634 lines
21 KiB
Rust
634 lines
21 KiB
Rust
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import syntax::{ast, ast_util};
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import ast::{ident, fn_ident, node_id, def_id};
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import mut::{expr_root, mut_field, deref, field, index, unbox};
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import syntax::codemap::span;
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import syntax::visit;
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import visit::vt;
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import std::{vec, str, option};
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import std::option::{some, none, is_none};
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// This is not an alias-analyser (though it would merit from becoming one, or
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// getting input from one, to be more precise). It is a pass that checks
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// whether aliases are used in a safe way.
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tag valid { valid; overwritten(span, ast::path); val_taken(span, ast::path); }
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tag copied { not_allowed; copied; not_copied; }
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type binding = @{node_id: node_id,
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span: span,
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local_id: uint,
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root_var: option::t<node_id>,
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unsafe_tys: [ty::t],
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mutable ok: valid,
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mutable copied: copied};
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type scope = {bs: [binding], ret_style: ast::ret_style};
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fn mk_binding(cx: ctx, id: node_id, span: span, root_var: option::t<node_id>,
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unsafe: [ty::t]) -> binding {
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ret @{node_id: id, span: span, local_id: cx.next_local,
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root_var: root_var, unsafe_tys: unsafe,
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mutable ok: valid, mutable copied: not_copied};
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}
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tag local_info { local(uint); }
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type copy_map = std::map::hashmap<node_id, ()>;
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type ctx = {tcx: ty::ctxt,
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local_map: std::map::hashmap<node_id, local_info>,
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mutable next_local: uint,
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copy_map: copy_map};
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fn check_crate(tcx: ty::ctxt, crate: @ast::crate) -> copy_map {
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// Stores information about object fields and function
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// arguments that's otherwise not easily available.
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let cx = @{tcx: tcx,
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local_map: std::map::new_int_hash(),
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mutable next_local: 0u,
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copy_map: std::map::new_int_hash()};
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let v = @{visit_fn: bind visit_fn(cx, _, _, _, _, _, _, _),
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visit_expr: bind visit_expr(cx, _, _, _),
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visit_decl: bind visit_decl(cx, _, _, _)
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with *visit::default_visitor::<scope>()};
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visit::visit_crate(*crate, {bs: [], ret_style: ast::return_val},
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visit::mk_vt(v));
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tcx.sess.abort_if_errors();
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ret cx.copy_map;
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}
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fn visit_fn(cx: @ctx, f: ast::_fn, _tp: [ast::ty_param], _sp: span,
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_name: fn_ident, _id: ast::node_id, sc: scope, v: vt<scope>) {
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visit::visit_fn_decl(f.decl, sc, v);
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let bs = alt f.proto {
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// Blocks need to obey any restrictions from the enclosing scope.
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ast::proto_block. | ast::proto_closure. { sc.bs }
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// Non capturing functions start out fresh.
