Take the file [file.y], compile it to generate tab.[ch] files and the
compile it (without linking) with gcc. It gives a warning in this step.
Can fix this warning?
Commands used and their output:
====
$ bison -vd file.y
$ gcc -Wall -c file.tab.c
file.tab.c:1349: warning: implicit declaration of function ‘yylex’
# A command that works, but it is out of scope for this message
$ gcc -Wall file.tab.o [other object files] -lfl
$
====
Is this warning something expected? I was thinking about adding yylex()
prototype to file.y, but I do not know what it is, and I could not find
it in documentation.
%start program
/* SEMANTIC RECORD */
/* char *id: For returning identifiers */
/*
Place to easily pasting/cutting the union declaration
*/
%union {
char *id;
}
/* Simple identifier */
/*
Place to exchange the IDENTIFIER token declarations
*/
%token IDENTIFIER
%type <id> IDENTIFIER
%token LET IN
/* "integer" keyword */
/* both INT e INTEGER exist? Removed INT, occurrences changed.
%token INT
*/
%token INTEGER
/* Same question for NUMBER: should it exist?
Replaced all of its occurrences with INTEGER
-> wrong, written numbers X 'integer' keyword. Changes undone
*/
%token NUMBER
/* FI was missing */
%token SKIP IF THEN ELSE FI END WHILE DO READ WRITE
/* ASSGNOP was missing */
%token ASSGNOP
%left '-' '+'
%left '*' '/'
%left '<' '>' '=' '' /* these where missing on the book, added */
%right '^ '
%{
#include <stdlib.h> /* For malloc in symbol table */
#include <string.h> /* For strcmp in symbol table */
#include <stdio.h> /* For error messages */
#include "st.h" /* The Symbol Table Module */
/* Redeclaration? Should not be #define YYDEBUG 1 / * for debugging / para
depuração */
/* Global variable 'Errors' to substitute the previously
undeclared variable 'errors' */
int Errors = 0;
int yyerror (char *s); // function header, removes a warning
int install( char* sym_name)
{
symrec *s;
s = getsym(sym_name);
if (s == 0)
s = putsym (sym_name);
else
{
Errors++;
printf("%s is already defined\n", sym_name);
return 0;
}
return 1;
}
int context_check(char* sym_name)
{
if ( getsym( sym_name ) == 0 )
{
printf("%s is an undeclared identifier\n", sym_name);
return 0;
}
return 1;
}
%}
%%
/* Grammar rules and actions */
program : LET declarations IN commands END ;
declarations : /* empty */
| INTEGER id_seq IDENTIFIER '.' { install( $3 ); }
;
id_seq : /* empty */
| id_seq IDENTIFIER ',' { install( $2 ); }
;
commands : /* empty */
| commands command ';'
;
command : SKIP
| READ IDENTIFIER { context_check( $2 ); }
| WRITE exp
| IDENTIFIER ASSGNOP exp { context_check( $1 ); }
| IF exp THEN commands ELSE commands FI
| WHILE exp DO commands END
;
/* expressions */
exp : NUMBER
/* in book it is $2, wrong */
| IDENTIFIER { context_check( $1 ); }
| exp '<' exp
| exp '=' exp
| exp '>' exp
| exp '+' exp
| exp '-' exp
| exp '' exp
| exp '/' exp
| exp '^ ' exp
| '(' exp ')'
;
%%
/* C subroutines */
/* não tem saída, a árvore de reconhec. fica implícita */
/* no output, implicit parse tree */
int main( int argc, char *argv[] )
{
extern FILE *yyin;
++argv; --argc;
yyin = fopen( argv[0], "r" );
// yydebug = 1; // line commented -> bad fix
// errors = 0; // initialization unneeded => line removed
yyparse ();
return 0;
}
int yyerror (char *s) /* called by yyparse() in error situations */
{
printf ("%s\n", s);
return 0;
}
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