conflicts.at   [plain text]


# Exercising Bison on conflicts.                         -*- Autotest -*-

# Copyright (C) 2002, 2003, 2004, 2005 Free Software Foundation, Inc.

# 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 2, 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, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
# 02110-1301, USA.

AT_BANNER([[Conflicts.]])


## ---------------- ##
## S/R in initial.  ##
## ---------------- ##

# I once hacked Bison in such a way that it lost its reductions on the
# initial state (because it was confusing it with the last state).  It
# took me a while to strip down my failures to this simple case.  So
# make sure it finds the s/r conflict below.

AT_SETUP([S/R in initial])

AT_DATA([[input.y]],
[[%expect 1
%%
exp: e 'e';
e: 'e' | /* Nothing. */;
]])

AT_CHECK([bison -o input.c input.y], 0, [],
[[input.y:4.9: warning: rule never reduced because of conflicts: e: /* empty */
]])

AT_CLEANUP


## ------------------- ##
## %nonassoc and eof.  ##
## ------------------- ##

AT_SETUP([%nonassoc and eof])

AT_DATA_GRAMMAR([input.y],
[[
%{
#include <stdio.h>
#include <stdlib.h>

#define YYERROR_VERBOSE 1
static void
yyerror (const char *msg)
{
  fprintf (stderr, "%s\n", msg);
}

/* The current argument. */
static const char *input = NULL;

static int
yylex (void)
{
  /* No token stands for end of file. */
  if (input && *input)
    return *input++;
  else
    return 0;
}

%}

%nonassoc '<' '>'

%%
expr: expr '<' expr
    | expr '>' expr
    | '0'
    ;
%%
int
main (int argc, const char *argv[])
{
  if (argc > 1)
    input = argv[1];
  return yyparse ();
}
]])

# Specify the output files to avoid problems on different file systems.
AT_CHECK([bison -o input.c input.y])
AT_COMPILE([input])

AT_PARSER_CHECK([./input '0<0'])
# FIXME: This is an actual bug, but a new one, in the sense that
# no one has ever spotted it!  The messages are *wrong*: there should
# be nothing there, it should be expected eof.
AT_PARSER_CHECK([./input '0<0<0'], [1], [],
         [syntax error, unexpected '<', expecting '<' or '>'
])

AT_PARSER_CHECK([./input '0>0'])
AT_PARSER_CHECK([./input '0>0>0'], [1], [],
         [syntax error, unexpected '>', expecting '<' or '>'
])

AT_PARSER_CHECK([./input '0<0>0'], [1], [],
         [syntax error, unexpected '>', expecting '<' or '>'
])

AT_CLEANUP



## ------------------------- ##
## Unresolved SR Conflicts.  ##
## ------------------------- ##

AT_SETUP([Unresolved SR Conflicts])

AT_KEYWORDS([report])

AT_DATA([input.y],
[[%token NUM OP
%%
exp: exp OP exp | NUM;
]])

AT_CHECK([bison -o input.c --report=all input.y], 0, [],
[input.y: conflicts: 1 shift/reduce
])

# Check the contents of the report.
AT_CHECK([cat input.output], [],
[[State 5 conflicts: 1 shift/reduce


Grammar

    0 $accept: exp $end

    1 exp: exp OP exp
    2    | NUM


Terminals, with rules where they appear

$end (0) 0
error (256)
NUM (258) 2
OP (259) 1


Nonterminals, with rules where they appear

$accept (5)
    on left: 0
exp (6)
    on left: 1 2, on right: 0 1


state 0

    0 $accept: . exp $end
    1 exp: . exp OP exp
    2    | . NUM

    NUM  shift, and go to state 1

    exp  go to state 2


state 1

    2 exp: NUM .

    $default  reduce using rule 2 (exp)


state 2

    0 $accept: exp . $end
    1 exp: exp . OP exp

    $end  shift, and go to state 3
    OP    shift, and go to state 4


state 3

    0 $accept: exp $end .

    $default  accept


state 4

    1 exp: . exp OP exp
    1    | exp OP . exp
    2    | . NUM

    NUM  shift, and go to state 1

    exp  go to state 5


state 5

    1 exp: exp . OP exp  [$end, OP]
    1    | exp OP exp .  [$end, OP]

    OP  shift, and go to state 4

    OP        [reduce using rule 1 (exp)]
    $default  reduce using rule 1 (exp)
]])

AT_CLEANUP



## ----------------------- ##
## Resolved SR Conflicts.  ##
## ----------------------- ##

AT_SETUP([Resolved SR Conflicts])

AT_KEYWORDS([report])

AT_DATA([input.y],
[[%token NUM OP
%left OP
%%
exp: exp OP exp | NUM;
]])

AT_CHECK([bison -o input.c --report=all input.y])

# Check the contents of the report.
AT_CHECK([cat input.output], [],
[[Grammar

    0 $accept: exp $end

    1 exp: exp OP exp
    2    | NUM


Terminals, with rules where they appear

$end (0) 0
error (256)
NUM (258) 2
OP (259) 1


Nonterminals, with rules where they appear

$accept (5)
    on left: 0
exp (6)
    on left: 1 2, on right: 0 1


state 0

    0 $accept: . exp $end
    1 exp: . exp OP exp
    2    | . NUM

    NUM  shift, and go to state 1

    exp  go to state 2


state 1

    2 exp: NUM .

    $default  reduce using rule 2 (exp)


state 2

    0 $accept: exp . $end
    1 exp: exp . OP exp

    $end  shift, and go to state 3
    OP    shift, and go to state 4


state 3

    0 $accept: exp $end .

