compiler/rustc_passes/src/weak_lang_items.rs

   1 //! Validity checking for weak lang items
   2
   3 use rustc_ast as ast;
   4 use rustc_ast::visit;
   5 use rustc_data_structures::fx::FxHashSet;
   6 use rustc_hir::lang_items::{self, LangItem};
   7 use rustc_hir::weak_lang_items::WEAK_LANG_ITEMS;
   8 use rustc_middle::middle::lang_items::required;
   9 use rustc_middle::ty::TyCtxt;
  10 use rustc_session::config::CrateType;
  11
  12 use crate::errors::{MissingLangItem, MissingPanicHandler, UnknownExternLangItem};
  13
  14 /// Checks the crate for usage of weak lang items, returning a vector of all the
  15 /// language items required by this crate, but not defined yet.
  16 pub fn check_crate(tcx: TyCtxt<'_>, items: &mut lang_items::LanguageItems, krate: &ast::Crate) {
  17     // These are never called by user code, they're generated by the compiler.
  18     // They will never implicitly be added to the `missing` array unless we do
  19     // so here.
  20     if items.eh_personality().is_none() {
  21         items.missing.push(LangItem::EhPersonality);
  22     }
  23     if tcx.sess.target.os == "emscripten" && items.eh_catch_typeinfo().is_none() {
  24         items.missing.push(LangItem::EhCatchTypeinfo);
  25     }
  26
  27     visit::Visitor::visit_crate(&mut WeakLangItemVisitor { tcx, items }, krate);
  28
  29     verify(tcx, items);
  30 }
  31
  32 struct WeakLangItemVisitor<'a, 'tcx> {
  33     tcx: TyCtxt<'tcx>,
  34     items: &'a mut lang_items::LanguageItems,
  35 }
  36
  37 impl<'ast> visit::Visitor<'ast> for WeakLangItemVisitor<'_, '_> {
  38     fn visit_foreign_item(&mut self, i: &'ast ast::ForeignItem) {
  39         if let Some((lang_item, _)) = lang_items::extract(&i.attrs) {
  40             if let Some(item) = LangItem::from_name(lang_item)
  41                 && item.is_weak()
  42             {
  43                 if self.items.get(item).is_none() {
  44                     self.items.missing.push(item);
  45                 }
  46             } else {
  47                 self.tcx.sess.emit_err(UnknownExternLangItem { span: i.span, lang_item });
  48             }
  49         }
  50     }
  51 }
  52
  53 fn verify(tcx: TyCtxt<'_>, items: &lang_items::LanguageItems) {
  54     // We only need to check for the presence of weak lang items if we're
  55     // emitting something that's not an rlib.
  56     let needs_check = tcx.crate_types().iter().any(|kind| match *kind {
  57         CrateType::Dylib
  58         | CrateType::ProcMacro
  59         | CrateType::Cdylib
  60         | CrateType::Executable
  61         | CrateType::Staticlib => true,
  62         CrateType::Rlib => false,
  63     });
  64     if !needs_check {
  65         return;
  66     }
  67
  68     let mut missing = FxHashSet::default();
  69     for &cnum in tcx.crates(()).iter() {
  70         for &item in tcx.missing_lang_items(cnum).iter() {
  71             missing.insert(item);
  72         }
  73     }
  74
  75     for &item in WEAK_LANG_ITEMS.iter() {
  76         if missing.contains(&item) && required(tcx, item) && items.get(item).is_none() {
  77             if item == LangItem::PanicImpl {
  78                 tcx.sess.emit_err(MissingPanicHandler);
  79             } else {
  80                 tcx.sess.emit_err(MissingLangItem { name: item.name() });
  81             }
  82         }
  83     }
  84 }