问题描述
我在为带有 flex/bison 的编译器创建前端时遇到了一个问题（现在我们正处于创建词法分析器和语法分析器的阶段，相应地使用 flex 和 bison ).
请注意，我对词法分析/解析和 flex/bison 完全陌生，因此非常欢迎所有提示。
我目前面临的问题是，我一直收到 Bison 的换行符语法错误。以下是文件：
词法分析器.l
%{
#include <stdio.h>
#include <stdlib.h>
#include "sym_hashing.h"
#include "fifostrq.h"
#include "parser.h"
FILE *new_file;
void add_bloc_number();
void reduce_bloc_number();
void singleLineComment();
void multiLineComment();
void handleError(char*);
void validateNum(char*);
void genericParse(char*);
DEQ* errQue;
%}
%option yylineno
%option noyywrap
alpha [A-Za-z]
digit [0-9]
identifier {alpha}({alpha}|{digit})*
integer (-?{digit}{1,5})
constString \"(\\.|[^"\\])*\"
other [\n\r\t\v\f]+
%%
"LET" {return(LET); }
"DO" {return(DO); }
"LOOP" {return(LOOP); }
"UNTIL" {return(UNTIL); }
"WHILE" {return(WHILE); }
"WEND" {return(WEND); }
"SUB" {return(SUB); }
"CALL" {return(CALL); }
"INPUT" {return(INPUT); }
"PRINT" {return(PRINT); }
"IF" {return(IF); }
"THEN" {return(THEN); }
"ELSE" {return(ELSE); }
"AND" {return(AND); }
"NOT" {return(NOT); }
"OR" {return(OR); }
"RETURN" {return(RETURN); }
"REM" {singleLineComment();}
"+" {return(PLUS);}
"-" {return(MINUS);}
"*" {return(STAR);}
"/" {return(DIV);}
"<" {return(LT);}
">" {return(GT);}
"<=" {return(LTEQUAL);}
">=" {return(GTEQUAL);}
"<>" {return(LTGT);}
";" {return(SEMICOLON);}
"," {return(COMMA);}
"(" {return(LPAREN);}
")" {return(RPAREN);}
"[" {return(LBRACK);}
"]" {return(RBRACK);}
"{" {return(LSWIGLY);}
"}" {return(RSWIGLY);}
"=" {printf("Found =\n"); return(ASSIGNMENT);}
"==" {return(EQUALS);}
"%*" {multiLineComment();}
{constString} { yylval.conststr=strdup(yytext); printf("Found %s\n",yylval.conststr); return(CONSTSTR);}
{integer} { yylval.constnum=strdup(yytext); printf("Found %s\n",yylval.constnum); validateNum(yylval.constnum); return(CONSTINT);}
{identifier} { yylval.name=strdup(yytext); printf("Found %s\n",yylval.name); return(IDENTIFIER);}
{other} {}
. { char* yycopy=strdup(yytext); genericParse(yycopy);}
%%
void genericParse(char * val) {
if (val[0] != '\0' && val[0] != ' ' && val != NULL) {
handleError(val);
}
}
void handleError(char * token) {
char * buff = malloc(sizeof(char) * (strlen(token) + 36));
sprintf(buff,"Lexer ERROR at line %d of token %s\n",line,token);
insertAtHead(errQue,buff);
}
void singleLineComment() {
int c;
while ((c = input()) != '\n' && c != EOF);
line++;
}
void validateNum(char * value) {
int num = atoi(value);
if (num < -32768 || num > 32767) {
handleError(value);
return;
}
}
void add_bloc_number() {
block_num = block_num + 1;
}
void reduce_bloc_number() {
block_num = block_num - 1;
}
void multiLineComment() {
int c,flag = 0;
for (;;) {
while ((c = input()) != '*' && c != EOF) {
if (c == '\n') {
line++;
}
}
if (c == '*') {
while ((c = input()) == '*') {
if (c == '\n') {
line++;
}
}
if (c == '%') {
break;
}
}
if (c == EOF) {
printf("ERROR: EOF in comment\n");
break;
}
}
}
gram.y