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_ { [] }
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};
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if f.decl.cf == ast::return_ref && !is_none(f.body.node.expr) {
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// FIXME this will be easier to lift once have DPS
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cx.tcx.sess.span_err(option::get(f.body.node.expr).span,
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"reference-returning functions may not " +
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"return implicitly");
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}
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v.visit_block(f.body, {bs: bs, ret_style: f.decl.cf}, v);
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}
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fn visit_expr(cx: @ctx, ex: @ast::expr, sc: scope, v: vt<scope>) {
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let handled = true;
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alt ex.node {
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ast::expr_call(f, args) {
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check_call(*cx, f, args);
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handled = false;
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}
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ast::expr_alt(input, arms) { check_alt(*cx, input, arms, sc, v); }
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ast::expr_put(val) {
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alt val {
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some(ex) {
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let root = expr_root(cx.tcx, ex, false);
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if mut_field(root.ds) {
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cx.tcx.sess.span_err(ex.span,
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"result of put must be" +
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" immutably rooted");
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}
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visit_expr(cx, ex, sc, v);
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}
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_ { }
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}
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}
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ast::expr_for_each(decl, call, blk) {
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check_for_each(*cx, decl, call, blk, sc, v);
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}
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ast::expr_for(decl, seq, blk) { check_for(*cx, decl, seq, blk, sc, v); }
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ast::expr_path(pt) {
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check_var(*cx, ex, pt, ex.id, false, sc);
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handled = false;
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}
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ast::expr_swap(lhs, rhs) {
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check_lval(cx, lhs, sc, v);
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check_lval(cx, rhs, sc, v);
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handled = false;
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}
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ast::expr_move(dest, src) {
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check_assign(cx, dest, src, sc, v);
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check_lval(cx, src, sc, v);
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}
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ast::expr_assign(dest, src) | ast::expr_assign_op(_, dest, src) {
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check_assign(cx, dest, src, sc, v);
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}
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ast::expr_ret(oexpr) {
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if sc.ret_style == ast::return_ref && !is_none(oexpr) {
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check_ret_ref(*cx, sc, option::get(oexpr));
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}
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handled = false;
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}
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_ { handled = false; }
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}
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if !handled { visit::visit_expr(ex, sc, v); }
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}
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fn register_locals(cx: ctx, pat: @ast::pat) {
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for each pat in ast_util::pat_bindings(pat) {
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cx.local_map.insert(pat.id, local(cx.next_local));
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cx.next_local += 1u;
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}
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}
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fn visit_decl(cx: @ctx, d: @ast::decl, sc: scope, v: vt<scope>) {
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visit::visit_decl(d, sc, v);
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alt d.node {
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ast::decl_local(locs) {
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for loc: @ast::local in locs {
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alt loc.node.init {
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some(init) {
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if init.op == ast::init_move {
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check_lval(cx, init.expr, sc, v);
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}
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}
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none. { }
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}
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register_locals(*cx, loc.node.pat);
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}
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}
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_ { }
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}
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}
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fn cant_copy(cx: ctx, b: binding) -> bool {
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alt b.copied {
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not_allowed. { ret true; }
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copied. { ret false; }
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not_copied. {}
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}
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let ty = ty::node_id_to_type(cx.tcx, b.node_id);
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if ty::type_allows_implicit_copy(cx.tcx, ty) {
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b.copied = copied;
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cx.copy_map.insert(b.node_id, ());
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if copy_is_expensive(cx.tcx, ty) {
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cx.tcx.sess.span_warn(b.span,
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"inserting an implicit copy for type " +
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util::ppaux::ty_to_str(cx.tcx, ty));
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}
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ret false;
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} else { ret true; }
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}
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fn check_call(cx: ctx, f: @ast::expr, args: [@ast::expr]) -> [binding] {
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let fty = ty::type_autoderef(cx.tcx, ty::expr_ty(cx.tcx, f));
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let ret_ref = ty::ty_fn_ret_style(cx.tcx, fty) == ast::return_ref;
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let arg_ts = ty::ty_fn_args(cx.tcx, fty);
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let mut_roots: [{arg: uint, node: node_id}] = [];
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let bindings = [];
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let i = 0u;
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for arg_t: ty::arg in arg_ts {
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let arg = args[i];
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let root = expr_root(cx.tcx, arg, false);
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if arg_t.mode == ast::by_mut_ref {
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alt path_def(cx, arg) {
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some(def) {
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let dnum = ast_util::def_id_of_def(def).node;
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mut_roots += [{arg: i, node: dnum}];
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}
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_ { }
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}
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}
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let root_var = path_def_id(cx, root.ex);
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let new_bnd = mk_binding(cx, arg.id, arg.span, root_var,
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inner_mut(root.ds));
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new_bnd.copied = alt arg_t.mode {
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ast::by_move. { copied }
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ast::by_ref. { ret_ref ? not_allowed : not_copied }
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ast::by_mut_ref. { not_allowed }
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};
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bindings += [new_bnd];
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i += 1u;
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}
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let f_may_close =
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alt f.node {
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ast::expr_path(_) { def_is_local(cx.tcx.def_map.get(f.id), true) }
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_ { true }
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};
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if f_may_close {
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let i = 0u;
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for b in bindings {
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if vec::len(b.unsafe_tys) > 0u && cant_copy(cx, b) {
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cx.tcx.sess.span_err(f.span,
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#fmt["function may alias with argument \
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%u, which is not immutably rooted",
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i]);
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}
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i += 1u;
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}
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}
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let j = 0u;
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for b in bindings {
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for ty in b.unsafe_tys {
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let i = 0u;
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for arg_t: ty::arg in arg_ts {
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let mut_alias = arg_t.mode == ast::by_mut_ref;
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if i != j &&
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ty_can_unsafely_include(cx, ty, arg_t.ty, mut_alias) &&
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cant_copy(cx, b) {
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cx.tcx.sess.span_err
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(args[i].span,
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#fmt["argument %u may alias with argument %u, \
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which is not immutably rooted",
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i, j]);
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}
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i += 1u;
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}
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}
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j += 1u;
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}
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// Ensure we're not passing a root by mutable alias.
