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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::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<Span>,
}
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<Span> {
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 };
}
|