%{
#include <stdio.h>
#include <string.h>
#include <malloc.h>
#include "fifostrq.h"
#include "sym_tab.h"
extern int column;
extern void yyrestart( FILE *input_file );
extern char *yytext;
extern FILE *yyin;
extern int yylineno;
extern int block_num;
int yyerror(const char *s);
int column;
%}
%locations
%define parse.error verbose
%define parse.lac full
%printer { fputs($$,yyo); } IDENTIFIER
%union
{
char *name;
char *constnum;
char *conststr;
}
%token IDENTIFIER
%token CONSTINT CONSTSTR
%token LET DO LOOP UNTIL WHILE WEND SUB
%token CALL INPUT PRINT IF THEN ELSE AND
%token NOT OR RETURN ASSIGNMENT NEWLINE
%token PLUS MINUS STAR DIV LT GT LTEQUAL GTEQUAL
%token LTGT SEMICOLON COMMA LPAREN RPAREN
%token LSWIGLY RSWIGLY EQUALS LBRACK RBRACK
%token MISC
%right ASSIGNMENT
%left LT GT LTEQUAL GTEQUAL LTGT EQUALS
%left AND OR
%right NOT
%left PLUS MINUS
%left STAR DIV
%type <name> IDENTIFIER
%type <constnum> CONSTINT
%type <conststr> CONSTSTR
%start program
%%
program:
statement_or_func
newline_statement_or_func_op
;
newline_statement_or_func_op:
/*empty*/
| NEWLINE statement_or_func newline_statement_or_func_op
;
statement_or_func:
sequence
| func_stat
;
sequence:
statement | sequence le statement
;
le:
NEWLINE
| SEMICOLON
;
brackets_seq:
LSWIGLY sequence RSWIGLY
;
brack_or_stat:
brackets_seq
| statement
;
statement:
/*empty*/
| decl_stat assignment_stat
| if_stat
| do_until_stat
| while_stat
| return_stat
| print_stat
| input_stat
| func_stat
| call_stat
/*comment stat is not needed,they are removed by the lexer*/
;
decl_stat:
LET declaration | decl_stat COMMA declaration
;
declaration:
IDENTIFIER
| assignment_stat
;
assignment_stat:
IDENTIFIER ASSIGNMENT expression
;
if_stat:
IF LPAREN condition RPAREN THEN brack_or_stat
elsepart
;
elsepart:
/*empty*/
| ELSE brack_or_stat
;
do_until_stat:
DO brack_or_stat LOOP UNTIL LPAREN condition RPAREN
;
while_stat:
WHILE LPAREN condition RPAREN brack_or_stat WEND
;
return_stat:
RETURN LPAREN expression RPAREN
;
/*with the grammar rule specified in the pdf,PRINT "*"; wouldn't work*/
print_stat:
PRINT CONSTSTR le
| PRINT CONSTSTR COMMA expression_list
;
expression_list:
expression | expression_list COMMA expression
;
input_stat:
INPUT CONSTSTR COMMA IDENTIFIER | input_stat COMMA IDENTIFIER
;
func_stat:
SUB IDENTIFIER funcbody
;
funcbody:
formalpars brackets_seq
;
formalpars:
LPAREN /*empty*/ RPAREN
| LPAREN formalparlist RPAREN
;
formalparlist:
IDENTIFIER | formalparlist COMMA IDENTIFIER
;
call_stat:
CALL IDENTIFIER actualpars
;
actualpars:
LPAREN /*empty*/ RPAREN
| LPAREN actualparlist RPAREN
;
actualparlist:
actualparitem | actualparlist COMMA actualparitem
;
actualparitem:
expression | IDENTIFIER
;
/*comment stat is not needed,it is removed by the parser regardless...*/
condition:
boolterm | condition OR boolterm
;
boolterm:
boolfactor | boolterm AND boolterm
;
boolfactor :
