-----Original Message----- From: boost-bounces@lists.boost.org [mailto:boost-bounces@lists.boost.org] On Behalf Of Hartmut Kaiser Sent: woensdag 9 februari 2005 14:42 To: boost@lists.boost.org Subject: RE: [boost] Wave C++ Review Begins Today - February 7, 2005
Michiel Salters wrote:
one serious bug in wave\cpplexer\re2clex\cpp_re2c_lexer.hpp: template <typename IteratorT, typename PositionT> inline lexer<IteratorT, PositionT>::lexer(IteratorT const &first, IteratorT const &last, PositionT const &pos, boost::wave::language_support language) : filename(pos.get_file()), at_eof(false) { memset(&scanner, '\0', sizeof(Scanner)); scanner.fd = -1; scanner.eol_offsets = aq_create(); scanner.first = scanner.act = (uchar *)&(*first); scanner.last = (uchar *)&(*last); ... [ IteratorT = std::string::iterator in the example ]
This assumes that the range [first,last] is dereferenacable and contiguous in memory. This of course is not mandated by the standard.
Yes, this is a known problem (see the Changelog file), I didn't realise, that it will assert on some systems. Seems, that I'll have to fix that soon ;-). This shouldn't be a problem on other systems, though, if you're using iterators acting on a continuous chunk of memory (such as std::string::iterator).
No, you're mistaken here and in the Changelog as well. Even std::string::iterator doesn't have to refer to contiguous memory. std::vector<char>::iterator would, though, so I built a string around that and found the actual bug (and a VC8 bug as well I think). The bug is that context<IteratorT> stores the two iterators first and last as const&. The cpp example passed .begin() and .end(), which are temporaries and they go out of scope. The result is that the context ends up with references to destructed iterators. Again, the VC8 STL iterator debugging found the problem on first access. Line 281, cpp_context.hpp I really have to say Dinkumware did a fine job here, this would have been very hard to find without these checks.
OTOH this isn't exactly a problem in the preprocessor library, it's merely a problem of the re2c generated lexer used in the driver. The other provided lexer (SLEX based) won't expose this problem (i.e. the cpp_tokens example shouldn't assert).
Might be (didn't get there yet), but it too uses cpp_context.hpp, right? BTW, if you try VC8, mail me for the string class I used. Using std::vector<char> directly appears to trigger a VC 8(beta1) bug with typenames longer than 2KB Regards, Michiel Salters This e-mail and any attachment is for authorised use by the intended recipient(s) only. It may contain proprietary material, confidential information and/or be subject to legal privilege. It should not be copied, disclosed to, retained or used by, any other party. If you are not an intended recipient then please promptly delete this e-mail and any attachment and all copies and inform the sender. Thank you.