折返Flex和Bison问题 [英] Problems with reentrant Flex and Bison
问题描述
我正在学习如何一起使用可重入的Bison和Flex.我已经有了一个没有可重入功能的简单计算器.但是，当我激活可重入功能并进行必要的修改时，我无法使它正常工作.
I'm learning how to use reentrant Bison and Flex together. I already got a simple calculator working without the reentrant capability. However when I activated the reentrant feature and made the necessary modifications, I couldn't get this to work.
这是代码:
scanner.l
%{
#include <stdio.h>
#include "parser.tab.h"
%}
%option 8bit reentrant bison-bridge
%option warn noyywrap nodefault
%option header-file="lex.yy.h"
DIGIT [0-9]
%%
"+" { return ADD; }
"-" { return SUB; }
"*" { return MUL; }
"/" { return DIV; }
{DIGIT}+ { *yylval = atof(yytext); return NUM; }
\n { return EOL; }
[ \t] { }
. { printf("What is this: %s.\n", yytext); }
%%
parser.y
%{
#include <stdio.h>
#include "lex.yy.h"
void yyerror(yyscan_t scanner, char const *msg);
%}
%define api.value.type {double}
%define parse.error verbose
%define api.pure
%lex-param {yyscan_t scanner}
%parse-param {yyscan_t scanner}
%token NUM EOL
%left ADD SUB
%left MUL DIV
%%
input: %empty
| input line
;
line: EOL { printf("|> ");}
| exp EOL { printf("|R> %.4lf\n", $exp); }
;
exp: NUM { $$ = $1; }
| exp ADD exp { $$ = $1 + $3; }
| exp SUB exp { $$ = $1 - $3; }
| exp MUL exp { $$ = $1 * $3; }
| exp DIV exp { $$ = $1 / $3; }
;
%%
void yyerror(yyscan_t scanner, char const *msg) {
fprintf(stderr, "Error: %s\n", msg);
}
main.c
#include <stdio.h>
#include "parser.tab.h"
#include "lex.yy.h"
int main(void) {
yyscan_t scanner;
yylex_init(&scanner);
yyset_in(stdin, scanner);
yyparse(scanner);
yylex_destroy(scanner);
return 0;
}
这是我正在使用的Makefile:
all: calc.x
parser.tab.c parser.tab.h: parser.y
bison -d parser.y
lex.yy.c lex.yy.h: scanner.l parser.tab.h
flex scanner.l
calc.x: lex.yy.c lex.yy.h parser.tab.c parser.tab.h
gcc main.c parser.tab.c lex.yy.c -o calc.x
clean:
rm calc.x lex.yy.c lex.yy.h parser.tab.c parser.tab.h *.o
正在运行make，出现以下错误:
Running make, I got the following error:
In file included from main.c:2:0:
parser.tab.h:66:14: error: unknown type name ‘yyscan_t’
int yyparse (yyscan_t scanner);
^
main.c: In function ‘main’:
main.c:12:3: warning: implicit declaration of function ‘yyparse’ [-Wimplicit-function-declaration]
yyparse(scanner);
^
In file included from parser.y:5:0:
lex.yy.h:282:1: error: unknown type name ‘YYSTYPE’
YYSTYPE * yyget_lval (yyscan_t yyscanner );
^
lex.yy.h:284:18: error: unknown type name ‘YYSTYPE’
void yyset_lval (YYSTYPE * yylval_param ,yyscan_t yyscanner );
^
lex.yy.h:332:17: error: unknown type name ‘YYSTYPE’
(YYSTYPE * yylval_param ,yyscan_t yyscanner);
^
parser.tab.c: In function ‘yyparse’:
parser.tab.c:1130:16: warning: implicit declaration of function ‘yylex’ [-Wimplicit-function-declaration]
yychar = yylex (&yylval, scanner);
^
Makefile:10: recipe for target 'calc.x' failed
make: *** [calc.x] Error 1
但是我不理解此错误和警告消息的来源，例如:
But I don't understand the origin of this error and warning messages, for instance:
main.c:12:3: warning: implicit declaration of function ‘yyparse’
但是yyparse已在parser.tab.h中定义，并且已包含在main.c中.另一个例子:
But yyparse is already defined at parser.tab.h and it's being included in main.c. Another example:
parser.tab.h:66:14: error: unknown type name ‘yyscan_t’
在parser.y中，我包括了扫描仪头lex.yy.h.
