src/librustc/middle/effect.rs

   1 // Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! Enforces the Rust effect system. Currently there is just one effect,
  12 //! `unsafe`.
  13 use self::RootUnsafeContext::*;
  14
  15 use dep_graph::DepNode;
  16 use ty::{self, Ty, TyCtxt};
  17 use ty::MethodCall;
  18 use lint;
  19
  20 use syntax::ast;
  21 use syntax_pos::Span;
  22 use hir::{self, PatKind};
  23 use hir::def::Def;
  24 use hir::intravisit::{self, FnKind, Visitor, NestedVisitorMap};
  25
  26 #[derive(Copy, Clone)]
  27 struct UnsafeContext {
  28     push_unsafe_count: usize,
  29     root: RootUnsafeContext,
  30 }
  31
  32 impl UnsafeContext {
  33     fn new(root: RootUnsafeContext) -> UnsafeContext {
  34         UnsafeContext { root: root, push_unsafe_count: 0 }
  35     }
  36 }
  37
  38 #[derive(Copy, Clone, PartialEq)]
  39 enum RootUnsafeContext {
  40     SafeContext,
  41     UnsafeFn,
  42     UnsafeBlock(ast::NodeId),
  43 }
  44
  45 fn type_is_unsafe_function(ty: Ty) -> bool {
  46     match ty.sty {
  47         ty::TyFnDef(.., f) |
  48         ty::TyFnPtr(f) => f.unsafety() == hir::Unsafety::Unsafe,
  49         _ => false,
  50     }
  51 }
  52
  53 struct EffectCheckVisitor<'a, 'tcx: 'a> {
  54     tcx: TyCtxt<'a, 'tcx, 'tcx>,
  55     tables: &'a ty::TypeckTables<'tcx>,
  56
  57     /// Whether we're in an unsafe context.
  58     unsafe_context: UnsafeContext,
  59 }
  60
  61 impl<'a, 'tcx> EffectCheckVisitor<'a, 'tcx> {
  62     fn require_unsafe_ext(&mut self, node_id: ast::NodeId, span: Span,
  63                           description: &str, is_lint: bool) {
  64         if self.unsafe_context.push_unsafe_count > 0 { return; }
  65         match self.unsafe_context.root {
  66             SafeContext => {
  67                 if is_lint {
  68                     self.tcx.sess.add_lint(lint::builtin::SAFE_EXTERN_STATICS,
  69                                            node_id,
  70                                            span,
  71                                            format!("{} requires unsafe function or \
  72                                                     block (error E0133)", description));
  73                 } else {
  74                     // Report an error.
  75                     struct_span_err!(
  76                         self.tcx.sess, span, E0133,
  77                         "{} requires unsafe function or block", description)
  78                         .span_label(span, &description)
  79                         .emit();
  80                 }
  81             }
  82             UnsafeBlock(block_id) => {
  83                 // OK, but record this.
  84                 debug!("effect: recording unsafe block as used: {}", block_id);
  85                 self.tcx.used_unsafe.borrow_mut().insert(block_id);
  86             }
  87             UnsafeFn => {}
  88         }
  89     }
  90
  91     fn require_unsafe(&mut self, span: Span, description: &str) {
  92         self.require_unsafe_ext(ast::DUMMY_NODE_ID, span, description, false)
  93     }
  94 }
  95
  96 impl<'a, 'tcx> Visitor<'tcx> for EffectCheckVisitor<'a, 'tcx> {
  97     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
  98         NestedVisitorMap::None
  99     }
 100
 101     fn visit_nested_body(&mut self, body: hir::BodyId) {
 102         let old_tables = self.tables;
 103         self.tables = self.tcx.body_tables(body);
 104         let body = self.tcx.hir.body(body);
 105         self.visit_body(body);
 106         self.tables = old_tables;
 107     }
 108
 109     fn visit_fn(&mut self, fn_kind: FnKind<'tcx>, fn_decl: &'tcx hir::FnDecl,
 110                 body_id: hir::BodyId, span: Span, id: ast::NodeId) {
 111
 112         let (is_item_fn, is_unsafe_fn) = match fn_kind {
 113             FnKind::ItemFn(_, _, unsafety, ..) =>
 114                 (true, unsafety == hir::Unsafety::Unsafe),
 115             FnKind::Method(_, sig, ..) =>
 116                 (true, sig.unsafety == hir::Unsafety::Unsafe),
 117             _ => (false, false),
 118         };
 119
 120         let old_unsafe_context = self.unsafe_context;
 121         if is_unsafe_fn {
 122             self.unsafe_context = UnsafeContext::new(UnsafeFn)
 123         } else if is_item_fn {
 124             self.unsafe_context = UnsafeContext::new(SafeContext)
 125         }
 126
 127         intravisit::walk_fn(self, fn_kind, fn_decl, body_id, span, id);
 128
 129         self.unsafe_context = old_unsafe_context
 130     }
 131
 132     fn visit_block(&mut self, block: &'tcx hir::Block) {
 133         let old_unsafe_context = self.unsafe_context;
 134         match block.rules {
 135             hir::UnsafeBlock(source) => {
 136                 // By default only the outermost `unsafe` block is
 137                 // "used" and so nested unsafe blocks are pointless
 138                 // (the inner ones are unnecessary and we actually
 139                 // warn about them). As such, there are two cases when
 140                 // we need to create a new context, when we're
 141                 // - outside `unsafe` and found a `unsafe` block
 142                 //   (normal case)
 143                 // - inside `unsafe`, found an `unsafe` block
 144                 //   created internally to the compiler
 145                 //
 146                 // The second case is necessary to ensure that the
 147                 // compiler `unsafe` blocks don't accidentally "use"
 148                 // external blocks (e.g. `unsafe { println("") }`,
 149                 // expands to `unsafe { ... unsafe { ... } }` where
 150                 // the inner one is compiler generated).
