rust/src/librustc/middle/cfg/construct.rs
Brandon Sanderson d80a62d84b Fix soundness hole in struct with expressions.
Fixes #18567. Struct{x:foo, .. with_expr} did not walk with_expr, which allowed
using moved variables in some cases.  The CFG for structs also built up with
with_expr happening before the fields, which is now reversed. (Fields are now
before the with_expr in the CFG)
2014-11-06 10:42:40 -08:00

642 lines
23 KiB
Rust

// Copyright 2012-2014 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.
use middle::cfg::*;
use middle::def;
use middle::graph;
use middle::typeck;
use middle::ty;
use syntax::ast;
use syntax::ast_util;
use syntax::ptr::P;
use util::nodemap::NodeMap;
struct CFGBuilder<'a, 'tcx: 'a> {
tcx: &'a ty::ctxt<'tcx>,
exit_map: NodeMap<CFGIndex>,
graph: CFGGraph,
fn_exit: CFGIndex,
loop_scopes: Vec<LoopScope>,
}
struct LoopScope {
loop_id: ast::NodeId, // id of loop/while node
continue_index: CFGIndex, // where to go on a `loop`
break_index: CFGIndex, // where to go on a `break
}
pub fn construct(tcx: &ty::ctxt,
blk: &ast::Block) -> CFG {
let mut graph = graph::Graph::new();
let entry = add_initial_dummy_node(&mut graph);
// `fn_exit` is target of return exprs, which lies somewhere
// outside input `blk`. (Distinguishing `fn_exit` and `block_exit`
// also resolves chicken-and-egg problem that arises if you try to
// have return exprs jump to `block_exit` during construction.)
let fn_exit = add_initial_dummy_node(&mut graph);
let block_exit;
let mut cfg_builder = CFGBuilder {
exit_map: NodeMap::new(),
graph: graph,
fn_exit: fn_exit,
tcx: tcx,
loop_scopes: Vec::new()
};
block_exit = cfg_builder.block(blk, entry);
cfg_builder.add_contained_edge(block_exit, fn_exit);
let CFGBuilder {exit_map, graph, ..} = cfg_builder;
CFG {exit_map: exit_map,
graph: graph,
entry: entry,
exit: fn_exit}
}
fn add_initial_dummy_node(g: &mut CFGGraph) -> CFGIndex {
g.add_node(CFGNodeData { id: ast::DUMMY_NODE_ID })
}
impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
fn block(&mut self, blk: &ast::Block, pred: CFGIndex) -> CFGIndex {
let mut stmts_exit = pred;
for stmt in blk.stmts.iter() {
stmts_exit = self.stmt(&**stmt, stmts_exit);
}
let expr_exit = self.opt_expr(&blk.expr, stmts_exit);
self.add_node(blk.id, [expr_exit])
}
fn stmt(&mut self, stmt: &ast::Stmt, pred: CFGIndex) -> CFGIndex {
match stmt.node {
ast::StmtDecl(ref decl, id) => {
let exit = self.decl(&**decl, pred);
self.add_node(id, [exit])
}
ast::StmtExpr(ref expr, id) | ast::StmtSemi(ref expr, id) => {
let exit = self.expr(&**expr, pred);
self.add_node(id, [exit])
}
ast::StmtMac(..) => {
self.tcx.sess.span_bug(stmt.span, "unexpanded macro");
}
}
}
fn decl(&mut self, decl: &ast::Decl, pred: CFGIndex) -> CFGIndex {
match decl.node {
ast::DeclLocal(ref local) => {
let init_exit = self.opt_expr(&local.init, pred);
self.pat(&*local.pat, init_exit)
}
