src/librustc_plugin_impl/load.rs

   1 //! Used by `rustc` when loading a plugin.
   2
   3 use crate::Registry;
   4 use rustc_ast::Crate;
   5 use rustc_errors::struct_span_err;
   6 use rustc_metadata::locator;
   7 use rustc_middle::middle::cstore::MetadataLoader;
   8 use rustc_session::Session;
   9 use rustc_span::symbol::{sym, Ident};
  10 use rustc_span::Span;
  11
  12 use std::borrow::ToOwned;
  13 use std::env;
  14 use std::mem;
  15 use std::path::PathBuf;
  16
  17 /// Pointer to a registrar function.
  18 type PluginRegistrarFn = fn(&mut Registry<'_>);
  19
  20 fn call_malformed_plugin_attribute(sess: &Session, span: Span) {
  21     struct_span_err!(sess, span, E0498, "malformed `plugin` attribute")
  22         .span_label(span, "malformed attribute")
  23         .emit();
  24 }
  25
  26 /// Read plugin metadata and dynamically load registrar functions.
  27 pub fn load_plugins(
  28     sess: &Session,
  29     metadata_loader: &dyn MetadataLoader,
  30     krate: &Crate,
  31 ) -> Vec<PluginRegistrarFn> {
  32     let mut plugins = Vec::new();
  33
  34     for attr in &krate.attrs {
  35         if !sess.check_name(attr, sym::plugin) {
  36             continue;
  37         }
  38
  39         for plugin in attr.meta_item_list().unwrap_or_default() {
  40             match plugin.ident() {
  41                 Some(ident) if plugin.is_word() => {
  42                     load_plugin(&mut plugins, sess, metadata_loader, ident)
  43                 }
  44                 _ => call_malformed_plugin_attribute(sess, plugin.span()),
  45             }
  46         }
  47     }
  48
  49     plugins
  50 }
  51
  52 fn load_plugin(
  53     plugins: &mut Vec<PluginRegistrarFn>,
  54     sess: &Session,
  55     metadata_loader: &dyn MetadataLoader,
  56     ident: Ident,
  57 ) {
  58     let (lib, disambiguator) =
  59         locator::find_plugin_registrar(sess, metadata_loader, ident.span, ident.name);
  60     let symbol = sess.generate_plugin_registrar_symbol(disambiguator);
  61     let fun = dylink_registrar(sess, ident.span, lib, symbol);
  62     plugins.push(fun);
  63 }
  64
  65 // Dynamically link a registrar function into the compiler process.
  66 fn dylink_registrar(
  67     sess: &Session,
  68     span: Span,
  69     path: PathBuf,
  70     symbol: String,
  71 ) -> PluginRegistrarFn {
  72     use rustc_metadata::dynamic_lib::DynamicLibrary;
  73
  74     // Make sure the path contains a / or the linker will search for it.
  75     let path = env::current_dir().unwrap().join(&path);
  76
  77     let lib = match DynamicLibrary::open(&path) {
  78         Ok(lib) => lib,
  79         // this is fatal: there are almost certainly macros we need
  80         // inside this crate, so continue would spew "macro undefined"
  81         // errors
  82         Err(err) => sess.span_fatal(span, &err),
  83     };
  84
  85     unsafe {
  86         let registrar = match lib.symbol(&symbol) {
  87             Ok(registrar) => mem::transmute::<*mut u8, PluginRegistrarFn>(registrar),
  88             // again fatal if we can't register macros
  89             Err(err) => sess.span_fatal(span, &err),
  90         };
  91
  92         // Intentionally leak the dynamic library. We can't ever unload it
  93         // since the library can make things that will live arbitrarily long
  94         // (e.g., an @-box cycle or a thread).
  95         mem::forget(lib);
  96
  97         registrar
  98     }
  99 }