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// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! Enforces the Rust effect system. Currently there is just one effect,
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/// `unsafe`.
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use middle::ty;
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use middle::typeck::{MethodCall, MethodMap};
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use util::ppaux;
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use syntax::ast;
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use syntax::codemap::Span;
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use syntax::visit;
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use syntax::visit::Visitor;
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#[deriving(Eq)]
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enum UnsafeContext {
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SafeContext,
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UnsafeFn,
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UnsafeBlock(ast::NodeId),
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}
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fn type_is_unsafe_function(ty: ty::t) -> bool {
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match ty::get(ty).sty {
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ty::ty_bare_fn(ref f) => f.purity == ast::UnsafeFn,
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ty::ty_closure(ref f) => f.purity == ast::UnsafeFn,
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_ => false,
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}
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}
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struct EffectCheckVisitor<'a> {
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tcx: &'a ty::ctxt,
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/// The method map.
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method_map: MethodMap,
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/// Whether we're in an unsafe context.
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unsafe_context: UnsafeContext,
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}
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impl<'a> EffectCheckVisitor<'a> {
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fn require_unsafe(&mut self, span: Span, description: &str) {
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match self.unsafe_context {
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SafeContext => {
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// Report an error.
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self.tcx.sess.span_err(span,
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format!("{} requires unsafe function or block",
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description))
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}
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UnsafeBlock(block_id) => {
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// OK, but record this.
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debug!("effect: recording unsafe block as used: {:?}", block_id);
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self.tcx.used_unsafe.borrow_mut().insert(block_id);
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}
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UnsafeFn => {}
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}
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}
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fn check_str_index(&mut self, e: @ast::Expr) {
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let base_type = match e.node {
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ast::ExprIndex(base, _) => ty::node_id_to_type(self.tcx, base.id),
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_ => return
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};
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debug!("effect: checking index with base type {}",
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ppaux::ty_to_str(self.tcx, base_type));
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match ty::get(base_type).sty {
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ty::ty_str(..) => {
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self.tcx.sess.span_err(e.span,
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"modification of string types is not allowed");
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}
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_ => {}
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}
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}
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}
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impl<'a> Visitor<()> for EffectCheckVisitor<'a> {
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fn visit_fn(&mut self, fn_kind: &visit::FnKind, fn_decl: &ast::FnDecl,
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block: &ast::Block, span: Span, node_id: ast::NodeId, _:()) {
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let (is_item_fn, is_unsafe_fn) = match *fn_kind {
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visit::FkItemFn(_, _, purity, _) =>
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(true, purity == ast::UnsafeFn),
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visit::FkMethod(_, _, method) =>
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(true, method.purity == ast::UnsafeFn),
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_ => (false, false),
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};
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let old_unsafe_context = self.unsafe_context;
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if is_unsafe_fn {
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self.unsafe_context = UnsafeFn
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} else if is_item_fn {
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self.unsafe_context = SafeContext
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}
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visit::walk_fn(self, fn_kind, fn_decl, block, span, node_id, ());
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self.unsafe_context = old_unsafe_context
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}
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fn visit_block(&mut self, block: &ast::Block, _:()) {
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let old_unsafe_context = self.unsafe_context;
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match block.rules {
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ast::DefaultBlock => {}
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ast::UnsafeBlock(source) => {
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// By default only the outermost `unsafe` block is
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// "used" and so nested unsafe blocks are pointless
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// (the inner ones are unnecessary and we actually
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// warn about them). As such, there are two cases when
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// we need to create a new context, when we're
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// - outside `unsafe` and found a `unsafe` block
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// (normal case)
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// - inside `unsafe` but found an `unsafe` block
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// created internally to the compiler
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//
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// The second case is necessary to ensure that the
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// compiler `unsafe` blocks don't accidentally "use"
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// external blocks (e.g. `unsafe { println("") }`,
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// expands to `unsafe { ... unsafe { ... } }` where
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// the inner one is compiler generated).
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if self.unsafe_context == SafeContext || source == ast::CompilerGenerated {
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self.unsafe_context = UnsafeBlock(block.id)
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}
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}
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}
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visit::walk_block(self, block, ());
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self.unsafe_context = old_unsafe_context
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}
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fn visit_expr(&mut self, expr: &ast::Expr, _:()) {
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match expr.node {
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ast::ExprMethodCall(_, _, _) => {
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let method_call = MethodCall::expr(expr.id);
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let base_type = self.method_map.borrow().get(&method_call).ty;
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debug!("effect: method call case, base type is {}",
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ppaux::ty_to_str(self.tcx, base_type));
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if type_is_unsafe_function(base_type) {
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self.require_unsafe(expr.span,
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"invocation of unsafe method")
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}
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}
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ast::ExprCall(base, _) => {
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let base_type = ty::node_id_to_type(self.tcx, base.id);
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debug!("effect: call case, base type is {}",
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ppaux::ty_to_str(self.tcx, base_type));
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if type_is_unsafe_function(base_type) {
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self.require_unsafe(expr.span, "call to unsafe function")
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}
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}
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ast::ExprUnary(ast::UnDeref, base) => {
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let base_type = ty::node_id_to_type(self.tcx, base.id);
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debug!("effect: unary case, base type is {}",
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ppaux::ty_to_str(self.tcx, base_type));
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match ty::get(base_type).sty {
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ty::ty_ptr(_) => {
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self.require_unsafe(expr.span,
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"dereference of unsafe pointer")
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}
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_ => {}
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}
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}
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ast::ExprAssign(base, _) | ast::ExprAssignOp(_, base, _) => {
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self.check_str_index(base);
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}
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ast::ExprAddrOf(ast::MutMutable, base) => {
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self.check_str_index(base);
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}
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ast::ExprInlineAsm(..) => {
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self.require_unsafe(expr.span, "use of inline assembly")
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}
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ast::ExprPath(..) => {
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match ty::resolve_expr(self.tcx, expr) {
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ast::DefStatic(_, true) => {
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self.require_unsafe(expr.span, "use of mutable static")
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}
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_ => {}
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}
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}
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_ => {}
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}
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visit::walk_expr(self, expr, ());
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}
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}
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pub fn check_crate(tcx: &ty::ctxt, method_map: MethodMap, krate: &ast::Crate) {
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let mut visitor = EffectCheckVisitor {
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tcx: tcx,
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method_map: method_map,
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unsafe_context: SafeContext,
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};
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visit::walk_crate(&mut visitor, krate, ());
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}
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