NOT LBRACK condition RBRACK
| LBRACK condition RBRACK
| expression relational_oper expression
;
expression:
optional_sign term | expression add_oper optional_sign term
;
term:
factor | term mul_oper factor
;
factor:
constant | LPAREN expression RPAREN | IDENTIFIER | call_stat
;
constant:
CONSTINT | CONSTSTR
;
relational_oper:
EQUALS | LT | LTEQUAL | LTGT | GTEQUAL | GT
;
add_oper:
PLUS | MINUS
;
mul_oper:
STAR | DIV
;
optional_sign:
/*empty*/
| add_oper
;
%%
int yydebug;
int main(int argc,char *argv[]){
#ifdef YYDEBUG
yydebug = 1;
#endif
createDEQ(&errQue);
if (argc != 2)
printf("\nUsage: lexyy <input file name> \n");
else
if ((yyin = fopen(argv[1],"r")) == NULL)
printf("\n<%s> not found.\n",argv[1]);
else {
yyrestart(yyin);
yyparse();
fclose(yyin);
}
printQueue(errQue);
freeDEQ( & errQue);
return 0;
}
int yyerror(const char *token) {
fflush(stdout);
char *buff = malloc(sizeof(char) * 1000);
sprintf(buff,"\n-----------------------\n%s\n%*s\n%*s\tLine: %d\tColumn: %d\tBlock: %d\n-----------------------\n",yytext,column,"^",token,yylineno,block_num);
insertAtHead(errQue,buff);
return 0;
}
static int yyprint(FILE *file,int type,YYSTYPE value) {
if (type == IDENTIFIER)
fprintf (stderr," = %s",value.name);
return 1;
}
BNF
<PROGRAM> ::= < STATEMENT-OR-FUNC >
(‘\n’ < STATEMENT-OR-FUNC >)*
<STATEMENT-OR-FUNC> ::= < SEQUENCE > |
<FUNC-STAT>
<SEQUENCE> ::= <STATEMENT> ( <LE> <STATEMENT> )*
<LE> ::= ‘\n’ | ‘;’
<BRACKETS-SEQ> ::= { <SEQUENCE> }
<BRACK-OR-STAT> ::= <BRACKETS-SEQ> | <STATEMENT>
<STATEMENT> ::= ε |
<DECL-STAT>
<ASSIGNMENT-STAT> |
<IF-STAT> |
<DO-UNTIL-STAT> |
<WHILE-STAT> |
<RETURN-STAT> |
<PRINT-STAT> |
<INPUT-STAT> |
<FUNC-STAT> |
<CALL-STAT> |
<COMMENT-STAT>
< DECL-STAT > ::= LET ASSIGNMENT-STAT (,DECLaraTION)*
< DECLaraTION > ::= ID | ASSIGNMENT-STAT
<ASSIGNMENT-STAT> ::= ID = <EXPRESSION>
...and others (irrelevant,read on)
输入文件
LET a,a1=2,n,i,max1=-1
a = 5;
b = 4;
Starting parse
Entering state 0
Reading a token: --(end of buffer or a NUL)
--accepting rule at line 29 ("LET")
Next token is token LET ()
Shifting token LET ()
Entering state 1
Reading a token: --accepting rule at line 100 (" ")
--accepting rule at line 98 ("a")
Next token is token IDENTIFIER ( = (null))
Shifting token IDENTIFIER ( = (null))
Entering state 23
Reducing stack by rule 2 (line 43):
$1 = token IDENTIFIER ( = (null))
-> $$ = nterm identifier ()
Stack Now 0 1
Entering state 24
Reading a token: --accepting rule at line 78 (",")
Next token is token COMMA ()
Reducing stack by rule 28 (line 107):
$1 = nterm identifier ()
-> $$ = nterm declaration ()
Stack Now 0 1
Entering state 25
Next token is token COMMA ()
Shifting token COMMA ()
Entering state 49
Reading a token: --accepting rule at line 100 (" ")
--accepting rule at line 98 ("a1")
Next token is token IDENTIFIER ( = (null))
Shifting token IDENTIFIER ( = (null))
Entering state 23
Reducing stack by rule 2 (line 43):
