unnamed-faq-68

     To: "Bart Niswonger" <NISWONGR@almaden.ibm.com>
     Subject: Re: flex 2.5: c++ scanners & start conditions
     In-reply-to: Your message of Tue, 06 Jan 1998 10:34:21 PST.
     Date: Tue, 06 Jan 1998 19:19:30 PST
     From: Vern Paxson <vern>
     
     > The problem is that when I do this (using %option c++) start
     > conditions seem to not apply.
     
     The BEGIN macro modifies the yy_start variable.  For C scanners, this
     is a static with scope visible through the whole file.  For C++ scanners,
     it's a member variable, so it only has visible scope within a member
     function.  Your lexbegin() routine is not a member function when you
     build a C++ scanner, so it's not modifying the correct yy_start.  The
     diagnostic that indicates this is that you found you needed to add
     a declaration of yy_start in order to get your scanner to compile when
     using C++; instead, the correct fix is to make lexbegin() a member
     function (by deriving from yyFlexLexer).
     
     		Vern