compiler/rustc_passes/src/weak_lang_items.rs

   1 //! Validity checking for weak lang items
   2
   3 use rustc_data_structures::fx::FxHashSet;
   4 use rustc_errors::struct_span_err;
   5 use rustc_hir as hir;
   6 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
   7 use rustc_hir::lang_items::{self, LangItem};
   8 use rustc_hir::weak_lang_items::WEAK_ITEMS_REFS;
   9 use rustc_middle::middle::lang_items::required;
  10 use rustc_middle::ty::TyCtxt;
  11 use rustc_session::config::CrateType;
  12 use rustc_span::symbol::Symbol;
  13 use rustc_span::Span;
  14
  15 struct Context<'a, 'tcx> {
  16     tcx: TyCtxt<'tcx>,
  17     items: &'a mut lang_items::LanguageItems,
  18 }
  19
  20 /// Checks the crate for usage of weak lang items, returning a vector of all the
  21 /// language items required by this crate, but not defined yet.
  22 pub fn check_crate<'tcx>(tcx: TyCtxt<'tcx>, items: &mut lang_items::LanguageItems) {
  23     // These are never called by user code, they're generated by the compiler.
  24     // They will never implicitly be added to the `missing` array unless we do
  25     // so here.
  26     if items.eh_personality().is_none() {
  27         items.missing.push(LangItem::EhPersonality);
  28     }
  29     if tcx.sess.target.is_like_emscripten && items.eh_catch_typeinfo().is_none() {
  30         items.missing.push(LangItem::EhCatchTypeinfo);
  31     }
  32
  33     {
  34         let mut cx = Context { tcx, items };
  35         tcx.hir().krate().visit_all_item_likes(&mut cx.as_deep_visitor());
  36     }
  37     verify(tcx, items);
  38 }
  39
  40 fn verify<'tcx>(tcx: TyCtxt<'tcx>, items: &lang_items::LanguageItems) {
  41     // We only need to check for the presence of weak lang items if we're
  42     // emitting something that's not an rlib.
  43     let needs_check = tcx.sess.crate_types().iter().any(|kind| match *kind {
  44         CrateType::Dylib
  45         | CrateType::ProcMacro
  46         | CrateType::Cdylib
  47         | CrateType::Executable
  48         | CrateType::Staticlib => true,
  49         CrateType::Rlib => false,
  50     });
  51     if !needs_check {
  52         return;
  53     }
  54
  55     let mut missing = FxHashSet::default();
  56     for &cnum in tcx.crates(()).iter() {
  57         for &item in tcx.missing_lang_items(cnum).iter() {
  58             missing.insert(item);
  59         }
  60     }
  61
  62     for (name, item) in WEAK_ITEMS_REFS.clone().into_sorted_vector().into_iter() {
  63         if missing.contains(&item) && required(tcx, item) && items.require(item).is_err() {
  64             if item == LangItem::PanicImpl {
  65                 tcx.sess.err("`#[panic_handler]` function required, but not found");
  66             } else if item == LangItem::Oom {
  67                 if !tcx.features().default_alloc_error_handler {
  68                     tcx.sess.err("`#[alloc_error_handler]` function required, but not found.");
  69                     tcx.sess.note_without_error("Use `#![feature(default_alloc_error_handler)]` for a default error handler.");
  70                 }
  71             } else {
  72                 tcx.sess.err(&format!("language item required, but not found: `{}`", name));
  73             }
  74         }
  75     }
  76 }
  77
  78 impl<'a, 'tcx> Context<'a, 'tcx> {
  79     fn register(&mut self, name: Symbol, span: Span) {
  80         if let Some(&item) = WEAK_ITEMS_REFS.get(&name) {
  81             if self.items.require(item).is_err() {
  82                 self.items.missing.push(item);
  83             }
  84         } else {
  85             struct_span_err!(self.tcx.sess, span, E0264, "unknown external lang item: `{}`", name)
  86                 .emit();
  87         }
  88     }
  89 }
  90
  91 impl<'a, 'tcx, 'v> Visitor<'v> for Context<'a, 'tcx> {
  92     type Map = intravisit::ErasedMap<'v>;
  93
  94     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
  95         NestedVisitorMap::None
  96     }
  97
  98     fn visit_foreign_item(&mut self, i: &hir::ForeignItem<'_>) {
  99         let check_name = |attr, sym| self.tcx.sess.check_name(attr, sym);
 100         let attrs = self.tcx.hir().attrs(i.hir_id());
 101         if let Some((lang_item, _)) = lang_items::extract(check_name, attrs) {
 102             self.register(lang_item, i.span);
 103         }
 104         intravisit::walk_foreign_item(self, i)
 105     }
 106 }