Re: Calling two times yyparse reloading yyin

[Ismael Moreno]

I forgot to mention that i've changed the delete instruction. As Tim said,
it's better free, or use brackets at the end of the delete sentence, since i
was deleting an array.
And strdup is needed, because ::c_str() returns const* char, instead of
char*.

On 11/29/05, Ismael Moreno <address@hidden> wrote:
>
> First of all, i've included an "old" version of this piece of code. I
> fixed after ask the yyin field, so sorry.
>
> Well, after using yyrestart and all what you said, now looks like the
> problem is in the first yyparse() function.
>
> I made an diagram with an "assigment" node as a testcase. This diagrams
> represents a very easy algorithm which returns 2+2. The assigment node
> contanis:
> Result <- 2+2
> Where "2+2" is the RValue and "Result" the LValue. It returns an
> exception: "basic_string::_S_construct NULL not valid".
> I've added debug tasks on the lex rules, so, where a token is identified,
> it shows in the console what token is under processing. In RValue, only the
> first number token is recognized.
> It is really odd, since i've made earlier some parsers with a different
> yyin from stdio.
> That's the remodeled piece of code:
>
>       *//RValue*
>       yyin = fmemopen(Text, strlen(Text) , "r");
>       *if*(yyin == NULL)
>               *throw*(cError("you-know-that"));
>
>       yyrestart(yyin);
>       yyparse();
>       sMemReg Instr;
>       Instr.Func = push_ax;
>       vm.putMemoryCell(Instr);
>
>       *//LValue (...)*
>
>
>
> I won't ask this if i hadn't tried before the parser. With yyin as stdin,
> expressions are parsed correctly.
>
> Again, thank you in advance.
>
>
> > yyparse() (well, yylex() really) can't (and won't) use your
> > function-local yyin.
> > Note that adjusting the code to use the global yyin won't necessarily
> > work; flex will only cleanly switch to the new yyin if it got an EOF
> > state on the original one.  Using yyrestart(), you to tell flex/bison
> > that a new "file" should be processed, even if the current/previous
> > one wasn't fully processed (so that flex can clear its internal cache).
> > So put a "yyrestart(yyin);" before each yyparse() and things should
> > work.
> > Depending on your lexer you may want to add a function of your own
> > (say, yy_new_file()) to your .l file, that not only calls yyrestart(),
> > but also sets the lexer state back to INITIAL (so that a parse error
> > inside a state in the first yyparse() does not break the second
> > yyparse()).
> > You typically want to test yyparse()'s return value too, so that
> > you can detect parse errors.
> >
> > > [snip]
> > >     delete Text;
> >
> > Memory allocated by malloc() (even indirectly via strdup()) should be
> > freed using free(), not delete.
> >
> > I'm not sure the strdup() is even needed - I would expect that
> >   fmemopen(RValue.c_str(), RValue.size (), "r");
> > works just as well.
> >
> >
>