$1 = token IDENTIFIER ( = (null))
-> $$ = nterm identifier ()
Stack Now 0 1 25 49
Entering state 24
Reading a token: --accepting rule at line 87 ("=")
Next token is token ASSIGNMENT ()
Shifting token ASSIGNMENT ()
Entering state 48
Reading a token: --accepting rule at line 95 ("2")
Next token is token CONSTINT ()
Reducing stack by rule 88 (line 264):
-> $$ = nterm optional_sign ()
Stack Now 0 1 25 49 24 48
Entering state 62
Next token is token CONSTINT ()
Shifting token CONSTINT ()
Entering state 97
Reducing stack by rule 76 (line 249):
$1 = token CONSTINT ()
-> $$ = nterm constant ()
Stack Now 0 1 25 49 24 48 62
Entering state 104
Reducing stack by rule 72 (line 245):
$1 = nterm constant ()
-> $$ = nterm factor ()
Stack Now 0 1 25 49 24 48 62
Entering state 103
Reading a token: --accepting rule at line 78 (",")
Next token is token COMMA ()
Reducing stack by rule 69 (line 235):
-> $$ = nterm mul_oper_op ()
Stack Now 0 1 25 49 24 48 62 103
Entering state 130
Reducing stack by rule 71 (line 241):
$1 = nterm factor ()
$2 = nterm mul_oper_op ()
-> $$ = nterm term ()
Stack Now 0 1 25 49 24 48 62
Entering state 102
Next token is token COMMA ()
Reducing stack by rule 66 (line 226):
-> $$ = nterm add_oper_op ()
Stack Now 0 1 25 49 24 48 62 102
Entering state 126
Reducing stack by rule 68 (line 232):
$1 = nterm optional_sign ()
$2 = nterm term ()
$3 = nterm add_oper_op ()
-> $$ = nterm expression ()
Stack Now 0 1 25 49 24 48
Entering state 78
Reducing stack by rule 30 (line 112):
$1 = nterm identifier ()
$2 = token ASSIGNMENT ()
$3 = nterm expression ()
-> $$ = nterm assignment_stat ()
Stack Now 0 1 25 49
Entering state 26
Reducing stack by rule 29 (line 108):
$1 = nterm assignment_stat ()
-> $$ = nterm declaration ()
Stack Now 0 1 25 49
Entering state 79
Next token is token COMMA ()
Shifting token COMMA ()
Entering state 49
Reading a token: --accepting rule at line 100 (" ")
--accepting rule at line 98 ("n")
Next token is token IDENTIFIER ( = (null))
Shifting token IDENTIFIER ( = (null))
Entering state 23
Reducing stack by rule 2 (line 43):
$1 = token IDENTIFIER ( = (null))
-> $$ = nterm identifier ()
Stack Now 0 1 25 49 79 49
Entering state 24
Reading a token: --accepting rule at line 78 (",")
Next token is token COMMA ()
Reducing stack by rule 28 (line 107):
$1 = nterm identifier ()
-> $$ = nterm declaration ()
Stack Now 0 1 25 49 79 49
Entering state 79
Next token is token COMMA ()
Shifting token COMMA ()
Entering state 49
Reading a token: --accepting rule at line 100 (" ")
--accepting rule at line 98 ("i")
Next token is token IDENTIFIER ( = (null))
Shifting token IDENTIFIER ( = (null))
Entering state 23
Reducing stack by rule 2 (line 43):
$1 = token IDENTIFIER ( = (null))
-> $$ = nterm identifier ()
Stack Now 0 1 25 49 79 49 79 49
Entering state 24
Reading a token: --accepting rule at line 78 (",")
Next token is token COMMA ()
