Re: [Boost-users] Spirit library - Problem with the copy constructor of the class rule<> ?

From: Joel de Guzman (djowel_at_[hidden])
Date: 2003-09-18 10:48:48

---- Original Message ----
From: Fritz Birnbacher

> Hello,
> 
> I am new in using boost and I played a little bit with the spirit library.
> 
> I tried following code using MSVC 7.1 and boost 1.30.2
> 
> #include"stdafx.h"
> #include<spirit.hpp>
> 
> using namespace boost::spirit;
> 
> rule<> GetRule()
> 
>     rule<> r = anychar_p;
>     return r;
> 
> 
> void Parse1()
> 
>     char s[] = "ABCD";
>     parse(s, GetRule());
> 
> 
> void Parse2()
> 
>     rule<> r = anychar_p;
>     char s[] = "ABCD";
>     parse(s,r);
> 
> 
> int _tmain()
> 
>     Parse1();
>     return 0;
> 
> 
> 
> Parse1() throws an exception (access violation)
> 
> Parse2() works correct.
> 
> 
> Is it a compiler problem or a problem in spirit or my problem ?

Neither.

You should not return rules from functions. Rules cannot be passed
by value. The copy and assignment operators do not follow the
standard C++ object behavior. Instead, you wrap rules inside grammars
and pass the grammar around.

For that matter, v1.7 has the notion of stored_rule(s) which, unlike
the rule, has C++ ctor/assign semantics, hence, can be passed around,
stored inside containers, etc.

HTH.

BTW, Spirit has its own mailing list:

Spirit-general mailing list
Spirit-general_at_[hidden]
https://lists.sourceforge.net/lists/listinfo/spirit-general

I took the liberty of cross-posting this there. See you there. 

-- 
Joel de Guzman
http://www.boost-consulting.com
http://spirit.sf.net