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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
use syntax::{ast, codemap, visit};
use syntax::attr::AttrMetaMethods;
use rustc::ast_map;
use rustc::lint::{Context, LintPass, LintArray};
use rustc::middle::ty::expr_ty;
use rustc::middle::{ty, def};
use rustc::util::ppaux::Repr;
use utils::unsafe_context;
declare_lint!(UNROOTED_MUST_ROOT, Deny,
"Warn and report usage of unrooted jsmanaged objects");
/// Lint for ensuring safe usage of unrooted pointers
///
/// This lint (disable with `-A unrooted-must-root`/`#[allow(unrooted_must_root)]`) ensures that `#[must_root]`
/// values are used correctly.
///
/// "Incorrect" usage includes:
///
/// - Not being used in a struct/enum field which is not `#[must_root]` itself
/// - Not being used as an argument to a function (Except onces named `new` and `new_inherited`)
/// - Not being bound locally in a `let` statement, assignment, `for` loop, or `match` statement.
///
/// This helps catch most situations where pointers like `JS<T>` are used in a way that they can be invalidated by a
/// GC pass.
pub struct UnrootedPass;
// Checks if a type has the #[must_root] annotation.
// Unwraps pointers as well
// TODO (#3874, sort of): unwrap other types like Vec/Option/HashMap/etc
fn lint_unrooted_ty(cx: &Context, ty: &ast::Ty, warning: &str) {
match ty.node {
ast::TyVec(ref t) | ast::TyFixedLengthVec(ref t, _) |
ast::TyPtr(ast::MutTy { ty: ref t, ..}) | ast::TyRptr(_, ast::MutTy { ty: ref t, ..}) =>
lint_unrooted_ty(cx, &**t, warning),
ast::TyPath(..) => {
match cx.tcx.def_map.borrow()[&ty.id] {
def::PathResolution{ base_def: def::DefTy(def_id, _), .. } => {
if ty::has_attr(cx.tcx, def_id, "must_root") {
cx.span_lint(UNROOTED_MUST_ROOT, ty.span, warning);
}
}
_ => (),
}
}
_ => (),
};
}
impl LintPass for UnrootedPass {
fn get_lints(&self) -> LintArray {
lint_array!(UNROOTED_MUST_ROOT)
}
/// All structs containing #[must_root] types must be #[must_root] themselves
fn check_struct_def(&mut self,
cx: &Context,
def: &ast::StructDef,
_i: ast::Ident,
_gen: &ast::Generics,
id: ast::NodeId) {
let item = match cx.tcx.map.get(id) {
ast_map::Node::NodeItem(item) => item,
_ => cx.tcx.map.expect_item(cx.tcx.map.get_parent(id)),
};
if item.attrs.iter().all(|a| !a.check_name("must_root")) {
for ref field in def.fields.iter() {
lint_unrooted_ty(cx, &*field.node.ty,
"Type must be rooted, use #[must_root] on the struct definition to propagate");
}
}
}
/// All enums containing #[must_root] types must be #[must_root] themselves
fn check_variant(&mut self, cx: &Context, var: &ast::Variant, _gen: &ast::Generics) {
let ref map = cx.tcx.map;
if map.expect_item(map.get_parent(var.node.id)).attrs.iter().all(|a| !a.check_name("must_root")) {
match var.node.kind {
ast::TupleVariantKind(ref vec) => {
for ty in vec.iter() {
lint_unrooted_ty(cx, &*ty.ty,
"Type must be rooted, use #[must_root] on the enum definition to propagate")
}
}
_ => () // Struct variants already caught by check_struct_def
}
}
}
/// Function arguments that are #[must_root] types are not allowed
fn check_fn(&mut self, cx: &Context, kind: visit::FnKind, decl: &ast::FnDecl,
block: &ast::Block, _span: codemap::Span, id: ast::NodeId) {
match kind {
visit::FkItemFn(i, _, _, _, _, _) |
visit::FkMethod(i, _, _) if i.as_str() == "new" || i.as_str() == "new_inherited" => {
return;
},
visit::FkItemFn(_, _, style, _, _, _) => match style {
ast::Unsafety::Unsafe => return,
_ => ()
},
_ => ()
}
if unsafe_context(&cx.tcx.map, id) {
return;
}
match block.rules {
ast::DefaultBlock => {
for arg in decl.inputs.iter() {
lint_unrooted_ty(cx, &*arg.ty,
"Type must be rooted")
}
}
_ => () // fn is `unsafe`
}
}
// Partially copied from rustc::middle::lint::builtin
// Catches `let` statements and assignments which store a #[must_root] value
// Expressions which return out of blocks eventually end up in a `let` or assignment
// statement or a function return (which will be caught when it is used elsewhere)
fn check_stmt(&mut self, cx: &Context, s: &ast::Stmt) {
match s.node {
ast::StmtDecl(_, id) |
ast::StmtExpr(_, id) |
ast::StmtSemi(_, id) if unsafe_context(&cx.tcx.map, id) => {
return
},
_ => ()
};
let expr = match s.node {
// Catch a `let` binding
ast::StmtDecl(ref decl, _) => match decl.node {
ast::DeclLocal(ref loc) => match loc.init {
Some(ref e) => &**e,
_ => return
},
_ => return
},
ast::StmtExpr(ref expr, _) => match expr.node {
// This catches deferred `let` statements
ast::ExprAssign(_, ref e) |
// Match statements allow you to bind onto the variable later in an arm
// We need not check arms individually since enum/struct fields are already
// linted in `check_struct_def` and `check_variant`
// (so there is no way of destructuring out a `#[must_root]` field)
ast::ExprMatch(ref e, _, _) |
// For loops allow you to bind a return value locally
ast::ExprForLoop(_, ref e, _, _) => &**e,
// XXXManishearth look into `if let` once it lands in our rustc
_ => return
},
_ => return
};
let t = expr_ty(cx.tcx, &*expr);
match t.sty {
ty::TyStruct(did, _) |
ty::TyEnum(did, _) => {
if ty::has_attr(cx.tcx, did, "must_root") {
cx.span_lint(UNROOTED_MUST_ROOT, expr.span,
&format!("Expression of type {} must be rooted", t.repr(cx.tcx)));
}
}
_ => {}
}
}
}
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