For some reason, it seems that I can’t fix the errrors I’m encountering, which are weird, specially the YYABORT one, since I’m defining %locations. My Flex version is 2.6.4 and my bison is 3.8. I’d love to hear some feedback since I’m being stuck here. Thx a lot in advance!

js.l:

%{
#include "js-parser.h"

#define YY_USER_ACTION 
    yylloc.first_line = yylloc.last_line; 
    yylloc.first_column = yylloc.last_column; 
    yylloc.last_column += yyleng; 
    if (yytext[yyleng-1] == 'n') { 
        yylloc.last_line++; 
        yylloc.last_column = 1; 
    };

void yyerror(YYLTYPE *loc, const char *s);
%}

%option yylineno

%%

"var"                                { return VAR; }
"const"                              { return CONST; }
"let"                                { return LET; }


[a-zA-Z_][a-zA-Z0-9_]*               { yylval.sval = strdup(yytext); return IDENTIFIER; }


[0-9]+(.[0-9]*)?([eE][-+]?[0-9]+)?|.[0-9]+([eE][-+]?[0-9]+)?    { yylval.ival = atoi(yytext); return NUMBER; }

"//"                                 { input(); while (input() != 'n'); }
"/*"                                 { do { while(input() != '*'); } while (input() != '/'); }


"+"                                  { return PLUS; }
"-"                                  { return MINUS; }
"*"                                  { return MULTIPLY; }
"/"                                  { return DIVIDE; }
"("                                  { return LPAREN; }
")"                                  { return RPAREN; }


"="                                  { return ASSIGN; }
";"                                  { return SEMICOLON; }



[ tn]+                             ;


.                                    { return yytext[0]; }


%%

js.y:

%{
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int yylex();
void yyerror(YYLTYPE *loc, const char *s);
int main();
%}

%locations

%union {
    int ival;
    char *sval;
};

%token <ival> IDENTIFIER
%token <ival> NUMBER

%token VAR CONST LET PLUS MINUS MULTIPLY DIVIDE LPAREN RPAREN ASSIGN SEMICOLON

%left PLUS MINUS
%left MULTIPLY DIVIDE

%right NEG

%type <ival> expr

%%

program:
    | program statement SEMICOLON
    ;

statement:
    type IDENTIFIER
    | type IDENTIFIER ASSIGN expr
    ;

type:
    VAR
    | CONST
    | LET
    ;

expr:
    NUMBER
    | IDENTIFIER
    | expr PLUS expr               { $$ = $1 + $3; }
    | expr MINUS expr              { $$ = $1 - $3; }
    | expr MULTIPLY expr           { $$ = $1 * $3; }
    | expr DIVIDE expr             { if ($3) $$ = $1 / $3; else { yyerror(@3, "division by zero"); }; }
    | LPAREN expr RPAREN           { $$ = $2; }
    | MINUS expr %prec NEG         { $$ = -$2; }
    ;

%%

void yyerror(YYLTYPE *loc, const char *s) {
    fprintf(stderr, "Error at %d: %sn", loc->first_line, s);
    YYABORT;
};

int main() {
    printf("Use this js parser");
    yyparse();
    return 0;
};

And the errors I’m encountering:

js.y:7:14: error: unknown type name ‘YYLTYPE’
    7 | void yyerror(YYLTYPE *loc, const char *s);
      |              ^~~~~~~
js.y: In function ‘yyparse’:
js.y:53:117: warning: implicit declaration of function ‘yyerror’; did you mean ‘yyerrok’? [-Wimplicit-function-declaration]
   53 |     | expr DIVIDE expr             { if ($3) $$ = $1 / $3; else { yyerror(@3, "division by zero"); }; }
      |                                                                                                                     ^      
      |                                                                                                                     yyerrok
js.y: At top level:
js.y:60:6: warning: conflicting types for ‘yyerror’; have ‘void(YYLTYPE *, const char *)’
   60 | void yyerror(YYLTYPE *loc, const char *s) {
      |      ^~~~~~~
js.y:53:117: note: previous implicit declaration of ‘yyerror’ with type ‘void(YYLTYPE *, const char *)’
   53 |     | expr DIVIDE expr             { if ($3) $$ = $1 / $3; else { yyerror(@3, "division by zero"); }; }
      |                                                                                                                     ^      
js.y: In function ‘yyerror’:
js.y:62:5: error: label ‘yyabortlab’ used but not defined
   62 |     YYABORT;
      |     ^~~~~~~

I've tried to declare YYABORT manually among many other tries, but I always end up with the same errors.