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effect.rs
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effect.rs
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// Copyright 2012-2013 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.
//! Enforces the Rust effect system. Currently there is just one effect,
//! `unsafe`.
use self::RootUnsafeContext::*;
use ty::{self, Ty, TyCtxt};
use ty::MethodCall;
use lint;
use syntax::ast;
use syntax_pos::Span;
use hir::{self, PatKind};
use hir::def::Def;
use hir::intravisit::{self, FnKind, Visitor, NestedVisitorMap};
#[derive(Copy, Clone)]
struct UnsafeContext {
push_unsafe_count: usize,
root: RootUnsafeContext,
}
impl UnsafeContext {
fn new(root: RootUnsafeContext) -> UnsafeContext {
UnsafeContext { root: root, push_unsafe_count: 0 }
}
}
#[derive(Copy, Clone, PartialEq)]
enum RootUnsafeContext {
SafeContext,
UnsafeFn,
UnsafeBlock(ast::NodeId),
}
fn type_is_unsafe_function(ty: Ty) -> bool {
match ty.sty {
ty::TyFnDef(.., f) |
ty::TyFnPtr(f) => f.unsafety() == hir::Unsafety::Unsafe,
_ => false,
}
}
struct EffectCheckVisitor<'a, 'tcx: 'a> {
tcx: TyCtxt<'a, 'tcx, 'tcx>,
tables: &'a ty::TypeckTables<'tcx>,
/// Whether we're in an unsafe context.
unsafe_context: UnsafeContext,
}
impl<'a, 'tcx> EffectCheckVisitor<'a, 'tcx> {
fn require_unsafe_ext(&mut self, node_id: ast::NodeId, span: Span,
description: &str, is_lint: bool) {
if self.unsafe_context.push_unsafe_count > 0 { return; }
match self.unsafe_context.root {
SafeContext => {
if is_lint {
self.tcx.sess.add_lint(lint::builtin::SAFE_EXTERN_STATICS,
node_id,
span,
format!("{} requires unsafe function or \
block (error E0133)", description));
} else {
// Report an error.
struct_span_err!(
self.tcx.sess, span, E0133,
"{} requires unsafe function or block", description)
.span_label(span, &description)
.emit();
}
}
UnsafeBlock(block_id) => {
// OK, but record this.
debug!("effect: recording unsafe block as used: {}", block_id);
self.tcx.used_unsafe.borrow_mut().insert(block_id);
}
UnsafeFn => {}
}
}
fn require_unsafe(&mut self, span: Span, description: &str) {
self.require_unsafe_ext(ast::DUMMY_NODE_ID, span, description, false)
}
}
impl<'a, 'tcx> Visitor<'tcx> for EffectCheckVisitor<'a, 'tcx> {
fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
NestedVisitorMap::None
}
fn visit_nested_body(&mut self, body: hir::BodyId) {
let old_tables = self.tables;
self.tables = self.tcx.body_tables(body);
let body = self.tcx.hir.body(body);
self.visit_body(body);
self.tables = old_tables;
}
fn visit_fn(&mut self, fn_kind: FnKind<'tcx>, fn_decl: &'tcx hir::FnDecl,
body_id: hir::BodyId, span: Span, id: ast::NodeId) {
let (is_item_fn, is_unsafe_fn) = match fn_kind {
FnKind::ItemFn(_, _, unsafety, ..) =>
(true, unsafety == hir::Unsafety::Unsafe),
FnKind::Method(_, sig, ..) =>
(true, sig.unsafety == hir::Unsafety::Unsafe),
_ => (false, false),
};
let old_unsafe_context = self.unsafe_context;
if is_unsafe_fn {
self.unsafe_context = UnsafeContext::new(UnsafeFn)
} else if is_item_fn {
self.unsafe_context = UnsafeContext::new(SafeContext)
}
intravisit::walk_fn(self, fn_kind, fn_decl, body_id, span, id);
self.unsafe_context = old_unsafe_context
}
fn visit_block(&mut self, block: &'tcx hir::Block) {
let old_unsafe_context = self.unsafe_context;
match block.rules {
hir::UnsafeBlock(source) => {
// By default only the outermost `unsafe` block is
// "used" and so nested unsafe blocks are pointless
// (the inner ones are unnecessary and we actually
// warn about them). As such, there are two cases when
// we need to create a new context, when we're
// - outside `unsafe` and found a `unsafe` block
// (normal case)
// - inside `unsafe`, found an `unsafe` block
// created internally to the compiler
//
// The second case is necessary to ensure that the
// compiler `unsafe` blocks don't accidentally "use"
// external blocks (e.g. `unsafe { println("") }`,
// expands to `unsafe { ... unsafe { ... } }` where
// the inner one is compiler generated).
