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Forbid modifications of strings in the compiler

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This disallows `str[0] = foo` along with `foo = &mut str[i]` to prevent strings
from being modified at runtime (except possibly through the `str` module)

Closes #8891
This commit is contained in:
Alex Crichton 2013-10-07 14:25:30 -07:00
parent 8eb28bb7dc
commit a69e4a55eb
2 changed files with 119 additions and 97 deletions
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198
src/librustc/middle/effect.rs
View File

@ -11,19 +11,14 @@
//! Enforces the Rust effect system. Currently there is just one effect,
/// `unsafe`.
use middle::ty::{ty_bare_fn, ty_closure, ty_ptr};
use middle::ty;
use middle::typeck::method_map;
use util::ppaux;
use syntax::ast::{UnDeref, ExprCall, ExprInlineAsm, ExprMethodCall};
use syntax::ast::{ExprUnary, unsafe_fn, ExprPath};
use syntax::ast;
use syntax::codemap::Span;
use syntax::visit::{fk_item_fn, fk_method};
use syntax::visit;
use syntax::visit::{Visitor,fn_kind};
use syntax::ast::{fn_decl,Block,NodeId,Expr};
use syntax::visit::Visitor;
#[deriving(Eq)]
enum UnsafeContext {
@ -32,29 +27,26 @@ enum UnsafeContext {
UnsafeBlock(ast::NodeId),
}
struct Context {
/// The method map.
method_map: method_map,
/// Whether we're in an unsafe context.
unsafe_context: UnsafeContext,
}
fn type_is_unsafe_function(ty: ty::t) -> bool {
match ty::get(ty).sty {
ty_bare_fn(ref f) => f.purity == unsafe_fn,
ty_closure(ref f) => f.purity == unsafe_fn,
ty::ty_bare_fn(ref f) => f.purity == ast::unsafe_fn,
ty::ty_closure(ref f) => f.purity == ast::unsafe_fn,
_ => false,
}
}
struct EffectCheckVisitor {
tcx: ty::ctxt,
context: @mut Context,
/// The method map.
method_map: method_map,
/// Whether we're in an unsafe context.
unsafe_context: UnsafeContext,
}
impl EffectCheckVisitor {
fn require_unsafe(&mut self, span: Span, description: &str) {
match self.context.unsafe_context {
match self.unsafe_context {
SafeContext => {
// Report an error.
self.tcx.sess.span_err(span,
@ -69,113 +61,125 @@ impl EffectCheckVisitor {
UnsafeFn => {}
}
}
fn check_str_index(&mut self, e: @ast::Expr) {
let base_type = match e.node {
ast::ExprIndex(_, base, _) => ty::node_id_to_type(self.tcx, base.id),
_ => return
};
debug2!("effect: checking index with base type {}",
ppaux::ty_to_str(self.tcx, base_type));
match ty::get(base_type).sty {
ty::ty_estr(*) => {
self.tcx.sess.span_err(e.span,
"modification of string types is not allowed");
}
_ => {}
}
}
}
impl Visitor<()> for EffectCheckVisitor {
fn visit_fn(&mut self, fn_kind:&fn_kind, fn_decl:&fn_decl,
block:&Block, span:Span, node_id:NodeId, _:()) {
fn visit_fn(&mut self, fn_kind: &visit::fn_kind, fn_decl: &ast::fn_decl,
block: &ast::Block, span: Span, node_id: ast::NodeId, _:()) {
let (is_item_fn, is_unsafe_fn) = match *fn_kind {
fk_item_fn(_, _, purity, _) => (true, purity == unsafe_fn),
fk_method(_, _, method) => (true, method.purity == unsafe_fn),
_ => (false, false),
};
let (is_item_fn, is_unsafe_fn) = match *fn_kind {
visit::fk_item_fn(_, _, purity, _) =>
(true, purity == ast::unsafe_fn),
visit::fk_method(_, _, method) =>
(true, method.purity == ast::unsafe_fn),
_ => (false, false),
};
let old_unsafe_context = self.context.unsafe_context;
if is_unsafe_fn {
self.context.unsafe_context = UnsafeFn
} else if is_item_fn {
self.context.unsafe_context = SafeContext
}
let old_unsafe_context = self.unsafe_context;
if is_unsafe_fn {
self.unsafe_context = UnsafeFn
} else if is_item_fn {
self.unsafe_context = SafeContext
}
visit::walk_fn(self,
fn_kind,
fn_decl,
block,
span,
node_id,
());
visit::walk_fn(self, fn_kind, fn_decl, block, span, node_id, ());
self.context.unsafe_context = old_unsafe_context
self.unsafe_context = old_unsafe_context
}
fn visit_block(&mut self, block:&Block, _:()) {
fn visit_block(&mut self, block: &ast::Block, _:()) {