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for {node: node, arg: arg} in mut_roots {
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let i = 0u;
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for b in bindings {
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if i != arg {
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alt b.root_var {
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some(root) {
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if node == root && cant_copy(cx, b) {
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cx.tcx.sess.span_err
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(args[arg].span,
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"passing a mutable reference to a \
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variable that roots another reference");
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break;
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}
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}
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none. { }
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}
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}
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i += 1u;
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}
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}
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ret bindings;
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}
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fn check_ret_ref(cx: ctx, sc: scope, expr: @ast::expr) {
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let root = expr_root(cx.tcx, expr, false);
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let bad = none;
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let mut_field = mut_field(root.ds);
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alt path_def(cx, root.ex) {
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none. { bad = some("temporary"); }
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some(ast::def_local(did)) | some(ast::def_binding(did)) |
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some(ast::def_arg(did, _)) {
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let cur_node = did.node;
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while true {
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alt cx.tcx.items.find(cur_node) {
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some(ast_map::node_arg(arg)) {
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if arg.mode == ast::by_move {
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bad = some("move-mode parameter");
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}
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break;
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}
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_ {}
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}
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alt vec::find({|b| b.node_id == cur_node}, sc.bs) {
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some(b) {
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if vec::len(b.unsafe_tys) > 0u {
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mut_field = true;
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break;
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}
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if is_none(b.root_var) {
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bad = some("function-local value");
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break;
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}
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if b.copied == copied {
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bad = some("implicitly copied reference");
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break;
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}
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b.copied = not_allowed;
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cur_node = option::get(b.root_var);
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}
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none. {
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bad = some("function-local value");
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break;
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}
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}
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}
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}
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// FIXME allow references to constants and static items?
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_ { bad = some("non-local value"); }
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}
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if mut_field { bad = some("mutable field"); }
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alt bad {
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some(name) {
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cx.tcx.sess.span_err(expr.span, "can not return a reference " +
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"to a " + name);
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}
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_ {}
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}
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}
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fn check_alt(cx: ctx, input: @ast::expr, arms: [ast::arm], sc: scope,
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v: vt<scope>) {
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v.visit_expr(input, sc, v);
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let root = expr_root(cx.tcx, input, true);
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for a: ast::arm in arms {
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let new_bs = sc.bs;
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let root_var = path_def_id(cx, root.ex);
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let pat_id_map = ast_util::pat_id_map(a.pats[0]);
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type info = {id: node_id, mutable unsafe: [ty::t], span: span};
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let binding_info: [info] = [];
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for pat in a.pats {
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for proot in *pattern_roots(cx.tcx, *root.ds, pat) {
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let canon_id = pat_id_map.get(proot.name);
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// FIXME I wanted to use a block, but that hit a
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// typestate bug.