ast::DeclItem(_) => {
pred
}
}
}
fn pat(&mut self, pat: &ast::Pat, pred: CFGIndex) -> CFGIndex {
match pat.node {
ast::PatIdent(_, _, None) |
ast::PatEnum(_, None) |
ast::PatLit(..) |
ast::PatRange(..) |
ast::PatWild(_) => {
self.add_node(pat.id, [pred])
}
ast::PatBox(ref subpat) |
ast::PatRegion(ref subpat) |
ast::PatIdent(_, _, Some(ref subpat)) => {
let subpat_exit = self.pat(&**subpat, pred);
self.add_node(pat.id, [subpat_exit])
}
ast::PatEnum(_, Some(ref subpats)) |
ast::PatTup(ref subpats) => {
let pats_exit = self.pats_all(subpats.iter(), pred);
self.add_node(pat.id, [pats_exit])
}
ast::PatStruct(_, ref subpats, _) => {
let pats_exit =
self.pats_all(subpats.iter().map(|f| &f.node.pat), pred);
self.add_node(pat.id, [pats_exit])
}
ast::PatVec(ref pre, ref vec, ref post) => {
let pre_exit = self.pats_all(pre.iter(), pred);
let vec_exit = self.pats_all(vec.iter(), pre_exit);
let post_exit = self.pats_all(post.iter(), vec_exit);
self.add_node(pat.id, [post_exit])
}
ast::PatMac(_) => {
self.tcx.sess.span_bug(pat.span, "unexpanded macro");
}
}
}
fn pats_all<'a, I: Iterator<&'a P<ast::Pat>>>(&mut self,
pats: I,
pred: CFGIndex) -> CFGIndex {
//! Handles case where all of the patterns must match.
let mut pats = pats;
pats.fold(pred, |pred, pat| self.pat(&**pat, pred))
}
fn pats_any(&mut self,
pats: &[P<ast::Pat>],
pred: CFGIndex) -> CFGIndex {
//! Handles case where just one of the patterns must match.
if pats.len() == 1 {
self.pat(&*pats[0], pred)
} else {
let collect = self.add_dummy_node([]);
for pat in pats.iter() {
let pat_exit = self.pat(&**pat, pred);
self.add_contained_edge(pat_exit, collect);
}
collect
}
}
fn expr(&mut self, expr: &ast::Expr, pred: CFGIndex) -> CFGIndex {
match expr.node {
ast::ExprBlock(ref blk) => {
let blk_exit = self.block(&**blk, pred);
self.add_node(expr.id, [blk_exit])
}
ast::ExprIf(ref cond, ref then, None) => {
//
// [pred]
// |
// v 1
// [cond]
// |
// / \
// / \
// v 2 *
// [then] |
// | |
// v 3 v 4
// [..expr..]
//
let cond_exit = self.expr(&**cond, pred); // 1
let then_exit = self.block(&**then, cond_exit); // 2
self.add_node(expr.id, [cond_exit, then_exit]) // 3,4
}
ast::ExprIf(ref cond, ref then, Some(ref otherwise)) => {
//
// [pred]
// |
// v 1
// [cond]
// |
// / \
// / \
// v 2 v 3
// [then][otherwise]
// | |
// v 4 v 5
// [..expr..]
//
let cond_exit = self.expr(&**cond, pred); // 1
let then_exit = self.block(&**then, cond_exit); // 2
let else_exit = self.expr(&**otherwise, cond_exit); // 3
self.add_node(expr.id, [then_exit, else_exit]) // 4, 5
}
ast::ExprIfLet(..) => {
self.tcx.sess.span_bug(expr.span, "non-desugared ExprIfLet");
}
ast::ExprWhile(ref cond, ref body, _) => {
//
// [pred]
// |
// v 1
// [loopback] <--+ 5
// | |
// v 2 |
// +-----[cond] |
// | | |
// | v 4 |
// | [body] -----+
// v 3
// [expr]
//
// Note that `break` and `continue` statements
// may cause additional edges.