Reducing stack by rule 28 (line 107):
$1 = nterm identifier ()
-> $$ = nterm declaration ()
Stack Now 0 1 25 49 79 49 79 49
Entering state 79
Next token is token COMMA ()
Shifting token COMMA ()
Entering state 49
Reading a token: --accepting rule at line 100 (" ")
--accepting rule at line 98 ("max1")
Next token is token IDENTIFIER ( = (null))
Shifting token IDENTIFIER ( = (null))
Entering state 23
Reducing stack by rule 2 (line 43):
$1 = token IDENTIFIER ( = (null))
-> $$ = nterm identifier ()
Stack Now 0 1 25 49 79 49 79 49 79 49
Entering state 24
Reading a token: --accepting rule at line 87 ("=")
Next token is token ASSIGNMENT ()
Shifting token ASSIGNMENT ()
Entering state 48
Reading a token: --accepting rule at line 95 ("-1")
Next token is token CONSTINT ()
Reducing stack by rule 88 (line 264):
-> $$ = nterm optional_sign ()
Stack Now 0 1 25 49 79 49 79 49 79 49 24 48
Entering state 62
Next token is token CONSTINT ()
Shifting token CONSTINT ()
Entering state 97
Reducing stack by rule 76 (line 249):
$1 = token CONSTINT ()
-> $$ = nterm constant ()
Stack Now 0 1 25 49 79 49 79 49 79 49 24 48 62
Entering state 104
Reducing stack by rule 72 (line 245):
$1 = nterm constant ()
-> $$ = nterm factor ()
Stack Now 0 1 25 49 79 49 79 49 79 49 24 48 62
Entering state 103
Reading a token: --accepting rule at line 76 ("
")
Next token is token NEWLINE ()
Reducing stack by rule 69 (line 235):
-> $$ = nterm mul_oper_op ()
Stack Now 0 1 25 49 79 49 79 49 79 49 24 48 62 103
Entering state 130
Reducing stack by rule 71 (line 241):
$1 = nterm factor ()
$2 = nterm mul_oper_op ()
-> $$ = nterm term ()
Stack Now 0 1 25 49 79 49 79 49 79 49 24 48 62
Entering state 102
Next token is token NEWLINE ()
Reducing stack by rule 66 (line 226):
-> $$ = nterm add_oper_op ()
Stack Now 0 1 25 49 79 49 79 49 79 49 24 48 62 102
Entering state 126
Reducing stack by rule 68 (line 232):
$1 = nterm optional_sign ()
$2 = nterm term ()
$3 = nterm add_oper_op ()
-> $$ = nterm expression ()
Stack Now 0 1 25 49 79 49 79 49 79 49 24 48
Entering state 78
Reducing stack by rule 30 (line 112):
$1 = nterm identifier ()
$2 = token ASSIGNMENT ()
$3 = nterm expression ()
-> $$ = nterm assignment_stat ()
Stack Now 0 1 25 49 79 49 79 49 79 49
Entering state 26
Reducing stack by rule 29 (line 108):
$1 = nterm assignment_stat ()
-> $$ = nterm declaration ()
Stack Now 0 1 25 49 79 49 79 49 79 49
Entering state 79
Next token is token NEWLINE ()
Reducing stack by rule 25 (line 97):
-> $$ = nterm comma_declaration_op ()
Stack Now 0 1 25 49 79 49 79 49 79 49 79
Entering state 117
Reducing stack by rule 26 (line 99):
$1 = token COMMA ()
$2 = nterm declaration ()
$3 = nterm comma_declaration_op ()
-> $$ = nterm comma_declaration_op ()
Stack Now 0 1 25 49 79 49 79 49 79
Entering state 117
Reducing stack by rule 26 (line 99):
$1 = token COMMA ()
$2 = nterm declaration ()