And inside parser.y, I'm including the scanner header lex.yy.h.
我已经在Internet上找到了这些解决方案:
I have found these solutions on the Internet:
- Configuring Bison and Flex without global or static variable
- Reentrant parsers with Flex and Bison
- Make a reentrant parser with Flex and Bison
- Writing re-entrant lexer with Flex
- Implementing re-entrant parsers in Bison and Flex
但是它们都不起作用，从而导致类似的错误.如果有人可以指导我完成这项任务，我将不胜感激.
But none of them work, resulting in similar errors. If someone could guide me in this quest I'll be grateful.
软件版本
OS:Debian(测试中)，Bison:3.0.4，Flex:2.5.39，GCC:5.2.1，Make:4.0.
OS: Debian (testing), Bison: 3.0.4, Flex: 2.5.39, GCC: 5.2.1, Make: 4.0.
推荐答案
我稍加修改便找到了解决方案.因此，问题来自flex和bison之间的循环依赖.
I found a solution after tinkering a bit. So the problems arise from a circular dependency between flex and bison.
解析器以这种方式生成调用flex例程:
The parser generated call flex routine in this way:
yychar = yylex (&yylval, scanner);
因此在野牛输入中，我们必须包括扫描仪头文件lex.yy.h
它的定义为:
So in the bison input we must include the scanner header file lex.yy.h
and it's define as:
int yylex (YYSTYPE * yylval_param ,yyscan_t yyscanner);
但是YYSTYPE是在解析器头文件parser.tab.h中定义的，在我的情况下，我对野牛说，我的类型将是double:
But YYSTYPE is defined inside the parser header parser.tab.h, in my case i said to bison that my type will be double:
typedef double YYSTYPE;
现在解决.在scanner.l内部，必须包含解析器标头，以便flex可以返回正确的令牌(未做任何更改).
Now the solution. Inside scanner.l you must include the parser headers so that flex can return correct tokens (nothing changed).
但是在parser.y内部，您必须同时包含两个头文件，如果仅包含lex.yy.h，则会报错:
But inside the parser.y you must include both headers file, if you include only the lex.yy.h it will complain:
lex.yy.h:282:1: error: unknown type name ‘YYSTYPE‘
因为YYSTYPE是在parser.tab.h内部定义的.最后，由于某种原因，野牛解析器甚至不知道yyscan_t是什么，甚至包括词法分析器标头:
because YYSTYPE is defined inside parser.tab.h. And finally, for some reason, the bison parser doesn't know what yyscan_t even including the lexer header:
error: unknown type name ‘yyscan_t’
一种解决方法是将其定义为无效:
One workaround is defining it to void:
%lex-param {void *scanner}
%parse-param {void *scanner}
请参见yyscan_t定义:flex的手册yyscan_t
所以这是最终结果:
scanner.l
%{
#include <stdio.h>
#include "parser.tab.h"
%}
%option 8bit reentrant bison-bridge
%option warn noyywrap nodefault
%option header-file="lex.yy.h"
//rest of the scanner
parser.y
%{
#include <stdio.h>
#include "parser.tab.h"
#include "lex.yy.h"
void yyerror(yyscan_t scanner, char const *msg);
%}
%define api.value.type {double}
%define parse.error verbose
%define api.pure
%lex-param {void *scanner}
%parse-param {void *scanner}
//rest of the input
main.c
#include <stdio.h>
#include "parser.tab.h"
#include "lex.yy.h"
int main(void) {
yyscan_t scanner;
yylex_init(&scanner);
yyset_in(stdin, scanner);
yyparse(scanner);
yylex_destroy(scanner);
return 0;
}
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