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fn match(x: info, canon: node_id) -> bool { x.id == canon }
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alt vec::find(bind match(_, canon_id), binding_info) {
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some(s) { s.unsafe += inner_mut(proot.ds); }
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none. {
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binding_info += [{id: canon_id,
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mutable unsafe: inner_mut(proot.ds),
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span: proot.span}];
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}
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}
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}
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}
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for info in binding_info {
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new_bs += [mk_binding(cx, info.id, info.span, root_var,
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copy info.unsafe)];
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}
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register_locals(cx, a.pats[0]);
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visit::visit_arm(a, {bs: new_bs with sc}, v);
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}
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}
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fn check_for_each(cx: ctx, local: @ast::local, call: @ast::expr,
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blk: ast::blk, sc: scope, v: vt<scope>) {
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v.visit_expr(call, sc, v);
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alt call.node {
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ast::expr_call(f, args) {
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let new_bs = sc.bs + check_call(cx, f, args);
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for proot in *pattern_roots(cx.tcx, [], local.node.pat) {
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new_bs += [mk_binding(cx, proot.id, proot.span, none,
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inner_mut(proot.ds))];
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}
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register_locals(cx, local.node.pat);
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visit::visit_block(blk, {bs: new_bs with sc}, v);
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}
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}
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}
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fn check_for(cx: ctx, local: @ast::local, seq: @ast::expr, blk: ast::blk,
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sc: scope, v: vt<scope>) {
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v.visit_expr(seq, sc, v);
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let root = expr_root(cx.tcx, seq, false);
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// If this is a mutable vector, don't allow it to be touched.
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let seq_t = ty::expr_ty(cx.tcx, seq);
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let ext_ds = *root.ds;
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alt ty::struct(cx.tcx, seq_t) {
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ty::ty_vec(mt) {
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if mt.mut != ast::imm {
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ext_ds += [@{mut: true, kind: index, outer_t: seq_t}];
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}
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}
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_ {}
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}
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let root_var = path_def_id(cx, root.ex);
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let new_bs = sc.bs;
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for proot in *pattern_roots(cx.tcx, ext_ds, local.node.pat) {
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new_bs += [mk_binding(cx, proot.id, proot.span, root_var,
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inner_mut(proot.ds))];
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}
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register_locals(cx, local.node.pat);
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visit::visit_block(blk, {bs: new_bs with sc}, v);
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}
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fn check_var(cx: ctx, ex: @ast::expr, p: ast::path, id: ast::node_id,
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assign: bool, sc: scope) {
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let def = cx.tcx.def_map.get(id);
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if !def_is_local(def, true) { ret; }
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let my_defnum = ast_util::def_id_of_def(def).node;
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let my_local_id =
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alt cx.local_map.find(my_defnum) { some(local(id)) { id } _ { 0u } };
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let var_t = ty::expr_ty(cx.tcx, ex);
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for b in sc.bs {
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// excludes variables introduced since the alias was made
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if my_local_id < b.local_id {
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for ty in b.unsafe_tys {
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if ty_can_unsafely_include(cx, ty, var_t, assign) {
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b.ok = val_taken(ex.span, p);
