Compile error when specifying prefixes with Flex and Bison

Question

I am trying to compile a simple bison parser using a given prefix - as was resolved in this question. I'm using Bison version 2.4.1 and flex version 2.5.35 (I can't use bison 2.6). I have been running into a compiler error that has me running around in circles:

Namely:

make
Making all in src
make[1]: Entering directory `/stage/pool14/eholum/yacc_example/src'
/bin/sh ../ylwrap parcalc.y y.tab.c parcalc.c y.tab.h parcalc.h y.output parcalc.output -- bison -y  -d -p="calcYY"
...yacc_example/src/parcalc.y:27.7-13: warning: type clash on default action: <result> != <>
conflicts: 4 shift/reduce
updating parcalc.h
gcc -DPACKAGE_NAME=\"calculator\" -DPACKAGE_TARNAME=\"calculator\" -DPACKAGE_VERSION=\"1.0\" -DPACKAGE_STRING=\"calculator\ 1.0\" -DPACKAGE_BUGREPORT=\"\" -DPACKAGE=\"calculator\" -DVERSION=\"1.0\" -I.     -g -O2 -MT parcalc.o -MD -MP -MF .deps/parcalc.Tpo -c -o parcalc.o parcalc.c
parcalc.c:1053: error: expected identifier or ‘(’ before ‘=’ token
parcalc.c:1061: error: expected identifier or ‘(’ before ‘=’ token
parcalc.c:1064: error: expected identifier or ‘(’ before ‘=’ token
parcalc.c:1067: error: expected identifier or ‘(’ before ‘=’ token
parcalc.c:1089: error: expected identifier or ‘(’ before ‘=’ token
parcalc.y:75:21: error: lexcalc.c: No such file or directory
make[1]: *** [parcalc.o] Error 1

I'm currently using automake, but I get the same error if I build using flex and bison then try compiling with c. Here's my Makefile.am:

bin_PROGRAMS = calculator
AM_YFLAGS = -d -p="calcYY"
calculator_SOURCES = parcalc.y lexcalc.l

Where the lex code is is in lexcalc.l (note I'm using %option to specify the prefix, but I get the same error when I use the cl flag):

%{
#include <stdio.h>
#include "parcalc.h"
%}

%option noyywrap
%option prefix="yy"

%%

[ \t] ; 

[0-9]+\.[0-9]+ { 
    yylval.flval = atof(yytext);
    return FLOAT;
}

[0-9]+ {
    yylval.inval = atoi(yytext);
    return INT;
}

- { return MINUS; }

\+ { return PLUS; }

\n {
    yylineno++; 
    return NEWLINE; 
}

. ;

%%

And the Bison code is in parcalc.y :

%{
#include <stdio.h>
%}

%token INT FLOAT PLUS MINUS NEWLINE;

%union {
    int inval;
    float flval;
    char oper;
    char result[100];
}

%type <inval> INT;
%type <flval> calc FLOAT
%type <oper> PLUS MINUS;
%type <result> line;

%%

lines:
     line lines
    | line
    ;

line:
      NEWLINE
    | calc NEWLINE {
        printf("Result = %f\n", $1);   
      }
    ;

calc :
      calc PLUS calc { 
        ($$ = $1 + $3);
      }
    | calc MINUS calc { 
        ($$ = $1 - $3); 
      }
    | INT { 
        ($$ = $1);
      }
    | FLOAT { 
        ($$ = $1); 
      }
    ;

%%

extern int calcYYparse();
extern FILE *calcYYin;

int main() {

    FILE *myfile = fopen("infile.txt", "r");

    if (!myfile) {
        fprintf(stderr, "can't open infile.txt\n");
        return 1;
    }

    calcYYin = myfile;

    do {
        calcYYparse();
    } while (!feof(calcYYin));

    return 0;
}

void calcYYerror(const char *s) {
    fprintf(stderr, "Unrecognized format\n");
}

I should note that everything seems to work fine when I discard the prefixes, so I'm guessing that there's something awry with how things are externally declared in the generated c files. Looking through those I haven't been able to figure it out yet. If anyone has messed around with multiple parsers and has some insight on how to make these things play nicely together I would really appreciate it.

Have you looked at the lines in the generated `parcalc.c` file about which the compiler complains? You shouldn't try to fix the problem by modifying that file, but the nature of the erroneous code may give you a clue as to what the problem is. — John Bollinger, Sep 18 '15 at 21:07
I would start with `parcalc.c:1053: error: expected identifier or ‘(’ before ‘=’ token` . If you look at `parcalc.c` on/around line 1053 does it give you any hints as to what it might be associated with? Giving the output in your question for the 5 lines/before after line 1053 could help. — Michael Petch, Sep 18 '15 at 21:08
Ah I just noticed one little thing that might be related. `AM_YFLAGS = -d -p="calcYY"` . In particular the `=` sign after `-p`. I believe it is literally turning the prefix to `=calcYY`. Try changing it to `-p"calcYY"`. — Michael Petch, Sep 18 '15 at 21:37
Ah, I replaced the AM_YFLAGS with what you suggested, @Michael, and I also realized that I have to be careful about how I name functions, given that yyparse, yylex, yyerror, yynerrs, yylval, yylloc, yychar and yydebug are changed by the bison -p option. I now seem to have a different error with no helpful info included in the message (/bin/sh ../ylwrap lexcalc.l lex.yy.c lexcalc.c -- flex make[1]: *** [lexcalc.c] Error 1) I'll update if I figure it out. — doggie_breath, Sep 18 '15 at 22:21
Have no idea if there are other issues, but figured at a minimum you ended up with variable names with `=` in it. — Michael Petch, Sep 18 '15 at 22:23
@Erik - I also recommend that if there are other errors not related to the issue I observed then it might be more appropriate to start a new question rather than update this one. Sounds like `error: expected identifier or ‘(’ before ‘=’ token` issue has been resolved. — Michael Petch, Sep 18 '15 at 22:45
@MichaelPetch I'll do that. Thanks for the help! I'll either update this with the new post or the solution if I figure it out. — doggie_breath, Sep 18 '15 at 22:51

doggie_breath · Accepted Answer · 2020-01-31T22:38:30.317

2

Thanks to Michael for spotting the issue with the prefix flag being passed to the bison compiler. Namely

AM_YFLAGS = -d -p="calcYY"

versus

AM_YFLAGS = -d -p"calcYY"

Also slightly related is that the prefix only changes yyparse, yylex, yyerror, yynerrs, yylval, yylloc, yychar and yydebug. So yyin did not need to change.

edited Jan 31 '20 at 22:38

answered Sep 18 '15 at 22:50

doggie_breath

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Compile error when specifying prefixes with Flex and Bison

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