src/librustc/middle/weak_lang_items.rs

   1 // Copyright 2014 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 //! Validity checking for weak lang items
  12
  13 use session::config;
  14 use middle::lang_items;
  15
  16 use rustc_data_structures::fx::FxHashSet;
  17 use rustc_target::spec::PanicStrategy;
  18 use syntax::ast;
  19 use syntax::symbol::Symbol;
  20 use syntax_pos::Span;
  21 use hir::def_id::DefId;
  22 use hir::intravisit::{Visitor, NestedVisitorMap};
  23 use hir::intravisit;
  24 use hir;
  25 use ty::TyCtxt;
  26
  27 macro_rules! weak_lang_items {
  28     ($($name:ident, $item:ident, $sym:ident;)*) => (
  29
  30 struct Context<'a, 'tcx: 'a> {
  31     tcx: TyCtxt<'a, 'tcx, 'tcx>,
  32     items: &'a mut lang_items::LanguageItems,
  33 }
  34
  35 /// Checks the crate for usage of weak lang items, returning a vector of all the
  36 /// language items required by this crate, but not defined yet.
  37 pub fn check_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
  38                              items: &mut lang_items::LanguageItems) {
  39     // These are never called by user code, they're generated by the compiler.
  40     // They will never implicitly be added to the `missing` array unless we do
  41     // so here.
  42     if items.eh_personality().is_none() {
  43         items.missing.push(lang_items::EhPersonalityLangItem);
  44     }
  45     if tcx.sess.target.target.options.custom_unwind_resume &
  46        items.eh_unwind_resume().is_none() {
  47         items.missing.push(lang_items::EhUnwindResumeLangItem);
  48     }
  49
  50     {
  51         let mut cx = Context { tcx, items };
  52         tcx.hir.krate().visit_all_item_likes(&mut cx.as_deep_visitor());
  53     }
  54     verify(tcx, items);
  55 }
  56
  57 pub fn link_name(attrs: &[ast::Attribute]) -> Option<Symbol> {
  58     lang_items::extract(attrs).and_then(|(name, _)| {
  59         $(if name == stringify!($name) {
  60             Some(Symbol::intern(stringify!($sym)))
  61         } else)* {
  62             None
  63         }
  64     })
  65 }
  66
  67 /// Returns whether the specified `lang_item` doesn't actually need to be
  68 /// present for this compilation.
  69 ///
  70 /// Not all lang items are always required for each compilation, particularly in
  71 /// the case of panic=abort. In these situations some lang items are injected by
  72 /// crates and don't actually need to be defined in libstd.
  73 pub fn whitelisted(tcx: TyCtxt, lang_item: lang_items::LangItem) -> bool {
  74     // If we're not compiling with unwinding, we won't actually need these
  75     // symbols. Other panic runtimes ensure that the relevant symbols are
  76     // available to link things together, but they're never exercised.
  77     if tcx.sess.panic_strategy() != PanicStrategy::Unwind {
  78         return lang_item == lang_items::EhPersonalityLangItem ||
  79             lang_item == lang_items::EhUnwindResumeLangItem
  80     }
  81
  82     false
  83 }
  84
  85 fn verify<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
  86                     items: &lang_items::LanguageItems) {
  87     // We only need to check for the presence of weak lang items if we're
  88     // emitting something that's not an rlib.
  89     let needs_check = tcx.sess.crate_types.borrow().iter().any(|kind| {
  90         match *kind {
  91             config::CrateType::Dylib |
  92             config::CrateType::ProcMacro |
  93             config::CrateType::Cdylib |
  94             config::CrateType::Executable |
  95             config::CrateType::Staticlib => true,
  96             config::CrateType::Rlib => false,
  97         }
  98     });
  99     if !needs_check {
 100         return
 101     }
 102
 103     let mut missing = FxHashSet::default();
 104     for &cnum in tcx.crates().iter() {
 105         for &item in tcx.missing_lang_items(cnum).iter() {
 106             missing.insert(item);
 107         }
 108     }
 109
 110     $(
 111         if missing.contains(&lang_items::$item) &&
 112            !whitelisted(tcx, lang_items::$item) &&
 113            items.$name().is_none() {
 114             if lang_items::$item == lang_items::PanicImplLangItem {
 115                 tcx.sess.err(&format!("`#[panic_handler]` function required, \
 116                                         but not found"));
 117             } else if lang_items::$item == lang_items::OomLangItem {
 118                 tcx.sess.err(&format!("`#[alloc_error_handler]` function required, \
 119                                         but not found"));
 120             } else {
 121                 tcx.sess.err(&format!("language item required, but not found: `{}`",
 122                                         stringify!($name)));
 123             }
 124         }
 125     )*
 126 }
 127
 128 impl<'a, 'tcx> Context<'a, 'tcx> {
 129     fn register(&mut self, name: &str, span: Span) {
 130         $(if name == stringify!($name) {
 131             if self.items.$name().is_none() {
 132                 self.items.missing.push(lang_items::$item);
 133             }
 134         } else)* {
 135             span_err!(self.tcx.sess, span, E0264,
 136                       "unknown external lang item: `{}`",
 137                       name);
 138         }
 139     }
 140 }
 141
 142 impl<'a, 'tcx, 'v> Visitor<'v> for Context<'a, 'tcx> {
 143     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'v> {
 144         NestedVisitorMap::None
 145     }
 146
 147     fn visit_foreign_item(&mut self, i: &hir::ForeignItem) {
 148         if let Some((lang_item, _)) = lang_items::extract(&i.attrs) {
 149             self.register(&lang_item.as_str(), i.span);
 150         }
 151         intravisit::walk_foreign_item(self, i)
 152     }
 153 }
 154
 155 impl<'a, 'tcx, 'gcx> TyCtxt<'a, 'tcx, 'gcx> {
 156     pub fn is_weak_lang_item(&self, item_def_id: DefId) -> bool {
 157         let lang_items = self.lang_items();
 158         let did = Some(item_def_id);
 159
 160         $(lang_items.$name() == did)||+
 161     }
 162 }
 163
 164 ) }
 165
 166 weak_lang_items! {
 167     panic_impl,         PanicImplLangItem,          rust_begin_unwind;
 168     eh_personality,     EhPersonalityLangItem,      rust_eh_personality;
 169     eh_unwind_resume,   EhUnwindResumeLangItem,     rust_eh_unwind_resume;
 170     oom,                OomLangItem,                rust_oom;
 171 }