Boost C++ Libraries: Ticket #287: wrong usage of ios_base::narrow

description changed; severity, milestone set

Marshall Clow — Fri, 29 May 2009 18:27:51 GMT

severity → Problem
description modified (diff)
milestone → Boost 1.40.0

Marshall sez: looking at the code in trunk, it appears that this patch has been (more or less) applied. I'm not sure about the constructor call to std:locale() for each character, though. {{

while(beg != end) {

#if !defined(BOOST_DATE_TIME_NO_LOCALE)

ss << std::use_facet<std::ctype<wchar_t> >(std::locale()).narrow(*beg++, 'X'); 'X' will cause exception to be thrown

#else

ss << ss.narrow(*beg++, 'X');

#endif

}

}}

Steven Watanabe — Sun, 31 May 2009 00:54:44 GMT

But the #else is still just as wrong as ever.

Andrey Semashev — Sun, 31 May 2009 11:32:22 GMT

I'm not sure we need or can fix the #else branch since there is no real wide character support without locales. As for extracting locale construction and facet extraction out of the loop - that's a good optimization. Anyway, the ticket can be closed, IMHO.

Steven Watanabe — Sun, 31 May 2009 13:29:32 GMT

At least the call to narrow should be removed to avoid giving the false impression that it's safe.

Andrey Semashev — Mon, 01 Jun 2009 09:14:35 GMT

Replying to steven_watanabe:

At least the call to narrow should be removed to avoid giving the false impression that it's safe.

I think this would be more appropriate:

char c = 'X'; // 'X' will cause exception to be thrown
const wchar_t wc = *beg++;
if (wc >= 0 && wc <= 127)
  c = static_cast< char >(wc);
ss << c;

Andrey Semashev — Mon, 01 Jun 2009 09:52:40 GMT

Went in revision 53529.

status, resolution changed

Andrey Semashev — Thu, 04 Jun 2009 08:39:58 GMT

status assigned → closed
resolution None → fixed

Merged into release branch at revision 53618. Will be released in 1.40.