let old_unsafe_context = self.unsafe_context;
let is_unsafe = match block.rules {
ast::UnsafeBlock(*) => true, ast::DefaultBlock => false
};
if is_unsafe && self.unsafe_context == SafeContext {
self.unsafe_context = UnsafeBlock(block.id)
}
let old_unsafe_context = self.context.unsafe_context;
let is_unsafe = match block.rules {
ast::UnsafeBlock(*) => true, ast::DefaultBlock => false
};
if is_unsafe && self.context.unsafe_context == SafeContext {
self.context.unsafe_context = UnsafeBlock(block.id)
}
visit::walk_block(self, block, ());
visit::walk_block(self, block, ());
self.context.unsafe_context = old_unsafe_context
self.unsafe_context = old_unsafe_context
}
fn visit_expr(&mut self, expr:@Expr, _:()) {
match expr.node {
ExprMethodCall(callee_id, _, _, _, _, _) => {
let base_type = ty::node_id_to_type(self.tcx, callee_id);
debug2!("effect: method call case, base type is {}",
ppaux::ty_to_str(self.tcx, base_type));
if type_is_unsafe_function(base_type) {
fn visit_expr(&mut self, expr: @ast::Expr, _:()) {
match expr.node {
ast::ExprMethodCall(callee_id, _, _, _, _, _) => {
let base_type = ty::node_id_to_type(self.tcx, callee_id);
debug2!("effect: method call case, base type is {}",
ppaux::ty_to_str(self.tcx, base_type));
if type_is_unsafe_function(base_type) {
self.require_unsafe(expr.span,
"invocation of unsafe method")
}
}
ast::ExprCall(base, _, _) => {
let base_type = ty::node_id_to_type(self.tcx, base.id);
debug2!("effect: call case, base type is {}",
ppaux::ty_to_str(self.tcx, base_type));
if type_is_unsafe_function(base_type) {
self.require_unsafe(expr.span, "call to unsafe function")
}
}
ast::ExprUnary(_, ast::UnDeref, base) => {
let base_type = ty::node_id_to_type(self.tcx, base.id);
debug2!("effect: unary case, base type is {}",
ppaux::ty_to_str(self.tcx, base_type));
match ty::get(base_type).sty {
ty::ty_ptr(_) => {
self.require_unsafe(expr.span,
"invocation of unsafe method")
"dereference of unsafe pointer")
}
_ => {}
}
ExprCall(base, _, _) => {
let base_type = ty::node_id_to_type(self.tcx, base.id);
debug2!("effect: call case, base type is {}",
ppaux::ty_to_str(self.tcx, base_type));
if type_is_unsafe_function(base_type) {
self.require_unsafe(expr.span, "call to unsafe function")
}
}
ExprUnary(_, UnDeref, base) => {
let base_type = ty::node_id_to_type(self.tcx, base.id);
debug2!("effect: unary case, base type is {}",
ppaux::ty_to_str(self.tcx, base_type));
match ty::get(base_type).sty {
ty_ptr(_) => {
self.require_unsafe(expr.span,
"dereference of unsafe pointer")
}
_ => {}
}
}
ExprInlineAsm(*) => {
self.require_unsafe(expr.span, "use of inline assembly")
}
ExprPath(*) => {
match ty::resolve_expr(self.tcx, expr) {
ast::DefStatic(_, true) => {
self.require_unsafe(expr.span, "use of mutable static")
}
_ => {}
}
}
_ => {}
}
ast::ExprAssign(base, _) | ast::ExprAssignOp(_, _, base, _) => {
self.check_str_index(base);
}
ast::ExprAddrOf(ast::MutMutable, base) => {
self.check_str_index(base);
}
ast::ExprInlineAsm(*) => {
self.require_unsafe(expr.span, "use of inline assembly")
}
ast::ExprPath(*) => {
match ty::resolve_expr(self.tcx, expr) {
ast::DefStatic(_, true) => {
self.require_unsafe(expr.span, "use of mutable static")
}
_ => {}
}
}
_ => {}
}
visit::walk_expr(self, expr, ());
visit::walk_expr(self, expr, ());
}
}
pub fn check_crate(tcx: ty::ctxt,
method_map: method_map,
crate: &ast::Crate) {
let context = @mut Context {
let mut visitor = EffectCheckVisitor {
tcx: tcx,
method_map: method_map,
unsafe_context: SafeContext,
};
let mut visitor = EffectCheckVisitor {
tcx: tcx,
context: context,
};
visit::walk_crate(&mut visitor, crate, ());
}

18
src/test/compile-fail/unsafe-modifying-str.rs Normal file
View File

@ -0,0 +1,18 @@
// Copyright 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.
fn main() {
let mut s = ~"test";
s[0] = 3; //~ ERROR: not allowed
s[0] += 3; //~ ERROR: not allowed
{
let _a = &mut s[0]; //~ ERROR: not allowed
}
}