mirror of
https://git.savannah.gnu.org/git/bison.git
synced 2026-03-09 20:33:03 +00:00
97ae878ec3
The current approach was too adhoc: the symbols were not sufficiently self-contained, in particular wrt memory management. The "new" guideline is the one that should have been followed from the start: let the symbols handle themslves, instead of leaving their users to it. It was justified by the will to avoid gratuitious moves and copies, but the current approach does not seem to be slower, yet it will probably be simpler to adjust to support move semantics from C++11. The documentation says that the %parse-param are available from the %destructor. In retrospect, that was a silly design decision, which we can break for variants, as its a new feature. It should be phased out for non-variants too. * data/variant.hh: A variant never knows if it stores something or not, it is up to its users to store this information. Yet, in parse.assert mode, make sure the empty/filled variants are properly used. (b4_symbol_constructor_define_): Don't call directly the symbol constructor, to save a useless temporary. * data/stack.hh (push): Steal the pushed value instead of duplicating it. This will simplify the callers of push, who handled this "move" approach themselves. * data/c++.m4 (basic_symbol): Let -1, as kind, denote the fact that a symbol is empty. This is needed for instance when shifting the lookahead: yyla is given as argument to "push", and its value is then moved on the stack. But then yyla must be declared "empty" so that its destructor won't be called. (basic_symbol::move): New. Move the responsibility of calling the destructor from yy_destroy to ~basic_symbol in the case of variants. * data/lalr1.cc (stack_symbol_type): Now a derived class from its previous value, so that we can add a constructor from a symbol_type. (by_state): State -1 means empty. (yypush_): Factor, by calling one overload from the other one, and using the new semantics of stack::push. No longer reclaim by hand the memory from rhs symbols, since now that we store objects with proper destructors, they will be reclaimed automatically. Conversely, be sure to delete yylhs. * tests/c++.at (C++ Variant-based Symbols): New "unit" test for symbols.
-*- outline -*- This directory contains data needed by Bison. * Skeletons Bison skeletons: the general shapes of the different parser kinds, that are specialized for specific grammars by the bison program. Currently, the supported skeletons are: - yacc.c It used to be named bison.simple: it corresponds to C Yacc compatible LALR(1) parsers. - lalr1.cc Produces a C++ parser class. - lalr1.java Produces a Java parser class. - glr.c A Generalized LR C parser based on Bison's LALR(1) tables. - glr.cc A Generalized LR C++ parser. Actually a C++ wrapper around glr.c. These skeletons are the only ones supported by the Bison team. Because the interface between skeletons and the bison program is not finished, *we are not bound to it*. In particular, Bison is not mature enough for us to consider that ``foreign skeletons'' are supported. * m4sugar This directory contains M4sugar, sort of an extended library for M4, which is used by Bison to instantiate the skeletons. * xslt This directory contains XSLT programs that transform Bison's XML output into various formats. - bison.xsl A library of routines used by the other XSLT programs. - xml2dot.xsl Conversion into GraphViz's dot format. - xml2text.xsl Conversion into text. - xml2xhtml.xsl Conversion into XHTML. ----- Copyright (C) 2002, 2008-2013 Free Software Foundation, Inc. This file is part of GNU Bison. This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>.