具体的code请参见： http://blog.csdn.net/lantianjialiang/article/details/7971327
只不过有两步需要修改：
bison -y -d parser.l –> bison -y -d -t parser.l
gcc y.tab.o lex.yy.o -o plusmins.exe –>gcc -g lex.yy.o y.tab.o -o
plusminis.exe
以下是debug的屏幕输出：
gdb plusminis.exe
…
Breakpoint 1, main () at parser.l:30
30 yyparse();
(gdb) set yydebug=1 // 使debug生效，也可以将 yydebug=1 放到main函数中去
(gdb) cont
Continuing.
Starting parse
Entering state 0 //进入状态0
Reducing stack by rule 2 (line 14):
$$ = nterm program ()
Stack now 0
Entering state 1 //进入状态1
Reading a token: 3 //等待用户输入，输入是3
Next token is token INTEGER ()
Shifting token INTEGER () //压栈
Entering state 3 //进入状态3
Reducing stack by rule 3 (line 18):
$1 = token INTEGER ()
- > $$ = nterm expr () //根据rule 3 expr: INTEGER，将INTEGER替换成expr
Stack now 0 1 //替换完成后，栈中的状态是0,1
Entering state 4 //进入状态4
Reading a token: Next token is token ‘\n’ ()
Shifting token ‘\n’ ()
Entering state 5 //进入状态5, 栈中的状态是0,1,4,
Reducing stack by rule 1 (line 13):
$1 = nterm program ()
$2 = nterm expr ()
$3 = token ‘\n’ ()
3
- > $$ = nterm program () //根据rule 1 program: program expr ‘\n’，将 program
expr ‘\n ‘替换成program，同时输出expr
Stack now 0
Entering state 1
-—————————
Reading a token: 3+3
Next token is token INTEGER ()
Shifting token INTEGER ()
Entering state 3
Reducing stack by rule 3 (line 18):
$1 = token INTEGER ()
-> $$ = nterm expr ()
Stack now 0 1
Entering state 4
Reading a token: Next token is token ‘+’ ()
Shifting token ‘+’ ()
Entering state 6
Reading a token: Next token is token INTEGER ()
Shifting token INTEGER ()
Entering state 3
Reducing stack by rule 3 (line 18):
$1 = token INTEGER ()
-> $$ = nterm expr ()
Stack now 0 1 4 6 //这里其实是状态机中的状态的入栈情况
Entering state 8
Reading a token: Next token is token ‘\n’ ()
Reducing stack by rule 4 (line 19):
$1 = nterm expr ()
$2 = token ‘+’ ()
$3 = nterm expr ()
$$ = nterm expr () //根据rule 4 expr ‘+’ expr { $$ = $1 + $3; }，会更新栈顶的expr值
Stack now 0 1
Entering state 4
Next token is token ‘\n’ ()
Shifting token ‘\n’ ()
Entering state 5
Reducing stack by rule 1 (line 13):
$1 = nterm program ()
$2 = nterm expr ()
$3 = token ‘\n’ ()
6
-> $$ = nterm program ()
Stack now 0
Entering state 1
-————————
Reading a token: s
invalid character
Next token is token ‘\n’ ()
syntax error
Error: popping nterm program ()
Stack now 0
Cleanup: discarding lookahead token ‘\n’ ()
Stack now 0
Program exited normally.
(gdb) quit
使用bison -y -d -t -v parser.l产生的状态机parser.output
State 8 conflicts: 2 shift/reduce
State 9 conflicts: 2 shift/reduce
Grammar
0 $accept: program $end
1 program: program expr '\n'
2 | /* empty */
3 expr: INTEGER
4 | expr '+' expr
5 | expr '-' expr
Terminals, with rules where they appear
$end (0) 0
'\n' (10) 1
'+' (43) 4
'-' (45) 5
error (256)
INTEGER (258) 3
Nonterminals, with rules where they appear
$accept (7)
on left: 0
program (8)
on left: 1 2, on right: 0 1
expr (9)
on left: 3 4 5, on right: 1 4 5
state 0
0 $accept: . program $end
$default reduce using rule 2 (program)
program go to state 1
state 1
0 $accept: program . $end
1 program: program . expr '\n'
$end shift, and go to state 2
INTEGER shift, and go to state 3
expr go to state 4
state 2
0 $accept: program $end .
$default accept
state 3
3 expr: INTEGER .
$default reduce using rule 3 (expr)
state 4
1 program: program expr . '\n'
4 expr: expr . '+' expr
5 | expr . '-' expr
'\n' shift, and go to state 5
'+' shift, and go to state 6
'-' shift, and go to state 7
state 5
1 program: program expr '\n' .
$default reduce using rule 1 (program)
state 6
4 expr: expr '+' . expr
INTEGER shift, and go to state 3
expr go to state 8
state 7
5 expr: expr '-' . expr
INTEGER shift, and go to state 3
expr go to state 9
state 8
4 expr: expr . '+' expr
4 | expr '+' expr .
5 | expr . '-' expr
'+' shift, and go to state 6
'-' shift, and go to state 7
'+' [reduce using rule 4 (expr)]
'-' [reduce using rule 4 (expr)]
$default reduce using rule 4 (expr)
state 9
4 expr: expr . '+' expr
5 | expr . '-' expr
5 | expr '-' expr .
'+' shift, and go to state 6
'-' shift, and go to state 7
'+' [reduce using rule 5 (expr)]
'-' [reduce using rule 5 (expr)]
$default reduce using rule 5 (expr)
refs: http://www.gnu.org/software/bison/manual/html_node/Understanding.html