    $default  accept


state 4

    1 exp: . exp OP exp
    1    | exp OP . exp
    2    | . NUM

    NUM  shift, and go to state 1

    exp  go to state 5


state 5

    1 exp: exp . OP exp  [$end, OP]
    1    | exp OP exp .  [$end, OP]

    $default  reduce using rule 1 (exp)

    Conflict between rule 1 and token OP resolved as reduce (%left OP).
]])

AT_CLEANUP


## -------------------------------- ##
## Defaulted Conflicted Reduction.  ##
## -------------------------------- ##

# When there are RR conflicts, some rules are disabled.  Usually it is
# simply displayed as:
#
#    $end           reduce using rule 3 (num)
#    $end           [reduce using rule 4 (id)]
#
# But when `reduce 3' is the default action, we'd produce:
#
#    $end           [reduce using rule 4 (id)]
#    $default    reduce using rule 3 (num)
#
# In this precise case (a reduction is masked by the default
# reduction), we make the `reduce 3' explicit:
#
#    $end           reduce using rule 3 (num)
#    $end           [reduce using rule 4 (id)]
#    $default    reduce using rule 3 (num)
#
# Maybe that's not the best display, but then, please propose something
# else.

AT_SETUP([Defaulted Conflicted Reduction])
AT_KEYWORDS([report])

AT_DATA([input.y],
[[%%
exp: num | id;
num: '0';
id : '0';
%%
]])

AT_CHECK([bison -o input.c --report=all input.y], 0, [],
[[input.y: conflicts: 1 reduce/reduce
input.y:4.6-8: warning: rule never reduced because of conflicts: id: '0'
]])

# Check the contents of the report.
AT_CHECK([cat input.output], [],
[[Rules never reduced

    4 id: '0'


State 1 conflicts: 1 reduce/reduce


Grammar

    0 $accept: exp $end

    1 exp: num
    2    | id

    3 num: '0'

    4 id: '0'


Terminals, with rules where they appear

$end (0) 0
'0' (48) 3 4
error (256)


Nonterminals, with rules where they appear

$accept (4)
    on left: 0
exp (5)
    on left: 1 2, on right: 0
num (6)
    on left: 3, on right: 1
id (7)
    on left: 4, on right: 2


state 0

    0 $accept: . exp $end
    1 exp: . num
    2    | . id
    3 num: . '0'
    4 id: . '0'

    '0'  shift, and go to state 1

    exp  go to state 2
    num  go to state 3
    id   go to state 4


state 1

    3 num: '0' .  [$end]
    4 id: '0' .  [$end]

    $end      reduce using rule 3 (num)
    $end      [reduce using rule 4 (id)]
    $default  reduce using rule 3 (num)


state 2

    0 $accept: exp . $end

    $end  shift, and go to state 5


state 3

    1 exp: num .

    $default  reduce using rule 1 (exp)


state 4

    2 exp: id .

    $default  reduce using rule 2 (exp)


state 5

    0 $accept: exp $end .

    $default  accept
]])

AT_CLEANUP




## -------------------- ##
## %expect not enough.  ##
## -------------------- ##

AT_SETUP([%expect not enough])

AT_DATA([input.y],
[[%token NUM OP
%expect 0
%%
exp: exp OP exp | NUM;
]])

AT_CHECK([bison -o input.c input.y], 1, [],
[input.y: conflicts: 1 shift/reduce
input.y: expected 0 shift/reduce conflicts
])
AT_CLEANUP


## --------------- ##
## %expect right.  ##
## --------------- ##

AT_SETUP([%expect right])

AT_DATA([input.y],
[[%token NUM OP
%expect 1
%%
exp: exp OP exp | NUM;
]])

AT_CHECK([bison -o input.c input.y])
AT_CLEANUP


## ------------------ ##
## %expect too much.  ##
## ------------------ ##

AT_SETUP([%expect too much])

AT_DATA([input.y],
[[%token NUM OP
%expect 2
%%
exp: exp OP exp | NUM;
]])

AT_CHECK([bison -o input.c input.y], 1, [],
[input.y: conflicts: 1 shift/reduce
input.y: expected 2 shift/reduce conflicts
])
AT_CLEANUP


## ------------------------------ ##
## %expect with reduce conflicts  ##
## ------------------------------ ##

AT_SETUP([%expect with reduce conflicts])

AT_DATA([input.y],
[[%expect 0
%%
program: a 'a' | a a;
a: 'a';
]])

AT_CHECK([bison -o input.c input.y], 1, [],
[input.y: conflicts: 1 reduce/reduce
input.y: expected 0 reduce/reduce conflicts
])
AT_CLEANUP


## ------------------------------- ##
## %no-default-prec without %prec  ##
## ------------------------------- ##

AT_SETUP([%no-default-prec without %prec])

AT_DATA([[input.y]],
[[%left '+'
%left '*'

%%

%no-default-prec;

e:   e '+' e
   | e '*' e
   | '0'
   ;
]])

AT_CHECK([bison -o input.c input.y], 0, [],
[[input.y: conflicts: 4 shift/reduce
]])
AT_CLEANUP


## ---------------------------- ##
## %no-default-prec with %prec  ##
## ---------------------------- ##

AT_SETUP([%no-default-prec with %prec])

AT_DATA([[input.y]],
[[%left '+'
%left '*'

%%

%no-default-prec;

e:   e '+' e %prec '+'
   | e '*' e %prec '*'
   | '0'
   ;
]])

AT_CHECK([bison -o input.c input.y])
AT_CLEANUP


## ---------------- ##
## %default-prec    ##
## ---------------- ##

AT_SETUP([%default-prec])

AT_DATA([[input.y]],
[[%left '+'
%left '*'

%%

%default-prec;

e:   e '+' e
   | e '*' e
   | '0'
   ;
]])

AT_CHECK([bison -o input.c input.y])
AT_CLEANUP