use rustc_ast::attr; use rustc_ast::entry::EntryPointType; use rustc_errors::error_code; use rustc_hir::def::DefKind; use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_ID, LOCAL_CRATE}; use rustc_hir::{ItemId, Node, CRATE_HIR_ID}; use rustc_middle::ty::query::Providers; use rustc_middle::ty::TyCtxt; use rustc_session::config::{sigpipe, CrateType, EntryFnType}; use rustc_session::parse::feature_err; use rustc_span::symbol::sym; use rustc_span::{Span, Symbol}; use crate::errors::{ AttrOnlyInFunctions, AttrOnlyOnMain, AttrOnlyOnRootMain, ExternMain, MultipleRustcMain, MultipleStartFunctions, NoMainErr, UnixSigpipeValues, }; struct EntryContext<'tcx> { tcx: TyCtxt<'tcx>, /// The function that has attribute named `main`. attr_main_fn: Option<(LocalDefId, Span)>, /// The function that has the attribute 'start' on it. start_fn: Option<(LocalDefId, Span)>, /// The functions that one might think are `main` but aren't, e.g. /// main functions not defined at the top level. For diagnostics. non_main_fns: Vec, } fn entry_fn(tcx: TyCtxt<'_>, (): ()) -> Option<(DefId, EntryFnType)> { let any_exe = tcx.sess.crate_types().iter().any(|ty| *ty == CrateType::Executable); if !any_exe { // No need to find a main function. return None; } // If the user wants no main function at all, then stop here. if attr::contains_name(&tcx.hir().attrs(CRATE_HIR_ID), sym::no_main) { return None; } let mut ctxt = EntryContext { tcx, attr_main_fn: None, start_fn: None, non_main_fns: Vec::new() }; for id in tcx.hir().items() { find_item(id, &mut ctxt); } configure_main(tcx, &ctxt) } // Beware, this is duplicated in `librustc_builtin_macros/test_harness.rs` // (with `ast::Item`), so make sure to keep them in sync. // A small optimization was added so that hir::Item is fetched only when needed. // An equivalent optimization was not applied to the duplicated code in test_harness.rs. fn entry_point_type(ctxt: &EntryContext<'_>, id: ItemId, at_root: bool) -> EntryPointType { let attrs = ctxt.tcx.hir().attrs(id.hir_id()); if attr::contains_name(attrs, sym::start) { EntryPointType::Start } else if attr::contains_name(attrs, sym::rustc_main) { EntryPointType::RustcMainAttr } else { if let Some(name) = ctxt.tcx.opt_item_name(id.owner_id.to_def_id()) && name == sym::main { if at_root { // This is a top-level function so can be `main`. EntryPointType::MainNamed } else { EntryPointType::OtherMain } } else { EntryPointType::None } } } fn attr_span_by_symbol(ctxt: &EntryContext<'_>, id: ItemId, sym: Symbol) -> Option { let attrs = ctxt.tcx.hir().attrs(id.hir_id()); attr::find_by_name(attrs, sym).map(|attr| attr.span) } fn find_item(id: ItemId, ctxt: &mut EntryContext<'_>) { let at_root = ctxt.tcx.opt_local_parent(id.owner_id.def_id) == Some(CRATE_DEF_ID); match entry_point_type(ctxt, id, at_root) { EntryPointType::None => { if let Some(span) = attr_span_by_symbol(ctxt, id, sym::unix_sigpipe) { ctxt.tcx.sess.emit_err(AttrOnlyOnMain { span, attr: sym::unix_sigpipe }); } } _ if !matches!(ctxt.tcx.def_kind(id.owner_id), DefKind::Fn) => { for attr in [sym::start, sym::rustc_main] { if let Some(span) = attr_span_by_symbol(ctxt, id, attr) { ctxt.tcx.sess.emit_err(AttrOnlyInFunctions { span, attr }); } } } EntryPointType::MainNamed => (), EntryPointType::OtherMain => { if let Some(span) = attr_span_by_symbol(ctxt, id, sym::unix_sigpipe) { ctxt.tcx.sess.emit_err(AttrOnlyOnRootMain { span, attr: sym::unix_sigpipe }); } ctxt.non_main_fns.push(ctxt.tcx.def_span(id.owner_id)); } EntryPointType::RustcMainAttr => { if ctxt.attr_main_fn.is_none() { ctxt.attr_main_fn = Some((id.owner_id.def_id, ctxt.tcx.def_span(id.owner_id))); } else { ctxt.tcx.sess.emit_err(MultipleRustcMain { span: ctxt.tcx.def_span(id.owner_id.to_def_id()), first: ctxt.attr_main_fn.unwrap().1, additional: ctxt.tcx.def_span(id.owner_id.to_def_id()), }); } } EntryPointType::Start => { if let Some(span) = attr_span_by_symbol(ctxt, id, sym::unix_sigpipe) { ctxt.tcx.sess.emit_err(AttrOnlyOnMain { span, attr: sym::unix_sigpipe }); } if ctxt.start_fn.is_none() { ctxt.start_fn = Some((id.owner_id.def_id, ctxt.tcx.def_span(id.owner_id))); } else { ctxt.tcx.sess.emit_err(MultipleStartFunctions { span: ctxt.tcx.def_span(id.owner_id), labeled: ctxt.tcx.def_span(id.owner_id.to_def_id()), previous: ctxt.start_fn.unwrap().1, }); } } } } fn configure_main(tcx: TyCtxt<'_>, visitor: &EntryContext<'_>) -> Option<(DefId, EntryFnType)> { if let Some((def_id, _)) = visitor.start_fn { Some((def_id.to_def_id(), EntryFnType::Start)) } else if let Some((local_def_id, _)) = visitor.attr_main_fn { let def_id = local_def_id.to_def_id(); Some((def_id, EntryFnType::Main { sigpipe: sigpipe(tcx, def_id) })) } else { if let Some(main_def) = tcx.resolutions(()).main_def && let Some(def_id) = main_def.opt_fn_def_id() { // non-local main imports are handled below if let Some(def_id) = def_id.as_local() && matches!(tcx.hir().find_by_def_id(def_id), Some(Node::ForeignItem(_))) { tcx.sess.emit_err(ExternMain { span: tcx.def_span(def_id) }); return None; } if main_def.is_import && !tcx.features().imported_main { let span = main_def.span; feature_err( &tcx.sess.parse_sess, sym::imported_main, span, "using an imported function as entry point `main` is experimental", ) .emit(); } return Some((def_id, EntryFnType::Main { sigpipe: sigpipe(tcx, def_id) })); } no_main_err(tcx, visitor); None } } fn sigpipe(tcx: TyCtxt<'_>, def_id: DefId) -> u8 { if let Some(attr) = tcx.get_attr(def_id, sym::unix_sigpipe) { match (attr.value_str(), attr.meta_item_list()) { (Some(sym::inherit), None) => sigpipe::INHERIT, (Some(sym::sig_ign), None) => sigpipe::SIG_IGN, (Some(sym::sig_dfl), None) => sigpipe::SIG_DFL, (_, Some(_)) => { // Keep going so that `fn emit_malformed_attribute()` can print // an excellent error message sigpipe::DEFAULT } _ => { tcx.sess.emit_err(UnixSigpipeValues { span: attr.span }); sigpipe::DEFAULT } } } else { sigpipe::DEFAULT } } fn no_main_err(tcx: TyCtxt<'_>, visitor: &EntryContext<'_>) { let sp = tcx.def_span(CRATE_DEF_ID); if tcx.sess.parse_sess.reached_eof.load(rustc_data_structures::sync::Ordering::Relaxed) { // There's an unclosed brace that made the parser reach `Eof`, we shouldn't complain about // the missing `fn main()` then as it might have been hidden inside an unclosed block. tcx.sess.delay_span_bug(sp, "`main` not found, but expected unclosed brace error"); return; } // There is no main function. let mut has_filename = true; let filename = tcx.sess.local_crate_source_file().unwrap_or_else(|| { has_filename = false; Default::default() }); let main_def_opt = tcx.resolutions(()).main_def; let diagnostic_id = error_code!(E0601); let add_teach_note = tcx.sess.teach(&diagnostic_id); // The file may be empty, which leads to the diagnostic machinery not emitting this // note. This is a relatively simple way to detect that case and emit a span-less // note instead. let file_empty = tcx.sess.source_map().lookup_line(sp.hi()).is_err(); tcx.sess.emit_err(NoMainErr { sp, crate_name: tcx.crate_name(LOCAL_CRATE), has_filename, filename, file_empty, non_main_fns: visitor.non_main_fns.clone(), main_def_opt, add_teach_note, }); } pub fn provide(providers: &mut Providers) { *providers = Providers { entry_fn, ..*providers }; }