// Copyright 2013 The Rust Project Developers. See the COPYRIGHT // file at the top-level directory of this distribution and at // http://rust-lang.org/COPYRIGHT. // // Licensed under the Apache License, Version 2.0 or the MIT license // , at your // option. This file may not be copied, modified, or distributed // except according to those terms. /** The compiler code necessary to support the cfg! extension, which expands to a literal `true` or `false` based on whether the given cfgs match the current compilation environment. */ use ast; use codemap::Span; use ext::base::*; use ext::base; use ext::build::AstBuilder; use attr; use attr::*; use parse::attr::ParserAttr; use parse::token::InternedString; use parse::token; use parse; use std::vec_ng::Vec; pub fn expand_cfg(cx: &mut ExtCtxt, sp: Span, tts: &[ast::TokenTree]) -> base::MacResult { let mut p = parse::new_parser_from_tts(cx.parse_sess(), cx.cfg(), tts.iter() .map(|x| (*x).clone()) .collect()); let mut cfgs = Vec::new(); // parse `cfg!(meta_item, meta_item(x,y), meta_item="foo", ...)` while p.token != token::EOF { cfgs.push(p.parse_meta_item()); if p.eat(&token::EOF) { break } // trailing comma is optional,. p.expect(&token::COMMA); } // test_cfg searches for meta items looking like `cfg(foo, ...)` let in_cfg = &[cx.meta_list(sp, InternedString::new("cfg"), cfgs)]; let matches_cfg = attr::test_cfg(cx.cfg().as_slice(), in_cfg.iter().map(|&x| x)); let e = cx.expr_bool(sp, matches_cfg); MRExpr(e) }