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}
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}
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} else if b.node_id == my_defnum {
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test_scope(cx, sc, b, p);
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}
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}
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}
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fn check_lval(cx: @ctx, dest: @ast::expr, sc: scope, v: vt<scope>) {
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alt dest.node {
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ast::expr_path(p) {
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let def = cx.tcx.def_map.get(dest.id);
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let dnum = ast_util::def_id_of_def(def).node;
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for b in sc.bs {
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if b.root_var == some(dnum) { b.ok = overwritten(dest.span, p); }
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}
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}
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_ { visit_expr(cx, dest, sc, v); }
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}
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}
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fn check_assign(cx: @ctx, dest: @ast::expr, src: @ast::expr, sc: scope,
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v: vt<scope>) {
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visit_expr(cx, src, sc, v);
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check_lval(cx, dest, sc, v);
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}
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fn test_scope(cx: ctx, sc: scope, b: binding, p: ast::path) {
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let prob = b.ok;
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alt b.root_var {
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some(dn) {
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for other in sc.bs {
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if other.node_id == dn {
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prob = other.ok;
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if prob != valid { break; }
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}
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}
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}
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_ {}
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}
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if prob != valid && cant_copy(cx, b) {
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let msg = alt prob {
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overwritten(sp, wpt) {
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{span: sp, msg: "overwriting " + ast_util::path_name(wpt)}
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}
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val_taken(sp, vpt) {
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{span: sp,
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msg: "taking the value of " + ast_util::path_name(vpt)}
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}
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};
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cx.tcx.sess.span_err(msg.span,
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msg.msg + " will invalidate reference " +
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ast_util::path_name(p) +
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", which is still used");
|
|
}
|
|
}
|
|
|
|
fn path_def(cx: ctx, ex: @ast::expr) -> option::t<ast::def> {
|
|
ret alt ex.node {
|
|
ast::expr_path(_) { some(cx.tcx.def_map.get(ex.id)) }
|
|
_ { none }
|
|
}
|
|
}
|
|
|
|
fn path_def_id(cx: ctx, ex: @ast::expr) -> option::t<ast::node_id> {
|
|
alt ex.node {
|
|
ast::expr_path(_) {
|
|
ret some(ast_util::def_id_of_def(cx.tcx.def_map.get(ex.id)).node);
|
|
}
|
|
_ { ret none; }
|
|
}
|
|
}
|
|
|
|
fn ty_can_unsafely_include(cx: ctx, needle: ty::t, haystack: ty::t, mut: bool)
|
|
-> bool {
|
|
fn get_mut(cur: bool, mt: ty::mt) -> bool {
|
|
ret cur || mt.mut != ast::imm;
|
|
}
|
|
fn helper(tcx: ty::ctxt, needle: ty::t, haystack: ty::t, mut: bool) ->
|
|
bool {
|
|
if needle == haystack { ret true; }
|
|
alt ty::struct(tcx, haystack) {
|
|
ty::ty_tag(_, ts) {
|
|
for t: ty::t in ts {
|
|
if helper(tcx, needle, t, mut) { ret true; }
|
|
}
|
|
ret false;
|
|
}
|
|
ty::ty_box(mt) | ty::ty_ptr(mt) {
|
|
ret helper(tcx, needle, mt.ty, get_mut(mut, mt));
|
|
}
|
|
ty::ty_uniq(t) { ret helper(tcx, needle, t, false); }
|
|
ty::ty_rec(fields) {
|
|
for f: ty::field in fields {
|
|
if helper(tcx, needle, f.mt.ty, get_mut(mut, f.mt)) {
|
|
ret true;
|
|
}
|
|
}
|
|
ret false;
|
|
}
|
|
ty::ty_tup(ts) {
|
|
for t in ts { if helper(tcx, needle, t, mut) { ret true; } }
|
|
ret false;
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
// These may contain anything.
|
|
ty::ty_fn(_, _, _, _, _) {
|
|
ret true;
|
|
}
|
|
ty::ty_obj(_) { ret true; }
|
|
// A type param may include everything, but can only be
|
|
// treated as opaque downstream, and is thus safe unless we
|
|
// saw mutable fields, in which case the whole thing can be
|
|
// overwritten.
|
|
ty::ty_param(_, _) {
|
|
ret mut;
|
|
}
|
|
_ { ret false; }
|
|
}
|
|
}
|
|
ret helper(cx.tcx, needle, haystack, mut);
|
|
}
|
|
|
|
fn def_is_local(d: ast::def, objfields_count: bool) -> bool {
|
|
ret alt d {
|
|
ast::def_local(_) | ast::def_arg(_, _) | ast::def_binding(_) |
|
|
ast::def_upvar(_, _, _) {
|
|
true
|
|
}
|
|
ast::def_obj_field(_, _) { objfields_count }
|
|
_ { false }
|
|
};
|
|
}
|
|
|
|
// Heuristic, somewhat random way to decide whether to warn when inserting an
|
|
// implicit copy.
