syntax_ext: Improve and simplify code generated by #[global_allocator]
Instead of ``` mod allocator_abi { /* methods */ } ``` we now generate ``` const _: () = { /* methods */ } ``` and use `std_path` for paths referring to standard library entities. This way we no longer need to generate `use` and `extern crate` imports, and `#[global_allocator]` starts working inside unnamed blocks.
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76b1ffaf6c
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@ -1,13 +1,12 @@
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use syntax::ast::{ItemKind, Mutability, Ty, TyKind, Unsafety, VisibilityKind};
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use syntax::ast::{self, Arg, Attribute, Expr, FnHeader, Generics, Ident, Item};
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use syntax::ast::{ItemKind, Mutability, Stmt, Ty, TyKind, Unsafety};
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use syntax::ast::{self, Arg, Attribute, Expr, FnHeader, Generics, Ident};
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use syntax::attr::check_builtin_macro_attribute;
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use syntax::ext::allocator::{AllocatorKind, AllocatorMethod, AllocatorTy, ALLOCATOR_METHODS};
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use syntax::ext::base::{Annotatable, ExtCtxt};
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use syntax::ext::build::AstBuilder;
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use syntax::ext::hygiene::SyntaxContext;
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use syntax::ptr::P;
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use syntax::source_map::respan;
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use syntax::symbol::{kw, sym};
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use syntax::symbol::{kw, sym, Symbol};
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use syntax_pos::Span;
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pub fn expand(
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@ -36,52 +35,31 @@ pub fn expand(
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span,
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kind: AllocatorKind::Global,
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global: item.ident,
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core: Ident::with_empty_ctxt(sym::core),
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cx: ecx,
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};
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// We will generate a new submodule. To `use` the static from that module, we need to get
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// the `super::...` path.
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let super_path = f.cx.path(f.span, vec![Ident::with_empty_ctxt(kw::Super), f.global]);
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// Generate item statements for the allocator methods.
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let stmts = ALLOCATOR_METHODS.iter().map(|method| f.allocator_fn(method)).collect();
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// Generate the items in the submodule
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let mut items = vec![
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// import `core` to use allocators
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f.cx.item_extern_crate(f.span, f.core),
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// `use` the `global_allocator` in `super`
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f.cx.item_use_simple(
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f.span,
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respan(f.span.shrink_to_lo(), VisibilityKind::Inherited),
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super_path,
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),
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];
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// Generate anonymous constant serving as container for the allocator methods.
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let const_ty = ecx.ty(span, TyKind::Tup(Vec::new()));
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let const_body = ecx.expr_block(ecx.block(span, stmts));
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let const_item =
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ecx.item_const(span, Ident::with_empty_ctxt(kw::Underscore), const_ty, const_body);
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// Add the allocator methods to the submodule
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items.extend(
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ALLOCATOR_METHODS
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.iter()
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.map(|method| f.allocator_fn(method)),
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);
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// Generate the submodule itself
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let name = f.kind.fn_name("allocator_abi");
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let allocator_abi = Ident::from_str(&name).gensym();
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let module = f.cx.item_mod(span, span, allocator_abi, Vec::new(), items);
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// Return the item and new submodule
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vec![Annotatable::Item(item), Annotatable::Item(module)]
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// Return the original item and the new methods.
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vec![Annotatable::Item(item), Annotatable::Item(const_item)]
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}
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struct AllocFnFactory<'a, 'b> {
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span: Span,
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kind: AllocatorKind,
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global: Ident,
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core: Ident,
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cx: &'b ExtCtxt<'a>,
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}
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impl AllocFnFactory<'_, '_> {
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fn allocator_fn(&self, method: &AllocatorMethod) -> P<Item> {
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fn allocator_fn(&self, method: &AllocatorMethod) -> Stmt {
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let mut abi_args = Vec::new();
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let mut i = 0;
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let ref mut mk = || {
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@ -105,25 +83,22 @@ impl AllocFnFactory<'_, '_> {
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Generics::default(),
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self.cx.block_expr(output_expr),
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);
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self.cx.item(
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let item = self.cx.item(
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self.span,
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Ident::from_str(&self.kind.fn_name(method.name)),
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self.attrs(),
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kind,
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)
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);
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self.cx.stmt_item(self.span, item)
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}
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fn call_allocator(&self, method: &str, mut args: Vec<P<Expr>>) -> P<Expr> {
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let method = self.cx.path(
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self.span,
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vec![
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self.core,
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Ident::from_str("alloc"),
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Ident::from_str("GlobalAlloc"),
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Ident::from_str(method),
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],
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);
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let method = self.cx.expr_path(method);
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let method = self.cx.std_path(&[
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Symbol::intern("alloc"),
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Symbol::intern("GlobalAlloc"),
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Symbol::intern(method),
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]);
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let method = self.cx.expr_path(self.cx.path(self.span, method));
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let allocator = self.cx.path_ident(self.span, self.global);
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let allocator = self.cx.expr_path(allocator);
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let allocator = self.cx.expr_addr_of(self.span, allocator);
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@ -153,16 +128,12 @@ impl AllocFnFactory<'_, '_> {
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args.push(self.cx.arg(self.span, size, ty_usize.clone()));
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args.push(self.cx.arg(self.span, align, ty_usize));
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let layout_new = self.cx.path(
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self.span,
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vec![
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self.core,
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Ident::from_str("alloc"),
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Ident::from_str("Layout"),
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Ident::from_str("from_size_align_unchecked"),
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],
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);
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let layout_new = self.cx.expr_path(layout_new);
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let layout_new = self.cx.std_path(&[
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Symbol::intern("alloc"),
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Symbol::intern("Layout"),
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Symbol::intern("from_size_align_unchecked"),
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]);
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let layout_new = self.cx.expr_path(self.cx.path(self.span, layout_new));
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let size = self.cx.expr_ident(self.span, size);
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let align = self.cx.expr_ident(self.span, align);
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let layout = self.cx.expr_call(self.span, layout_new, vec![size, align]);
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@ -13,9 +13,10 @@ fn main() {
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#[global_allocator]
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pub static GLOBAL: A = A(AtomicUsize::new(0));
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let n = GLOBAL.0.load(Ordering::SeqCst);
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let s = Box::new(0);
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helper::work_with(&s);
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assert_eq!(GLOBAL.0.load(Ordering::SeqCst), 1);
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assert_eq!(GLOBAL.0.load(Ordering::SeqCst), n + 1);
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drop(s);
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assert_eq!(GLOBAL.0.load(Ordering::SeqCst), 2);
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assert_eq!(GLOBAL.0.load(Ordering::SeqCst), n + 2);
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}
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@ -17,9 +17,10 @@ mod submodule {
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}
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fn main() {
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let n = submodule::GLOBAL.0.load(Ordering::SeqCst);
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let s = Box::new(0);
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helper::work_with(&s);
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assert_eq!(submodule::GLOBAL.0.load(Ordering::SeqCst), 1);
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assert_eq!(submodule::GLOBAL.0.load(Ordering::SeqCst), n + 1);
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drop(s);
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assert_eq!(submodule::GLOBAL.0.load(Ordering::SeqCst), 2);
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assert_eq!(submodule::GLOBAL.0.load(Ordering::SeqCst), n + 2);
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}
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