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// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// Verifies that the types and values of static items
// are safe. The rules enforced by this module are:
//
// - For each *mutable* static item, it checks that its **type**:
// - doesn't have a destructor
// - doesn't own an owned pointer
//
// - For each *immutable* static item, it checks that its **value**:
// - doesn't own owned, managed pointers
// - doesn't contain a struct literal or a call to an enum variant / struct constructor where
// - the type of the struct/enum has a dtor
//
// Rules Enforced Elsewhere:
// - It's not possible to take the address of a static item with unsafe interior. This is enforced
// by borrowck::gather_loans
use middle::ty;
use syntax::ast;
use syntax::visit::Visitor;
use syntax::visit;
use syntax::print::pprust;
fn safe_type_for_static_mut(cx: &ty::ctxt, e: &ast::Expr) -> Option<String> {
let node_ty = ty::node_id_to_type(cx, e.id);
let tcontents = ty::type_contents(cx, node_ty);
debug!("safe_type_for_static_mut(dtor={}, managed={}, owned={})",
tcontents.has_dtor(), tcontents.owns_managed(), tcontents.owns_owned())
let suffix = if tcontents.has_dtor() {
"destructors"
} else if tcontents.owns_managed() {
"managed pointers"
} else if tcontents.owns_owned() {
"owned pointers"
} else {
return None;
};
Some(format!("mutable static items are not allowed to have {}", suffix))
}
struct CheckStaticVisitor<'a, 'tcx: 'a> {
tcx: &'a ty::ctxt<'tcx>,
in_const: bool
}
pub fn check_crate(tcx: &ty::ctxt) {
visit::walk_crate(&mut CheckStaticVisitor { tcx: tcx, in_const: false },
tcx.map.krate())
}
impl<'a, 'tcx> CheckStaticVisitor<'a, 'tcx> {
fn with_const(&mut self, in_const: bool, f: |&mut CheckStaticVisitor<'a, 'tcx>|) {
let was_const = self.in_const;
self.in_const = in_const;
f(self);
self.in_const = was_const;
}
}
impl<'a, 'tcx, 'v> Visitor<'v> for CheckStaticVisitor<'a, 'tcx> {
fn visit_item(&mut self, i: &ast::Item) {
debug!("visit_item(item={})", pprust::item_to_string(i));
match i.node {
ast::ItemStatic(_, mutability, ref expr) => {
match mutability {
ast::MutImmutable => {
self.with_const(true, |v| v.visit_expr(&**expr));
}
ast::MutMutable => {
match safe_type_for_static_mut(self.tcx, &**expr) {
Some(msg) => {
self.tcx.sess.span_err(expr.span, msg.as_slice());
}
None => {}
}
}
}
}
_ => self.with_const(false, |v| visit::walk_item(v, i))
}
}
/// This method is used to enforce the constraints on
/// immutable static items. It walks through the *value*
/// of the item walking down the expression and evaluating
/// every nested expression. if the expression is not part
/// of a static item, this method does nothing but walking
/// down through it.
fn visit_expr(&mut self, e: &ast::Expr) {
debug!("visit_expr(expr={})", pprust::expr_to_string(e));
if !self.in_const {
return visit::walk_expr(self, e);
}
match e.node {
ast::ExprField(..) | ast::ExprTupField(..) | ast::ExprVec(..) |
ast::ExprBlock(..) | ast::ExprTup(..) => {
visit::walk_expr(self, e);
}
ast::ExprAddrOf(ast::MutMutable, _) => {
span_err!(self.tcx.sess, e.span, E0020,
"static items are not allowed to have mutable slices");
},
ast::ExprBox(..) |
ast::ExprUnary(ast::UnUniq, _) => {
span_err!(self.tcx.sess, e.span, E0022,
"static items are not allowed to have custom pointers");
}
_ => {
let node_ty = ty::node_id_to_type(self.tcx, e.id);
match ty::get(node_ty).sty {
ty::ty_struct(did, _) |
ty::ty_enum(did, _) => {
if ty::has_dtor(self.tcx, did) {
self.tcx.sess.span_err(e.span,
"static items are not allowed to have destructors");
return;
}
}
_ => {}
}
visit::walk_expr(self, e);
}
}
}
}
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