// Is the condition considered part of the loop?
let loopback = self.add_dummy_node([pred]); // 1
let cond_exit = self.expr(&**cond, loopback); // 2
let expr_exit = self.add_node(expr.id, [cond_exit]); // 3
self.loop_scopes.push(LoopScope {
loop_id: expr.id,
continue_index: loopback,
break_index: expr_exit
});
let body_exit = self.block(&**body, cond_exit); // 4
self.add_contained_edge(body_exit, loopback); // 5
self.loop_scopes.pop();
expr_exit
}
ast::ExprWhileLet(..) => {
self.tcx.sess.span_bug(expr.span, "non-desugared ExprWhileLet");
}
ast::ExprForLoop(ref pat, ref head, ref body, _) => {
//
// [pred]
// |
// v 1
// [head]
// |
// v 2
// [loopback] <--+ 7
// | |
// v 3 |
// +------[cond] |
// | | |
// | v 5 |
// | [pat] |
// | | |
// | v 6 |
// v 4 [body] -----+
// [expr]
//
// Note that `break` and `continue` statements
// may cause additional edges.
let head = self.expr(&**head, pred); // 1
let loopback = self.add_dummy_node([head]); // 2
let cond = self.add_dummy_node([loopback]); // 3
let expr_exit = self.add_node(expr.id, [cond]); // 4
self.loop_scopes.push(LoopScope {
loop_id: expr.id,
continue_index: loopback,
break_index: expr_exit,
});
let pat = self.pat(&**pat, cond); // 5
let body = self.block(&**body, pat); // 6
self.add_contained_edge(body, loopback); // 7
self.loop_scopes.pop();
expr_exit
}
ast::ExprLoop(ref body, _) => {
//
// [pred]
// |
// v 1
// [loopback] <---+
// | 4 |
// v 3 |
// [body] ------+
//
// [expr] 2
//
// Note that `break` and `loop` statements
// may cause additional edges.
let loopback = self.add_dummy_node([pred]); // 1
let expr_exit = self.add_node(expr.id, []); // 2
self.loop_scopes.push(LoopScope {
loop_id: expr.id,
continue_index: loopback,
break_index: expr_exit,
});
let body_exit = self.block(&**body, loopback); // 3
self.add_contained_edge(body_exit, loopback); // 4
self.loop_scopes.pop();
expr_exit
}
ast::ExprMatch(ref discr, ref arms, _) => {
//
// [pred]
// |
// v 1
// [discr]
// |
// v 2
// [cond1]
// / \
// | \
// v 3 \
// [pat1] \
// | |
// v 4 |
// [guard1] |
// | |
// | |
// v 5 v
// [body1] [cond2]
// | / \
// | ... ...
// | | |
// v 6 v v
// [.....expr.....]
//
let discr_exit = self.expr(&**discr, pred); // 1
let expr_exit = self.add_node(expr.id, []);
let mut cond_exit = discr_exit;
for arm in arms.iter() {
cond_exit = self.add_dummy_node([cond_exit]); // 2
let pats_exit = self.pats_any(arm.pats.as_slice(),
cond_exit); // 3
let guard_exit = self.opt_expr(&arm.guard,
pats_exit); // 4
let body_exit = self.expr(&*arm.body, guard_exit); // 5
self.add_contained_edge(body_exit, expr_exit); // 6
}
expr_exit
}
ast::ExprBinary(op, ref l, ref r) if ast_util::lazy_binop(op) => {
//
// [pred]
// |
// v 1
// [l]
// |
// / \
// / \
// v 2 *
// [r] |
// | |
// v 3 v 4
// [..exit..]
