err!(self.tcx.sess, e.span, E0021,
119 "static items are not allowed to have managed pointers");
122 ast::ExprUnary(ast::UnUniq, _) => {
123 span_err!(self.tcx.sess, e.span, E0022,
124 "static items are not allowed to have custom pointers");
127 let node_ty = ty::node_id_to_type(self.tcx, e.id);
129 match ty::get(node_ty).sty {
130 ty::ty_struct(did, _) |
131 ty::ty_enum(did, _) => {
132 if ty::has_dtor(self.tcx, did) {
133 self.report_error(e.span,
134 Some("static items are not allowed to have \
135 destructors".to_string()));
141 visit::walk_expr(self, e, is_const);