1use rustc_ast::expand::allocator::{
2 ALLOCATOR_METHODS, AllocatorMethod, AllocatorMethodInput, AllocatorTy, global_fn_name,
3};
4use rustc_ast::ptr::P;
5use rustc_ast::{
6 self as ast, AttrVec, Expr, Fn, FnHeader, FnSig, Generics, ItemKind, Mutability, Param, Safety,
7 Stmt, StmtKind, Ty, TyKind,
8};
9use rustc_expand::base::{Annotatable, ExtCtxt};
10use rustc_span::{Ident, Span, Symbol, kw, sym};
11use thin_vec::{ThinVec, thin_vec};
12
13use crate::errors;
14use crate::util::check_builtin_macro_attribute;
15
16pub(crate) fn expand(
17 ecx: &mut ExtCtxt<'_>,
18 _span: Span,
19 meta_item: &ast::MetaItem,
20 item: Annotatable,
21) -> Vec<Annotatable> {
22 check_builtin_macro_attribute(ecx, meta_item, sym::global_allocator);
23
24 let orig_item = item.clone();
25
26 let (item, is_stmt, ty_span) = if let Annotatable::Item(item) = &item
29 && let ItemKind::Static(box ast::StaticItem { ty, .. }) = &item.kind
30 {
31 (item, false, ecx.with_def_site_ctxt(ty.span))
32 } else if let Annotatable::Stmt(stmt) = &item
33 && let StmtKind::Item(item) = &stmt.kind
34 && let ItemKind::Static(box ast::StaticItem { ty, .. }) = &item.kind
35 {
36 (item, true, ecx.with_def_site_ctxt(ty.span))
37 } else {
38 ecx.dcx().emit_err(errors::AllocMustStatics { span: item.span() });
39 return vec![orig_item];
40 };
41
42 let span = ecx.with_def_site_ctxt(item.span);
44 let f = AllocFnFactory { span, ty_span, global: item.ident, cx: ecx };
45
46 let stmts = ALLOCATOR_METHODS.iter().map(|method| f.allocator_fn(method)).collect();
48
49 let const_ty = ecx.ty(ty_span, TyKind::Tup(ThinVec::new()));
51 let const_body = ecx.expr_block(ecx.block(span, stmts));
52 let const_item = ecx.item_const(span, Ident::new(kw::Underscore, span), const_ty, const_body);
53 let const_item = if is_stmt {
54 Annotatable::Stmt(P(ecx.stmt_item(span, const_item)))
55 } else {
56 Annotatable::Item(const_item)
57 };
58
59 vec![orig_item, const_item]
61}
62
63struct AllocFnFactory<'a, 'b> {
64 span: Span,
65 ty_span: Span,
66 global: Ident,
67 cx: &'a ExtCtxt<'b>,
68}
69
70impl AllocFnFactory<'_, '_> {
71 fn allocator_fn(&self, method: &AllocatorMethod) -> Stmt {
72 let mut abi_args = ThinVec::new();
73 let args = method.inputs.iter().map(|input| self.arg_ty(input, &mut abi_args)).collect();
74 let result = self.call_allocator(method.name, args);
75 let output_ty = self.ret_ty(&method.output);
76 let decl = self.cx.fn_decl(abi_args, ast::FnRetTy::Ty(output_ty));
77 let header = FnHeader { safety: Safety::Unsafe(self.span), ..FnHeader::default() };
78 let sig = FnSig { decl, header, span: self.span };
79 let body = Some(self.cx.block_expr(result));
80 let kind = ItemKind::Fn(Box::new(Fn {
81 defaultness: ast::Defaultness::Final,
82 sig,
83 generics: Generics::default(),
84 contract: None,
85 body,
86 define_opaque: None,
87 }));
88 let item = self.cx.item(
89 self.span,
90 Ident::from_str_and_span(&global_fn_name(method.name), self.span),
91 self.attrs(),
92 kind,
93 );
94 self.cx.stmt_item(self.ty_span, item)
95 }
96
97 fn call_allocator(&self, method: Symbol, mut args: ThinVec<P<Expr>>) -> P<Expr> {
98 let method = self.cx.std_path(&[sym::alloc, sym::GlobalAlloc, method]);
99 let method = self.cx.expr_path(self.cx.path(self.ty_span, method));
100 let allocator = self.cx.path_ident(self.ty_span, self.global);
101 let allocator = self.cx.expr_path(allocator);
102 let allocator = self.cx.expr_addr_of(self.ty_span, allocator);
103 args.insert(0, allocator);
104
105 self.cx.expr_call(self.ty_span, method, args)
106 }
107
108 fn attrs(&self) -> AttrVec {
109 thin_vec![self.cx.attr_word(sym::rustc_std_internal_symbol, self.span)]
110 }
111
112 fn arg_ty(&self, input: &AllocatorMethodInput, args: &mut ThinVec<Param>) -> P<Expr> {
113 match input.ty {
114 AllocatorTy::Layout => {
115 let size = Ident::from_str_and_span("size", self.span);
121 let align = Ident::from_str_and_span("align", self.span);
122
123 let usize = self.cx.path_ident(self.span, Ident::new(sym::usize, self.span));
124 let ty_usize = self.cx.ty_path(usize);
125 args.push(self.cx.param(self.span, size, ty_usize.clone()));
126 args.push(self.cx.param(self.span, align, ty_usize));
127
128 let layout_new =
129 self.cx.std_path(&[sym::alloc, sym::Layout, sym::from_size_align_unchecked]);
130 let layout_new = self.cx.expr_path(self.cx.path(self.span, layout_new));
131 let size = self.cx.expr_ident(self.span, size);
132 let align = self.cx.expr_ident(self.span, align);
133 let layout = self.cx.expr_call(self.span, layout_new, thin_vec![size, align]);
134 layout
135 }
136
137 AllocatorTy::Ptr => {
138 let ident = Ident::from_str_and_span(input.name, self.span);
139 args.push(self.cx.param(self.span, ident, self.ptr_u8()));
140 self.cx.expr_ident(self.span, ident)
141 }
142
143 AllocatorTy::Usize => {
144 let ident = Ident::from_str_and_span(input.name, self.span);
145 args.push(self.cx.param(self.span, ident, self.usize()));
146 self.cx.expr_ident(self.span, ident)
147 }
148
149 AllocatorTy::ResultPtr | AllocatorTy::Unit => {
150 panic!("can't convert AllocatorTy to an argument")
151 }
152 }
153 }
154
155 fn ret_ty(&self, ty: &AllocatorTy) -> P<Ty> {
156 match *ty {
157 AllocatorTy::ResultPtr => self.ptr_u8(),
158
159 AllocatorTy::Unit => self.cx.ty(self.span, TyKind::Tup(ThinVec::new())),
160
161 AllocatorTy::Layout | AllocatorTy::Usize | AllocatorTy::Ptr => {
162 panic!("can't convert `AllocatorTy` to an output")
163 }
164 }
165 }
166
167 fn usize(&self) -> P<Ty> {
168 let usize = self.cx.path_ident(self.span, Ident::new(sym::usize, self.span));
169 self.cx.ty_path(usize)
170 }
171
172 fn ptr_u8(&self) -> P<Ty> {
173 let u8 = self.cx.path_ident(self.span, Ident::new(sym::u8, self.span));
174 let ty_u8 = self.cx.ty_path(u8);
175 self.cx.ty_ptr(self.span, ty_u8, Mutability::Mut)
176 }
177}