//
let l_exit = self.expr(&**l, pred); // 1
let r_exit = self.expr(&**r, l_exit); // 2
self.add_node(expr.id, [l_exit, r_exit]) // 3,4
}
ast::ExprRet(ref v) => {
let v_exit = self.opt_expr(v, pred);
let b = self.add_node(expr.id, [v_exit]);
self.add_returning_edge(expr, b);
self.add_node(ast::DUMMY_NODE_ID, [])
}
ast::ExprBreak(label) => {
let loop_scope = self.find_scope(expr, label);
let b = self.add_node(expr.id, [pred]);
self.add_exiting_edge(expr, b,
loop_scope, loop_scope.break_index);
self.add_node(ast::DUMMY_NODE_ID, [])
}
ast::ExprAgain(label) => {
let loop_scope = self.find_scope(expr, label);
let a = self.add_node(expr.id, [pred]);
self.add_exiting_edge(expr, a,
loop_scope, loop_scope.continue_index);
self.add_node(ast::DUMMY_NODE_ID, [])
}
ast::ExprVec(ref elems) => {
self.straightline(expr, pred, elems.iter().map(|e| &**e))
}
ast::ExprCall(ref func, ref args) => {
self.call(expr, pred, &**func, args.iter().map(|e| &**e))
}
ast::ExprMethodCall(_, _, ref args) => {
self.call(expr, pred, &*args[0], args.slice_from(1).iter().map(|e| &**e))
}
ast::ExprIndex(ref l, ref r) |
ast::ExprBinary(_, ref l, ref r) if self.is_method_call(expr) => {
self.call(expr, pred, &**l, Some(&**r).into_iter())
}
ast::ExprSlice(ref base, ref start, ref end, _) => {
self.call(expr,
pred,
&**base,
start.iter().chain(end.iter()).map(|x| &**x))
}
ast::ExprUnary(_, ref e) if self.is_method_call(expr) => {
self.call(expr, pred, &**e, None::<ast::Expr>.iter())
}
ast::ExprTup(ref exprs) => {
self.straightline(expr, pred, exprs.iter().map(|e| &**e))
}
ast::ExprStruct(_, ref fields, ref base) => {
let field_cfg = self.straightline(expr, pred, fields.iter().map(|f| &*f.expr));
self.opt_expr(base, field_cfg)
}
ast::ExprRepeat(ref elem, ref count) => {
self.straightline(expr, pred, [elem, count].iter().map(|&e| &**e))
}
ast::ExprAssign(ref l, ref r) |
ast::ExprAssignOp(_, ref l, ref r) => {
self.straightline(expr, pred, [r, l].iter().map(|&e| &**e))
}
ast::ExprIndex(ref l, ref r) |
ast::ExprBinary(_, ref l, ref r) => { // NB: && and || handled earlier
self.straightline(expr, pred, [l, r].iter().map(|&e| &**e))
}
ast::ExprBox(ref p, ref e) => {
self.straightline(expr, pred, [p, e].iter().map(|&e| &**e))
}
ast::ExprAddrOf(_, ref e) |
ast::ExprCast(ref e, _) |
ast::ExprUnary(_, ref e) |
ast::ExprParen(ref e) |
ast::ExprField(ref e, _, _) |
ast::ExprTupField(ref e, _, _) => {
self.straightline(expr, pred, Some(&**e).into_iter())
}
ast::ExprInlineAsm(ref inline_asm) => {
let inputs = inline_asm.inputs.iter();
let outputs = inline_asm.outputs.iter();
let post_inputs = self.exprs(inputs.map(|a| {
debug!("cfg::construct InlineAsm id:{} input:{}", expr.id, a);
let &(_, ref expr) = a;
&**expr
}), pred);
let post_outputs = self.exprs(outputs.map(|a| {
debug!("cfg::construct InlineAsm id:{} output:{}", expr.id, a);
let &(_, ref expr, _) = a;
&**expr
}), post_inputs);
self.add_node(expr.id, [post_outputs])
}
ast::ExprMac(..) |
ast::ExprFnBlock(..) |
ast::ExprProc(..) |
ast::ExprUnboxedFn(..) |
ast::ExprLit(..) |
ast::ExprPath(..) => {
self.straightline(expr, pred, None::<ast::Expr>.iter())
}
}
}
fn call<'a, I: Iterator<&'a ast::Expr>>(&mut self,
