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From: Kaz Kylheku <kaz@kylheku.com>
Newsgroups: comp.compilers
Subject: Re: stop yyparse() at <<EOF>>
Date: Sun, 27 Dec 2015 10:59:48 -0500 (EST)
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On 2015-12-22, Jens Kallup <jkallup@web.de> wrote:
> (\"([a-zA-Z0-9_])*\")* {
>    printf("1: %s\n",yytext); strcpy(yytext,"");
>    BEGIN(STRINGER);
>    strcpy(yytext,"");

[ snip ]
>
> Is that a Bug, or my mistakes?

Not saying this is the crash, but do not modify yytext; it is (or may
be) a pointer directly into the lexical analyzer's buffer, and not a
copy.

You might be confusing the flex scanner somehow by putting a null in
there.

> string_expr
>      : _STRING_ { printf("---> %s\n",yylval.text); }
>      ;


You haven't shown any lexer code which sets up yylval.text and returns
the _STRING_ token.

The lex rules you have surrounding your STRINGER state don't return
anything.

[Good points.  In recent versoins of flex, yytext points into the
input buffer and chaning what it points to is asking for trouble.
If you need to change it, make a copy.
Also, there's no BEGIN(INITIAL) to reset the start states. -John]