mirror of
https://git.savannah.gnu.org/git/bison.git
synced 2026-03-09 12:23:04 +00:00
c44a782a4e
Currently it is the front end that passes the symbol types to the
backend. For instance:
%token <ival> NUM
%type <ival> exp1 exp2
exp1: NUM { $$ = $1; }
exp2: NUM { $<ival>$ = $<ival>1; }
In both cases, $$ and $1 are passed to the backend as having type
'ival' resulting in code like `val.ival`. This is troublesome in the
case of api.value.type=union, since in that the case the code this:
%define api.value.type union
%token <int> NUM
%type <int> exp1 exp2
exp1: NUM { $$ = $1; }
exp2: NUM { $<int>$ = $<int>1; }
because in this case, since the backend does not know the symbol being
processed, it is forced to generate casts in both cases: *(int*)(&val)`.
This is unfortunate in the first case (exp1) where there is no reason
at all to use a cast instead of `val.NUM` and `val.exp1`.
So instead delegate the computation of the actual value type to the
backend: pass $<ival>$ as `symbol-number, ival` and $$ as
`symbol-number, MULL`, instead of passing `ival` before.
* src/scan-code.l (handle_action_dollar): Find the symbol the action
is about, not just its tyye. Pass both symbol-number, and explicit
type tag ($<tag>n when there is one) to b4_lhs_value and b4_rhs_value.
* data/bison.m4 (b4_symbol_action): adjust to the new signature to
b4_dollar_pushdef.
* data/c-like.m4 (_b4_dollar_dollar, b4_dollar_pushdef): Accept the
symbol-number as new argument.
* data/c.m4 (b4_symbol_value): Accept the symbol-number as new
argument, and use it.
(b4_symbol_value_union): Accept the symbol-number as new
argument, and use it to prefer ready a union member rather than
casting the union.
* data/yacc.c (b4_lhs_value, b4_rhs_value): Accept the new
symbol-number argument.
Adjust uses of b4_dollar_pushdef.
* data/glr.c (b4_lhs_value, b4_rhs_value): Adjust.
* data/lalr1.cc (b4_symbol_value_template, b4_lhs_value): Adjust
to the new symbol-number argument.
* data/variant.hh (b4_symbol_value, b4_symbol_value_template): Accept
the new symbol-number argument.
* data/java.m4 (b4_symbol_value, b4_rhs_data): New.
(b4_rhs_value): Use them.
* data/lalr1.java: Adjust to b4_dollar_pushdef, and use b4_rhs_data.
This package contains the GNU Bison parser generator.
* Installation
** Build
See the file INSTALL for generic compilation and installation
instructions.
Bison requires GNU m4 1.4.6 or later. See:
https://ftp.gnu.org/gnu/m4/m4-1.4.6.tar.gz
** Internationalization
Bison supports two catalogs: one for Bison itself (i.e., for the
maintainer-side parser generation), and one for the generated parsers
(i.e., for the user-side parser execution). The requirements between
both differ: bison needs ngettext, the generated parsers do not. To
simplify the build system, neither are installed if ngettext is not
supported, even if generated parsers could have been localized. See
http://lists.gnu.org/archive/html/bug-bison/2009-08/msg00006.html for
more details.
* Questions
See the section FAQ in the documentation (doc/bison.info) for
frequently asked questions. The documentation is also available in
PDF and HTML, provided you have a recent version of Texinfo installed:
run "make pdf" or "make html".
If you have questions about using Bison and the documentation does
not answer them, please send mail to <help-bison@gnu.org>.
* Bug reports
Please send bug reports to <bug-bison@gnu.org>. Be sure to include the
version number from 'bison --version', and a complete, self-contained test
case in each bug report.
* Copyright statements
For any copyright year range specified as YYYY-ZZZZ in this package,
note that the range specifies every single year in that closed interval.
-----
Local Variables:
mode: outline
fill-column: 76
ispell-dictionary: "american"
End:
Copyright (C) 1992, 1998-1999, 2003-2005, 2008-2015, 2018 Free Software
Foundation, Inc.
This file is part of GNU bison, the GNU Compiler Compiler.
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/>.
# LocalWords: parsers ngettext Texinfo pdf html YYYY ZZZZ ispell american
# LocalWords: MERCHANTABILITY