if self.unsafe_context.root == SafeContext || source == hir::CompilerGenerated {
self.unsafe_context.root = UnsafeBlock(block.id)
}
}
hir::PushUnsafeBlock(..) => {
self.unsafe_context.push_unsafe_count =
self.unsafe_context.push_unsafe_count.checked_add(1).unwrap();
}
hir::PopUnsafeBlock(..) => {
self.unsafe_context.push_unsafe_count =
self.unsafe_context.push_unsafe_count.checked_sub(1).unwrap();
}
hir::DefaultBlock => {}
}
intravisit::walk_block(self, block);
self.unsafe_context = old_unsafe_context
}
fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
match expr.node {
hir::ExprMethodCall(..) => {
let method_call = MethodCall::expr(expr.id);
let base_type = self.tables.method_map[&method_call].ty;
debug!("effect: method call case, base type is {:?}",
base_type);
if type_is_unsafe_function(base_type) {
self.require_unsafe(expr.span,
"invocation of unsafe method")
}
}
hir::ExprCall(ref base, _) => {
let base_type = self.tables.expr_ty_adjusted(base);
debug!("effect: call case, base type is {:?}",
base_type);
if type_is_unsafe_function(base_type) {
self.require_unsafe(expr.span, "call to unsafe function")
}
}
hir::ExprUnary(hir::UnDeref, ref base) => {
let base_type = self.tables.expr_ty_adjusted(base);
debug!("effect: unary case, base type is {:?}",
base_type);
if let ty::TyRawPtr(_) = base_type.sty {
self.require_unsafe(expr.span, "dereference of raw pointer")
}
}
hir::ExprInlineAsm(..) => {
self.require_unsafe(expr.span, "use of inline assembly");
}
hir::ExprPath(hir::QPath::Resolved(_, ref path)) => {
if let Def::Static(def_id, mutbl) = path.def {
if mutbl {
self.require_unsafe(expr.span, "use of mutable static");
} else if match self.tcx.hir.get_if_local(def_id) {
Some(hir::map::NodeForeignItem(..)) => true,
Some(..) => false,
None => self.tcx.sess.cstore.is_foreign_item(def_id),
} {
self.require_unsafe_ext(expr.id, expr.span, "use of extern static", true);
}
}
}
hir::ExprField(ref base_expr, field) => {
if let ty::TyAdt(adt, ..) = self.tables.expr_ty_adjusted(base_expr).sty {
if adt.is_union() {
self.require_unsafe(field.span, "access to union field");
}
}
}
_ => {}
}
intravisit::walk_expr(self, expr);
}
fn visit_pat(&mut self, pat: &'tcx hir::Pat) {
if let PatKind::Struct(_, ref fields, _) = pat.node {
if let ty::TyAdt(adt, ..) = self.tables.pat_ty(pat).sty {
if adt.is_union() {
for field in fields {
self.require_unsafe(field.span, "matching on union field");
}
}
}
}
intravisit::walk_pat(self, pat);
}
}
pub fn check_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) {
let mut visitor = EffectCheckVisitor {
tcx: tcx,
tables: &ty::TypeckTables::empty(),
unsafe_context: UnsafeContext::new(SafeContext),
};
tcx.hir.krate().visit_all_item_likes(&mut visitor.as_deep_visitor());
}