Re: [boost] Program_options workarounds?

From: Vladimir Prus (ghost_at_[hidden])
Date: 2005-01-20 03:50:39

On Thursday 06 January 2005 16:38, John Maddock wrote:
> The following section of code in utf8_codecvt_factet.hpp seems to be rather
> mixed up:
>
> #if BOOST_WORKAROUND(__BORLANDC__,BOOST_TESTED_AT(0x551))
> #ifndef _RWSTD_NO_NAMESPACE
> using std::codecvt;
> using std::min;
> #ifdef _RWSTD_NO_MBSTATE_T
> using std::mbstate_t;
> #endif
> #endif
>
> This section imports codecvt, min and mbstate_t into the *global
> namespace*, why?

I don't know. This was a fix sent by an user (Pavel Vozenilek, I think) for 
some specific borland version. We failed to figure out why this works and 
what's the exact problem with that compiler.

> Isn't this a "bad thing" in general?

I don't think so, in general. mbstate_t was in global namespace in C, after 
all.

> I can't see why it would be necessary anyway.
>
> #elif defined(__COMO__) || defined(_MSC_VER) && _MSC_VER <= 1300
> typedef ::mbstate_t mbstate_t;
>
> Surely this has no effect at best, or is illegal at worst?  Remember we're
> in the global namespace here.  
> Commenting this out has no effect on VC7 BTW 
> (and VC6 doesn't build the lib anyway), can't comment on Commeau though.
>
> #elif defined(BOOST_NO_STDC_NAMESPACE)
> typedef std::mbstate_t mbstate_t;
> namespace std{
> using ::codecvt;
>
> Again why import mbstate_t into the global namespace, especially as this
> does not happen for std conforming compilers?

Pavel, seems like the std::mbstate_t -> mbstate_t change was part of your 
patch (applied in revision 1.10 of utf_codecvt_facet.hpp). Do you remember 
why it was necessary?

> Finally importing codecvt into namespace std:: is almost always likely to
> be an error: BOOST_NO_STDC_NAMESPACE refers to C library code, I don't know
> of any std lib that has codecvt, but doesn't put it in namespace std
> already.
>
> In any case it doesn't build as is with gcc-2.95 (with or without STLport),
> but changing that to:
>
> #elif defined(BOOST_NO_STDC_NAMESPACE)
> namespace std{
> using ::mbstate_t;
> } // namespace std
>
> and likewise changing the similar workaround convert.hpp to:
>
> #if BOOST_WORKAROUND(__ICL, <= 700) || defined(BOOST_NO_STDC_NAMESPACE)
> #include <wchar.h>
> namespace std
> {
> using ::mbstate_t;
> }
> #endif
>
> Gets it compiling with gcc-2.95 + STLport.
>
> Hope this helps,

Yes, it does. Thank you! 
I'm just now trying to merge workarounds in program_options' and 
serialization's version of that file, so your suggestions are very welcome.

- Volodya