$3 = nterm comma_declaration_op ()
-> $$ = nterm comma_declaration_op ()
Stack Now 0 1 25 49 79 49 79
Entering state 117
Reducing stack by rule 26 (line 99):
$1 = token COMMA ()
$2 = nterm declaration ()
$3 = nterm comma_declaration_op ()
-> $$ = nterm comma_declaration_op ()
Stack Now 0 1 25 49 79
Entering state 117
Reducing stack by rule 26 (line 99):
$1 = token COMMA ()
$2 = nterm declaration ()
$3 = nterm comma_declaration_op ()
-> $$ = nterm comma_declaration_op ()
Stack Now 0 1 25
Entering state 50
Next token is token NEWLINE ()
Shifting token NEWLINE ()
Entering state 42
Reducing stack by rule 10 (line 70):
$1 = token NEWLINE ()
-> $$ = nterm le ()
Stack Now 0 1 25 50
Entering state 80
Reducing stack by rule 27 (line 103):
$1 = token LET ()
$2 = nterm declaration ()
$3 = nterm comma_declaration_op ()
$4 = nterm le ()
-> $$ = nterm decl_stat ()
Stack Now 0
Entering state 14
Reading a token: --accepting rule at line 98 ("a")
Next token is token IDENTIFIER ( = (null))
Shifting token IDENTIFIER ( = (null))
Entering state 23
Reducing stack by rule 2 (line 43):
$1 = token IDENTIFIER ( = (null))
-> $$ = nterm identifier ()
Stack Now 0 14
Entering state 46
Reading a token: --accepting rule at line 100 (" ")
--accepting rule at line 87 ("=")
Next token is token ASSIGNMENT ()
Shifting token ASSIGNMENT ()
Entering state 48
Reading a token: --accepting rule at line 100 (" ")
--accepting rule at line 95 ("5")
Next token is token CONSTINT ()
Reducing stack by rule 88 (line 264):
-> $$ = nterm optional_sign ()
Stack Now 0 14 46 48
Entering state 62
Next token is token CONSTINT ()
Shifting token CONSTINT ()
Entering state 97
Reducing stack by rule 76 (line 249):
$1 = token CONSTINT ()
-> $$ = nterm constant ()
Stack Now 0 14 46 48 62
Entering state 104
Reducing stack by rule 72 (line 245):
$1 = nterm constant ()
-> $$ = nterm factor ()
Stack Now 0 14 46 48 62
Entering state 103
Reading a token: --accepting rule at line 77 (";")
Next token is token SEMICOLON ()
Reducing stack by rule 69 (line 235):
-> $$ = nterm mul_oper_op ()
Stack Now 0 14 46 48 62 103
Entering state 130
Reducing stack by rule 71 (line 241):
$1 = nterm factor ()
$2 = nterm mul_oper_op ()
-> $$ = nterm term ()
Stack Now 0 14 46 48 62
Entering state 102
Next token is token SEMICOLON ()
Reducing stack by rule 66 (line 226):
-> $$ = nterm add_oper_op ()
Stack Now 0 14 46 48 62 102
Entering state 126
Reducing stack by rule 68 (line 232):
$1 = nterm optional_sign ()
$2 = nterm term ()
$3 = nterm add_oper_op ()
-> $$ = nterm expression ()
Stack Now 0 14 46 48
Entering state 78
Reducing stack by rule 30 (line 112):
$1 = nterm identifier ()
$2 = token ASSIGNMENT ()
$3 = nterm expression ()
-> $$ = nterm assignment_stat ()
Stack Now 0 14
Entering state 47
Reducing stack by rule 16 (line 85):
$1 = nterm decl_stat ()
$2 = nterm assignment_stat ()
-> $$ = nterm statement ()
Stack Now 0
