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1 // Copyright 2012 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
4 //
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
10
11
12 use dep_graph::DepNode;
13 use hir::map as ast_map;
14 use hir::def_id::{CRATE_DEF_INDEX};
15 use session::{config, Session};
16 use syntax::ast::NodeId;
17 use syntax::attr;
18 use syntax::codemap::Span;
19 use syntax::entry::EntryPointType;
20 use hir::{Item, ItemFn};
21 use hir::intravisit::Visitor;
22
23 struct EntryContext<'a, 'tcx: 'a> {
24 session: &'a Session,
25
26 map: &'a ast_map::Map<'tcx>,
27
28 // The top-level function called 'main'
29 main_fn: Option<(NodeId, Span)>,
30
31 // The function that has attribute named 'main'
32 attr_main_fn: Option<(NodeId, Span)>,
33
34 // The function that has the attribute 'start' on it
35 start_fn: Option<(NodeId, Span)>,
36
37 // The functions that one might think are 'main' but aren't, e.g.
38 // main functions not defined at the top level. For diagnostics.
39 non_main_fns: Vec<(NodeId, Span)> ,
40 }
41
42 impl<'a, 'tcx> Visitor<'tcx> for EntryContext<'a, 'tcx> {
43 fn visit_item(&mut self, item: &'tcx Item) {
44 let def_id = self.map.local_def_id(item.id);
45 let def_key = self.map.def_key(def_id);
46 let at_root = def_key.parent == Some(CRATE_DEF_INDEX);
47 find_item(item, self, at_root);
48 }
49 }
50
51 pub fn find_entry_point(session: &Session, ast_map: &ast_map::Map) {
52 let _task = ast_map.dep_graph.in_task(DepNode::EntryPoint);
53
54 let any_exe = session.crate_types.borrow().iter().any(|ty| {
55 *ty == config::CrateTypeExecutable
56 });
57 if !any_exe {
58 // No need to find a main function
59 return
60 }
61
62 // If the user wants no main function at all, then stop here.
63 if attr::contains_name(&ast_map.krate().attrs, "no_main") {
64 session.entry_type.set(Some(config::EntryNone));
65 return
66 }
67
68 let mut ctxt = EntryContext {
69 session: session,
70 map: ast_map,
71 main_fn: None,
72 attr_main_fn: None,
73 start_fn: None,
74 non_main_fns: Vec::new(),
75 };
76
77 ast_map.krate().visit_all_items(&mut ctxt);
78
79 configure_main(&mut ctxt);
80 }
81
82 // Beware, this is duplicated in libsyntax/entry.rs, make sure to keep
83 // them in sync.
84 fn entry_point_type(item: &Item, at_root: bool) -> EntryPointType {
85 match item.node {
86 ItemFn(..) => {
87 if attr::contains_name(&item.attrs, "start") {
88 EntryPointType::Start
89 } else if attr::contains_name(&item.attrs, "main") {
90 EntryPointType::MainAttr
91 } else if item.name.as_str() == "main" {
92 if at_root {
93 // This is a top-level function so can be 'main'
94 EntryPointType::MainNamed
95 } else {
96 EntryPointType::OtherMain
97 }
98 } else {
99 EntryPointType::None
100 }
101 }
102 _ => EntryPointType::None,
103 }
104 }
105
106
107 fn find_item(item: &Item, ctxt: &mut EntryContext, at_root: bool) {
108 match entry_point_type(item, at_root) {
109 EntryPointType::MainNamed => {
110 if ctxt.main_fn.is_none() {
111 ctxt.main_fn = Some((item.id, item.span));
112 } else {
113 span_err!(ctxt.session, item.span, E0136,
114 "multiple 'main' functions");
115 }
116 },
117 EntryPointType::OtherMain => {
118 ctxt.non_main_fns.push((item.id, item.span));
119 },
120 EntryPointType::MainAttr => {
121 if ctxt.attr_main_fn.is_none() {
122 ctxt.attr_main_fn = Some((item.id, item.span));
123 } else {
124 span_err!(ctxt.session, item.span, E0137,
125 "multiple functions with a #[main] attribute");
126 }
127 },
128 EntryPointType::Start => {
129 if ctxt.start_fn.is_none() {
130 ctxt.start_fn = Some((item.id, item.span));
131 } else {
132 span_err!(ctxt.session, item.span, E0138,
133 "multiple 'start' functions");
134 }
135 },
136 EntryPointType::None => ()
137 }
138 }
139
140 fn configure_main(this: &mut EntryContext) {
141 if this.start_fn.is_some() {
142 *this.session.entry_fn.borrow_mut() = this.start_fn;
143 this.session.entry_type.set(Some(config::EntryStart));
144 } else if this.attr_main_fn.is_some() {
145 *this.session.entry_fn.borrow_mut() = this.attr_main_fn;
146 this.session.entry_type.set(Some(config::EntryMain));
147 } else if this.main_fn.is_some() {
148 *this.session.entry_fn.borrow_mut() = this.main_fn;
149 this.session.entry_type.set(Some(config::EntryMain));
150 } else {
151 // No main function
152 let mut err = this.session.struct_err("main function not found");
153 if !this.non_main_fns.is_empty() {
154 // There were some functions named 'main' though. Try to give the user a hint.
155 err.note("the main function must be defined at the crate level \
156 but you have one or more functions named 'main' that are not \
157 defined at the crate level. Either move the definition or \
158 attach the `#[main]` attribute to override this behavior.");
159 for &(_, span) in &this.non_main_fns {
160 err.span_note(span, "here is a function named 'main'");
161 }
162 err.emit();
163 this.session.abort_if_errors();
164 } else {
165 err.emit();
166 }
167 }
168 }