95 lines
2.9 KiB
Rust
95 lines
2.9 KiB
Rust
// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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/*
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* The compiler code necessary to support the `push_unsafe!` and
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* `pop_unsafe!` macros.
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*
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* This is a hack to allow a kind of "safety hygiene", where a macro
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* can generate code with an interior expression that inherits the
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* safety of some outer context.
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*
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* For example, in:
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*
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* ```rust
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* fn foo() { push_unsafe!( { EXPR_1; pop_unsafe!( EXPR_2 ) } ) }
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* ```
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*
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* the `EXPR_1` is considered to be in an `unsafe` context,
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* but `EXPR_2` is considered to be in a "safe" (i.e. checked) context.
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*
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* For comparison, in:
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*
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* ```rust
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* fn foo() { unsafe { push_unsafe!( { EXPR_1; pop_unsafe!( EXPR_2 ) } ) } }
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* ```
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*
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* both `EXPR_1` and `EXPR_2` are considered to be in `unsafe`
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* contexts.
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*
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*/
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use ast;
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use codemap::Span;
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use ext::base::*;
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use ext::base;
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use ext::build::AstBuilder;
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use feature_gate;
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use ptr::P;
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enum PushPop { Push, Pop }
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pub fn expand_push_unsafe<'cx>(cx: &'cx mut ExtCtxt, sp: Span, tts: &[ast::TokenTree])
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-> Box<base::MacResult+'cx> {
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expand_pushpop_unsafe(cx, sp, tts, PushPop::Push)
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}
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pub fn expand_pop_unsafe<'cx>(cx: &'cx mut ExtCtxt, sp: Span, tts: &[ast::TokenTree])
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-> Box<base::MacResult+'cx> {
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expand_pushpop_unsafe(cx, sp, tts, PushPop::Pop)
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}
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fn expand_pushpop_unsafe<'cx>(cx: &'cx mut ExtCtxt, sp: Span, tts: &[ast::TokenTree],
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pp: PushPop) -> Box<base::MacResult+'cx> {
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feature_gate::check_for_pushpop_syntax(
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cx.ecfg.features, &cx.parse_sess.span_diagnostic, sp);
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let mut exprs = match get_exprs_from_tts(cx, sp, tts) {
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Some(exprs) => exprs.into_iter(),
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None => return DummyResult::expr(sp),
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};
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let expr = match (exprs.next(), exprs.next()) {
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(Some(expr), None) => expr,
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_ => {
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let msg = match pp {
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PushPop::Push => "push_unsafe! takes 1 arguments",
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PushPop::Pop => "pop_unsafe! takes 1 arguments",
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};
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cx.span_err(sp, msg);
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return DummyResult::expr(sp);
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}
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};
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let source = ast::UnsafeSource::CompilerGenerated;
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let check_mode = match pp {
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PushPop::Push => ast::BlockCheckMode::PushUnsafeBlock(source),
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PushPop::Pop => ast::BlockCheckMode::PopUnsafeBlock(source),
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};
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MacEager::expr(cx.expr_block(P(ast::Block {
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stmts: vec![],
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expr: Some(expr),
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id: ast::DUMMY_NODE_ID,
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rules: check_mode,
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span: sp
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})))
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}
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