Entering state 13
Next token is token SEMICOLON ()
Shifting token SEMICOLON ()
Entering state 43
Reducing stack by rule 11 (line 71):
$1 = token SEMICOLON ()
-> $$ = nterm le ()
Stack Now 0 13
Entering state 45
Reading a token: --accepting rule at line 76 ("
")
Next token is token NEWLINE ()
Reducing stack by rule 15 (line 83):
-> $$ = nterm statement ()
Stack Now 0 13 45
Entering state 77
Next token is token NEWLINE ()
Shifting token NEWLINE ()
Entering state 42
Reducing stack by rule 10 (line 70):
$1 = token NEWLINE ()
-> $$ = nterm le ()
Stack Now 0 13 45 77
Entering state 45
Reading a token: --accepting rule at line 98 ("b")
Next token is token IDENTIFIER ( = (null))
Reducing stack by rule 15 (line 83):
-> $$ = nterm statement ()
Stack Now 0 13 45 77 45
Entering state 77
Next token is token IDENTIFIER ( = (null))
Reducing stack by rule 7 (line 60):
-> $$ = nterm le_statement_op ()
Stack Now 0 13 45 77 45 77
Entering state 116
Reducing stack by rule 8 (line 62):
$1 = nterm le ()
$2 = nterm statement ()
$3 = nterm le_statement_op ()
-> $$ = nterm le_statement_op ()
Stack Now 0 13 45 77
Entering state 116
Reducing stack by rule 8 (line 62):
$1 = nterm le ()
$2 = nterm statement ()
$3 = nterm le_statement_op ()
-> $$ = nterm le_statement_op ()
Stack Now 0 13
Entering state 44
Reducing stack by rule 9 (line 66):
$1 = nterm statement ()
$2 = nterm le_statement_op ()
-> $$ = nterm sequence ()
Stack Now 0
Entering state 12
Reducing stack by rule 5 (line 56):
$1 = nterm sequence ()
-> $$ = nterm statement_or_func ()
Stack Now 0
Entering state 11
Next token is token IDENTIFIER ( = (null))
Reducing stack by rule 3 (line 50):
-> $$ = nterm newline_statement_or_func_op ()
Stack Now 0 11
Entering state 41
Reducing stack by rule 1 (line 38):
$1 = nterm statement_or_func ()
$2 = nterm newline_statement_or_func_op ()
-> $$ = nterm program ()
Stack Now 0
Entering state 10
Next token is token IDENTIFIER ( = (null))
Error: popping nterm program ()
Stack Now 0
Cleanup: discarding lookahead token IDENTIFIER ( = (null))
Stack Now 0
^
Syntax error,unexpected IDENTIFIER,expecting $end
Process finished with exit code 1
从我的角度来看，我不明白这有什么意义。它找到了一个标识符（由于 yyerror 函数损坏，我无法弄清楚它指的是哪个令牌），它是 null (?) 并且它期待一个 EOF(?)
Next token is token IDENTIFIER ( = (null))
在接受 'b' 标识符后，它错误地将（某些东西？我不明白是哪个字符）标识为标识符，而不是在 EQUALS、CONSTINT 和 LE 标记上进行识别。
编辑： 我添加了更多调试信息（行、列、块）
^
Syntax error,expecting $end Line: 3 Column: 0 Block: 0
输入如下：
SUB fib (n,ret)
{
LET
low,high;
IF ( n == 0 OR n == 1)
THEN
ret = n;
ELSE
{
high = call fib(n-1,high);
low = call fib(n-2,low)
ret = high + low;
}
RETURN ret
}
我收到此错误：
ret
^
Syntax error,expecting $end Line: 3 Column: 0 Block: 0
这显然与上述相同。出于某种原因，在分号之后，它总是期望一个 $end。我无法弄清楚这种行为是从哪里引起的。据我所知，它将堆栈减少到状态 0，即：
State 0
0 $accept: . program $end
...但问题是我不明白为什么它会减少到这个，或者如何解决这个问题。
对这三点的任何帮助都非常感谢。
非常感谢。
解决方法
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