|
|
fn copy_is_expensive(tcx: ty::ctxt, ty: ty::t) -> bool {
|
|
fn score_ty(tcx: ty::ctxt, ty: ty::t) -> uint {
|
|
ret alt ty::struct(tcx, ty) {
|
|
ty::ty_nil. | ty::ty_bot. | ty::ty_bool. | ty::ty_int. |
|
|
ty::ty_uint. | ty::ty_float. | ty::ty_machine(_) |
|
|
ty::ty_char. | ty::ty_type. | ty::ty_native(_) |
|
|
ty::ty_ptr(_) { 1u }
|
|
ty::ty_box(_) { 3u }
|
|
ty::ty_constr(t, _) | ty::ty_res(_, t, _) { score_ty(tcx, t) }
|
|
ty::ty_fn(_, _, _, _, _) | ty::ty_native_fn(_, _, _) |
|
|
ty::ty_obj(_) { 4u }
|
|
ty::ty_str. | ty::ty_vec(_) | ty::ty_param(_, _) { 50u }
|
|
ty::ty_uniq(t) { 1u + score_ty(tcx, t) }
|
|
ty::ty_tag(_, ts) | ty::ty_tup(ts) {
|
|
let sum = 0u;
|
|
for t in ts { sum += score_ty(tcx, t); }
|
|
sum
|
|
}
|
|
ty::ty_rec(fs) {
|
|
let sum = 0u;
|
|
for f in fs { sum += score_ty(tcx, f.mt.ty); }
|
|
sum
|
|
}
|
|
};
|
|
}
|
|
ret score_ty(tcx, ty) > 8u;
|
|
}
|
|
|
|
type pattern_root = {id: node_id, name: ident, ds: @[deref], span: span};
|
|
|
|
fn pattern_roots(tcx: ty::ctxt, base: [deref], pat: @ast::pat)
|
|
-> @[pattern_root] {
|
|
fn walk(tcx: ty::ctxt, base: [deref], pat: @ast::pat,
|
|
&set: [pattern_root]) {
|
|
alt pat.node {
|
|
ast::pat_wild. | ast::pat_lit(_) {}
|
|
ast::pat_bind(nm) {
|
|
set += [{id: pat.id, name: nm, ds: @base, span: pat.span}];
|
|
}
|
|
ast::pat_tag(_, ps) | ast::pat_tup(ps) {
|
|
let base = base + [@{mut: false, kind: field,
|
|
outer_t: ty::node_id_to_type(tcx, pat.id)}];
|
|
for p in ps { walk(tcx, base, p, set); }
|
|
}
|
|
ast::pat_rec(fs, _) {
|
|
let ty = ty::node_id_to_type(tcx, pat.id);
|
|
for f in fs {
|
|
let mut = ty::get_field(tcx, ty, f.ident).mt.mut != ast::imm;
|
|
let base = base + [@{mut: mut, kind: field, outer_t: ty}];
|
|
walk(tcx, base, f.pat, set);
|
|
}
|
|
}
|
|
ast::pat_box(p) {
|
|
let ty = ty::node_id_to_type(tcx, pat.id);
|
|
let mut = alt ty::struct(tcx, ty) {
|
|
ty::ty_box(mt) { mt.mut != ast::imm }
|
|
};
|
|
walk(tcx, base + [@{mut: mut, kind: unbox, outer_t: ty}], p, set);
|
|
}
|
|
}
|
|
}
|
|
let set = [];
|
|
walk(tcx, base, pat, set);
|
|
ret @set;
|
|
}
|
|
|
|
fn inner_mut(ds: @[deref]) -> [ty::t] {
|
|
for d: deref in *ds { if d.mut { ret [d.outer_t]; } }
|
|
ret [];
|
|
}
|
|
|
|
// Local Variables:
|
|
// mode: rust
|
|
// fill-column: 78;
|
|
// indent-tabs-mode: nil
|
|
// c-basic-offset: 4
|
|
// buffer-file-coding-system: utf-8-unix
|
|
// compile-command: "make -k -C $RBUILD 2>&1 | sed -e 's/\\/x\\//x:\\//g'";
|
|
// End:
|