Re: Problem with std::codecvt::out()

[Thomas Maeder]

"JH Trauntvein" <j.trauntvein@comcast.net> writes:

> In the folloiwng code fragment, I am attempting to convert a multi-byte
> string into a wide string using the std::codecvt::out() function.  I
> have found that when I do so, the compiler complains that it cannot
> find a match but then proceeds to list an exact match as the one and
> only candidate.

The match isn't exact.


>     using namespace std;
>     String rtn;
>     char temp[MB_LEN_MAX];
>     wchar_t val = static_cast<wchar_t>(m_c);
>     mbstate_t state = { 0 };
>     wchar_t *next1;
>     char *next2;
>     int result;
>
>     result = use_facet<codecvt<wchar_t, char, mbstate_t> >(locale).out(
>        state,
>        &val,
>        &val + 1,
>        next1,
>        &(temp[0]),
>        temp + sizeof(temp),
>        next2);
>     if(result != codecvt_base::error)
>        rtn = String(temp,next2);
>     return rtn;

Next time please post just enough code to allow your audience to see
what you are seeing.

> Here is a copy of the compiler error message:
>
> /home/jon/work/cora/coratools/advxml/Elements.cpp: In member function
> 'virtual AdvXMLParser::String AdvXMLParser::CharRef::GetData()
> const':
> /home/jon/work/cora/coratools/advxml/Elements.cpp:471: error: no
> matching function for call to 'std::codecvt<wchar_t, char,
> mbstate_t>::out(mbstate_t&, wchar_t*, wchar_t*, wchar_t*&, char*,
> char*, char*&) const'
> /usr/lib/gcc/i386-redhat-linux/4.0.1/../../../../include/c++/4.0.1/bits/codecvt.h:121:
> note: candidates are: std::codecvt_base::result
> std::__codecvt_abstract_base<_InternT, _ExternT,
> _StateT>::out(_StateT&, const _InternT*, const _InternT*, const
> _InternT*&, _ExternT*, _ExternT*, _ExternT*&) const [with _InternT =
> wchar_t, _ExternT = char, _StateT = mbstate_t]

The parameter 3 (0-based) has type const _InternT*& [with _InternT =
wchar_t]. You attempt to pass a wchar_t *&.

There is no implicit conversion vrom wchar_t * & to wchar_t const * &.


What do you get if you define

wchar_t const *next1;

?