Re: AW: Segmentation Fault in yyparse() method

[lfinsto1]

> The result of debugging in short:
> In the version with segmentation fault (gcc 4.1.2):
>
> 33117     if (yychar == YYEMPTY)
> (gdb)
> 33120         yychar = YYLEX;
> (gdb)
>
> Program received signal SIGSEGV, Segmentation fault.
> yyparse () at fullParser.tab.c:33120
> 33120         yychar = YYLEX;
>
>
> I don't get why it doesn't get to the breakpoint. Are there any
> instructions, that are performed, that the debugger doesn't show?
>
> Debugging just lex.yy.c runs through without a "segmentation fault".

I'm not entirely certain, but isn't `YYLEX' a macro?  If it is, the
debugger isn't going to help you very much.  This is one of the main
reasons Stroustrup is so against the use of macros, and for what it's
worth, I think he's right.

You're going to have to find out what the definition of `YYLEX' is.  I
doubt very much that it's a bug in Flex or lex.  However, it's not really
a question for this list.  I use Flex by itself occasionally, but I tend
to write `yylex' by hand when using Bison.  I suspect that `YYLEX' is
trying to read from an invalid area of memory, and my prime suspect is an
uninitialized pointer or one that's been deleted, but not set to 0.  Maybe
even one that has been set to 0, if `YYLEX' doesn't catch this error,
which wouldn't surprise me.

Laurence