[boost] Re: lexical_cast(Was: FYI)

From: Kevlin Henney (kevlin_at_[hidden])
Date: 2003-03-13 08:24:42

In article <4.3.2.7.2.20030313072035.025d4968_at_[hidden]>, Beman
Dawes <bdawes_at_[hidden]> writes
>
>>Just to let you know that a new version is now in CVS.
>>
>>However, it appears to break under the regression test. I expected it to
>>break for VC6, but it is apparently failing to compile under VC7 and
>>Intel 7.0... which is more than a little bizarre because I have been
>>using VC7 as the main test compiler and Terje checked it against Intel
>>7.0. Both compile and run cleanly.
>
>VC++7 is not giving trouble with any tests other than lexical_cast_test. On 
>it, the message begins:
>
>D:\boost\site-RC_1_30_0\boost\lexical_cast.hpp(142) : error C2065: 
>'InputStreamable' : undeclared identifier

Which of course, is not the case :-> The problem does not appear to be
with the code.

>The error messages from various date_time library fails for both Intel 
>and  VC++ 6.0 are similar. Here is the Intel message:
>
>D:\boost\site-RC_1_30_0\boost/lexical_cast.hpp(137): error: no operator 
>"<<" matches these operands operand types are: 
>std::basic_stringstream<wchar_t, std::char_traits<wchar_t>, 
>std::allocator<wchar_t>> << const std::basic_string<char, 
>std::char_traits<char>, std::allocator<char>> return stream << input;

This suggests that the compiler has deduced wchar_t as being the
appropriate type for the stream when it should be char. This relies on
rather straightforward full template specialisation, which would seem
odd to get wrong.

>Plus Robin Hu's posting:
>
>>A word on the lexical_cast_test.cpp: everything will be ok if you
>>commented all tests about std::wstring and wchar_t with
>>
>>#ifndef BOOST_NO_STD_WSTRING
>>#endif
>
>Both seem to indicate a wstring/wchar_t problem.

The problem is related to wstring and wchar_t, but is not related to
compiler/library support for them.

Kevlin
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