 151                 if self.unsafe_context.root == SafeContext || source == hir::CompilerGenerated {
 152                     self.unsafe_context.root = UnsafeBlock(block.id)
 153                 }
 154             }
 155             hir::PushUnsafeBlock(..) => {
 156                 self.unsafe_context.push_unsafe_count =
 157                     self.unsafe_context.push_unsafe_count.checked_add(1).unwrap();
 158             }
 159             hir::PopUnsafeBlock(..) => {
 160                 self.unsafe_context.push_unsafe_count =
 161                     self.unsafe_context.push_unsafe_count.checked_sub(1).unwrap();
 162             }
 163             hir::DefaultBlock => {}
 164         }
 165
 166         intravisit::walk_block(self, block);
 167
 168         self.unsafe_context = old_unsafe_context
 169     }
 170
 171     fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
 172         match expr.node {
 173             hir::ExprMethodCall(..) => {
 174                 let method_call = MethodCall::expr(expr.id);
 175                 let base_type = self.tables.method_map[&method_call].ty;
 176                 debug!("effect: method call case, base type is {:?}",
 177                         base_type);
 178                 if type_is_unsafe_function(base_type) {
 179                     self.require_unsafe(expr.span,
 180                                         "invocation of unsafe method")
 181                 }
 182             }
 183             hir::ExprCall(ref base, _) => {
 184                 let base_type = self.tables.expr_ty_adjusted(base);
 185                 debug!("effect: call case, base type is {:?}",
 186                         base_type);
 187                 if type_is_unsafe_function(base_type) {
 188                     self.require_unsafe(expr.span, "call to unsafe function")
 189                 }
 190             }
 191             hir::ExprUnary(hir::UnDeref, ref base) => {
 192                 let base_type = self.tables.expr_ty_adjusted(base);
 193                 debug!("effect: unary case, base type is {:?}",
 194                         base_type);
 195                 if let ty::TyRawPtr(_) = base_type.sty {
 196                     self.require_unsafe(expr.span, "dereference of raw pointer")
 197                 }
 198             }
 199             hir::ExprInlineAsm(..) => {
 200                 self.require_unsafe(expr.span, "use of inline assembly");
 201             }
 202             hir::ExprPath(hir::QPath::Resolved(_, ref path)) => {
 203                 if let Def::Static(def_id, mutbl) = path.def {
 204                     if mutbl {
 205                         self.require_unsafe(expr.span, "use of mutable static");
 206                     } else if match self.tcx.hir.get_if_local(def_id) {
 207                         Some(hir::map::NodeForeignItem(..)) => true,
 208                         Some(..) => false,
 209                         None => self.tcx.sess.cstore.is_foreign_item(def_id),
 210                     } {
 211                         self.require_unsafe_ext(expr.id, expr.span, "use of extern static", true);
 212                     }
 213                 }
 214             }
 215             hir::ExprField(ref base_expr, field) => {
 216                 if let ty::TyAdt(adt, ..) = self.tables.expr_ty_adjusted(base_expr).sty {
 217                     if adt.is_union() {
 218                         self.require_unsafe(field.span, "access to union field");
 219                     }
 220                 }
 221             }
 222             _ => {}
 223         }
 224
 225         intravisit::walk_expr(self, expr);
 226     }
 227
 228     fn visit_pat(&mut self, pat: &'tcx hir::Pat) {
 229         if let PatKind::Struct(_, ref fields, _) = pat.node {
 230             if let ty::TyAdt(adt, ..) = self.tables.pat_ty(pat).sty {
 231                 if adt.is_union() {
 232                     for field in fields {
 233                         self.require_unsafe(field.span, "matching on union field");
 234                     }
 235                 }
 236             }
 237         }
 238
 239         intravisit::walk_pat(self, pat);
 240     }
 241 }
 242
 243 pub fn check_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) {
 244     let _task = tcx.dep_graph.in_task(DepNode::EffectCheck);
 245
 246     let mut visitor = EffectCheckVisitor {
 247         tcx: tcx,
 248         tables: &ty::TypeckTables::empty(),
 249         unsafe_context: UnsafeContext::new(SafeContext),
 250     };
 251
 252     tcx.hir.krate().visit_all_item_likes(&mut visitor.as_deep_visitor());
 253 }