call_expr: &ast::Expr,
pred: CFGIndex,
func_or_rcvr: &ast::Expr,
args: I) -> CFGIndex {
let method_call = typeck::MethodCall::expr(call_expr.id);
let return_ty = ty::ty_fn_ret(match self.tcx.method_map.borrow().find(&method_call) {
Some(method) => method.ty,
None => ty::expr_ty(self.tcx, func_or_rcvr)
});
let func_or_rcvr_exit = self.expr(func_or_rcvr, pred);
let ret = self.straightline(call_expr, func_or_rcvr_exit, args);
if return_ty == ty::FnDiverging {
self.add_node(ast::DUMMY_NODE_ID, [])
} else {
ret
}
}
fn exprs<'a, I: Iterator<&'a ast::Expr>>(&mut self,
mut exprs: I,
pred: CFGIndex) -> CFGIndex {
//! Constructs graph for `exprs` evaluated in order
exprs.fold(pred, |p, e| self.expr(e, p))
}
fn opt_expr(&mut self,
opt_expr: &Option<P<ast::Expr>>,
pred: CFGIndex) -> CFGIndex {
//! Constructs graph for `opt_expr` evaluated, if Some
opt_expr.iter().fold(pred, |p, e| self.expr(&**e, p))
}
fn straightline<'a, I: Iterator<&'a ast::Expr>>(&mut self,
expr: &ast::Expr,
pred: CFGIndex,
subexprs: I) -> CFGIndex {
//! Handles case of an expression that evaluates `subexprs` in order
let subexprs_exit = self.exprs(subexprs, pred);
self.add_node(expr.id, [subexprs_exit])
}
fn add_dummy_node(&mut self, preds: &[CFGIndex]) -> CFGIndex {
self.add_node(ast::DUMMY_NODE_ID, preds)
}
fn add_node(&mut self, id: ast::NodeId, preds: &[CFGIndex]) -> CFGIndex {
assert!(!self.exit_map.contains_key(&id));
let node = self.graph.add_node(CFGNodeData {id: id});
if id != ast::DUMMY_NODE_ID {
assert!(!self.exit_map.contains_key(&id));
self.exit_map.insert(id, node);
}
for &pred in preds.iter() {
self.add_contained_edge(pred, node);
}
node
}
fn add_contained_edge(&mut self,
source: CFGIndex,
target: CFGIndex) {
let data = CFGEdgeData {exiting_scopes: vec!() };
self.graph.add_edge(source, target, data);
}
fn add_exiting_edge(&mut self,
from_expr: &ast::Expr,
from_index: CFGIndex,
to_loop: LoopScope,
to_index: CFGIndex) {
let mut data = CFGEdgeData {exiting_scopes: vec!() };
let mut scope_id = from_expr.id;
while scope_id != to_loop.loop_id {
data.exiting_scopes.push(scope_id);
scope_id = self.tcx.region_maps.encl_scope(scope_id);
}
self.graph.add_edge(from_index, to_index, data);
}
fn add_returning_edge(&mut self,
_from_expr: &ast::Expr,
from_index: CFGIndex) {
let mut data = CFGEdgeData {
exiting_scopes: vec!(),
};
for &LoopScope { loop_id: id, .. } in self.loop_scopes.iter().rev() {
data.exiting_scopes.push(id);
}
self.graph.add_edge(from_index, self.fn_exit, data);
}
fn find_scope(&self,
expr: &ast::Expr,
label: Option<ast::Ident>) -> LoopScope {
match label {
None => {
return *self.loop_scopes.last().unwrap();
}
Some(_) => {
match self.tcx.def_map.borrow().find(&expr.id) {
Some(&def::DefLabel(loop_id)) => {
for l in self.loop_scopes.iter() {
if l.loop_id == loop_id {
return *l;
}
}
self.tcx.sess.span_bug(
expr.span,
format!("no loop scope for id {}",
loop_id).as_slice());
}
r => {
self.tcx.sess.span_bug(
expr.span,
format!("bad entry `{}` in def_map for label",
r).as_slice());
}
}
}
}
}
fn is_method_call(&self, expr: &ast::Expr) -> bool {
let method_call = typeck::MethodCall::expr(expr.id);
self.tcx.method_map.borrow().contains_key(&method_call)
}
}