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//! Used by `rustc` when loading a plugin.
use crate::errors::{LoadPluginError, MalformedPluginAttribute};
use crate::Registry;
use libloading::Library;
use rustc_ast::Attribute;
use rustc_metadata::locator;
use rustc_session::cstore::MetadataLoader;
use rustc_session::Session;
use rustc_span::symbol::{sym, Ident};
use std::env;
use std::mem;
use std::path::PathBuf;
/// Pointer to a registrar function.
type PluginRegistrarFn = fn(&mut Registry<'_>);
/// Read plugin metadata and dynamically load registrar functions.
pub fn load_plugins(
sess: &Session,
metadata_loader: &dyn MetadataLoader,
attrs: &[Attribute],
) -> Vec<PluginRegistrarFn> {
let mut plugins = Vec::new();
for attr in attrs {
if !attr.has_name(sym::plugin) {
continue;
}
for plugin in attr.meta_item_list().unwrap_or_default() {
match plugin.ident() {
Some(ident) if plugin.is_word() => {
load_plugin(&mut plugins, sess, metadata_loader, ident)
}
_ => {
sess.emit_err(MalformedPluginAttribute { span: plugin.span() });
}
}
}
}
plugins
}
fn load_plugin(
plugins: &mut Vec<PluginRegistrarFn>,
sess: &Session,
metadata_loader: &dyn MetadataLoader,
ident: Ident,
) {
let lib = locator::find_plugin_registrar(sess, metadata_loader, ident.span, ident.name);
let fun = dylink_registrar(lib).unwrap_or_else(|err| {
// This is fatal: there are almost certainly macros we need inside this crate, so
// continuing would spew "macro undefined" errors.
sess.emit_fatal(LoadPluginError { span: ident.span, msg: err.to_string() });
});
plugins.push(fun);
}
/// Dynamically link a registrar function into the compiler process.
fn dylink_registrar(lib_path: PathBuf) -> Result<PluginRegistrarFn, libloading::Error> {
// Make sure the path contains a / or the linker will search for it.
let lib_path = env::current_dir().unwrap().join(&lib_path);
let lib = unsafe { Library::new(&lib_path) }?;
let registrar_sym = unsafe { lib.get::<PluginRegistrarFn>(b"__rustc_plugin_registrar") }?;
// Intentionally leak the dynamic library. We can't ever unload it
// since the library can make things that will live arbitrarily long
// (e.g., an Rc cycle or a thread).
let registrar_sym = unsafe { registrar_sym.into_raw() };
mem::forget(lib);
Ok(*registrar_sym)
}
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