CODEWITHSUNDEEP
compiler-constructionbison
kin
kin

Reputation: 173

bison grammar error when adding a rule

Hi I m trying to make a very simple grammar and failing miserably when I try to combine 2 rules:

The flex file:

%option never-interactive
%option yylineno


D   [0-9]
L   [a-zA-Z_]
A   [a-zA-Z_0-9]
WS  [ \t\v\n\f]

%%
"keyword"       { printf("KEYWORD: %s\n", yytext); return KEYWORD; }
[+-]?{D}+       { yylval = atoi(yytext); return L_SINT32; }
{L}{A}*     { printf("ID: %s\n", yytext); return IDENTIFIER;    }
";"         { return EOS;       }
{WS}        { }
.           { printf("OTHER\n"); return 0; }

%%

and the corresponding bison file:

%token L_SINT32
%token EOS
%token IDENTIFIER KEYWORD
%start stmt_list

%%


idlist  : IDENTIFIER        { printf("IDENT\n"); }
    | idlist IDENTIFIER { printf("IDENT, IDENT\n"); }
    ;

stmt    : KEYWORD IDENTIFIER ';'
    | idlist ';'    { printf("EXP\n"); }
    ;

stmt_list
    : stmt
    | stmt_list stmt
;

%%

When I try to use that on the input

id0 id1 id2;
keyword id1;

I get:

ID: id0
IDENT
ID: id1
IDENT, IDENT
ID: id2
IDENT, IDENT
error -> syntax error

Can someone points me out why is that ?

Upvotes: 0

Views: 42

Answers (1)

rici
rici

Reputation: 241691

When your lexer sees a semicolon:

";"         { return EOS;       }

What your parser is looking for:

| idlist ';'    { printf("EXP\n"); }

EOS will have some value created by bison and put in the generated header file; it might be 258. ';', on the other hand, has the value ';' (i.e. 0x3B or 59).

I'd get rid of EOS and just return ';' from the lexer.

Upvotes: 1

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